24Al Level Structure and the Corresponding 23Mg(p,) 24Al Astrophysical Reaction
Rate. CHRISTOPHER DEATRICK (Western Michigan University,
Kalamazoo, Mi, 49008) DARIUSZ SEWERYNIAK (Argonne National Laboratory,
Argonne, IL, 60439)
24Al Level Structure
and the Corresponding 23Mg(p,) 24Al Astrophysical Reaction Rate.
Christopher J. Deatrick (Western Michigan University, Kalamazoo,
MI 49008) Dariusz Seweryniak (Argonne National Laboratory, Argonne,
IL 60439) In order to better understand the processes involved in
heavy nuclide production in explosive stellar environments, the breakout
process from the CNO cycles to the NeNa cycle and to the MgAl cycle
must be quantified. Better numerical values of proton capture rates
are deduced for the 23Mg(p,) 24Al reaction by studying nuclear energy
levels in 24Al above the proton capture threshold using high-resolution
-ray spectroscopy and -ray angular distribution analysis. 24Al
nuclei were produced by colliding an 16O beam delivered by the Argonne
Tandem-Linac Accelerator System with a 10B target . Excited states
in 24Al were populated after evaporating two neutrons from the compound
system. Gamma rays emitted from these states were detected with the
GAMASPHERE array of Compton-suppressed Ge detectors. The Argonne
Fragment Mass Analyzer was used to separate reaction products from
the beam and assign mass and atomic numbers. As a result, states
above and below the proton threshold were studied in detail resulting
in an improved 24Al level scheme. The analysis of the first state
above the proton threshold indicates that the reaction rate contribution
of this state could differ by a factor of up to 9 from that of previous
calculations in the 0.1-0.5 GK temperature range.
3D Simulation for the ATLAS Education and Outreach Group. BRIAN
AMADIO (Rensselaer Polytechnic Institute, Troy, NY, 12180)
MICHAEL BARNETT (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
ATLAS is a particle
detector under construction at the Large Hadron Collider facility
at the CERN Laboratory in Geneva, Switzerland. The project will be
the most expansive physics experiment ever attempted. The ATLAS Education
and Outreach Group was started to provide information to students
and the general public about the importance of this project. A three-dimensional
interactive simulation of ATLAS was created, which allows users to
explore the detector. This simulation, named the ATLAS Multimedia
Educational Laboratory for Interactive Analysis (AMELIA), allows
users to view detailed models of each part of the detector, as well
as view event data in 3D. A similar project is called ATLANTIS, which
allows users to examine events in only two dimensions. Currently
ATLANTIS allows more sophisticated analysis of events. AMELIA will
provide similar functionality, but in a more intuitive way, which
will be much friendlier to the public.
A Catalog of Candidate High-Redshift Blazars for GLAST. TERSI
ARIAS (San Francisco State University, San Francisco, CA, 94132)
JENNIFER CARSON (Stanford Linear Accelerator Center, Stanford, CA, 94025)
High-redshift blazars
are promising candidates for detection by the Gamma-ray Large Area
Space Telescope (GLAST). GLAST, expected to be launched in the Fall
of 2007, is a high-energy gamma-ray observatory designed for making
observations of celestial gamma-ray sources in the energy band extending
from 10 MeV to more than 200 GeV. It is estimated that GLAST will
find several thousand blazars. The motivations for measuring the
gamma-ray emission from distant blazars include the study of the
high-energy emission processes occurring in these sources and an
indirect measurement of the extragalactic background light. In anticipation
of the launch of GLAST we have compiled a catalog of candidate high-redshift
blazars. The criteria for sources chosen for the catalog were: high
radio emission, high redshift, and a flat radio spectrum. A preliminary
list of 307 radio sources brighter than 70mJy with a redshift z =
2.5 was acquired using data from the NASA Extragalactic Database.
Flux measurements of each source were obtained at two or more radio
frequencies from surveys and catalogs to calculate their radio spectral
indices . The sources with a flat-radio spectrum ( = 0.5) were
selected for the catalog, and the final catalog includes about 200
sources.
A Geant4 Simulation of the COUPP Bubble Chamber. CHARLES
CAPPS (Carnegie Mellon University, Pittsburgh, PA, 15289)
ANDREW SONNENSCHEIN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
It is known that
a sensitivity on the order of 1 event per year per ton of detector
material is necessary to detect a WIMP (Weakly Interacting Massive
Particle) dark matter candidate. After successful veto of cosmic
radiation, the neutron background will become the greatest obstacle
for COUPP (Chicagoland Observatory for Underground Particle Physics)
to achieve this level of sensitivity. Thus, understanding the COUPP
bubble chamber's response to low-energy neutrons (< 50 MeV) is
crucial. A Geant4 simulation of the COUPP bubble chamber response
to an Am/Be neutron source is described. The recoil energy spectra
given by the simulation are presented. Simulation results of event
rate as a function of chamber pressure are compared to experimental
data. Moreover, multiple bubble events--indicative of neutrons--are
examined. The ratio of single to multiple bubble events is determined
for different energy thresholds. To verify Geant4 for neutrons in
this energy regime, cross-sections and differential cross-sections
are computed from the simulation and compared to the JENDL, JEFF,
and ENDF nuclear databases. Elements present in the COUPP experiment
are considered. Good agreement is found between simulation cross-sections
and the above nuclear databases.
A Numerical Model of the Critical Charge Density Surface of Ultra High Energy
Cosmic Ray Induced Extensive Air Showers Using the SCILAB Programming
Language. ALLEN SHARPER (Florida A&M University, Tallahassee, FL, 32301)
HELIO TAKAI (Brookhaven National Laboratory, Upton, NY, 11973)
A numerical model
of the critical charge density surface of ultra high-energy cosmic
ray (UHECR) induced extensive air showers (EAS) has been computed.
The critical charge density surface defines the surface for specula
reflection of radio waves with frequency less than the natural oscillation
frequency (plasma frequency) of the EAS charges. Using a numerical
model to understand how radio waves reflect from the air shower will
help improve the design of devices (antennas, arrays) used to detect
the reflected waves. The numerical model will allow the power and
direction of the reflected waves to be calculated which will provide
a map of the spatial distribution of reflected wave power and polarization
incident to the surface of the earth. The program of the numerical
model, written in the SCILAB language, calculates the density of
ionization electrons as a function of radial distance from the shower
axis and location along the axis. The cosmic ray tracing model is
part of the Mixed Apparatus for Radar investigation of Cosmic-rays
of High Ionization (MARIACHI) project. The MARIACHI project, consist
of research that investigates an unconventional way of detecting
UHECR. Based upon a method successfully used to detect meteors entering
the upper atmosphere. Mariachi seeks to listen to television signals
reflected off the ionization trail of an UHECR.
A Plasma Gun for the Next Generation of Spallation Neutron Source H- Ion Sources. JUSTIN CARMICHAEL (Worcester Polytechnic Institute, Worcester, MA, 1609) ROBERT F. WELTON (Oak Ridge National
Laboratory, Oak Ridge, TN, 37831)
The ion source
for the Spallation Neutron Source (SNS) is required produce 40-50
mA of H- current depending on emittance with a duty factor of ~7%
for baseline facility operation. The SNS Power Upgrade Project requires
this current to be increased to 75-100 mA at the same duty factor.
In its present form, the baseline SNS ion source is unable to deliver
this performance over sustained periods of time. A new generation
of RF-driven, multicusp, ion sources based on external antennas are
therefore being designed to meet these requirements. It was found
that by injecting a stream of plasma particles from a simple, steady-state,
DC glow-discharge into the RF-plasma (i) H- production can be dramatically
increased and (ii) H- pulse rise time can be significantly reduced.
The design of a suitable plasma gun is presented which features a
hollow anode and mechanical compatibility with the new ion sources.
The Finite Element Method (FEM) has been employed to optimize the
design: coupled fluid dynamic, heat transfer, mechanical stress and
deformation, and ion/electron trajectory simulations were performed.
Several design improvements over earlier versions were implemented
such as the addition of an extraction system. The FEM simulations
showed that the design of the new plasma gun is sufficient to handle
the thermal stresses resulting from a 1 kW load on the cathode face.
The ion/electron simulations demonstrated a high degree of control
over the plasma beam, allowing for manipulation of the intensity,
mean energy, and divergence of the streaming plasma. The extraction
system also allows for selective emission of electrons or ions. It
is anticipated that the plasma beam can be optimized with the extraction
system to significantly increase the H- current in the new ion sources.
A Portable Water Cherenkov Detector: Measuring Particle Flux at Different Altitudes. LUKAS BAUMGARTEL (University
of New Mexico, Albuquerque, NM, 87131) BRENDA DINGUS (Los Alamos National Laboratory, Los
Alamos, NM, 87545)
High-energy cosmic
particles initiate extensive air showers (EAS) as they interact with
the air molecules in Earth’s upper atmosphere. If the primary particle
carries sufficient energy, the shower reaches the ground. With an
array of photo-multiplier tubes (PMT’s) located in a pool of water,
the direction and energy of the primary particle can be reconstructed
from the Cherenkov light generated as the EAS hits the detector.
Milagro is one such detector, and has observed high energy (~1TeV)
gammas and protons from high energy cosmic phenomena such as active
galactic nuclei and supernova. A new detector called HAWC (High Altitude
Water Cherenkov), similar to Milagro but with new electronics and
high-altitude location (4000m), data was taken at University of New
Mexico to perfect the measurement method and to characterize how
other factors, such as weather, tank configuration, and power sources
affect count rates. Once these variables were well understood, the
detector was used to measure particle flux at four different altitudes:
1540m, 2650m, 3231m, and 4308m. The rates of the low energy electromagnetic
particles were found to increase with altitude, and had values of
4.38 kHz, 4.82 kHz, 5.50 kHz, and 6.92 kHz, respectively. The 2650m
data was taken at the Milagro site as a reference point. Based on
the current data acquisition and analysis algorithm used for Milagro,
singles rates at the HAWC site should be less than a factor of two
greater then they are at Milagro. The rates measured at >4000m
were 1.44 times greater than the rates at Milagro, leading to the
conclusion that singles rates at a HAWC site >4000m will have
a negligible effect on triggering and pulse height measurement.
A Preliminary CCD Cosmetic Grading System for the Dark Energy Survey Camera
Focal Plane CCDs. SARAH CARLSON (DePauw University, Greencastle, IN,
46135) JUAN ESTRADA (Fermi National Accelerator Laboratory, Batavia,
IL, 60510)
The Dark Energy
Survey (DES) is a 5000 sq-degrees sky survey that will strive to
make more precise measurements of dark energy. The DES team at Fermilab
is responsible for the construction of the Dark Energy Camera (DECam)
that will be mounted along with corrective optics and electronics
on the Blanco 4-meter telescope at the Cerro Tololo Inter-American
Observatory (CTIO) in Chile. The camera will be comprised of 62 image
charge-coupled devices (CCDs) and 8 guiding, focusing and aligning
CCDs. These CCDs are made of silicon and manufactured at Lawrence-Berkley
National Laboratory (LBNL). Part of the task of building the DECam
is understanding how each CCD functions. This understanding includes
knowing the limitations of each CCD. Cosmetic defects can be crippling
to the performance of a CCD. Cosmetic defects include white and dark
pixels, bad columns, as well as defects caused by dark current and
quantum efficiency (QE) non-uniformity problems. Dark current is
a small electric current generated by the thermal motion of the silicon
atoms in the CCD. QE is the measure of the CCD’s sensitivity to a
certain wavelength. Using the popular astronomical source detection
program Source Extractor we make two separate analyses: a flat-fielding
analysis and a uniformity analysis which includes both the dark current
and QE uniformity. Catalogs of all the defects found are created
for each analysis and analyzed. To be an acceptable candidate for
the DECam focal plane, each CCD must meet the requirement of no more
than 5% non-usable image area. Using this requirement as a starting
point, we have devised a preliminary cosmetic grading system to be
used for each CCD. Each CCD will be given two grades, one for the
flat-fielding analysis and one for the uniformity analysis. The CCD
will receive a grade of 0 if the affected area is 2.5% or less of
the total CCD area. A grade of 1 will be given if the affected area
is between 2.5% and 5% of the total CCD area. A grade of 2 will be
given if the affected area is 5% or more of the total CCD area. Our
logic for giving each CCD two grades instead of one overall grade
is that we will be able to better characterize CCDs, and if the occasion
should arise that we need to pick between groups of CCDs for the
DECam focal plane the two grades will assist us in making our choice.
A Study of Gas Electron Multiplier (GEM) Foils. MATTHEW RUMORE (Worcester Polytechnic
Insitute, Worcester, MA,
1609) CRAIG WOODY (Brookhaven National Laboratory, Upton, NY, 11973)
Advances have been
made in the field of high-energy nuclear physics due to the increased
usage of Gas Electron Multiplier (GEM) foils, which are known for
their versatility and their ability to detect and amplify charge.
For instance, GEM foils will be implemented in the Pioneering High
Energy Nuclear Interaction eXperiment (PHENIX) and Solenoidal Tracker
At RHIC (STAR) experiments at the Relativistic Heavy Ion Collider
(RHIC) for the detection of signals from high-energy particle interactions.
The reliable production of GEM foils depends on a study of their
properties and operating conditions. Two of the most important properties
are the absolute gain and the gain stability over time. To test the
gain, each foil is placed in an Argon/Carbon Dioxide environment
in the ratio of 70:30. An alpha particle emitted above the foil by
an Americium-241 source ionizes the gas and produces a cluster of
electrons. This primary charge is then collected and amplified by
the GEM foil. The amplified signals are read out through a conductive
pad on the bottom of the GEM detector using a digital oscilloscope.
Because the amount of primary charge is known, the absolute gain
will be calculated for each GEM foil as a function of voltage. The
gain stability measurements entail taking successive gain measurements
over time for a constant voltage. The manufacturing process strongly
influences the performance of each GEM foil. As a result, a number
of foils produced under different manufacturing conditions were studied
in terms of their overall gain and gain stability. This study, which
will mostly likely continue until August 2006, will allow the scientific
community to understand the properties of the GEM foils and improve
the ability to manufacture better foils in the future.
A Twin Ionization Chamber Arrangement for the Study of 12C(a,)16O Through
the ß-Delayed a Spectrum of 16N. ALESSANDRO
LAURO (University of Chicago, Chicago, IL, 60637) ERNST REHM (Argonne
National Laboratory, Argonne, IL, 60439)
The most fundamental
reactions that describe the complex process of helium burning during
stellar evolution include the 12C(a,)16O reaction and the 3 4He 12C + reaction. While the latter has been studied quantitatively
over the last decades, the properties of the 12C(a,)16O
are surrounded by a great deal of uncertainty due to its very small
cross section of 10-41 cm2.
Despite this restriction, the 12C(a,)16O reaction can be studied indirectly by observing the ß-delayed
a spectrum of 16N. While it is energetically impossible for ground state 16O
to a decay to 12C,
it is possible to examine 16O*,
excited states of 16O, that result from the ß-decay of 16N. Even though the branching ratio of this reaction favors
decay over a decay by a factor of about 105, a precise measurement of a-particles can be carried out by
a specially designed dual twin ionization chamber located at the
Argonne Tandem Linear Accelerator System (ATLAS) at Argonne National
Laboratory. An important step in this experiment involves the calibration
of the ionization chamber using a Pu-Be neutron source in order to
test the a emission produced by the 10B(n,a)7Li
and 6Li(n,a)t
reactions. It is from this procedure that a new method of obtaining
information about the emission angle of a-particles from the source
has been found.
Afterglow Radiation from Gamma-Ray Bursts. HUGH DESMOND
(Katholieke Universiteit Leuven, Leuven, Belgium, 3000) WEIQUN ZHANG
(Stanford Linear Accelerator Center, Stanford, CA, 94025)
Gamma-ray bursts
(GRB) are huge fluxes of gamma rays that appear randomly in the sky
about once a day. It is now commonly accepted that GRBs are caused
by a stellar object shooting off a powerful plasma jet along its
rotation axis. After the initial outburst of gamma rays, a lower
intensity radiation remains, called the afterglow. Using the data
from a hydrodynamical numerical simulation that models the dynamics
of the jet, we calculated the expected light curve of the afterglow
radiation that would be observed on earth. We calculated the light
curve and spectrum and compared them to the light curves and spectra
predicted by two analytical models of the expansion of the jet (which
are based on the Blandford and McKee solution of a relativistic isotropic
expansion; see Sari's model and Granot's model). We found that the
light curve did not decay as fast as predicted by Sari; the predictions
by Granot were largely corroborated. Some results, however, did not
match Granot's predictions, and more research is needed to explain
these discrepancies.
AMELIA: ATLAS Multimedia Educational Lab for Interactive Analysis. DAVID MEDOVOY (Columbia University, New
York, NY, 10027) MICHAEL
BARNETT (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
AMELIA is an educational
software program designed to allow the public to view, on a home
computer, a 3D model of ATLAS detector at CERN, as well as visualization
of recorded particle tracks. Models of the detector’s geometry, created
in ‘3ds Max,’ are loaded by the software, which is written using
the C++ language and the ‘Irrlicht’ visualization engine. Particle
track data in the JiveXML file format is loaded and displayed simultaneously.
The use of the standard JiveXML format allows for file-type compatibility
with other software, such as the 2D visualization tool ATLANTIS.
The ‘camera’ is fully movable by the user, and custom cutaway views
can be created based on the camera’s position, to facilitate viewing
the interior parts of the detector, as well the particle tracks within.
Tracks are color-coded based on particle type, and will soon be individually
selectable. Programs exist to visualize particle track data in 3D,
and to simplify scientific data for outreach purposes, but only AMELIA
is designed for both. Further, AMELIA is the only project of its
kind designed to take advantage of technology developed for video
games. An early 2007 public release is anticipated.
Analysis of a Proposed Very Long Baseline Neutrino
Oscillation Experiment. CHRISTINE LEWIS (Columbia
University, New York, NY, 10027)
MILIND DIWAN (Brookhaven National Laboratory, Upton, NY, 11973)
The Very Long Baseline
Neutrino Oscillation (VLBNO) study aims to determine how to best
design a second generation experiment to measure the neutrino oscillation
parameters and possible violation of charge/parity (CP) invariance.
Using the General Long Baseline Experiment Simulation (GLoBES) software
and considering a 500kT water Cherenkov detector at 1300km, corresponding
to a baseline from Fermilab to the Homestake mine, we calculate the
sensitivity to 13 and the CP phase. We find that with 2500kT*MW*107s
of neutrino running and 5000kT*MW*107s of antineutrino running the experiment could measure sin2213 to
9-14% and dCP to
~15° at 1s. Moreover, the experiment is sensitive to non-zero sin2213 as
low as 4x10-3 at
99% confidence.
Analysis of Beam Deviation Due to Quadrupole Misalignment
Caused by Ambient Ground Motion in the Relativistic Heavy Ion
Collider. BRANDON BELEW (Rensselaer Polytechnic Institute, Troy, NY, 12180) CHRISTOPH MONTAG (Brookhaven National Laboratory, Upton, NY, 11973)
Within the Relativistic
Heavy Ion Collider (RHIC) and particle accelerators in general, proper
alignment of the focusing and defocusing quadrupole magnets is essential
to maintaining a stable beam orbit. However, it is also a fact that
there will always be some misalignment due to ambient ground motion.
The extent of this displacement is given by a simple linear formula
of time, distance and a site-specific constant (the ‘ATL Rule’).
Using known values of the beta function, phase advance, and focusing
strength at the RHIC quadrupoles, code was written to simulate expected
beam deviation at specific monitor points according to the ATL rule,
for arbitrary values of the constant A. This expected deviation was
then compared with actual logged beam data over the course of several
months to arrive at the site-specific value of A. The end result,
the constant of ambient ground motion specific to the RHIC location,
was calculated to be around 3e-11 mm^2/m*s. Knowing this value will
allow for more accurate predictions of future beam deviation, and
facilitate the proper application of correcting dipole magnets to
counteract these effects.
Analysis of Creep in Polyvinyl Chloride for the NOvA Detector. CHRISTINE
MIDDLETON (Wesleyan University, Middletown, CT,
6459) HANS JOSTLEIN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
This analysis is
an attempt to predict creep in the NOvA
detector, a proposed electron neutrino detector for the NuMI beamline
at Fermilab. The NOvA
detector is constructed of large PVC extrusions which contain 25
ktons of scintillating oil. Due to the scale of this detector and
the proposed experiment length of 20 years, creep in the structural
PVC of the detector is a concern. Creep data was taken on 18 samples
over 188 days. Stress levels ranged from 500 PSI to 2100 PSI, with
2 samples being tested at each stress. A variety of models and fit
functions from the literature were used, however a best fit function
was not readily apparent. Although the data could be fit reasonably
well, these functions were unable to give a reasonable prediction
for the creep after 20 years. In order to improve these results,
more data is needed which represents the secondary and tertiary creep
stages. We anticipate being able to study this behavior using accelerated
high temperature creep tests.
Analysis of Off-Nuclear X-Ray Sources in Galaxy NGC 4945. SARAH
HARRISON (Massachusetts Institute of Technology, Cambridge, MA, 22901)
GRZEGORZ MADEJSKI (Stanford Linear Accelerator Center, Stanford,
CA, 94025)
Recently, X-ray
astronomy has been used to investigate objects such as galaxies,
clusters of galaxies, Active Galactic Nuclei (AGN), quasars, starburst
superbubbles of hot gas, X-ray binary systems, stars, supernova remnants,
and interstellar and intergalactic material. By studying the x-ray
emission patterns of these objects, we can gain a greater understanding
of their structure and evolution. We analyze X-ray emission from
the galaxy NGC 4945 using data taken by the Chandra X-ray Observatory.
The Chandra Interactive Analysis of Observations (CIAO) software
package was used to extract and fit energy spectra and to extract
light curves for the brightest off-nuclear sources in two different
observations of NGC 4945 (January, 2000 and May, 2004). A majority
of sources were closely fit by both absorbed power law and absorbed
bremsstrahlung models, with a significantly poorer Χ2/dof for the absorbed blackbody model, and most sources had little
variability. This indicates that the sources are accreting binary
systems with either a neutron star or black hole as the compact object.
The calculated luminosities were about 1038 erg/s, which implies that the mass of the accreting object is
close to 10 solar masses and must be a black hole.
Analysis of the properties of particles emerging from Deep Inelastic Scattering
off a range of nuclei. SERERES JOHNSTON
(Andrews University, Berrien
Springs, MI, 49103) KAWTAR HAFIDI (Argonne National Laboratory, Argonne, IL, 60439)
Hadronization,
the process by which a struck quark evolves into a hadron, is not
well understood in the nuclear medium. Experiments done with medium
energy electron beams and multiple nuclear targets can investigate
hadronization at nuclear scales. Understanding this process would
provide insight into the confinement property of the nuclear strong
force. The data collected by the E02-104 Nuclear Semi Inclusive Deep
Inelastic Scattering experiment, performed at Jefferson Laboratory
with a 5 GeV electron beam, can be used to characterize hadronization
as a function of multiple variables. E02-104 ran with several solid
targets of differing atomic radius and the data taken is sensitive
to early hadronization processes. Programs were written which compared
the hadron attenuation and transverse momentum broadening in the
three nuclear targets, carbon, iron, and lead. Greater attenuation
is observed in large nuclei. Hadron attenuation is described by the
multiplicity ratio, RhM, which is a multivariable function. The high statistics of the
E02-104 data allowed its dependence on four different variables to
be examined in detail. The quark energy loss indicated by the transverse
momentum broadening is seen to increase with the square of the nuclear
distance traveled. This agrees with QCD predictions based on quark
energy loss through gluon radiation. There is also some evidence
that the transverse momentum broadening approaches a limit in larger
nuclei. Not enough nuclear targets were examined for this last result
to be definitive.
Analysis Strategy of Powder Diffraction Data with 2-D Detector. ABHIK KUMAR (Austin College, Sherman, TX, 75090) APURVA
MEHTA (Stanford Linear Accelerator Center, Stanford, CA, 94025)
To gain a clearer
understanding of orientation and grain deformation of crystalline
materials, x-ray powder diffraction has played an integral role in
extracting three-dimensional structural information from one-dimensional
diffraction patterns. Powder diffraction models identical geometry
to the intersection of a normal right cone with a plane. The purpose
of this paper is to develop a general expression defining the conic
sections based on the geometry of a powder diffraction experiment.
Applying the derived formulation of a diffraction arc to experimental
data will give insight to the molecular and structural properties
of the sample in question. Instead of using complex three-dimensional
Euclidian geometry, we define the problem solving technique with
a simpler two-dimensional transformation approach to arrive at a
final equation describing the conic sections. Using the diffraction
geometry parameters, we can use this equation to calibrate the diffractometer
from the diffraction pattern of a known reference material, or to
determine the crystalline lattice structure of the compound.
Analytical Data Acquisition via Radar of Ionization
Electrons in Cosmic-ray Extensive Air Showers. JEREMY
MARTIN (FAMU-FSU College of Engineering, Tallahassee, FL, 32310)
HELIO TAKAI (Brookhaven National Laboratory, Upton, NY, 11973)
Ultrahigh-energy
cosmic-rays initiate cosmic showers of high-energy, electrically
charged particles upon interaction with the atmosphere of the earth.
Evidence of radio wave reflection is collected from ultrahigh-energy
comic-ray (UHECR)-induced extensive air showers (EAS) of high energy
electrically charged particles when entering the stratosphere. Optimal
detection of UHECR entails facilitating a more pertinent understanding
of the high-energy particle and its celestial origin. The challenge
is using a type of radar detection to separate the radio signals
reflected by EAS from radio waves reflected from other sources (i.e.,
clouds, meteor trails, air crafts, emissions from lightening). This
requires an approach involving Fourier transform, power spectrum
analysis, as well as other series evaluation techniques to discriminate
between the EAS reflected waves which contain data from high ionization
particle interaction and oscillations that are irrelevant to this
research. To distinguish EAS radio waves from other atmospheric sources
of radio waves, a set of software tools were developed. Using this
uniquely developed data acquisition software, randomly reflected
radio waves about the atmosphere can be manipulated from their intrinsic
state to isolate the power spectrum of the EAS waveforms in an attempt
to efficiently identify these particular signatures of undulation
in greater proportion. By analyzing the frequencies of these signals
the intention is to later demonstrate a correlation between the radio
waves occurring in specific VHF radio frequencies and cosmic-ray
events detected by other means. This research is a portion of a process
in which the goal is to develop a basis for further study of UHECR
within the Mixed Apparatus for Radar Investigation of Cosmic-rays
of High Ionizations (MARIACHI) project, which seeks to develop radar
detection techniques for related studies of high energy physics.
Calculation of Particle Bounce and Transit Times on General Geometry Flux Surfaces. DOUGLAS SWANSON (Yale University, New
Haven, CT, 6520) DR. JONATHAN MENARD (Princeton
Plasma Physics Laboratory, Princeton, NJ,
8543)
Minimizing magnetohydrodynamic
(MHD) instabilities is essential to maximizing the plasma pressure
and the fusion power output from toroidal plasmas. One such instability
is the resistive wall mode (RWM). Plasma rotation above a critical
frequency has been observed to stabilize the RWM. The critical frequency
is predicted in some theories to depend strongly on characteristic
bounce and transit times particles take to complete orbits. Bounce
times are orbit times for particles with large magnetic moments that
are trapped poloidally in banana orbits. Transit times are orbit
times for particles with small magnetic moments that are able to
complete full poloidal circuits around the plasma. Previous calculations
of these bounce and transit times have assumed high aspect ratio
and circular flux surfaces, approximations unsuitable for the National
Spherical Torus Experiment (NSTX). Analytic solutions for the bounce
and transit times were derived as functions of particle energy and
magnetic moment for low aspect ratio and elliptical flux surfaces.
Numeric solutions for arbitrary aspect ratio and flux surface geometry
were also computed using Mathematica and IDL and agree with the analytic
forms. The solutions were found to scale as the elongation at low
aspect ratio, and as the square root of the elongation at high aspect
ratio. For typical values of the parameters the bounce and transit
times can differ from the high aspect ratio, circular results by
as much as 40%. Analytic transformations to map the high aspect ratio,
circular solutions into the general geometry solutions are being
investigated. Such transformations could be easily incorporated into
existing stability codes such as MARS to refine models of RWM rotational
stabilization.
Calibration of Small Pb-Glass Photomultiplier Cells in the FPD++ (Forward Pion
Detector). SHAWN PEREZ (State University of New
York at Stony Brook, Stony Brook, NY, 11790) LESLIE BLAND (Brookhaven
National Laboratory, Upton, NY, 11973)
The FPD++ (Forward
Pion Detector) at Brookhaven National Lab, consists of two matrices
of Pb-glass bars viewed by photomultiplier tubes that are positioned
left and right of the colliding beam axis. These detectors are used
to explore transverse single spin asymmetries through analysis of
forward pion production and its corresponding jet shape. In order
to extract information from polarized proton - proton collisions,
the FPD++ had to be calibrated cell by cell. Reconstructed di-photon
invariant mass is associated with the highest energy cell in the
inner matrix. Distributions of high tower invariant mass are fit
by a Gamma function to describe background in the detectors and a
Gaussian to describe the Pi0 peak. The absolute gain of each tower
is then varied until the Pi0 peak is centered at its known position
of .135 GeV/c^2. Once the relative gain correction factors of each
iteration performed have converged, the cells have been calibrated.
Currently the Small cells of the FPD++ are calibrated within an accuracy
of 2%, while the large cells still need to be calibrated. Comparing
the summed energy spectra of polarized up and down proton collisions
in the west-north and west-south modules of the FPD++, will reveal
more information about transverse single spin asymmetries and possibly
the relative contributions from the Collins and Sivers effect toward
these asymmetries observed in forward pion production. The Collins
and Sivers effect are theoretical models developed to explain transverse
single spin asymmetries, dependent on spin and transverse momentum
distribution functions or fragmentation functions. Analyzing the
pseudorapidity (-ln(tan(/2)) dependence on particle production will
explore parton distributions within the proton.
CCD Quantum Efficiency Characterization for LSST. XIAOQIAN ZHANG (Cornell University, Ithaca, NY, 14853) JAMES S. FRANK (Brookhaven National Laboratory, Upton, NY, 11973)
The optical performance
of charge coupled devices (CCDs), the fundamental units used for
digital cameras, can be characterized by their quantum efficiency.
The Large Synoptic Survey Telescope (LSST) project, an ongoing project
aiming for completion in 2013, needs a high-efficiency digital camera
with 3.2 Giga-pixels of CCDs for its acquisition of astronomical
images. The CCDs used in this camera need to attain nearly 50 % quantum
efficiency in the near-infrared (1000nm) while operating in a vacuum
Dewar at a temperature of 173K. To test this requirement, instrumentation
of a device that measures quantum efficiency of manufactured CCDs
is under development at Brookhaven National Laboratory (BNL) and
is based partially on the similar instrumentation developed in 2004
and 2005 in the Lawrence Berkeley National Laboratory (LBNL). This
device consists of multiple light sources, a shutter, several filters,
a coupled monochromator, a 12-inch diameter integrating sphere, a
black box, and a dewar where the cooled CCD is to be placed. The
equipment is assembled in the order listed above so that the monochromator
first selects the desired wavelength of light emitted from the light
source. This beam is then monitored in the integrating sphere, and
made uniform through the black box before it reaches the CCD in the
dewar. Picoammeters and photodiodes are placed in several locations
for light intensity measurements. After examining the light leakage
of the integrating sphere, calibration of the coupled monochromator
was performed using a Hg light source. Properties of gratings, filters,
and slits were studied by comparing measured spectral lines of Hg
and Xe light source. A LabView program was developed and used to
operate the assembled devices and take readings from the photodiodes.
These programs, devices, and data will be used to measure the quantum
efficiency as a function of wavelength in CCDs currently under development
for LSST.
Centrality Determination in Heavy Ion Collisions for the Pioneering High Energy
Nuclear Interaction eXperiment (PHENIX) at the Relativistic Heavy
Ion Collider (RHIC). ELI LANSEY (Yeshiva University, New
York, NY, 10033) ALEXANDER MILOV (Brookhaven National Laboratory, Upton, NY, 11973)
In the physics
of Relativistic Heavy Ions (RHI), the centrality related parameters
(such as the number of participating nucleons or number of binary
collisions between nucleons) are the essential characteristics of
the collisions. The majority of publications from all four RHIC experiments
related to RHI physics present their results as functions of one
or more centrality-related parameters. Centrality's precise determination
is therefore critical to understand most of the RHI results. The
distribution of the number of participating nucleons can be obtained
with the commonly used Glauber model. In the PHENIX experiment, this
distribution is related to the number of particle hits in the Beam-Beam
Counters via statistics of the Negative Binomial Distribution (NBD).
These properties allow us to achieve two principle goals: to validate
the commonly used theoretical model and to establish an accurate
relationship between the observable quantity (number of hits) and
the number of participating nucleons. Using the data collected during
full energy (200 GeV) Au+Au Run4 of the PHENIX experiment we studied
the parameters of the NBD, their systematic dependencies and accuracy
to which they can be determined. The work is done by using the MINUIT
minimization tool in the ROOT environment. This work will contribute
to future analysis by many members of the PHENIX collaboration, yielding
better measurements of the centrality-related parameters.
Characterization of an Electromagnetic Calorimeter for the Proposed International
Linear Collider. MERIDETH FREY (Wellesley College, Wellesley, MA, 2481)
NORMAN GRAF (Stanford Linear Accelerator Center, Stanford, CA, 94025)
The International
Linear Collider (ILC) is part of a new generation of accelerators
enabling physicists to gain a deeper understanding of the fundamental
components of the universe. The proposed ILC will accelerate positrons
and electrons towards each other with two facing linear colliders,
each twenty kilometers long. Designing and planning for the future
accelerator has been undertaken as a global collaboration, with groups
working on several possible detectors to be used at the ILC. The
following research at the Stanford Linear Accelerator Center (SLAC)
pertained to the design of an electromagnetic calorimeter. The energy
and spatial resolution of the calorimeter was tested by using computer
simulations for proposed detectors. In order to optimize this accuracy,
different designs of the electromagnetic calorimeter were investigated
along with various methods to analyze the data from the simulated
detector. A low-cost calorimeter design was found to provide energy
resolution comparable to more expensive designs, and new clustering
algorithms offered better spatial resolution. Energy distribution
and shape characteristics of electromagnetic showers were also identified
to differentiate various showers in the calorimeter. With further
research, a well-designed detector will enable the ILC to observe
new realms of physics.
Characterization of Long Cosmic Ray Muon Tracks in IceCube detector at South
Pole. DANIEL HART (Southern University, Baton
Rouge, LA, 70813)
AZRIEL GOLDSCHMIDT (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Ice Cube is studying
high-energy neutrino astronomy. IceCube uses an array of optical
modules to detect faint Cerenkov light produced by muons. These muons
are the result of nuetrino interactions with matter. Using the information
received from data acquisition systems at the South Pole, software
was developed using the C language to read this data and use it to
produce possible muon paths. Events were filtered through by placing
cuts on the calculated paths that passed through the full geometry
of IceCube, had velocity within 5% the speed of light, and were of
low multiplicity. This resulted in path distance distributions that
showed exponential decay of modules to receive light as a function
of distance. The probability curves produced, followed along the
same traits. However, the distance distributions were not exactly
smooth as would be expected, and the selection of paths that were
to be considered as neutrino candidates behaved similarly. These
impurities are interpreted as the integration of multiple muons in
a single event. In further studies, the plan is not only to add in
more data from additional days, but also to employ more sophisticated
methods for separating true events from those produced by multiple
muons.
Characterization of Sub-diffusion within Benard-Rayleigh Advective Cells by
Examination of a Velocity Field with Additive Noise. MARSHA
LAROSEE (University of Michigan, Dearborn,
Mi, 48128) BEN CARRERAS (Oak Ridge National
Laboratory, Oak Ridge, TN, 37831)
Normal diffusion
worked out by Einstein and Taylor is modeled by averaged particle ‘Brownian
motion’ such that a given particle’s motion is determined by random collisions with surrounding particles. Less well understood is
the subject of anomalous diffusion, which is studied in many fields
where diffusion influences the system (e.g. heat, fluids, chemical
kinetics). The distinction between normal diffusion, a random mechanism
and anomalous diffusion, that is a mixture of random and deterministic processes, is the time scale at which the transport occurs. Both
diffusion and anomalous diffusion follow a power law relation < r s > 1/s ˜ t q(s),
where q(s) = 1/2, < 1/2, > 1/2 for diffusion, sub-diffusion,
and super-diffusion. Thus, sub-diffusion and super-diffusion scale
with time differently than random motion predicts. In order to study
sub-diffusion a deterministic model must be used while adding randomness,
or noise to the system. A model referred to as the random walk with
pauses or trapping events was investigated in order to characterize
sub-diffusion in a fluid system. The system that was studied is an
array of Benard Rayleigh advective cells where the velocity fields
cause 10,000 tracer particles to circulate within a cell. Noise added
to the velocity field causes diffusion between cells. Moments of
the displacement were calculated as a function of time while varying
the frequency and magnitude of noise in order to magnify the region
where sub-diffusion is observed. Frequency of the additive noise
extended the time frame in which sub-diffusion was observed and appears
to extend the time frame non-linearly. Moments of the displacement
show that the diffusive exponent q(s) is the same for all higher
moments which indicates scale invariance, or q(s) = constant. This
property is characteristic of both anomalous and normal diffusion.
The exponent observed q(s) ~ 0.4, was larger than the typical exponent
of sub-diffusive systems q(s) ~ 1/3. The reason for this is undetermined
but may indicate an influence of normal diffusion within the system
and future investigation is planned.
Characterizing the Charge Collection of the 0.13 µm IBMPIX Prototype Pixel
Detector. ANJALI TRIPATHI (Massachusetts Institute of Technology, Cambridge, MA, 2139) RONALD LIPTON (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
Central to collider
physics experiments are silicon detectors, which track the trajectory
of particles produced during collisions. With the drive for ever
more precise resolution in particle tracking, a prototype pixel detector
(IBMPIX) manufactured by IBM in a 0.13 µm RF CMOS process, was investigated
to understand its charge collection and individual pixel behavior.
As a Monolithic Active Pixel Sensor, it was comprised of arrays of
pixels (10µm by 150µm) divided into three diode types - a standard
N-well, a deep (or triple) N-well, and a control without a diode.
To measure the pixel to pixel variations from the readout electronics,
a signal generator pulsed charge directly into the analog circuitry,
bypassing the diodes, at different threshold settings. Upon characterizing
the response of the readout electronics for each pixel, a pulsed
1.06 µm Nd:YAG laser was used to determine the relationship between
the input charge and the output pulse width. This pulse width was
the amount of time that the input charge was above a set threshold.
With the data from both the laser and the signal generator, a mathematical
model was made for charge diffusion across the chip. From the signal
generator tests, the readout electronics showed significant pixel
to pixel variation. This variation was nearly proportional to the
threshold current setting. Additionally, testing of the diodes yielded
a precise equation relating pulse-width to charge. For an idealized
laser beam of zero width, a diffusion length of approximately 80
microns was determined. The source of the pixel to pixel variation
can be attributed to gain variations due to the fabrication. Further
studies should employ a laser with a spot size contained within one
pixel, include a diffusion model incorporating variable beam width,
and use an additional current source to set the threshold value.
Comparison of Non-Redundant Array and Double Pinhole CoherenceMeasurements with Soft X-rays. GABRIEL WEIL (Northwestern
University, Evanston, IL, 60201) JAN LUNING (Stanford Linear Accelerator Center, Stanford, CA, 94025)
Experiments on
the future Linac Coherent Light Source (LCLS) and other Free Electron
Lasers will need to be performed on a single-shot basis. The double
pinhole method of measuring spatial coherence requires a separate
measurement, with a different pinhole separation distance, for each
length scale sampled. This limits its utility for LCLS. A potential
alternative uses a Non-Redundant Array (NRA) of apertures designed
to probe the coherence over the range of length scales defined by
their physical extent, in a single measurement. This approach was
tested by comparing diffraction patterns from soft x-rays incident
on double pinhole and NRA absorption mask structures. The double
pinhole fringe visibility data serve as discrete reference points
that verify the continuous spectrum of the NRA coherence data. The
results present a quantitative analysis of the double pinhole coherence
measurements and a qualitative comparison to the NRA images.
Conceptual Overview of the NPDGamma Experiment. JOSEPH JANOSIK (University
of Dayton, Dayton, OH, 45469) W. SCOTT WILBURN (Los Alamos National Laboratory, Los Alamos, NM, 87545)
The magnitude of
the weak force is not yet well defined. The NPDGamma experiment at
the Los Alamos Neutron Science Center will soon be taking data that
will place bounds on the hadronic weak coupling constant Hπ1.
This experiment uses polarized cold neutrons which capture on a liquid
hydrogen (proton) target, and emit gamma rays that have a directional
dependence on the spin of the incident neutrons only according to
the weak force. Thus, a measured asymmetry in gamma ray detection
can be used to extrapolate the weak coupling. The asymmetry is expected
to be very small, around 5 x 10-8,
so careful experimental design and construction have been executed
to ensure accuracy of this measurement. This document provides a
conceptual overview of the workings of this experiment.
Construction and Commissioning of a Micro-Mott Polarimeter
for Photocathode Research and Development. APRIL
COOK (Monmouth College, Monmouth, IL, 61462) MARCY STUTZMAN (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
Thomas Jefferson
National Accelerator Facility uses polarized electrons to further
the understanding of the atomic nucleus. The polarized source produces
electrons by directing laser light onto a specially prepared gallium
arsenide (GaAs) photocathode. During the course of this project,
an off-beamline micro-Mott polarimeter has been built and commissioned
within the Source Lab for photocathode research and development.
A polarimeter measures the polarization, or spin direction, of electrons.
The micro-Mott runs at 30 keV and can be used directly in the Source
Lab, off of the main accelerator beamline. Construction of the Mott
system began with a polarized source, which consists of a vacuum
chamber complete with a cesiator and nitrogen triflouride (NF3) to
activate the photocathode, residual gas analyzer (RGA), ultra-high
vacuum pumps, an electrostatic deflector to bend the electron beam
90 degrees, and electrostatic lenses. The polarimeter is housed in
an adjacent vacuum chamber. The circularly polarized laser light
enters the polarized source, hits the GaAs photocathode, and liberates
polarized electrons. The original longitudinally-polarized electrons
are transformed into transversely-polarized electrons by the electrostatic
bend. They are then directed onto a gold target inside the Mott and
scattered for data analysis. The polarized source has been commissioned,
achieving photoemission from the activated GaAs crystal, and the
electrostatic optics have been tuned to direct the electrons onto
the gold target. Nearly ten percent of the electrons from the photocathode
reach the target, giving adequate current for polarization measurement.
The micro-Mott polarimeter will aid in photocathode research and
pre-qualification of material for use in the injector.
Construction of the La-Bi-O Phase Equilibria: The Search for Inorganic Scintillators. STEVEN VILAYVONG (North Carolina A&T State University, Greensboro, NC, 27411) YETTA PORTER-CHAPMAN (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Scintillators have
been around forever, however the demand for scintillators has risen
exponentially since World War II. This need for viable scintillators
to be used in the detection of ionizing radiation has spurred research
around the world. The New Detector Group of the Department of Functional
Imaging in the Life Sciences Division of Lawrence Berkeley National
Laboratory conducts systematic searches of various compounds to find
the most effective scintillator. Much of their work focuses on compounds
that contain Bismuth (III) and Lanthanum (III) ions. Bismuth (III)
ions have the capability to be luminescent sometimes providing intrinsic
scintillation as seen in the commonly used scintillator, Bi4Ge3O12, (BGO). Phases containing lanthanum (III) ions are also investigated
to utilize their sites for cerium (III) (another luminescent ion)
doping. In this work, various molar ratios of La2O3 and
Bi2O3 were
reacted by solid state chemistry techniques to find phases that may
exhibit scintillation. To be classified as a good scintillator, one
must characterize these phases by x-ray diffraction (XRD), fluorescence
spectroscopy, and pulsed x-ray measurements. Four La-Bi-O phases,
La0.176Bi0.824O1.5, La0.12Bi1.88O3, La4Bi2O9, and an unknown phase were found however, none are good scintillators.
Design, Fabrication and Measurement of Nb/Si multilayers and Nb Transmission
Filters. SUNEIDY LEMOS FIGUEREO (University
of Puerto Rico, Rio Piedras, P.R, 979)
DAVID ATTWOOD (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
The extreme ultraviolet
(EUV) region of the electromagnetic spectrum is being used in multilayer
optical systems to design technology projected for use in the fabrication
of nano-electronics. Multilayer optical systems with high reflectivity
have been produced in the soft x-ray and EUV regions of the spectrum.
Due to the limited understanding of the Nb/Si optical systems, our
research group fabricated and measured Nb/Si multilayers and Nb transmission
filters for the soft x-ray and EUV regions. Multilayer optical systems
are used in applications ranging from EUV lithography to synchrotron
radiation. The films were deposited using dc magnetron sputtering
in the Center for X-Ray Optics at the Lawrence Berkeley National
Laboratory. Reflectivity and transmission measurements were performed
at the Advanced Light Source beamline 6.3.2. The Nb/Si multilayer
mirrors fabricated have a reflectivity of approximately 65% in the
extreme ultraviolet region, which makes these systems practical for
applications where a high reflectivity is required, such as Astronomy
and instrumentation development. Transmission measurements of up
to 90% were observed in the soft x-ray and EUV regions as well. Future
work in the research group includes the design and fabrication of
an Nb/Si multilayer with a B4C interface. The Nb/B4C/Si optical systems
are expected to have a higher reflectivity than Nb/Si systems.
Detection of Ionizing Radiation Based on Metastable States of Polymer Dispersed
Liquid Crystals. TIMOTHY PHUNG (University
of California, Berkeley, Berkeley, CA, 94720)
CARL HABER (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Polymer dispersed
liquid crystals (PDLCs) may be a suitable medium for future tracking
detectors used in particle physics. Such a detector will work in
analogy with the bubble chamber by using the metastable states in
LC materials. A PDLC cell is fabricated and the optical transmission
of the cell is measured as a function of the voltage applied across
the cell and the temperature. The optical transmission of the PDLC
is found to be temperature dependent below the nematic-isotropic
phase transition temperature when a field is applied across the cell
as is reported in the literature. When no field is applied, the PDLC
cell is strongly temperature dependent near the nematic-isotropic
phase transition temperature, which also agrees with previous results.
Future research in this area will focus on finding the metastable
phenomena that exist near phase transitions of LC materials and on
the use of electric fields to shift the transition temperature.
Determining Micromechanical Strain in Nitinol. MATTHEW
STRASBERG (Cornell University, Ithaca, NY, 14850) APURVA MEHTA (Stanford
Linear Accelerator Center, Stanford, CA, 94025)
Nitinol is a superelastic
alloy made of equal parts nickel and titanium. Due to its unique
shape memory properties, nitinol is used to make medical stents,
lifesaving devices used to allow blood flow in occluded arteries.
Micromechanical models and even nitinol-specific finite element analysis
(FEA) software are insufficient for unerringly predicting fatigue
and resultant failure. Due to the sensitive nature of its application,
a better understanding of nitinol on a granular scale is being pursued
through X-ray diffraction techniques at the Stanford Synchrotron
Radiation Laboratory (SSRL) at the Stanford Linear Accelerator Center
(SLAC). Through analysis of powder diffraction patterns of nitinol
under increasing tensile loads, localized strain can be calculated.
We compare these results with micromechanical predictions in order
to advance nitinol-relevant FEA tools. From this we hope to gain
a greater understanding of how nitinol fatigues under multi-axial
loads.
Development of Emittance Analysis Software for Ion Beam Characterization. MARIANO PADILLA (Fullerton College, Fullerton, CA, 92832) YUAN LIU (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Transverse beam
emittance is a crucial property which describes the angular and spatial
spread of charged particle beams. It is a figure of merit frequently
used to determine the quality of ion beams, the compatibility of
an ion beam with a given beam transport system, and the ability to
suppress neighboring isotopes at on-line mass separator facilities.
Generally a high quality beam is characterized by a small emittance.
In order to determine and improve the quality of ion beams used at
the Holifield Radioactive Ion beam Facility (HRIBF) for nuclear physics
and nuclear astrophysics research, the emittances of the ion beams
are measured at the off-line Ion Source Test Facilities. In this
project, an emittance analysis software was developed to perform
various data processing tasks for noise reduction and to evaluate
root-mean-square emittance, Twiss parameters, and area emittance
of different beam fractions. The software also provides 2D and 3D
graphical views of the emittance data, beam profiles, emittance contours,
and ellipses. Noise exclusion is essential for accurate determination
of beam emittance values. A Self-Consistent, Unbiased Elliptical
Exclusion (SCUBEEx) method is employed. Numerical data analysis techniques
such as interpolation and nonlinear fitting are also incorporated
into the software. The software will provide a simplified and fast
tool for comprehensive emittance analyses. The main functions of
the software package have been completed. In preliminary tests with
real experimental emittance data, the analysis results using the
software were proven to be correct.
Development of Nanofluidic Cells for Ultrafast X-ray Studies of Water. MELVIN IRIZARRY (University of Puerto Rico, Mayaguez,
PR, 667) AARON LINDENBEREG (Stanford Linear Accelerator Center, Stanford,
CA, 94025)
In order to study
the molecular structure and dynamics of liquid water with soft x-ray
probes, samples with nanoscale dimensions are needed. This paper
describes a simple method for preparing nanofluidic water cells.
The idea is to confine a thin layer of water between two silicon
nitride windows. The windows are 1 mm × 1 mm and 0.5 mm × 0.5 mm
in size and have a thickness of 150 nm. The thickness of the water
layer was measured experimentally by probing the infrared spectrum
of water in the cells with a Fourier Transform InfraRed (FTIR) apparatus
and from soft x-ray static measurements at the Advanced Light Source
(ALS) at Lawrence Berkeley National Laboratory. Water layers ranging
from 10 nm to more than 2 µm were observed. Evidence for changes
in the water structure compared to bulk water is observed in the
ultrathin cells.
Development of Powder Diffraction Analysis Tools for a Nanocrystalline Specimen:
An Emphasis upon NiTi (Nitinol). ERICH
OWENS (Albion College, Albion, MI, 49224)
APURVA MEHTA (Stanford Linear Accelerator Center, Stanford, CA, 94025)
Powder diffraction
is a specialized technique whose investigatory limits are constrained
by the scale of the crystallized substance being scanned versus the
probe beam used. When disparate in scale, with the photon spot size
larger than the crystal being probed, many are employed, the resulting
diffraction image being cast from all possible incident angles, constructing
-arcs containing information about the crystalline structure of
the material under examination. Of particular interest to our collaboration
is the structure of Nitinol, a superelastic Nickel-Titanium alloy,
whose phase transformations and load bearing deformations can be
studied by usage of diffraction, with wide sweeping biomedical uses.
Analysis of this data is complicated by phase transformation and
material fluorescence, which make difficult the computational modeling
of the peaks within concentric -arcs. We endeavored to construct
a series of computational tools (the amalgamation of them known as
2DPeakFinder) for refining and extracting this relevant data, toward
the end of employing previously developed algorithms in the material’s
structural analysis. We succeeded to a large degree with the use
of an iterative algorithm to navigate radial complexity of the signal
and manage to retain a distinction between useful signal and superfluous
background noise. The tools developed in this project are a small
step in readily streamlining the analysis and physical modeling of
a Nanocrystalline material’s structural properties.
Diffusion-controlled Apparatus' for Microgravity. PRADEEP
RAJENDRAN (Stanford University, Stanford, CA, 94305) DR. P. THIYAGARAJAN (Argonne National Laboratory, Argonne, IL, 60439)
Large photoactive
yellow protein (PYP) crystals are being grown using diffusion-controlled
apparatus’ for microgravity (DCAMs) for proposed neutron crystallography
experiments. The basis for this experiment is that a short strong
hydrogen bond (SSHB) appears to play an important role in the function
of PYP in the photocycle. In order to fully understand the structure
and dynamics of the SSHB, it is necessary to accurately locate the
nuclear position of the proton (or deuteron) with respect to the
heavy atoms involved in the hydrogen bond. Pervious attempts to grow
PYP crystals using the batch and hanging drop method have had limited
success. The resolution of diffraction data collected from PYP crystals
grown using these methods was determined to be between 0.95 to
1.40 . PYP crystallizes best between a concentration range of 2.3
M to 2.5 M. Two DCAM units have been set up. The units have a concentration
of 1.6 M and 2.0 M (ND4)2SO4 in
the small chamber, respectively, and a concentration of 3.0 M (ND4)2SO4 in the large chambers. As the higher concentration solution
in the large chamber equilibrates with the lower concentration solution
in the small chamber through the diffusion control plug, the concentration
increases within the "button" containing the PYP sample,
causing crystallization to begin. Large PYP crystals have been grown
following these procedures using DCAMs.
Eddy Current Non-destructive Inspection Using Giant Magnetoresistive Technology. STEVEN GARDNER (Brigham Young University - Idaho, Rexburg, ID, 83460) DENNIS C. KUNERTH, PH.D. (Idaho National Laboratory, Idaho Falls, ID, 83415)
A prototype eddy
current probe utilizing giant Magnetoresistive technology was found
to have the following benefits: 1. It functions at very low frequencies
(DC to 30 kHz) and deep sample depths. 2. The probe can be characterized
to reveal thickness of an aluminum sample up to 10 mm thick, and
much thicker in stainless steel and other less conductive metals.
3. The probe design uses a noise reduction coil and shield system
which increases signal to noise ratio by nulling drive coil noise.
This probe would be ideal for testing thickness of metals with low
magnetic permeability. It is also effective at locating defects greater
than 0.25 mm on the surface or within the depth of penetration as
determined by the relationship depth (m) = v(1/
(p*f*µ0*µr*s)) where µ0 is
the permeability of free space, µr is the relative magnetic permeability and s is
the electrical conductivity. Its limitations include: 1. It was unable
to function at frequencies greater than 30 kHz. 2. It was not able
to detect defects smaller than .25 mm or surface defects which did
not extend this same distance or more into the metal. Attempts were
also made to operate the probe using pulse and linear sweep drives.
These attempts did not create satisfactory results. Much of the lack
of success could be due to the fact that it was not possible to null
the drive signal using the noise reduction coil for either the pulse
or the sweep drive methods. The inability to resolve small defects,
and the limitations on the frequency range appear to be caused by
the large coil geometry and the inductance change introduced by the
iron shield.
Effect of Acid Agitation on Buffered Chemical Polishing
of Niobium for Radiofrequency Cavities. SARA
MOHON (The College of William and Mary, Williamsburg, VA, 23186) ANDY WU (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
The performance
of niobium superconducting radiofrequency (SRF) cavities can be affected
by the smoothness of their inner surfaces. Smoother inner surfaces
tend to result in better performance. Normally, smooth niobium surfaces
are obtained by buffered chemical polish (BCP). BCP is necessary
to remove the damaged layer created during fabrication and machining
of the cavities. Previous experiments conducted in the Surface Science
Lab at Thomas Jefferson National Accelerator Facility have shown
that the morphology of niobium surfaces may be altered via different
agitation constraints during BCP. The focus of this research is a
systematic study of the effect of agitation on the BCP treatment
of niobium. Six samples of niobium, each one square centimeter in
size, were prepared using a 1:1:2 BCP mixture for 75 minutes. A control
sample was also analyzed with no BCP treatment. Each BCP treated
sample was agitated after a certain amount of time, varying from
0 to 75 minutes. After this treatment, the samples were examined
by a 3D profilometer, where quantitative information about surface
morphology was extracted. Qualitative inspection of the surface of
each sample was performed a metallographic optical microscope (MOM).
It was found that the surface roughness increased up to a certain
asymptotic limit as the time interval between agitations increased,
and that a green unidentified cloud-like material appeared above
the inner surface area of niobium samples when there was no agitation.
The MOM photographs show evidence that the BCP mixture attacked the
grain boundaries and defect locations more than it did elsewhere,
making a BCP treated surface rougher in comparison to some other
polishing methods. The treated samples became smoother as the time
interval between agitations decreased although they never become
as smooth as the control sample. Smoother surfaces were also found
in areas where the green cloud formed than in areas where it was
absent. A model is proposed to qualitatively explain the experimental
results. Further investigation is warranted for different BCP ratios
to see if a smoother surface finish is possible and what agitation
it requires. In addition, a BCP study of how larger grain samples
affect niobium surface morphology is promising to the improvement
of SRF cavities. These endeavors and the experimental results are
useful for the BCP treatment of niobium SRF cavities to be used in
particle accelerators.
Effects of Tellurium Precipitates in CdZnTe (CZT)
Radiation Detectors. KYLE KOHMAN (Kansas State University, Manhattan, KS, 66506)
ALEKSEY BOLOTNIKOV (Brookhaven National Laboratory, Upton, NY, 11973)
CdZnTe (CZT) crystal
is a material that has great potential for high-resolution detection
of gamma and X-rays because of its high gamma ray stopping power,
durability, and abilities to be made portable operated at room temperature.
It is well known that tellurium (Te) precipitates may affect performance
of CZT detectors; however, it is not specifically known how, or to
what extent these inclusions affect spectral response in CZT detectors.
This study sought a quantitative correlation between precipitate
sizes and concentrations of CZT material and the spectral response
of the material as a detector. Te precipitate sizes and concentrations
were observed in CZT crystals using an infrared microscope coupled
with a digital camera. A program written in Interactive Data Language
(IDL) counted Te precipitates within sample images at different magnifications
throughout the material and characterized each individual inclusion
by size and location. The crystals were then made into Frisch-ring
detectors by placing gold contacts on each side and wrapping them
in Teflon tape and copper. Spectral responses of the detectors were
measured by placing them into a pre-amplifier connected to standard
nuclear instrumentation module components. The results indicate that
detector response has a strong dependence on concentrations of Te
precipitates greater than 5 µm. 1-µm precipitates were very close
to the resolution limit of the IR system and so accuracy was insufficient
for quantitative measurements of correlations between device spectral
responses, precipitate concentrations, and crystal thicknesses (etch
pit technique would be more appropriate for measurements of such
small precipitates). Nevertheless, based on these measurements, an
upper limit can be given. Te precipitates with diameters
Effects of UV light on a fluorescent dust cloud. ENRIQUE
MERINO (Ramapo College of New Jersey, Mahwah, NJ, 7430) ANDREW POST-ZWICKER
(Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)
Dusty plasma research
has applications ranging from microchip fabrication to the study
of planetary rings. Typically, the behavior of laboratory dusty plasmas
is studied by laser scattering techniques. A new diagnostic technique
developed at the Science Education Laboratory at the Princeton Plasma
Physics Laboratory uses a 100W ultra-violet (UV) light to illuminate
a fluorescent organic dust cloud created in an argon DC glow discharge
plasma. By using the UV light, the fluorescent particles can be clearly
seen during and after cloud formation and their 3D properties analyzed.
This technique has been successfully used to study formation and
transport of the dust cloud. Observations have shown that after the
dust cloud has formed, the UV light causes rotation of the edge of
the cloud (˜ 3mm/s), while particles in the center of the cloud remain
stable. Displacements of several millimeters up and towards the UV
light have also been recorded by modulating the UV light. Through
the use of a Langmuir probe, changes in the charge of the plasma
were recorded whenever UV light was introduced. These changes occurred
both in the presence of a dust cloud and with a clean plasma as well.
Although these experiments were helpful in demonstrating that UV
light had an effect on the plasma, it is left as future work to determine
the effect of UV light on the dust particles themselves and propose
analytical models for the displacements experienced.
Energizing a Superconducting Solenoid for Applications in Precise Mass Measurements. DAVID DANAHER (Monmouth College, Monmouth, IL, 61462)
GUY SAVARD (Argonne National Laboratory, Argonne, IL, 60439)
The precise mass
measurement of ions is the main objective of the Canadian Penning
Trap (CPT) collaboration at Argonne National Laboratory. The mass
measurements require a beam from the Argonne Tandem Linear Accelerator
System (ATLAS) to fuse with a target to create the desired reaction
products. A new beamline has nearly been completed in Area II of
ATLAS for the purpose of taking mass measurements of ions with greater
divergence angles that were previously hard or nearly impossible
to measure, which diverge due to alpha decay and are refocused for
later measurement. A solenoid can be used to refocus the ions before
they can be sent through the rest of the system and, consequently,
measured. This component of the new beamline in Area II is a superconducting
solenoid with a 68 centimeter inner bore and a central field of 1.5
Tesla, weighing over 10 tons with all of the necessary shielding
and support in place. For the solenoid to produce a magnetic field,
it must be energized and continually carry a current of about 200
Amps within its coils. The process of energizing such a device is
a subtle exercise and requires creating a vacuum within the solenoid,
pre-cooling of the cryostat with liquid Nitrogen, filling the cryostat
with liquid Helium, running a cryo-compressor to limit Helium boil-off,
and well-regulated power sources to bring the solenoid to maximum
field. Once carefully assembled, however, the components of the energization
process may be used to safely energize and de-energize the system
time and time again. My project was to help locate all the components
of the energization process, facilitate the interconnections between
components, and, finally, to aide with the powering of the magnet.
Error Reduction in Polarization Measurement. DONALD JONES (Acadia University, Wolfville, NS,
0) ROBERT MICHAELS (Thomas Jefferson National Accelerator Facility, Newport
News, VA, 23606)
One of the greatest
barriers to definitive conclusions in any scientific experiment is
the accumulation of errors. Due to the precision required in parity-violation
experiments, an effort has been made in Hall A at Jefferson Lab (JLab)
to reduce the cumulative error by targeting specific sources. A particular
focus has been placed on reduction of error in beam polarization
measurements. Compton polarimetry is utilized at JLab because of
its unique advantage of allowing polarization to be determined while
an experiment is running, without interrupting the beam. Electrical
signals produced by scattered photons and electrons are used to determine
beam polarization. The helicity of the beam is reversed every 33
milliseconds (ms) and the asymmetry that arises from pulse measurements
during consecutive 33 ms intervals, is used to calculate beam polarization.
While this asymmetry has been created in the past by counting photons,
electrons or electron-photon coincidences, this method gives rise
to many systematic errors. New methods are being sought to more accurately
calculate polarization. The focus of this research has been to determine
whether signal integration can be used to effectively reduce the
error to under the 1% level within a feasible time frame. Extensive
tests have been done to determine the reliability of signal integration
across the full 33ms gate, in order to determine if the background
noise is too great to make this technique useful. Because of difficulties
encountered, and the lack of beam operation during the time this
research was done, a pulse generator was used to simulate the electrical
pulses that arise from electron scattering in the Compton polarimeter.
The data from the pulse-generated asymmetry indicates that polarization
can be accurately determined within three hours of beam operation.
Because experiments can last for days, this is a reasonable length
of time. To ensure the reliability of this technique, the results
were then verified using Monte Carlo simulations. The results of
this research show that this method of beam polarization measurement
has great promise of being able to reduce the measurement error from
the present 3%, to below 1%. This method has yet to be tested during
beam operation, but its success would enhance future parity violation
experiments.
Experimental Studies of Electrode Biased Compact Toroid Plasmas in the Magnetic
Reconnection Experiment. ELIJAH
MARTIN (North Carolina State University, Raleigh, NC, 27609)
DR. MASAAKI YAMADA (Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)
Compact Toroid
(CT) plasmas such as Field-Reversed Configurations (FRC’s) and Spheromaks
are known to exhibit a global instability known as the tilt mode,
where the magnetic moment of the CT tilts to align itself with the
external magnetic field, as well other non-rigid body instabilities.
Possible tilt stabilizing mechanisms for these instabilities include
external field shaping, nearby passive stabilizers, and plasma rotation.
This research focuses on reducing the growth of the tilt instability
by introducing toroidal rotation in spheromaks formed in the Magnetic
Reconnection Experiment (MRX). Rotation is introduced by the use
of interior and exterior electrodes; the result is a Jbias x
Binternal torque
on the CT plasma which in turn leads to toroidal rotation of the
CT plasma. In order to power the bias electrode a 450 V 8800 µF capacitor
bank capable of delivering up to 450 amperes was constructed along
with the required control and triggering circuitry. Solid state switches
allow for fast turn on and turn off times of Jbias. The bias current and the voltage drop across the electrodes
are measured using a current shunt and voltage divider respectively,
and the resulting flow in the CT plasma is measured with a Mach probe.
Internal arrays of magnetic probes and optical diagnostics will be
used to parameterize the performance of the CT plasma during bias.
Construction and testing of all necessary components and diagnostics
is complete; preliminary experiments were designed such that the
resistivity of the plasma could be determined. It was found that
a typical CT plasma has a resistivity of 34.1 ± 3.6 ohm m, a leaky
capacitor model of the CT plasma was applied to determine the resistivity
theoretically. A theoretical resistivity of 4.9 x 10-3 ohm
m was calculated based on conditions of a typical CT plasma. The
strong disagreement between experimentally and theoretically determined
values is hypothesized to be due to non-optimal control of CT plasmas
formed in MRX. The focus of future research will be optimizing control
of the CT plasma; agreement between the model and experiment will
then be studied as well as experiments designed to induce toroidal
rotation.
Formation and Transport of a Fluorescent Dust Cloud: a New Diagnostic Technique
in Dusty Plasma Research. ENRIQUE
MERINO (Ramapo College of New Jersey, Mahwah, NJ, 7430) ANDREW
POST-ZWICKER (Princeton Plasma Physics Laboratory, Princeton, NJ,
8543)
Dusty plasma research
has applications ranging from microchip fabrication to the study
of planetary rings. Typically, the behavior of laboratory dusty plasmas
is studied by laser scattering techniques which give a 2D slice of
the dust cloud or by the use of 3D particle image velocimetry methods
(PIV). Although these diagnostic techniques allow for the study of
cloud formation, they require extensive computer processing or simulations
to study the formation processes. A new diagnostic technique has
been devised to study 3D behavior and cloud formation, without the
need for the complicated and usually expensive methods mentioned
above. A fluorescent organic dust is used to create a cloud in an
argon DC glow discharge plasma, illuminated by a 100W ultra-violet
(UV) light. By using UV light, the fluorescent particles can be clearly
seen during cloud formation and their 3D properties analyzed. One
question remaining, however, is whether the UV light perturbs the
plasma by changing the local charge balance or actively changing
the dust cloud charge by photoelectric emission. In fact, initial
observations show that particles in the back of the dust cloud experience
a displacement towards the UV light, while particles in the front
move away from it. Velocities ranging in the order of 1.5 mm/sec
to 3 mm/sec were recorded for different areas of the cloud. Future
work will use a Langmuir probe to separate changes in plasma parameters
from changes in dust charge.
G0++: Creating a User Interface
for Fastbus Data. JONATHAN HOOD (University
of Maryland, College
Park, MD, 20742) TANJA HORN (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
The G0 collaboration
at Thomas Jefferson National Accelerator Facility (Jefferson Lab)
investigates the contribution of strange quarks to the fundamental
properties of the nucleon. To do this, the G0 experiment sends a
highly energized electron beam into a target, such as liquid hydrogen.
When the electrons in the beam collide with nucleons in the target,
a spray of particles radiates from the collision point. This spray
of particles travels across a magnetic field into a variety of particle
detectors, resulting in large amounts of unanalyzed data. Data taken
during the G0 experiment pertaining to the time of flight and amplitudes
of particle trajectories is referred to as Fastbus data, which is
organized by Root, a C++ interpreter designed for manipulating large
number of data points. For the G0 experiment, Fastbus data provide
a general evaluation of the performance of the detector and electronic
systems. Therefore, an efficient analysis of these data is essential
at the startup and during the running of an experiment. The goal
of this project was to make the Fastbus data more accessible, especially
to people who are not familiar with the Root language. To do this,
a good understanding of the data acquisition and its analysis was
required. By collaborating with scientists at the National Jefferson
Laboratory, a design was constructed and implemented. Scientists
need to look at the data in many different ways, and the program
was designed to include a variety of tools that allows them to do
so. In order to analyze the data quickly and effectively, a Graphical
User Interface (GUI) was programmed to give users a convenient way
to create, display, and manipulate graphs. The interface has been
constructed with many useful tools that aid scientists in the G0
experiment, including such features as the ability to add cuts to
remove unwanted data points and the ability to fit the data with
numerical equations. The program, titled “G0++: GoFast Goes Fast” will
be used by G0 scientists, and eventually the program could be used
for general Hall C data analysis in a C++ framework.
Gain Mapping and Response Uniformity Testing of the Hamamatsu R8900 Multianode
Photomultiplier Tube and the Burle Planacon Microchannel Plate
Photomultiplier Tube for the Picosecond Timing Project. MELINDA
MORANG (University of Chicago, Chicago, IL, 60637) KAREN BYRUM (Argonne National Laboratory, Argonne, IL, 60439)
Research is currently
underway for the development of a microchannel plate photomultiplier
tube with picosecond timing capabilities, a property that would be
extremely useful in many fields of physics and in radiology. It is
important in a research and development study such as this one to
fully understand the currently available technology, and the study
presented in this paper focuses on characterizing gain and response
uniformity in the Hamamatsu R8900-00-M16 multianode photomultiplier
tube (R8900) and the Burle Planacon 85011-501 microchannel plate
photomultiplier tube (MCPPMT). The tubes were tested using a dark
box setup in which a moveable fiber carrying an LED pulse could be
directed into each pixel in the tube. The gains for each pixel of
ten R8900 tubes and for part of an MCPPMT were calculated, and a
horizontal scan in 1mm steps was performed across the breadth of
the R8900 and across one quadrant of an MCPPMT. Plots showing the
signal output in the horizontal scans showed that the MCPPMT had
much greater response uniformity across the tube, but due to time
and equipment restraints, these results are only preliminary, and
more extensive study of uniformity is necessary, as is study of many
other properties of these tubes.
GEANT Simulations of the Preshower Calorimeter for CLAS12 Upgrade of the Forward
Electromagnetic Calorimeter. KRISTIN WHITLOW (University
of Florida, Gainesville, FL, 32612) STEPAN STEPANYAN (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
Hall B at the Thomas
Jefferson National Accelerator Facility uses the CEBAF (Continuous
Electron Beam Accelerator Facility) Large Acceptance Spectrometer
(CLAS) to study the structure of the nucleon. The accelerator is
currently planning to upgrade from using a 6 GeV beam to a 12 GeV
beam. With the beam upgrade, more high-energy pions will be created
from the interaction of the beam and the target. Above 6 GeV, the
angle between the two-decay photons of high-energy pions becomes
too small for the current electromagnetic calorimeter (EC) of CLAS
to differentiate between two photon clusters and single photon events.
Thus, a preshower calorimeter will be added in front of the EC to
enable finer granularity and ensure better cluster separation for
all CLAS experiments at higher energies. In order to optimize cost
without compromising the calorimeter’s performance, three versions
of the preshower varying in number of scintillator and lead layers
were compared by their resolution and efficiency. Through the use
of GSIM, a GEANT detector simulation program for CLAS, po’s and single photons were passed through the CLAS detector with
the added preshower calorimeter (CLAS12 EC). The resolution of the
CLAS12 EC was calculated from the Gaussian fit of the sampling fraction,
the energy CLAS12 EC detected over the Monte Carlo simulated momentum.
The single photon detection efficiency was determined from the energy
and position of the photon hits. The resolution measured in the five-modules
version was 0.0972, the four-modules version was 0.111, and three-modules
version was 0.149. Both the five- and four-modules versions had 99%
efficiency above 0.5 GeV while the 3 module version had 99% efficiency
above 1.5 GeV. Based on these results, the suggested preshower configuration
is the four-modules version containing twelve layers of scintillator
and fifteen layers of lead because it is the most realistic choice
to construct in resolution, efficiency and cost. The next step will
be to do additional GSIM simulations to verify that the four-modules
version has acceptable po mass
reconstruction and continue Research and Development (R&D) analysis
on the preshower calorimeter.
Generation of Theoretical Spectra for Hot Dense Matter. ELIAS
ALLISON, MATILDA FERNANDEZ, & AJIT HIRA (Northern New
Mexico Community College, Espanola, NM, 87532)
DR. RICHARD W. LEE (Lawrence Livermore
National Laboratory, Livermore, CA, 94550)
The focus of this
project is to use computer codes to generate spectroscopic for data
plasmas and for hot dense matter, and to use these theoretical spectra
to interpret experimental results. These theoretical spectra are
important because of their applications in the study of ionized matter
and magnetic fields near the surfaces of the sun and stars, the origin
of cosmic rays, the dispersion and broadening of signals traveling
through interstellar space, the realization of controlled release
of nuclear fusion energy, and the development of new electronic devices,
among others. The computer codes model specified interactions for
elements ranging from Helium to Iron, with a particular interest
in lithium-like, helium-like and hydrogenic ionic species. Some of
the important events included in the model are collisional ionization
and recombination, radiative, bound-free processes, bound-bound processes,
auto-ionization and electron capture. At present the focus of the
project is the design and implementation of a good dynamic interface
to improve the use of existing codes.
Hold-up Time Measurements for Various Targets. EMILY
PRETTYMAN (DePaul University, Chicago, IL, 60614) KEN CARTER (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
At Oak Ridge National
Laboratory the Holifield Radioactive Ion Beam Facility (HRIBF) produces
radioactive ion beams (RIBs) typically by proton-induced fission
on an actinide target. The RIB yields depend on the chemical and
physical properties of the target used, such as the chemical compound,
density and temperature. The rates at which chemical elements are
released from the target ion source, called hold-up times, can give
yield information and information about the movement of chemical
elements within the target material and the ion source. This information
may be useful in designing optimal targets and choosing operating
conditions to maximize production of specific isotopes. Hold-up times
are measured using the UNISOR isotope separator, connected to the
tandem accelerator. Typically, the proton beam is left on until the
element of interest reaches equilibrium between production and release.
The proton beam is then turned off and the decrease of the release
is observed using a moving tape collector and a germanium detector.
Hold-up times have been measured using a pressed-powder Uranium Carbide
(UCx)
target at different temperatures for four elements: 78Ge, 92Sr, 128Sn, and 130Sb. In addition, hold-up times have been measured using two ThO2 targets
of different densities for 132Te. For the various elements measured, as the temperature increases
the hold-up times tend to decrease as expected. In addition, the
denser ThO2 target
has drastically longer hold-up time than the less dense ThO2 target
for 132Te.
The current analysis was done by fitting the data with two exponential
decay functions and as expected the hold-up times decrease as target
temperature increases and the porous ThO2 target has shorter hold-up times and higher yields than the
denser ThO2 target.
Another attempt to fit the data would be to use equations which take
into account diffusion and effusion with the goal of determining
the ratios between diffusion and effusion to see which process dominates.
There is still more work that must be done before conclusions can
be drawn about the best design of a target and the most efficient
operating conditions to maximize the yields.
Host Galaxies of X-Shaped Radio Sources. ALESSONDRA
SPRINGMANN (Wellesley College, Wellesley, MA,
2481) TEDDY CHEUNG (Stanford Linear Accelerator Center, Stanford, CA, 94025)
The majority of
radiation from galaxies containing active galactic nuclei (AGNs)
is emitted not by the stars composing the galaxy, but from an active
source at the galactic center, most likely a supermassive black hole.
Of particular interest are radio galaxies, the active galaxies emitting
much of their radiation at radio wavelengths. Within each radio galaxy,
an AGN powers a pair of collimated jets of relativistic particles,
forming a pair of giant lobes at the end of the jets and thus giving
a characterisitic double-lobed appearance. A particular class of
radio galaxies have an “X”-shaped morphology: in these, two pairs
of lobes appear to originate from the galactic center, producing
a distinctive X-shape. Two main mechanisms have been proposed to
explain the X-shape morphology: one being through the merger of a
binary supermassive black hole system and the second being that the
radio jets are expanding into an asymmetric medium. By analyzing
radio host galaxy shapes, we probe the distribution of the stellar
mass to compare the differing model expectations regarding the distribution
of the surrounding gas and stellar material about the AGN.
Hydrocode Simulations of Mach Stem Formation. STEPHEN DAUGHERTY (Vanderbilt University, Nashville, TN, 37235) DENNIS PAISLEY (Los Alamos National Laboratory, Los
Alamos, NM, 87545)
The study of shock
waves often makes use of metallic disks propelled at high velocities
to act as impactors. There are a number of ways to supply flyers
with energy, but it takes some scheming to achieve extreme accelerations;
a laser can focus a large amount of energy into a small area, but
at some point thermal effects will take over, scattering much of
the pulse energy and heating the sample. One solution is to strike
a cone with a high-energy pulse and allow the resulting shock to
converge toward the center. The shock reflected from the center will
move at supersonic speed behind the incident shock, causing a flat
energy disk—a Mach wave—to propagate through the center of the cone.
The Mach wave will carry a high energy density to the base of the
cone, where it can be transferred to a flyer.
Improvement of PEP-II Linear Optics with a MIA-Derived Virtual Accelerator. BEN CERIO (Colgate University, Hamilton, NY, 13346)
YITON YAN (Stanford Linear Accelerator Center, Stanford, CA, 94025)
In several past
studies, model independent analysis, in conjunction with a virtual
accelerator model, has been successful in improving PEP-II linear
geometric optics. In many cases, optics improvement yielded an increase
in machine luminosity. In this study, an updated characterization
of linear optics is presented. With the PEP-II beam position monitor
(BPM) system, four independent beam centroid orbits were extracted
and used to determine phase advances and linear Green’s functions
among BPM locations. A magnetic lattice model was then constructed
with a singular value decomposition-enhanced least-square fitting
of phase advances and Green’s functions, which are functions of quadrupole
strengths, sextupole feed-downs, as well as BPM errors, to the corresponding
measured quantities. The fitting process yielded a machine model
that matched the measured linear optics of the real machine and was
therefore deemed the virtual accelerator. High beta beat, as well
as linear coupling, was observed in both LER and HER of the virtual
accelerator. Since there was higher beta beating in LER, focus was
shifted to the improvement of this ring. By adjusting select quadrupoles
of the virtual LER and fitting the resulting beta functions and phase
advances to those of the desired lattice, the average beta beat of
the virtual machine was effectively reduced. The new magnet configuration
was dialed into LER on August 10, 2006, and beta beat was reduced
by a factor of three. After fine tuning HER to match the improved
LER for optimal collision, a record peak luminosity of 12.069x1033 cm-2s-1 was
attained on August 16, 2006.
Indium Zinc Oxide Active Channel Layer in Transparent Thin Film Transistors. ANDREW CAVENDOR (Colorado School
of Mines, Golden, CO, 80401) DAVID GINLEY (National Renewable Energy
Laboratory, Golden, CO, 89401)
Amorphous indium
zinc oxide (IZO) shows promise for being the active channel layer
in a transparent thin film transistor (TTFT). In the last 2 years,
oxide based transistors have begun to be investigated showing the
promise to replace amorphous silicon (a-Si) and microcrystalline
silicon TFTs to lead to transparent electronics. IZO is a lead candidate
because it can be deposited at room temperature and is amorphous,
making it suitable for flexible substrates. Also, IZO has higher
Hall mobility (µh) > 30
cm2V-1s-1 than
conventional materials (< 1 cm2V-1s-1), which makes faster TFT switching times possible. We used DC
magnetron sputtering with O2/Ar gas from 0-10% to optimize the active channel layer, for
transistors. Addition of O2 to the sputter gas reduces the carrier concentration () while
preserving high mobility µh. Amorphous IZO films were produced at 70/30 atomic percent In/Zn
with µh as
high as ~55 cm2V-1s-1 and as low as ~1016 cm-3. TFT devices were made in the gate down method through photolithography.
The source and drain were produced at 84/16 atomic percent In/Zn,
to achieve good conductivity ~2000 S cm-1. Films were incorporated into functional transistors which showed
on-to-off current ratios ~106.
Investigating the Polarization Effects of Free Electrons
Through a Longitudinal Stern-Gerlach Apparatus. RACHEL
SPARKS (Old Dominion University, Norfolk, VA, 23517) DR. DOUGLAS W. HIGINBOTHAM (Thomas Jefferson National Accelerator
Facility, Newport News, VA, 23606)
Otto Stern and
Walther Gerlach completed an experiment in 1922 that opened many
important questions and discoveries about the quantum mechanical
world. Known as the Stern-Gerlach experiment, a beam of neutral silver
atoms was passed through an inhomogeneous transverse magnetic field
and then projected onto a screen. Classically, one would expect the
screen to display a single blob of silver atoms; however, two blobs
appeared. The breakthrough from this experiment was that the electron
has an intrinsic spin, similar to a rotating top. Attempts have been
made to conduct the Stern-Gerlach experiment with a beam of free
electrons; but the Lorentz force, along with the Heisenberg uncertainty
principle, blurs the splitting of the beam. In 1928, Brillouin suggested
that a longitudinal Stern-Gerlach apparatus would minimize the effect
of the Lorentz force. While this idea was dismissed in 1930 by Wolfgang
Pauli, recent papers have shown that Brillouin's idea may have been
valid. A computer simulation for an experiment to use the longitudinal
Stern-Gerlach was completed this summer by analyzing the effect of
different spin separations of the beam. Enhancement of the polarization
was seen even using a realistic spread in the electron's momentum.
Thus, it appears feasible to conduct an experiment that will investigate
Brillouin's idea. In the future, this could be done in the Jefferson
Lab test cave with equipment that is readily available.
Investigation of the Optical Properties
of Light-Emitting Diodes for Use in Fluorescence-Based Detection
of Biological Threat Particles. SHAWN BALLENGER (Florence-Darlington Technical College,
Florence, SC, 29501) NORM ANHEIER (Pacific Northwest National Laboratory,
Richland, WA, 99352)
The optical properties
of ultra-violet (UV) light-emitting diodes (LEDs) are being investigated
to determine the LEDs’ applicability in detecting biological particles
using intrinsic fluorescence. When a biological material fluoresces
it gives off a specific spectrum. This spectrum can be analyzed to
identify threat particles from the background interferents. Pulsed
laser excitation has previously been used to induce fluorescence
in biological materials; however, the continued improvement in LED
technology has made LEDs a viable alternative to lasers, which would
enable the development of economical detectors for biological threats.
Digital logic pulsing techniques were used to drive the LEDs, and
an integrating sphere was used to measure the LEDs’ average optical
power as the duty-cycle and pulse repetition frequency (PRF) was
varied. The digital logic pulsing techniques were successful in driving
the LEDs; however, alternative pulsing techniques need to be developed
to extract additional optical power from the LEDs. Once the LED driver
circuit is properly developed, experiments investigating the LEDs’ ability
to produce fluorescence in biological particles can be done to determine
if the LED is a viable alternative to the more costly laser source.
Java Based Interface for Particle Fragmentation Studies at the NASA Space Radiation
Laboratory. JENNIFER MABANTA (St. Joseph's
College, Patchogue, NY, 11772)
DR. MICHAEL SIVERTZ (Brookhaven National Laboratory, Upton, NY, 11973)
Before extended
space missions can occur, protective measures must be in place for
astronauts as prolonged exposure to radiation fields can have harmful
and sometimes permanent effects. The purpose of the research done
at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National
Laboratory (BNL) is to gain a better understanding of the cosmic
rays in space and develop the most efficient countermeasure for the
voyagers. Proton and heavy-ion beams from the BNL Booster accelerator
are directed along a beam line to NSRL. By mimicking cosmic rays
with the beam, the lab provides a controlled area in which to study
the effects of the rays. The most harmful of the rays is iron, and
the least destructive and most abundant is hydrogen. Of particular
interest to NASA is the process of fragmentation, or the way in which
heavy ions, like iron, break up into lighter less dangerous ions,
such as protons. Currently, the methods used by the scientists to
conduct analysis on fragmentation data are cumbersome at best. A
program needed to be created to facilitate the studies being conducted
at NSRL. A program called “Fragmentation Process” was developed which
provides a graphical user interface (GUI) for the scientists interested
in fragmentation data. This Java-based program, written using an
Emacs text editor, allows the user to collect data while the beam
is on and provides graphs generated by the data in real time. These
graphs can be made while data is still being taken or at the end
with the total data sample collected. The graphs are displayed using
a program called Ghostview and provide the scientist with a measure
of the fragmentation in the beam. Prior to this, the work required
to generate these graphs could take up to a week. Now, by utilizing
the program, the calculations and resulting graphs are done immediately.
Comparison of these graphs and the graphs generated prior to the
creation of the GUI show that the program is displaying accurate
information. The increased efficiency in studying fragmentation data
at NSRL will be of great value to NASA and researchers will be able
to gain a deeper understating of fragmentation and develop the most
effective shielding or other countermeasures for our astronauts.
Jet-Like Event Simulations for the FPD++ Calorimeter at STAR. CHRISTOPHER
MILLER (Stony Brook University, Stony Brook, NY, 11794) LES
BLAND (Brookhaven National Laboratory, Upton, NY, 11973)
The Forward Pion
Detector upgrade (FPD++) to the STAR experiment at Brookhaven National
Laboratory is capable of detecting photons at high rapidity. Most
of these photons are produced from the decay of neutral pions (p0)
which are fragments of quark or gluon jets that have undergone small
angle scattering in proton+proton collisions. My project was to quantify
the average production of these photons with azimuthal symmetry about
the forward jet axis. Asymmetries can arise in the fragmentation
of forward scattered quarks and gluons from particles produced by
spectators to the quark/gluon scattering. These asymmetries can serve
as backgrounds to measurements that aim to establish the spin dependence
of forward jet production. In order to accomplish my goal, I used
a Monte Carlo generator called PYTHIA 6.222 to simulate the particle
production at a total center of mass energy of 200 GeV. The correlation
between the energy of each photon and its distance from the thrust
axis, calculated from the photon’s momentum sum vector, was histogrammed.
The results were averaged over many events and a visualization of
the jet shape was created, which allowed for a further analysis to
quantify its azimuthal symmetry. In the end, the computer generated
simulation showed a falling exponential trend of the jet shape from
the leading pion and a small asymmetry between the left and right
section of the jet. These results give an estimation of the underlying
event background.
Jovian Planet Formation in 50 AU Binary Star Systems. CHRISTIAN LYTLE (University
of St. Thomas, St. Paul, MN, 55105) ANDY NELSON (Los Alamos National Laboratory, Los
Alamos, NM, 87545)
The detection of
Jovian planets in large-separation binaries (>100 AU) has motivated
investigation into the probability of planet formation in approximately
50 AU and smaller systems. We have run smoothed-particle hydrodynamics
(SPH) simulations of binary systems with circumstellar disks and
compared our results with others in the literature. Cooling based
both on a fraction of the orbital period and a fully radiative model
are implemented, but neither produce gravitational instabilities
of the magnitude required for long term fragmentation of the disks,
due primarily to the strong heating which occurs when the disks are
near periapse. These results are in conflict with simulations from
the literature that have produced fragmentation in disks with morphologies
similar to ours. We propose that the inconsistencies are attributable
to numerical deficiencies (low resolution and fixed gravitational
softening) and unrealistic initial conditions present in the previous
work.
Laser Induced Fluorescence Motional Stark Effect Control & Data Acquisition
Application. PATRICK MALONEY (Carleton College, Northfield, MN, 55057) JILL FOLEY (Princeton Plasma Physics Laboratory, Princeton, NJ,
8543)
The motional Stark
effect (MSE) is a standard technique for measuring spatially resolved
magnetic fields in plasma experiments. These fields are found with
a beam of neutral hydrogen atoms which when traveling through a magnetic
field perceive a Lorentz electric field in their own frame. The resulting
electric field causes observable line splitting in hydrogen’s spectral
lines, which is proportional to the electric field. The polarization
of the lines gives the field direction. However, while MSE is extremely
effective for fields > 1 T, it can be difficult to measure weaker
fields as a consequence of spectral line overlap. A dominant source
of the overlap is from different emission lines being red and blue
shifted across finite sized collection optics, an effect referred
to as geometric broadening. To counter this effect, a method using
Laser-Induced Fluorescence (LIF) to excite a single atomic transition
at a time in the hydrogen beam has been proposed. Using this technique,
the exact energy and thus wavelength of incoming photons is set by
the laser, allowing geometric broadening effects to be completely
ignored. Already the combination of MSE and LIF has been able to
measure magnetic fields on the order of tens of Gauss in neutral
gases but has yet to be tested on plasma. The purpose of this project
has been to implement a data acquisition and control system with
LabView for the MSE-LIF development laboratory, including the new
Spiral Antenna Helicon High Intensity Background (SAHHIB) experiment,
a plasma test bed for LIF-MSE. The resulting program displays and
records a variety of measurements including pressures at critical
points in the vacuum system, laser and RF power characteristics,
and most importantly, time dependent LIF signals used to find magnetic
field magnitude and direction. The program is useful because previous
measurements were primarily taken by hand making the collection of
experimental parameters tedious. The data acquisition and control
application developed to study LIF-MSE may also be employed for studying
different instabilities in the helicon plasma source SAHHIB. Should
the LIF-MSE device on SAHHIB prove successful, it will eventually
be employed at the National Spherical Torus experiment (NSTX).
Limited Streamer Tube System for Detecting Contamination in the Gas Used in
the BaBar Instrumented Flux Return. LAURA
HUNTLEY (Franklin & Marshall College, Lancaster, PA, 17603)
MARK CONVERY (Stanford Linear Accelerator Center, Stanford, CA, 94025)
The Resistive Plate
Chambers (RPCs) initially installed in the Instrumented Flux Return
(IFR) of the BaBar particle detector have proven unreliable and inefficient
for detecting muons and neutral hadrons. In the summer of 2004, the
BaBar Collaboration began replacing the RPCs with Limited Streamer
Tubes (LSTs). LST operation requires a mixture of very pure gases
and an operating voltage of 5500 V to achieve maximum efficiency.
In the past, the gas supplies obtained by the BaBar Collaboration
have contained contaminants that caused the efficiency of the IFR
LSTs to drop from approximately 90% to approximately 60%. Therefore,
it was necessary to develop a method for testing this gas for contaminants.
An LST test system was designed and built using two existing LSTs,
one placed 1 cm above the other. These LSTs detect cosmic muons in
place of particles created during the BaBar experiment. The effect
of gas contamination was mimicked by reducing the operating voltage
of the test system in order to lower the detection efficiency. When
contaminated gas was simulated, the coincidence rate and the percent
coincidence between the LSTs in the test system dropped off significantly,
demonstrating that test system can be used as an indicator of gas
purity. In the fall of 2006, the LST test system will be installed
in the gas storage area near the BaBar facility for the purpose of
testing the gas being sent to the IFR.
Measuring the Point Spread Function of a High Resolution
Charge-Coupled Device. ANNA DERBAKOVA (University
of North Carolina - Chapel Hill, Chapel Hill, NC, 27028) PAUL
O'CONNOR (Brookhaven National Laboratory, Upton, NY, 11973)
When a diffraction-limited
point source of light passes through an optical system, it acquires
aberrations from imperfections in the optics and becomes blurred
due to lateral diffusion of photogenerated charge within the semiconductor
detector. The quality of the optical system is characterized by the
point spread function (PSF) which measures the amount of blurring
that is present. The purpose of this experiment was to produce a
light spot much smaller than a CCD pixel (15 x 15 µm square), characterize
this light spot, and then use it to measure the PSF of a high resolution
prototype charge-coupled device (CCD), which will later form the
basis of the CCD camera in the Large Synoptic Survey Telescope (LSST).
The point source for this experiment was obtained by coupling a diode
laser to an optical fiber 4 µm in diameter. A light spot was obtained
by imaging this point source using a long working-distance microscope
objective. In order to characterize this light spot, the knife-edge
scan technique was used. Here, the point source was directed at a
detector (photodiode) and a razor blade was scanned laterally through
the focal region in increments of 0.1 µm at various axial positions.
The amount of light incident on the detector was measured as a current
using a picoammeter. The intensity was plotted versus position and
fitted with an Erf function from which the rms spread, s, of the
spot was determined. The rms spread of the light spot was measured
to be: s = 1.18 µm. This spot was then projected onto the surface
of the CCD and images were acquired as the point source was stepped
across the CCD in sub-pixel increments. By summing the intensity
in a fixed pixel window as the light spot is scanned across the edge
of the window, the PSF can be obtained (“virtual knife-edge” technique).
Subtracting the light-spot size in quadrature from the width of the
fit to the virtual knife edge scans results in an estimate for the
PSF of the CCD. The result in this case is s = 7.25 µm or a FWHM
of 17.06 µm which is the contribution of charge diffusion to the
broadening of the image in the CCD. The results of this experiment
will be useful in determining the optimum parameters for future prototype
CCDs that will be used in the LSST high resolution CCD camera.
Measurement of Fair Weather Air Conductivity. KAMIL
ZAKHOUR (Florence Darlington Technical College, Florence, SC, 29501) (509) 375-2081 (Pacific Northwest National Laboratory, Richland, WA, 99352)
Measurement of
Fair Weather Air Conductivity at the Hanford Site Dallas Monroe Jr.,
Natissa McClester and Kamil Zakhour Department of Civil Engineering
Technology Florence Darlington Technical College Florence, South
Carolina Bruce Watson, Paul Sabin, Sakher Khayyat, Jeff Griffin Applied
Physics and Materials Characterization Sciences Group Pacific Northwest
National Laboratory Richland, Washington ABSTRACT For the past 4
years, staff at the US Department of Energy’s Pacific Northwest National
Laboratory have been investigating the generation, and transport
of radiation-induced ions near the ground. Baseline measurements
of fair weather atmospheric conductivity are required in order to
estimate ions lifetimes and predict ions detectability downwind of
a radioactive source. Using a Gerdien condenser, atmospheric conductivity
measurements were made over a two week period, July 10-21, 2006 in
the 300 Area of the Hanford Site. Experimental data, during that
time period, show some uniformity, with atmospheric conductivity
values ranging from 1.4 to1.8 x 10^ -14 S/m. These results are consistent
with published values for arid rural desert regions throughout the
world. Weather conditions were similar over the two weeks that the
experiments were performed. Therefore; to obtain more valid background
atmospheric conductivities, future experiments should look into variable
weather conditions and evaluate their effects on atmospheric conductivities
at the site.
Mixed Apparatus Radar Investigation of Atmospheric
Cosmic Rays of High Ionization Via the Triple Inverted V Array
Antenna. ALISHIA FERRELL (Florida A & M University, Tallahassee, FL, 32307)
HELIO TAKAI (Brookhaven National Laboratory, Upton, NY, 11973)
The observation
of ultra high energy cosmic rays (UHECR) is an ongoing mystery. There
are two main issues surrounding these subatomic mechanisms. The first
of the two is how do these mechanisms accelerate to such high energies?
The second question is where are these mechanisms located in our
universe? By studying these intense mechanisms we are only brushing
the tip of the iceberg to our elusive universe. The Mixed Apparatus
for Radar Investigation of Atmospheric Cosmic Rays of High Ionization
(MARIACHI) will search for UHECR by detecting radio signals reflected
from the extensive air showers (EAS) of charged particles created
when the UHECR interacts with the earth’s atmosphere. The task given
was to design and build a portable, reconfigurable receiving antenna
that is tunable to multiple Very High Frequency (VHF) frequencies.
This receiving antenna also known as the Triple Inverted V Array
Antenna (TIVAA) is based on a half-wave inverted v dipole design.
TIVAA consists of three dipoles using metal tubes. The length of
each dipole is variable leading to a change in the optimally detected
frequency. Additionally, the angle of each v can be altered; orientation
of the dipole array may also be altered as well. Mounted on a patio
umbrella frame that was modified specifically as the antenna frame,
which can be folded downward in a straight line for ease of portability
the TIVAA is positioned at a specific location above the ground to
minimize destructive interference with ground reflected waves. The
TIVAA has special features which make it unique. The orientation
of this receiving antenna can be altered, as well as the polar angle
of each quarter wave element. The design has been chosen to optimize
detection of radio signals which may consist of multiple polarizations.
The results (to produce radio signals from local television and FM
radio stations) aid the TIVAA in demonstrating the ability to tune
well, to gain good isotropic reception, as well as attract other
phenomena such as meteors and lighting. The TIVAA design may form
the basis of a future array of antennas providing timing, direction,
and ranging information for UHECR induced EAS.
Model Independent Analysis of Beam Position Monitor Data in the Spallation
Neutron Source Accumulator Ring. STEPHEN
THORSON (University of Wisconsin, Madison, WI, 53706) SARAH COUSINEAU (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Model independent
analysis (MIA) has been proposed as a method to obtain certain particle
accelerator parameters from turn-by-turn beam position monitor (BPM)
data. In particular, the accelerator physics group at the Spallation
Neutron Source (SNS) is interested in using MIA to determine the
magnetic optics of the SNS accumulator ring, especially the betatron
function. This analysis was performed using MATLAB® software package
and an online model of the SNS accelerator. The MIA method has several
advantages over other optics measurement techniques. It requires
few details about the accelerator specifications, is stable against
random measurement noise, and does not require alteration of magnet
currents. Drawbacks of applying this method are that the betatron
function is only accurate to a scale factor which is difficult to
calculate, and the method requires good BPM gain calibration and
at least 150 turns of good BPM data, as determined by sensitivity
tests with simulated data. After analysis of several sets of measurements,
it was determined that the MIA beta function measurement deviates
by up to 20% from the theoretical model. It is unclear at this time
if this is due to a problem with the BPM data, or if the beta function
in the machine truly varies this much from the model. Further work
in this area will include using MIA to calculate the measured chromaticity
of the beam, and measurement and analysis of BPM data sets with more
than 200 turns.
Modeling Soil Activation Underneath the Alternating
Gradient Synchrotron (AGS) Complex, Building 912, at Brookhaven
National Laboratory. ISADEL EDDY (Mount Allison University, Sackville, NB,
0) DR. KIN YIP (Brookhaven National Laboratory, Upton, NY, 11973)
When high-energy
protons hit a target in Building 912 of the AGS complex at Brookhaven
National Laboratory large numbers of secondary particles are produced.
These secondary particles then bombard all materials around the target
and activate some of it; i. e., some of the atoms become radioactive.
Most of these radioactive atoms quickly decay back to stable atoms;
however, some are induced into the soil and are potentially dispersible.
Tritium, which easily leaches into the soil, and sodium-22, which
leaches relatively slowly, are fairly stable isotopes with half-lives
of 12.43 and 2.60 years respectively, making them the radionuclides
of primary concern for this project. Shielding, made primarily of
steel, concrete, and earth, was built around the targets to contain
the spread of radiation. With the three dimensional geometry of Monte
Carlo N Particle Extended (MCNPX) simulation software, detailed structure
of all matter near the targets was modeled. MCNPX was used to simulate
the particle interactions between the matter surrounding the target,
the proton beams, and the secondary particles in order to evaluate
the amount of radiation flux, or number of neutrons per cm2, present
in the soil underneath Building 912. Three regions of radiation flux
were ultimately identified. The highest amount of radiation was found
to be located near the targets where it reached 1.4x10-4 neutrons
per cm2 per incident proton around Target A and 2.7x10-4 neutrons
per cm2 per incident proton around Target D. The radiation flux was,
however, relatively high all along the beam lines. The radiation
flux also dramatically decreased with soil depth. At five meters
below Targets A and D, the radiation flux was 4x10-7 and 5x10-7 neutrons
per cm2 per incident proton respectively. Radiation flux, along with
the total number of protons that were accelerated, is needed in order
to determine soil activation. This work is part of a project to document
the extent of soil activation underneath Building 912 at Brookhaven
National Laboratory.
Modeling X-ray Imaging with Monte Carlo N-Particle Software. JEREMIAH
RUESCH (California State University Chico, Chico, CA, 95929) DR. TIMOTHY RONEY (Idaho National Laboratory, Idaho
Falls, ID, 83415)
Monte Carlo simulation
uses stochastic (random sampling) processes to solve equations that
are difficult to solve by other means. For radiation transport the
Boltzmann equation may be solved by Monte Carlo methods. Monte Carlo
N-Particle (MCNP), a stochastic approach to solving the Boltzmann
equation is utilized for our study. To ensure accuracy between the
output of MCNP and known analytic results, a simple geometry is created
with a monoenergetic pencil beam source shooting through a homogeneous
material to a single detector element. The simulation was performed
for three material thicknesses. The simulated detector response is
used to derive the x-ray linear attenuation coefficient (LAC) of
the material from Beer’s Law and compared to the known LAC of the
material for the energy of the source. The processed MCNP results
were less than one percent different from the known LAC. To begin
modeling the radiographic imaging process the material was changed
to be spatially varying, the single detector element was replaced
by a linear detector array of six elements, and the source changed
from a pencil beam to a cone-beam configuration. The source was centered
vertically on the linear detector array with the face of the array
perpendicular to the source. The distance between source and detector
is held fixed. The object is defined as a rectangular block of iron
with a rectangular aluminum insert. The object is located so that
its face is perpendicular to the source, a distance of two centimeters
from the detector array, and is then held fixed in this location.
Moving the source and detector array to one end of the object, a
run of MCNP is taken, creating a single vertical line of image data.
The source and detector array are then moved a distance of one detector
width and the simulation is repeated yielding an adjoining detector
line. This process is repeated until the entire object is scanned
and a two-dimensional image is produced. The images produced in this
manner appear to have qualitative spatial and contrast features in
agreement with our intuition. We have demonstrated the potential
for using a stochastic particle transport modeling code (MCNP) to
simulate x-ray imaging and have developed confidence in the numerical
results by comparing derived quantities with known quantities (linear
attenuation coefficients). Comparisons with experimental data are
needed to validate the methods employed. This will be our next step.
Monitoring Displays for GLAST: Building ISOC Status Displays for the Large
Area Telescope Aboard the Gamma Ray Large Area Space Telescope
(GLAST) Observatory. CHRISTINA KETCHUM (Lewis and Clark College, Portland, OR, 97219)
ROB CAMERON (Stanford Linear Accelerator Center, Stanford, CA, 94025)
In September 2007
the Gamma Ray Large Area Space Telescope (GLAST) is scheduled to
launch aboard a Delta II rocket in order to put two high-energy gamma-ray
detectors, the Large Area Telescope (LAT) and the GLAST Burst Monitor
(GBM) into low earth orbit. The Instrument Science Operations Center
(ISOC) at SLAC is responsible for the LAT operations for the duration
of the mission, and will therefore build an operations center including
a monitoring station at SLAC to inform operations staff and visitors
of the status of the LAT instrument and GLAST. This monitoring station
is to include sky maps showing the location of GLAST in its orbit
as well as the LAT’s projected field of view on the sky containing
known gamma-ray sources. The display also requires a world map showing
the locations of GLAST and three Tracking and Data Relay Satellites
(TDRS) relative to the ground, their trail lines, and "footprint" circles
indicating the range of communications for each satellite. The final
display will also include a space view showing the orbiting and pointing
information of GLAST and the TDRS satellites. In order to build the
displays the astronomy programs Xephem, DS9, SatTrack, and STK were
employed to model the position of GLAST and pointing information
of the LAT instrument, and the programming utilities Python and Cron
were used in Unix to obtain updated information from database and
load them into the programs at regular intervals. Through these methods
the indicated displays were created and combined to produce a monitoring
display for the LAT and GLAST.
Nanosecond-length Electron Pulses for a Time-of-Flight Mass Spectrometer. LIANNE MARTINEZ (University of Nevada Las Vegas, Las
Vegas, NV, 89123) HERBERT FUNSTEN AND PAUL JANZEN (Los Alamos National
Laboratory, Los Alamos, NM, 87545)
The Spatially Isochronous
Time-of-Flight (SITOF) mass spectrometer is a rapid mass analysis
of gaseous samples at a high mass resolution in a small volume. The
mass spectrometer incorporates a pulsed electron ionization source
within the drift region itself, eliminating a separate ion source
and its associated mass, power, and volume resources. Gas in the
drift region is ionized at the same time by the pulsed electron source,
and the ions are accelerated by a linear electric field in the drift
region so that their time-of-flight in the drift region is independent
of the location at which they were ionized. The current proof-of-concept
pulsed electron source uses a channel electron multiplier stimulated
by a weak radioactive source to produce electron pulses approximately
10 ns long. These pulses have been characterized, and development
has started on a pulsed electron source which uses a microchannel
plate stack to multiply photoelectrons produced from a fast ultraviolet
LED. This method produces electron pulses of a shorter duration,
over a larger area, at a controllable frequency. We discuss the time
dispersion of the pulsed electron source, its dependence on detector
bias and gain, and its impact on the mass resolution of the SITOFS
mass spectrometer.
Noise Performance of Next-Generation Electronics for the SuperCDMS 25kg Experiment. PETER BROOKS (Stanford University, Stanford, CA, 94305) FRITZ DEJONGH (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
The Cryogenic Dark
Matter Search (CDMS) is a direct detection experiment looking for
signatures of elastic scattering between dark matter and atomic nuclei
in high purity, cryogenic silicon and germanium crystals. In order
to discover rare dark matter events against an overwhelming background
of natural radioactive decay processes, the experiment relies on
high-precision measurements of ionization and phonon signals from
these interactions. To increase the sensitivity of the detector,
it will be necessary to scale the size of the experiment beyond the
current 5.85 kg of detector mass. In order to scale the necessary
electronics to the 25kg scale for the proposed SuperCDMS experiment,
a prototype electronics board has been developed, which condenses
all of the current electronics system onto a single circuit board
by digitizing the signal as soon as possible and analyzing offline
in software. Statistical and Fourier analysis have been performed
on the prototype board, both without signals and with test signals
mimicking the actual detector signal, in a number of operating modes
for the board. These analyses show that the noise performance of
the prototype board is comparable to that of the current system,
and it is believed that with further refinement the noise could be
improved to offer better precision than the current CDMS electronics.
This development is an important step in demonstrating the feasibility
of a 25kg SuperCDMS experiment.
Novel Coarsening of Pb Nanostructures on Si(111) 7 X 7. CHARLES
PYE (University of Kansas, Lawrence, KS, 66044) MICHAEL TRINGIDES (Ames Laboratory, Ames, IA, 50011)
This work investigated
the feasibility of using electron back scattered diffraction (EBSD)
to associate, or differentiate, metal fracture fragments. The objective
of this work was to determine an empirical basis for the hypothesis
that a minimum sequence of grains can be used to identify a metal
fracture line beyond a reasonable doubt. Crystallographic misorientations
between individual grains were determined using EBSD along several
lines (point-to-origin vectors) of metal crystals within the microstructure
of a 304 stainless steel. From a given starting crystal, a grid of
vectors was used to do relative referencing comparison of the grain
orientation profiles along each vector. A radial grid was used with
5° spacing between vectors at a radius of 11.5 times the average
grain diameter. Misorientation angle between grains was calculated
by averaging the misorientation angles within a single grain and
referencing this average misorientation angle back to the origin
grain. The average vector matched 2.6±2 grains with adjacent vectors
out of 16.9±7 grains characterized per vector. In point by point
matching, vectors placed 5° apart had 83±11% of data points match
in the first 2.5 grains away from the origin, with that falling to
36±10% in the last 2.5 grains characterized in the vector. The extent
of point to point matching confirms that this method can properly
identify when similar or dissimilar profiles are being compared.
This leads to the conclusion that a relatively low number of grains
need to be analyzed to uniquely characterize a fracture line by relative
crystallographic orientations. It also opens the possibility to a
more extensive statistical review of concepts and data.
Numerical Simulations of Electric and Magnetic Fields for the Pulse Line Ion
Accelerator. SAMUEL PEREZ (Contra Costa College, San Pablo, CA, 94806)
ENRIQUE HENESTROZA (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
The Pulse Line
Ion Accelerator (PLIA) is a (slow-wave) helical structure whose purpose
is to accelerate charged particles. It uses a voltage pulse to generate
a traveling electric field along its length. In order to efficiently
produce a working PLIA and know how to use it, a simulation of the
PLIA was created and the electric and magnetic fields it produces
were plotted using the Electromagnetic Field Solver “CST Microwave
Studio”. In addition to the plots offered by Microwave Studio, more
specialized plots were created using the particle code WARP. The
geometry is simple: a helix embedded in dielectric material inside
a conducting box with a cylindrical vacuum through its center. The
voltage pulse is applied on a loop around one end of the helix, thus
coupling inductively to the helix. A coarse mesh was used at first
so that adjustments could be made quickly. Once the simulation correctly
produces a traveling wave, the helix was changed to its final dimensions
and a finer mesh was used to generate sufficient data. The plots
created by CST Microwave Studio show that the electric field travels
the length of the PLIA at about 1/60 the speed of light, the expected
value given the permittivity of the dielectric material, the helix
dimensions, and the beam pipe radius. The field does not begin to
move until after the voltage pulse ended. There are actually two
fields, a positive and a negative field, which move with the negative
field ahead of the positive field. The field is also defocusing in
the transverse direction so that positive charges will be sent outward
into the walls of the PLIA. In order to successfully use the PLIA,
the beam will have to enter the structure so that it only interacts
with the positive field. It is also necessary to have powerful solenoids
around the PLIA to focus the beam. Continued work on the PLIA could
prove it as an inexpensive slow-wave accelerator for use in Fusion
research.
Nucleation Properties of Materials Deposited onto Carbon Nanotubes at Low Temperatures. DAMION CAMPBELL & LIONEL COHEN (The City College of New York, New York, NY, 10031) MYRON STRONGIN (Brookhaven National Laboratory, Upton, NY, 11973)
Nano-science is
recognized as the new emerging field for the 21th century. In order
to reliably manufacture nano-sized devices, the electronic properties
of low dimensional materials, which maybe drastically different from
their bulk values, need to be understood. Carbon nanotubes (CNTs)
are fascinating one-dimensional objects: they can be insulating,
metallic or even superconducting depending on the chirality. They
have also been found to be ideal templates to engineer one-dimensional
nano-wires. In this work, thin gold films have been deposited onto
CNTs coated with amorphous Ge in ultra-high vacuum at low temperatures.
The morphology of the Au films under different annealing procedures
is examined using high-resolution TEM (transmission electron microscopy).
Under suitable conditions, Au nano-clusters are seen to form percolated
continuous structures on CNTs, making them effectively one-dimensional
nano-wires. Preliminary transport and optical studies have been carried
out on arrays of CNTs and CNTs coated with Au. Different behaviors
of CNTs arrays have been observed with and without Au coating, providing
a method to alter their electronic properties. This work is a small
portion of a much larger project aimed at understanding the charge
dynamics in low dimensional systems and CNTs-based nano-composite
materials. This research and education project is an ongoing collaboration
between the City College of New York and Brookhaven National Laboratory
(BNL) and will continue much beyond the 10-week period of the joint
DOE/NSF FaST (Faculty and Student Team) summer program. The City
College students involved will have an opportunity to work at the
nation’s premier large-scale facilities, such as the National Synchrotron
Light Source and the Center for Functional Nano-materials at BNL.
Optical and Mechanical Design Features of the Qweak
Main Detector. ELLIOTT JOHNSON (North Dakota State University, Fargo, ND, 58105)
DAVE MACK (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
Cerenkov radiation
is emitted when charged particles exceed the local speed of light
within a transparent medium. In experimental particle physics, this
radiation can be used to detect high-energy particles. The Cerenkov
radiation detector being used in the Qweak experiment at Thomas Jefferson
National Accelerator Facility (Jefferson Lab) has unique design features
compared with previous detectors, imposing more specific requirements
on the detector’s radiator components. The new design includes a
glue joint in the beam pathway, and side-mounting Photomultiplier
Tubes (PMT’s) instead of the traditional end-on layout, a change
that allows increased detector mobility during beam operation. The
system implements aluminum trays to support the glue joints and terminal
cap pieces that hold the ends of the quartz bars. Ultra-pure artificial
quartz (Spectrosil 2000) bars with a large resistance to radiation
damage are needed for a high transmission of UV photons. Dimensional
and optical specifications of these bars were assessed with the use
of a Coordinate Measuring Machine (CMM) and a traveling microscope.
Presented here is a synopsis of the high-precision measurements performed
on the radiator bars, as well as a summary of the R&D conducted
to develop a usable detector integrating the new design features.
The quality assurance procedures developed will be essential for
future detector projects involving quartz detectors.
Optimization of Shield Mass for a Low Power, Fast-Spectrum Liquid-Metal Cooled
Surface Reactor System. ROBERT FORESMAN (Pomona College, Claremont, CA, 91711)
DAVID I. POSTON (Los Alamos National Laboratory, Los Alamos, NM, 87545)
Extending our presence
farther into space furnishes opportunities for research science,
potential human colonization beyond Earth, and a more mature understanding
of the cosmos. One of the foremost challenges in this effort is the
identification of a low-cost power source that will accommodate scientific
instrumentation and mission necessities for long periods of time.
Low power nuclear reactors that utilize well-tested materials and
concepts such as stainless steel and water shields can operate in
the 25 kW electrical range. By short-circuiting exotic designs, these
reactors reduce the cost and time of development in the face of a
strict US budget. Gamma radiation dose to the Stirling alternator
power conversion system and total astronaut dose can be kept to their
nominal minimums of 20 MRad and 5 Rem/yr by burying the reactor in
lunar surface material (regolith) on Moon missions.1 An alternative option is to install a permanent water shield
on the reactor. Minimization of additional shield mass for such a
system is an interesting engineering problem that is ideally suited
to a radiation transport software program called MCNPX (Monte Carlo
Neutral Particle). MCNPX output files contain criticality statistics
to ensure a stable reaction and allow direct determination of dosages.
Shield thickness, placement of interstitial, high-Z shield elements,
and boron concentration in shield water will be treated as variables
for system optimization. Initial simulations show that roughly 93%
of the gamma dose to astronauts at 800 meters from the reactor core
is due to radiative capture in the water shield. A borated water
shield that meets astronaut dosage requirements and has a total mass
of roughly 5,000 kg can be constructed utilizing interstitial stainless-steel
layers of varied thickness. This total shield mass of 5000 kg must
be compared to the total mass of a buried system configuration including
burying equipment. Further investigations include the addition of
different shielding materials such as depleted uranium throughout
the shield as well as moving the reactor core off-center within the
water shield. 1Marcille,
T. F., Dixon, D. D., Fischer, G. A., Doherty, S. P., Poston, D. I.,
and Kapernick, R. J. Design Of a Low Power, Fast-Spectrum, Liquid-Metal
Cooled Surface Reactor System. Nuclear Systems Design Group, Los
Alamos National Laboratory, Los Alamos, NM 87544., pp 1-3.
Particle Physics in the High School Classroom. CANDICE HUMPHERYS (Brigham Young University - Idaho, Rexburg, ID, 83460) HELIO TAKAI (Brookhaven National Laboratory, Upton, NY, 11973)
The main goal of
the Mixed Apparatus for Radar Investigation of Atmospheric Cosmic
rays of High Ionization (MARIACHI) project is to explore the detection
of ultra high energy cosmic rays via radio signals. To confirm that
the data received using radio is legitimate, scintillator detectors
(a known way to detect cosmic rays) have also been set up to collect
data and have been placed in high school classrooms on Long Island.
MARIACHI is involving students as participants in the project and
faces two main problems: (a) the world of modern physics is absent
from the high school physics curriculum and (b) techniques for data
analysis need to be introduced. To bridge the gap between a cosmic
ray shower being recorded by the scintillator setup and the actual
physics phenomena, we have developed two low-cost experiments. First,
the existence of atoms can be shown by the phenomenon of Brownian
motion (particles in a fluid move randomly). Software was tried out
successfully to test the practicality of tracking a particular particle
to plot its position and show its randomness. The second experimental
apparatus is a novel cloud chamber with a strong magnetic field.
With this cloud chamber in the classroom, tracks from comic ray particles
(as well as particles from other sources of radiation) can be visualized
and students can get a grasp on what the scintillators are detecting.
This particular cloud chamber exposes students to a wide range of
modern physics from the existence of elementary particles to the
relation between energy and matter through electron-positron production
events. To introduce the first steps of data analysis, tutorials
were developed to allow students and teachers alike to analyze the
scintillator data to look for any possible problems with the detectors
or interesting correlations with external parameters such as barometric
pressure. The tutorials were tested by two high school students and
their feedback was used to improve them.
Phase Separation Between Perpendicular and Parallel Ferromagnetic Ordering
in a Quantum Well Model of Ga1-xMnxAs. ALEX BRANDT
(Minnesota State University Moorhead, Moorhead, MN, 56563) RANDY FISHMAN (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Dilute-magnetic
semiconductors (DMS) are promising materials for spintronic applications
(electronics that take advantage of spin to carry information). Ga1-xMnxAs
is the most commonly studied DMS system. The direction of the ferromagnetic
ordering in a quantum well model of Ga1-xMnxAs with doping x is determined. The magnetic order is perpendicular
to the plane for low carrier densities, n < n1,
and becomes parallel within the plane for higher carrier densities,
n > n2.
However, it is not known if phase separation occurs between regions
having carrier density n1 and
moments pointing perpendicular to the plane, and others having n2 > n1 and moments within the plane. The first two wave functions of
the carriers in the quantum well are used in calculating the energy
of the system as a function of angle and filling. The energy is then
minimized with respect to angle, and the chemical potential is calculated.
Phase separation occurs in the system if the chemical potential at
two different fillings is the same. A Maxwell construction indicates
phase separation occurs between n1 =
3.1% and n2 =
5.3% for x = 0.35. The complete phase diagram for this system is
calculated. Phase separation of the ferromagnetic phases in a quantum
well may imply that some regions are magnetically ordered up to higher
temperatures. This might allow the design of spintronic devices that
can operate at room temperature.
Programmatic Analysis of the FPD++ "Large" Cell
Module. JONATHAN LANGDON (Stony Brook University, Stony Brook, NY, 11794) LESLIE BLAND (Brookhaven National Laboratory, Upton, NY, 11973)
The Forward Pion
Detector second edition (FPD++) at Brookhaven National Laboratory’s
STAR Experiment is composed of lead glass cells. These cells detect
photons which are produced in high energy collisions of gold nuclei
or protons. In the calorimeter, there are two distinct types of cells.
The first type is referred to as the "small cells" and
the second type is known as the "Large Cells." The smaller
cells are preferable due to the higher spatial granularity that can
be achieved. In the previous version of the Forward Pion Detector
(FPD), the small cells were the only types that were used. However,
in order to improve the spatial coverage of the calorimeter in the
future Forward Meson Spectrometer (FMS), large cells must be used.
To assist in the characterization of the large cells, I have written
analysis routines to assure the quality of the calibration and the
future analysis of the large cells. The ultimate goal is to create
a robust, quantitative comparison of the cluster properties of the
two cell types. Theoretically, it is possible to show correlations
between the transverse size of showers formed by photons impacting
the calorimeter in either the small cell module or the large cell
module. Awaiting calibration, it is possible to characterize some
of the properties of clusters formed in the large cells. To accomplish
this, I wrote a Physics Analysis Workstation (PAW) script along with
a FORTRAN program to analyze raw data from the FPD++. I found evidence
of cross module pion decay. This reassures that once the calibration
of the large cells is completed, it should be possible to draw comparisons
between the two cell types and eventually allow for thorough cross
type reconstructions.
Properties of Light Vector mesons in Dense Nuclei. SCARLET NORBERG (Kent State University, Kent,
OH, 44243) DENNIS WEYGAND (Thomas Jefferson National Accelerator
Facility, Newport News, VA, 23606)
The strong force
is a fundamental force, which describes the forces in the nucleus,
and is expressed by Quantum Chromodynamics (QCD). In dense and hot
matter, masses may change while the underlying symmetries remain
intact. In addition, coupling constants may change. Thus properties
of vector mesons, such as their masses and widths, may change in
dense or hot matter. These modifications are related to the partial
restoration of chiral symmetry at high density and/or temperature.
The g7 experiment was performed using the Large Acceptance Spectrometer
(CLAS) at Jefferson Lab using a tagged photon beam of energies up
to 4 GeV on various nuclear targets. Because the photon can penetrate
the nuclear volume, the interaction occurs approximately uniformly
throughout the nuclear medium. The properties of the lightest vector
mesons, rho, omega, and phi are investigated through their rare leptonic
decay to e+e-. This decay channel is preferred over hadronic modes
in order to eliminate the final state interactions of the decay products
in the nuclear matter. The goal of this study is to examine any changes
in the mass and/or width of rho, omega and phi produced in the nuclear
medium. In this study, the mass and width of the rho meson have been
measured in both a light nuclear target, deuterium, an intermediate
target, carbon, and a heavy target, iron. The spectral function of
the rho meson was compared to the correct resonance form, a Breit-Wigner
function modified by an electromagnetic propagator (1/m3) required
by the e+e- decay. It was found that the mass and width of the rho
meson does not change in carbon nor deuterium. In iron, while the
mass of the meson is stable, there is an indication that the width
changes by about 2 sigma, consistent with collisional broadening
effects. Implications of the results of g7 will have a major impact
on the interpretation of experiments of the low mass e+e- pairs currently
being performed in high-energy heavy ion collisions at the Relativistic
Heavy Ion Collider (RHIC) at Brookhaven.
Quark Propagation and Hadronization in the Nuclear Medium. GRANT
LARSEN (University of Chicago, Chicago, IL, 60637) KAWTAR HAFIDI (Argonne National Laboratory, Argonne, IL, 60439)
Hadrons are color
neutral combinations of quarks. The theory of the strong, or color,
force is not yet entirely clear on how quarks break free of gluons
(the particles that hold hadrons together), and form new hadrons,
a process known as hadronization. Because of confinement, an exotic
effect of the strong force, no color charged particle (such as a
quark) can exist in solitude. Therefore, to measure such particles,
an indirect process is required. Firing electrons at targets in the
right energy range can strike a quark hard enough to make this process
of hadronization occur, but slowly enough that this process occurs
within the small space of the target’s nucleus. This was done with
a 5.014 GeV beam in Thomas Jefferson National Accelerator Facility
in Newport News, Virginia, on targets of deuterium, carbon, iron,
and lead. The number of pions emitted from the heavier target compared
to the number emitted from deuterium (normalized by the total number
of events recorded in each case) was measured for the carbon, iron,
and lead targets. This multiplicity ratio was compared between the
different atoms and for pions that had different energies available,
took different fractions of that energy, and that lost different
amounts of that energy to gluon radiation. Also measured were quantities
directly related to the energy loss of quarks propagating in the
nuclear medium and the distance they do so before becoming hadrons.
Using these data, relationships between the momentum and energy the
electron imparts to the quark, the energy lost radiating gluons,
the distance the quark goes before hadronizing, the fraction of the
energy available that the hadron ends up with, and the likelihood
that the nucleus reabsorbs the hadron can all be inferred. These
results confirm the expectations of theorists as well as back up
the results of related experiments, expanding the results to different
kinematical ranges. These data also give theorists more information
to work with to understand these processes. Still more interesting
kinematical ranges, details of the effects of nuclear size, and the
dependence of these processes on the flavor of the struck quark,
are all yet to be investigated. All of these goals can be met using
the forthcoming 11 GeV upgrade to Jefferson Lab.
Radioactive Ion Beam Production from a Thorium Oxide Target. DAVID
BUNCE (University of North Texas, Denton, TX, 76203) H. K. CARTER
(Oak Ridge National Laboratory, Oak Ridge, TN, 37831)
Radioactive Ion
Beams (RIB) are crucial for nuclear astrophysics and nuclear structure
studies. Such beams can be produced at the Holifield Radioactive
Ion Beam Facility at ORNL. Previously, Uranium Carbide was used as
a target to create RIB. It is expected that a Thorium Oxide (ThO2) target has a higher yield for isotopes with an atomic mass
between 80 and 90 than Uranium Carbide target. Previously, an 8 g/cm3 target
was used to create the RIB, but the yields were much lower than expected.
A 0.8 g/cm3 target
might produce better isotope yields than an 8 g/cm3 target. However, a 0.8 g/cm3 target is not dense enough to stop a 40 MeV proton beam in the
current setup. The goal of this project is to correct for a fully
stopped beam in the low-density target and to compare isotope yields
between the high and low-density targets. To correct for a fully
stopped beam, the isotope yields are measured for two different proton
energies; 30 MeV and 40 MeV. From this comparison, estimation for
a fully stopped beam can be made. For the measurement of the RIB
isotope yield, individual masses can be separated from the RIB using
an online mass separator. The RIB is collected onto a tape, which
switches from the collection position to a measurement position very
rapidly. The beam composition is analyzed by gamma ray spectroscopy
using a germanium detector and peak-fitting software. This project
has shown that the isotope yields for the 30 MeV beam and the 40
MeV beam are very similar within the studied isotopes. Also, the
low density ThO2 target
had a much better yield of isotopes than the high density target.
However, the isotope yield is still much lower than that of Uranium
Carbide. It is clear that the physical properties of a ThO2 target affect the yields of isotopes. However, it is not know
why the isotope yields for ThO2 are still not high enough to compete against a Uranium Carbide
target for atomic masses 80-90. Further study is required to continue
to increase the total yield of isotopes with an atomic mass of 80
through 90 to surpass Uranium Carbide.
RF TE011 Cavity Prototyping and Characterization for
Surface Science Studies. JARED
NANCE (Beloit College, Beloit, WI, 53511)
HAIPENG WANG (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
Understanding the
properties of superconducting materials is crucial to the future
development of accelerating structures. According to BCS theory,
superconductors possess a very small surface impedance at RF frequencies.
For superconducting particle accelerators operating at RF frequencies
such as the Continuous Electron Beam Accelerator Facility (CEBAF),
this means that there is some mechanism by which the energy stored
in the RF fields can be dissipated, and the accelerator's performance
degraded. The SRF (Superconducting RF) group at Thomas Jefferson
National Accelerator Facility has developed a cavity which will be
used for testing the surface impedance of flat superconducting samples.
The cavity is optimized for operation at superconducting temperatures
of 2K. The intent of the design is to store energy in the form of
a dominant TE011 mode
resonance at 7.5GHz. The TE011 mode is well suited for surface science studies because of its
inherently high ratio of power stored to power dissipated (the Quality
(Q) factor), as well as its simple and well understood cylindrical
symmetry. The complex geometry of the cavity itself is not, however,
exclusive to the TE011 mode;
a large number of resonances are permitted, all with varying characteristics
and symmetries. Without conclusive knowledge of which resonant mode
the samples are exposed to, the field at the surface of the sample
cannot be known exactly. Therefore, correct identification and characterization
of the TE011 mode
is critical for the experiment. Vector Network Analysis techniques
were used to characterize the fields by monitoring the response of
the Scattering (S) Parameters to perturbations of the cavity geometry.
The S-Parameters of a network (the cavity) are a measure of the reflectance
and transmittance of that network. Resonance conditions in the cavity
can therefore be detected by interpreting peaks in the S-Parameter
spectra as stored or dissipated energy in the cavity. The results
of the analysis indicate that the TE011 mode
is in fact the dominant main cavity mode at 7.5GHz, in agreement
with theory.
Sensitivity Study of the Relative Fraction of top/anti-top events Produced
via Gluon-fusion. KELLY GREENLAND (Lock Haven University of Pennsylvania, Lock Haven, PA, 17745) DR. RICARDO EUSEBI (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
In high-energy
experimental particle physics, a primary goal is to study particles
that the scientists create, and by studying those particles physicists
results aid in confirming the validity of the standard model of particles.
To date, the standard model is the best representative model of basic
particles, and confirming the model helps to reassure physicists
the model is indeed on the right path. At the Fermi National Accelerator
Laboratory a circular particle accelerator, called the Tevatron,
accelerates protons and anti-protons to approximately 0.999 times
the speed of light before colliding with each other. The proton's
constituents, gluons and quarks, may interact with enough energy
to create particles not initially present. If a quark and anti-quark
interact they will annihilate and may produce a top/anti-top quark
pair. Also, a gluon may fuse with another gluon to produce a top/anti-top
pair. This study focuses on finding the accuracy with which scientists
can measure the ratio of top/anti-top pairs created by quark/anti-quark
annihilation to that created by gluon-fusion. The degree of accuracy
of measuring the relative fractions was determined via computer simulation.
Initially gluon-fusion and quark-annihilation top/anti-top events
were generated by Monte-Carlo simulations. Next, matrix element probabilities
were determined for each event. Using these probabilities, a set
of templates were created. Finally, in preparation to analyze the
data, a likelihood was constructed based on the templates. The likelihood
was never run on data, but only on Monte-Carlo simulations to obtain
the degree of accuracy, or sensitivity, that this method can provide.
Past studies claim an accuracy measurement of 22%. This study shows
a strong improvement of the ratio to approximately 15%. While this
is clearly an improvement, the expected degree of accuracy cannot
yet ensure that the ratios predicted by the standard model, regarding
production top/anti-top events, are indeed correct.
Simulation of a Very Long Baseline Neutrino Beam. JORDAN HEIM (Purdue University, West
Lafayette, IN, 47906) MARY BISHAI (Brookhaven National Laboratory, Upton, NY, 11973)
Observations
indicating that the number of solar neutrinos incident upon Earth
is fewer than predicted by the Standard Solar Model have led to
the theory that the neutrinos are experiencing a phenomenon known
as oscillation, where one flavor of neutrino becomes another. The
confirmation of this theory is crucial to understanding the behavior
of neutrinos. By employing a man-made neutrino beam, the energies
and types of neutrinos can be carefully controlled and the expected
numbers of neutrinos, taking into account oscillation, thus known.
Computer simulations of the particle interactions throughout the
beamline's many components were carried out with various pieces
of software including MARS, GEANT, and Fluka05. This data was then
analyzed using packages such as GloBeS, and ROOT to create histograms
of the physical phenomena. Repeating these exercises, while varying
simulation parameters such as target properties, beam energy, and
the length of the decay pipe, allowed the optimal characteristics
to be found. With a predetermined far-detector distance of 1300Km,
it was found that as the target length and density is increased,
more particle interactions can be observed, as expected. Also,
using a beam energy of forty to sixty GeV and using a shorter,
but wider decay tunnel provides the best balance between reducing
the unwanted high energy contribution while maintaining a reasonable
flux rate at the far detector. These results provide guidelines
for building a successful project which will yield an answer for
the value of the mixing parameter which dictates the oscillating
behavior of the particles and will reveal CP (charge parity) violation.
Simulation of Radioactive Ions for the Tevatron. JOSEPH
BOUIE III (Southern University, Baton Rouge, LA, 70813)
TERRENCE REESE (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
To generate a
very pure and intense neutrino beam for Neutrino Physics experiments,
it has been proposed to use the beta-decay of radioactive ions
stored in a high energy decay ring. The original proposal was to
use parts of the existing CERN infrastructure, namely the Proton
Synchrotron (PS) and the Super Proton Synchrotron (SPS), to accelerate
the ions to 100GeV, but recent work has shown that it would be
advantageous to go to even higher energies. The Tevatron, located
at Fermi National Accelerated Laboratory, will be retired from
Collider Physics in a few years, and could be used for this purpose.
However, the decay products from the ions will present a significant
heat load to the superconducting magnets, which will limit the
number of ions that can be accelerated. To understand where the
limit is, a simulation of heat deposition from the decay products
is needed.
Simulation of the BaBar Drift Chamber. RACHEL
ANDERSON (University of Wisconsin - Eau Claire, Eau Claire, WI,
54701) JOCHEN DINGFELDER (Stanford Linear Accelerator Center, Stanford,
CA, 94025)
The BaBar drift
chamber (DCH) is used to measure the properties of charged particles
created from e+ e- collisions
in the PEP-II asymmetric-energy storage rings by making precise
measurements of position, momentum and ionization energy loss (dE/dx). In October of 2005, the PEP-II storage rings operated with
a luminosity of 10x1033 cm-2 s-1; the goal for 2007 is a luminosity of 20x1033 cm-2s-1,
which will increase the readout dead time, causing uncertainty
in drift chamber measurements to become more significant in physics
results. The research described in this paper aims to reduce position
and dE/dx uncertainties by improving our understanding of the BaBar drift
chamber performance. A simulation program --- called GARFIELD---
is used to model the behavior of the drift chamber with adjustable
parameters such as gas mixture, wire diameter, voltage, and magnetic
field. By exploring the simulation options offered in GARFIELD,
we successfully produced a simulation model of the BaBar drift
chamber. We compared the time-to-distance calibration from BaBar
to that calculated by GARFIELD to validate our model as well as
check for discrepancies between the simulated and calibrated time-to-distance
functions, and found that for a 0° entrance angle there is a very
good match between calibrations, but at an entrance angle of 90° the
calibration breaks down. Using this model, we also systematically
varied the gas mixture to find one that would optimize chamber
operation, which showed that the gas mixture of 80:20 Helium:isobutane
is a good operating point, though more calculations need to be
done to confirm that it is the optimal mixture.
Simulations of the ILC Electron Gun and Electron Bunching System. CHRISTIAN HAAKONSEN (McGill University, Montreal,
QC, 0) AXEL BRACHMANN (Stanford Linear Accelerator Center, Stanford,
CA, 94025)
The International
Linear Collider (ILC) is a proposed electron-positron collider,
expected to provide insight into important questions in particle
physics. A part of the global R&D effort for the ILC is the
design of its electron gun and electron bunching system. The present
design of the bunching system has two sub-harmonic bunchers, one
operating at 108 MHz and one at 433MHz, and two 5-cell 1.3 GHz
(L-band) bunchers. This bunching system has previously been simulated
using the Phase and Radial Motion in Electron Linear Accelerators
(PARMELA) software, and those simulations indicated that the design
provides sufficient bunching and acceleration. Due to the complicated
dynamics governing the electrons in the bunching system we decided
to verify and expand the PARMELA results using the more recent
and independent simulation software General Particle Tracer (GPT).
GPT tracks the motion and interactions of a set of macro particles,
each of which represent a number of electrons, and provides a variety
of analysis capabilities. To provide initial conditions for the
macro particles, a method was developed for deriving the initial
conditions from detailed simulations of particle trajectories in
the electron gun. These simulations were performed using the Egun
software. For realistic simulation of the L-band bunching cavities,
their electric and magnetic fields were calculated using the Superfish
software and imported into GPT. The GPT simulations arrived at
similar results to the PARMELA simulations for sub-harmonic bunching.
However, using GPT it was impossible to achieve an efficient bunching
performance of the first L-band bunching cavity. To correct this,
the first L-band buncher cell was decoupled from the remaining
4 cells and driven as an independent cavity. Using this modification
we attained results similar to the PARMELA simulations. Although
the modified bunching system design performed as required, the
modifications are technically challenging to implement. Further
work is needed to optimize the L-Band buncher design.
Single and Double GEM X-Ray based Detectors. ERIC HUEY
(Southern University A&M, Baton Rouge, LA, 70811)
DR. DAVID PETER SIDDONS (Brookhaven National Laboratory, Upton, NY, 11973)
The purpose of
this research is to present results obtained from testing of a
single and double GEM X-ray gaseous detectors. The detectors have
been designed, assembled, and tested at NSLS controls and detector’s
group at BNL. The single and the double GEM detectors are intended
to provide a noise and discharge free amplification to be used
for Extended X-ray Absorption Fine Structure (EXAFS) procedure.
A voltage of 450 volts across the single GEM provided a maximum
gain of 900. A voltage of 350 volts across each of the double GEM
provided a gain of 9000 without stressing the GEM and creating
the possibility of discharges.
Software for The Perfect PID. KURTIS
GEERLINGS (Michigan State University, East Lansing, MI, 48825)
HOLGER MEYER (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
The Main Injector
Particle Production Experiment (MIPP, FNAL E-907) promises to
shed light on many aspects of the particle physics world, from
proton radiography to nuclear physics and from neutrino flux
measurements to non-perturbative QCD. MIPP uses several detectors
in order to obtain nearly 100 percent acceptance for charged
particles over a vast momentum range, yielding nearly perfect
particle identification. The detectors include two beam cerenkovs,
a time projection chamber (TPC), a threshold cerenkov, a ring
imaging cerenkov (RICH), a time-of-flight system and an electromagnetic/hadronic
calorimeter. While the detectors are very important, without
software to analyze the data, no physics can be discovered. The
MIPP software, written mainly in C++, includes packages to reconstruct
tracks of charged particles in the TPC and packages to fit rings
to the cerenkov radiation in the RICH. Equally important is the
monte carlo package, which allows one to compare simulations
with data. To most effectively test the analysis software with
the simulation, the monte carlo must output its data in the same
format as the experimental data. This process is often called
digitization. In the case of the threshold cerenkov, it represents
converting exact timing information from the simulation into
a time to digital converter (TDC) signal, and the number of photoelectrons
detected into an analog to digital converter (ADC) signal. This
way, the monte carlo information resembles the data coming from
detectors. Another important aspect to consider is testing and
debugging of existing code. Since many people have contributed
to the MIPP software, it is important to debug and test code
written by other people. This helps to ensure that the software
does what it is supposed to, and results are not based on false
analysis.
Speeding up the Raster Scanning Methods used in the X-Ray Fluorescence Imaging
of the. MANISHA TURNER (Norfolk State University, Norfolk, VA, 23504)
UWE BERGMANN (Stanford Linear Accelerator Center, Stanford, CA, 94025)
Progress has
been made at the Stanford Linear Accelerator Center (SLAC) toward
deciphering the remaining 10-20% of ancient Greek text contained
in the Archimedes palimpsest. The text is known to contain valuable
works by the mathematician, including the Method of Mechanical
Theorems, the Equilibrium of Planes, On Floating Bodies, and
several diagrams as well. The only surviving copy of the text
was recycled into a prayer book in the Middle Ages. The ink used
to write on the goat skin parchment is partly composed of iron,
which is visible by x-ray radiation. To image the palimpsest
pages, the parchment is framed and placed in a stage that moves
according to the raster method. When an x-ray beam strikes the
parchment, the iron in the ink is detected by a germanium detector.
The resulting signal is converted to a gray-scale image on the
imaging program, Rasplot. It is extremely important that each
line of data is perfectly aligned with the line that came before
it because the image is scanned in two directions. The objectives
of this experiment were to determine the best parameters for
producing well-aligned images and to reduce the scanning time.
Imaging half a page of parchment during previous beam time for
this project was achieved in thirty hours. Equations were produced
to evaluate count time, shutter time, and the number of pixels
in this experiment. On Beamline 6-2 at the Stanford Synchrotron
Radiation Laboratory (SSRL), actual scanning time was reduced
by one fourth. The remaining pages were successfully imaged and
sent to ancient Greek experts for translation.
Star Formation and Feedback in Adaptive Mesh Refinement
Cosmological Simulations. SAM
SKILLMAN (Harvey Mudd College, Claremont, CA, 91711) BRIAN O'SHEA (Los Alamos National Laboratory, Los
Alamos, NM, 87545)
Correctly simulating
star formation within large-scale cosmological simulations is
currently a problem of great interest. This is in part due to
the recent explosion of observational data from projects such
as the Sloan Digital Sky Survey, DEEP, and 2dF. Using ENZO, an
adaptive mesh refinement(AMR) with N-body plus hydrodynamics
cosmological code, I explore three star formation algorithms
which lead to a range of star formation histories. Stellar feedback
models are coupled to each of the star formation algorithms,
and provide thermal, kinetic, and metal feedback in our simulations.
Each star formation algorithm uses several parameters which I
vary in order to gain an understanding of their effect on the
star formation history of the universe.
Structural and Functional Studies of Multidrug Binding Protein, AcrR. DENAE CLAMPITT (Western Illinois University, Macomb, IL, 61455)
EDWARD YU (Ames Laboratory, Ames, IA, 50011)
This project
addresses fundamental questions regarding the nature of multi-ligand
recognition in transcriptional regulators. The primary target
is the Escherichia coli AcrR
repressor that regulates the multidrug transporter AcrB. The
215-residue AcrR consists of two domains, the C-terminal multi-ligand
binding and the N-terminal DNA binding domains. Upon binding
a wide variety of structurally diverse ligands in the C-terminal
region, it triggers conformational change at the N-terminal domain,
prohibiting the binding of AcrR to its target DNA. The sum result
is the over-expression of the AcrB transporter, which, in turn,
promotes efflux from the cell, thus protecting it from toxic
substances. How can AcrR and other transcriptional repressors
recognize a variety of toxic chemicals? To gain insight into
the mechanism that AcrR uses to recognize multi-ligand, we crystallized
the AcrR protein, and studied its function using circular dichroism
and tryptophan fluorescence measurements. We also measured the
binding affinities of rhodamine-6G, ciprofloxacin, and ethidium
bromide with AcrR. As AcrR is capable of recognizing a variety
of toxic chemicals, this research has the potential to contribute
to the development of protein-based chemical sensors.
Study of the Effect on Larger Wire Diameter on Drift
Chamber Performa. NATALIE HANSEN (Brigham Young University, Provo, UT, 84606) MAC MESTAYER (Thomas Jefferson National Accelerator
Facility, Newport News, VA, 23606)
A wire chamber
is essentially a gas-filled box traversed by anode (sense) and
cathode (field) wires held at a high electric potential difference
that is used to detect charged particles. Electrons are freed
as a particle ionizes gas atoms in its path. These electrons
travel along field lines and register as a current when reaching
the sense wires. The distance between wires, the gas composition
and the voltage difference between wires all determine the detection
efficiency. The drift chambers for the Continuous Electron Beam
Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS)
detector at Jefferson Lab use a 90% argon and 10% CO2 gas
mixture and sense wires of 20 µm diameter. Proposed changes for
a planned upgrade include increasing the sense wire diameter
to 30 µm, which, however, may lead to increased levels of noise.
This project focused on assembling a prototype chamber to test
the effect of changing the sense wire diameter. A previously
built chamber was restrung with 30 µm wire, leaving one 20 µm
wire for comparison. The associated electronic equipment and
gas system were set up and the chamber is operational. The experimental
results were plots of count rate versus voltage for different
discriminator settings. Individual plots show a hint of a high
voltage plateau around 1500 - 1525 V, despite the fact that much
of the data were inconsistent, presumably due to bursts of external,
electronic noise. When the hit rate was plotted versus gas gain
rather than voltage, the individual graphs for different discriminator
settings came very close to a universal curve. Any slight deviations
from that curve may be due to the increased probability of spontaneous
electron emission (noise) from the field wire. Increasing the
sense wire radius and the voltage seems to yield only a modest
increase of noise levels.
Suitability of a New Calorimeter for Identifying Exotic Meson Candidates. CRAIG
BOOKWALTER (Florida State University, Tallahassee, FL, 32306) PAUL EUGENIO (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)
Exotic mesons,
particles that have quantum numbers that are inaccessible to
conventional quark-model mesons, are predicted by quantum chromodynamics
(QCD), but past experiments seeking to identify exotic candidates
have produced controversial results. The HyCLAS experiment (E04005)
at Thomas Jefferson National Accelerator Facility (TJNAF) proposes
the use of the Continuous Electron Beam Accelerator Facility
(CEBAF) Large Acceptance Spectrometer (CLAS) in Hall B to study
the photoproduction of exotic mesons. However, the base detector
package at CLAS is not ideal for observing and measuring neutral
particles, particularly at forward angles. The Deeply Virtual
Compton Scattering (DVCS) experiment at TJNAF has commissioned
a new calorimeter for detecting small-angle photons, but studies
must be performed to determine its suitability for a meson spectroscopy
experiment. The ηπ system has been under especial scrutiny
in the community as a source for potential exotics, so the new
calorimeter's ability at reconstructing these resonances must
be evaluated. To achieve this, the invariant mass of showers
in the calorimeter are reconstructed. Also, two electroproduction
reaction channels analogous to photoproduction channels of interest
to HyCLAS are examined in DVCS data. It is found that, while
not ideal, the new calorimeter will allow access to additional
reaction channels, and its inclusion in HyCLAS is warranted.
Results in basic shower reconstruction show that the calorimeter
has good efficiency in resolving π0 decays, but its η reconstruction is not as strong. When
examining ep epπ0η, preliminary reconstruction of the ηπ0 system
shows faint signals in the a0(980) region. In the ep e n π+ η channel, preliminary reconstruction of the ηπ+ system
gave good signals in the a0(980) and a2(1320) regions, but statistics were poor. While more analyses
are necessary to improve statistics and remove background, these
preliminary results support the claim that the DVCS calorimeter
will be a valuable addition to CLAS for upcoming exotic meson
searches in photoproduction.
Systematic Search for Lanthanum or Bismuth Oxide Scintillators. ALEISHA BAKER (North Carolina
Agricultural & Technical State University, Greensboro, NC, 27411) STEPHEN DERENZO (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
More than ever,
there is need for new or improved scintillators to keep up with
the advancements in radiation detection technology. Known scintillators
decay slowly, have low light output, and can be difficult to
manufacture. In efforts to discover new ideal scintillators,
researchers must search, synthesize, and characterize compounds
that exhibit luminescent traits. This research focused on 12
bismuth and lead compounds. Candidates were synthesized by means
of a solid-state chemistry technique known as the ceramic method.
The products were characterized using x-ray diffraction, fluorescence
spectroscopy, and pulsed x-ray measurements. The compounds studied
did not show attributes of a high scintillation. However, since
several of the band gaps have band gaps greater than 3.5 eV,
they may be modified to form semiconductor scintillators in the
future.
Systematic studies of the Faraday Effect on glass interfaces. DANIEL
CARRERO (Stony Brook University, Stony Brook, NY, 11794) DR. CAROL SCARLETT (Brookhaven National Laboratory, Upton, NY, 11973)
The investigation
into anomalous space-time curvature has shown strong signals of
heavy consequence to this experiment. The understanding of said
signals must be investigated in order to determine whether or not
these signals are of consequence to anomalous space-time curvature
due to photon interactions with an alternating magnetic field,
or other effects including systematic anomalies. With respect to
these systematic effects, the study of birefringence as a result
of a possible Faraday Effect on glass windows used to encase a
vacuum of 1x10-9 Torr was explored. A Relativistic Heavy Ion Collider
(RHIC) quadra-pole magnet housing this vacuum will be ramped at
a frequency of 80 mHz where residual magnetic field on the order
of 200 gauss will represent a changing flux through the glass caps
at the ends. Photon interactions propagating through the vacuum
via an external laser will be subject to any briefringent effects
of the glass. Such effects can cause deviations in our beam at
the characteristic frequency of 80 mHz which when resolved on a
photo receiver can mask any true, non systematic effects. In an
effort to understand this, the development of an independent system
isolating the glass windows was implemented. Using a motorized
rotating stage, two permanent magnets each having a magnitude of
.1 Tesla, was placed on the stage positioned 2cm form the window
interface such that the overall magnetic field through the window
was on the order of 200 gauss. A He-Ne laser beam with a wavelength
the of 514nm was then propagated through the window and magnetic
field onto a photo receiver. The stage rotating at a frequency
of 80 mHz generated a changing magnetic flux such that any birefringence
effects will be resolved onto the photo receiver at the characteristic
frequency of 80 mHz. Data was then collected from the photo receiver
in 5 minute intervals totaling 25 Hrs. This data, using Fortran
code, was then Fourier analyzed such that any signals residing
in a frequency range of 0 Hz-.1 Hz can be determined. Analyzing
this data demonstrated that within the bounds of the sensitivity
of the photo receiver and Fortran code, no signal was determined.
The understanding of this effect helps rule out one systematic
effect that can cause illegitimate results. These ramifications
open other avenues for investigation, possibly minimizing systematic
effects ultimately leaving true physical results.
The ChicaneTracker Module in the ORBIT Injection Upgrade. DANIEL
COUPLAND (Albion College, Albion, MI, 49224)
SARAH COUSINEAU (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
The accumulator
ring in the Spallation Neutron Source (SNS) will accumulate up
to 1014 protons at a time from a 1 GeV linear accelerator to produce
neutrons by spallation. In order to satisfy radiation hazard requirements,
no more than 0.02% of the beam in the SNS ring may be lost by collisions
with the beam pipe. Since most accelerators lose 1-2% of their
beam, the SNS must be far more effective in beam loss control than
any previous high-intensity accelerator. This requires very precise
understanding of the mechanisms which contribute to beam loss.
One of the main sources of loss in the accelerator is in the injection
area of the ring, where H- particles are converted to protons by
passing through a thin foil that strips off the electrons. Some
of the H- particles are not fully stripped, and live for a short
time as H0 particles
in excited quantum states before decaying in the ring magnetic
fields. If the magnetic fields are not optimized, particles that
decay may be deflected from the paths intended for either H- or
protons and become lost in the accelerator. The SNS project will
upgrade the beam power in the year 2010, and this will require
a redesign of the injection region of the ring. Testing of new
design schemes will be done primarily with the Objective Ring Beam
Injection and Tracking Code (ORBIT), a modular simulation package
designed at SNS specifically for modeling high intensity rings.
In this project, the ORBIT code was upgraded to allow precise simulations
of the injection region of the ring. This work included installing
code that performs detailed tracking of all three relevant states
of hydrogen through the dipole magnetic fields in the injection
region, and determines on each step which neutral particles decay
into protons. The physical configuration of the chicane is customizable,
allowing particle positions to be compared to the real location
of the beam pipe and losses to be determined. The code is configured
to allow parallel runs on multiple machines to accommodate computationally
intensive tests. Results from this code were benchmarked with previous
studies of excited-state decay done by Danilov and Galambos et
al, and showed excellent agreement. Future modifications to the
ORBIT injection region code may include a foil heating routine
and propagation through higher-order magnetic fields. The updated
ORBIT code will provide an important tool for optimizing the new
injection region design.
The Development of a Calibration System for Pulsed Laser Tests of Silicon Pixel
Detectors for the International Linear Collider. KATHERINE
PHILLIPS (North Carolina State University, Raleigh, NC, 27607)
MARCO BATTAGLIA (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
The International
Linear Collider is the next large scale facility in accelerator
particle physics, designed to study the Higgs sector and new physics
beyond the Standard Model. Efforts are underway to develop silicon
pixel detectors for use in the vertex tracker. These detectors
must meet strict specifications, including the requirement that
the chips thickness does not exceed about 50 microns. In order
to assess the feasibility to meet this requirement with monolithic
CMOS pixel sensors, a number of prototype chips, named MimosaV,
have been back-thinned from 450 to 50 and 39 microns. The MimosaV
chip response is tested by electrons, radioactive sources, and
lasers before and after back-thinning. The lasers consist of a
solid state diode coupled to an optical fiber terminated on a collimating
lens doublet. The goal of this project is to setup a laser calibration
system to ensure that possible variations in chip response are
to due to the chip post-processing and not due to the laser source
instabilities. The experimental setup consists of a 1060 nm laser,
a photodiode to read the laser's output, readout electronics, and
a data acquisition (DAQ) analog-to-digital converter board. Laser
pulses of 100 ns length are converted to voltages through a photodiode,
and the signal is then sent to the readout electronics, which amplify,
shape, and lengthen the pulse. The signal is then sent to DAQ board,
which samples the input signal every 10 microseconds. A LabVIEW
program stores peak values and computes the average peak value,
the standard deviation, and the error. Statistical analysis removes
peaks due to noise. It was observed that the setup takes twenty
minutes before it gathers precise and consistent peak values. However,
after this warming-up period, the peak values are stable to better
than 1%, well within the tolerance of the measurements. When the
pulse length is shortened, the peak value decreases in a non-linear
fashion. The stability could be improved by adding a reset functionality
into the readout electronics. More investigation is needed into
possible causes of the warming-up time. It will also be necessary
to develop a more consistent way to align and secure the laser
in place. The present laser calibration system will be added to
the chip test setup and will provide calibration for all future
tests of monolithic pixel chips.
The Effect of the Earth's Atmosphere on LSST Photometry. ALEXANDRA
RAHLIN (Massachusetts Institute of Technology, Cambridge, MA, 2139)
DAVID L. BURKE (Stanford Linear Accelerator Center, Stanford, CA,
94025)
The Large Synoptic
Survey Telescope (LSST), a ground-based telescope currently under
development, will allow a thorough study of dark energy by measuring,
more completely and accurately than previously, the rate of expansion
of the universe and the large-scale structure of the matter in
it. The telescope utilizes a broadband photometric system of six
wavelength bands to measure the redshifts of distant objects. The
earth's atmosphere makes it difficult to acquire accurate data,
since some of the light passing through the atmosphere is scattered
or absorbed due to Rayleigh scattering, molecular absorption, and
aerosol scattering. Changes in the atmospheric extinction distribution
due to each of these three processes were simulated by altering
the parameters of a sample atmospheric distribution. Spectral energy
distributions of standard stars were used to simulate data acquired
by the telescope. The effects of changes in the atmospheric parameters
on the photon flux measurements through each wavelength band were
observed in order to determine which atmospheric conditions must
be monitored most closely to achieve the desired 1% uncertainty
on flux values. It was found that changes in the Rayleigh scattering
parameter produced the most significant variations in the data;
therefore, the molecular volume density (pressure) must be measured
with at most 8% uncertainty. The molecular absorption parameters
produced less significant variations and could be measured with
at most 62% uncertainty. The aerosol scattering parameters produced
almost negligible variations in the data and could be measured
with >100% uncertainty. These atmospheric effects were found
to be almost independent of the redshift of the light source. The
results of this study will aid the design of the atmospheric monitoring
systems for the LSST.
The Efficiency of Stripe Removal from a Galactic Map. CAROLYN
MELDGIN (Harvey Mudd College, Claremont, CA, 91711) GEORGE SMOOT (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
The Galactic
Emissions Mapping project (GEM) aims to isolate the radiation emitted
by the Milky Way and other galaxies from the cosmic microwave background
radiation. Two dimensional scans of the sky at different frequencies
allow separation of the cosmic microwave background from the galactic
signals. Signals are most informative in the microwave spectrum,
where the frequency of the light is in the 0.5 to 5 GHz range,
because the intensity of the galactic signal relative to the cosmic
microwave background changes most rapidly. In recent years, widely
available technology such as cell phones and microwave ovens have
increased terrestrial noise, making the galactic signal extremely
difficult to analyze. GEM uses data taken in 1999, when terrestrial
sources of microwaves were less common. These scans were taken
at 2.3 GHz in Cachoeria Paulista, Brazil. The scans have striped
flaws caused by microwaves from a nearby radio station diffracting
over the top of the shielding around the antenna. This paper describes
the use of filtering techniques involving Fourier transforms to
reduce or remove the striped flaws. It also describes a metric,
based on the Principle of Maximum Entropy, to determine the efficiency
of different stripe-removal filters.
The Occasional Appearance of
Carbon in Type Ia Supernovae. JEROD PARRENT (University
of Oklahoma, Norman, OK, 73071) R. C. THOMAS (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Recent observations
made by the Nearby Supernova Factory reveal C II absorption features
below 14,000 km/s in the early photospheric spectra of the Type
Ia Supernova (SN Ia) 2006D. The largest of these features is attributed
to C II λ6580, which dissipates before maximum brightness.
Only a handful of SNe Ia have been observed to contain the C II λ6580
feature. This is the largest observed carbon feature in SN Ia thus
far and is additional evidence that carbon, and hence unburned
material, can be detected at early times in SN Ia spectra. Presently,
certain 3D hydro-dynamical SN Ia deflagration models contain unburned
carbon and oxygen below the W7 (1D deflagration model) cutoff of
14,000 km/s. These observations support explosion models that contain
unburned material at low velocities, such as 3D deflagrations and
certain delayed-detonations. The sporadic nature of observed carbon
features in SN Ia and its implications for explosion models will
be discussed. We also emphasize the importance of obtaining spectrapolarimetry
data in order to test for asymmetries in the supernova.
The Systematic Study of the Faraday Effect on Glass. JOSEPH HEARD (Community College of Philadelphia, Philadelphia, PA, 19150) DR. CAROL SCARLETT (Brookhaven National Laboratory, Upton, NY, 11973)
Systematic Studies
of the Faraday effect on glass. In the midst of ongoing experiments
to detect axion interactions a question arose concerning the systematic
effects on the experiment. Specifically, whether laser beam deviation
through a vacuum can cause skewed data. This was a concern due
to the birefringence effects caused by electromagnetic fields radiating
away from the glass interface enclosed in a vacuum. A separate
experiment dedicated to determining if such an effect exists was
needed. The experiment used a Newport motorized rotating stage
on which two permanent magnets were mounted. Each magnet had a
magnitude of .1 tesla. The stage was placed 2 cm. from a glass
window interface. The magnetic field generated was measured at
200 gauss. A laser beam of wavelength 514 nm was directed through
the glass and magnetic field on to a photo receiver. The rotation
device was set into motion at an 80 mHz frequency. The photo receiver
collected data every 0.1 seconds for 25 hours. Data collection
occurred in five minute cycles. The 300 data periods were then
averaged together to eliminate random fluctuations. The data was
analyzed using Fast Fourier Transforms (FFT). The data analysis
involved taking the FFT of the raw data to produce plots of amplitude
versus frequency. FFT’d "white noise" produces a 1/f
curve. The derivative of this curve is then taken. This technique
eliminates the drift of the laser, which flattens out the 1/f curve.
Any random fluctuations are reduced significantly, improving the
resolution of any true signal. After analyzing the results of the
experiment it is apparent that, if any Faraday effect is present,
it does not deviate the laser beam's path enough to create any
influence on the overall experiment data. Thus axion interaction
experiments that employ this technique do not suffer from any corrupted
data.
The Target View Screen and Related Imaging Systems at the Spallation Neutron
Source. KATHLEEN GOETZ (Middlebury College, Middlebury, VT,
5753) THOMAS J. SHEA (Oak Ridge National
Laboratory, Oak Ridge, TN, 37831)
The most intuitive
method for monitoring a beam is to create a dynamic image at the
location of interest. At this point in time, the Target View Screen
System (TVS) is being employed to monitor the proton beam immediately
before the spallation target. The Target View Screen system has
produced very useful data during the commissioning of SNS but will
soon succumb to radiation damage. As a result another similar radiation
resistant system is being designed for permanent installation.
Other proposed systems that use similar imaging technology include
a view screen for the ring to target beam transport (RTBT) line,
a pepper pot emittance meter for the linear accelerator front end
and a neutron beam imager for neutron beam line six. A large portion
of time is also being devoted to running the Target View Screen
system in its last days of operation and analyzing the data being
produced. Approximately one terabyte of data has been acquired.
Thermal Analysis of the ILC Superconducting Magnets. IAN ROSS
(Rose-Hulman Institute of Technology, Terre
Haute, IN, 47803)
JOHN WEISEND (Stanford Linear Accelerator Center, Stanford, CA, 94025)
Critical to a
particle accelerator’s functioning, superconducting magnets serve
to focus and aim the particle beam. The Stanford Linear Accelerator
Center (SLAC) has received a prototype superconducting quadrupole
designed and built by the Centro de Investigaciones Energticas,
Medioambientales y Tecnolgicas (CIEMAT) to be evaluated for the
International Linear Collider (ILC) project. To ensure proper functioning
of the magnet, the device must be maintained at cryogenic temperatures
by use of a cooling system containing liquid nitrogen and liquid
helium. The cool down period of a low temperature cryostat is critical
to the success of an experiment, especially a prototype setup such
as this one. The magnet and the dewar each contain unique heat
leaks and material properties. These differences can lead to tremendous
thermal stresses. The system was analyzed mathematically, leading
to ideal liquid helium and liquid nitrogen flow rates during the
magnet’s cool-down to 4.2 K, along with a reasonable estimate of
how long this cool-down will take. With a flow rate of ten gaseous
liters of liquid nitrogen per minute, the nitrogen shield will
take approximately five hours to cool down to 77 K. With a gaseous
helium flow rate of sixty liters per minute, the magnet will take
at least nineteen hours to cool down to a temperature of 4.2 K.
Time Synchronization Between Data Acquisition Boards Using GPS Signals. JOSEPH WYCKOFF (Eastern Illinois University, Charleston, IL, 61920) THOMAS JORDAN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)
Since Cosmic
Rays move at an incredible speed, timing is an important part in
the components in the detectors used to measure them. QuarkNet
has many sites surrounding the country running cosmic ray shower
studies. It uses Data AcQuisition (DAQ) boards to convert the timing
signals from Photo Multiplier Tubes (PMT) to an ANSII format that
is readable using a terminal emulator program on a computer. The
sites upload their data to a central server so users can run analysis,
using data from all over the nation. Therefore timing is important
so that students using data from different GPS sources can sort
the data and see if an event happened at the same time in two different
areas. An experiment was completed using 2 different GPS antennae
to test the timing difference between two DAQ boards that received
signals at identical times. A pulse generator set at 10 Hz to mimic
a signal was used. The experiment was run for two periods of thirty
minutes where the GPS antennae were switched between the two DAQ
boards after the first period. The results of the tests showed
that the detectors had a difference in timing of 121 nanoseconds
with one of the detectors having a bias of 12 nanoseconds. The
experiment showed that while using the QuarkNet detectors a user
could only confidently say which detector fired first if there
is more than a 100 ns difference in the signals. These results
are in agreement with previous calculations of the timing difference
between detectors using separate GPS antennae. More tests should
be done to examine whether the timing difference between two DAQ
boards could be reduced or if the timing difference will cause
a problem to research that is being conducted.
Upgrading the digital electronics of the bunch current monitors at the Stanford
linear accelerator center. JOSH KLINE
(Sacramento State, Sacramento, CA, 95813) ALAN FISHER (Stanford Linear Accelerator Center, Stanford, CA, 94025)
The testing of
the upgrade prototype for the bunch current monitors (BCMs) in
the PEP-II storage rings at the Stanford Linear Accelerator Center
(SLAC) is the topic of this paper. Bunch current monitors are used
to measure the charge in the electron/positron bunches traveling
in particle storage rings. The BCMs in the PEP-II storage rings
need to be upgraded because components of the current system have
failed and are known to be failure prone with age, and several
of the integrated chips are no longer produced making repairs difficult
if not impossible. The main upgrade is replacing twelve old (1995)
field programmable gate arrays (FPGAs) with a single Virtex II
FPGA. The prototype was tested using computer synthesis tools,
a commercial signal generator, and a fast pulse generator.
Using Boosted Decision Trees to Separate Signal and Background in B→Xsγ Decays. JAMES BARBER (University of Massachusetts, Amherst, Amherst, MA,
1003) PHILIP BECHTLE (Stanford Linear Accelerator Center, Stanford, CA, 94025)
The measurement
of the branching fraction of the flavor changing neutral current B→Xsγ transition can be used to expose physics outside the Standard
Model. In order to make a precise measurement of this inclusive
branching fraction, it is necessary to be able to effectively separate
signal and background in the data. In order to achieve better separation,
an algorithm based on Boosted Decision Trees (BDTs) is implemented.
Using Monte Carlo simulated events, `forests' of trees were trained
and tested with different sets of parameters. This parameter space
was studied with the goal of maximizing the figure of merit, Q,
the measure of separation quality used in this analysis. It is
found that the use of 1000 trees, with 100 values tested for each
variable at each node, and 50 events required for a node to continue
separating give the highest figure of merit, Q = 18.37.
Using LabVIEW for Complete Systems Control of an ECR Thin Film Deposition System. BRANDON BENTZLEY (The College
of New Jersey, Ewing, NJ,
8628) ANDREW POST-ZWICKER (Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)
Interest in studying
an electron cyclotron resonance (ECR) deposition system is fueled
by ECR’s better deposition rates and precision relative to traditional
deposition systems; however, the ECR deposition system is extremely
complex and requires that its gas flow control, magnets, 2.45 GHz
source, and other components all work in concert. Operating the
system requires an experienced user to constantly compensate for
the dynamics of the system, such as argon gas pressure and magnetic
field strength. A method of computer automation, such as LabVIEW,
permits the system to operate itself, allowing for less experienced
operators, reproducible conditions, and a safer working environment.
LabVIEW, in conjunction with National Instruments hardware, sends
and receives voltage signals and serial commands in order to control
microwave power, magnet current, target bias voltage, vacuum and
compressed-gas valve position, chamber pressure, and robotics commands.
The VI takes many factors into account simultaneously, such as
chamber pressure, ion current and spectroscopic data, in order
to make decisions about the system state. LabVIEW was found to
produce easy to manage, consistent, and reproducible conditions
by simplifying complex procedures, such as system startup routines
and robotics commands, to a click of a button, by compensating
both accurately and quickly for changes in plasma conditions, and
by checking the state of the system in order to prevent system
malfunction.
Using sub-teraherz spectroscopy to detect unique absorption spectra of trace
explosives. ROBERT DIETZ (Iowa State University, Ames, IA, 50010)
HUAL TE-CHIEN (AND SAMI GOPALSAMI) (Argonne National Laboratory, Argonne, IL, 60439)
A heat-cell spectrometer
consisting of a heat cell, a backward wave oscillator (BWO), and
a hot-electron bolometer were employed to identify unique absorption
spectra for trace explosives in sub-teraherz frequencies (~220-370
GHz) at low vapor pressures. Close agreement between the Jet Propulsion
Laboratory’s simulated absorption spectra for acetonitrile (CH3CN)
and our experimentally determined spectra for acetonitrile lend
confidence to the accuracy of our results with respect to the heavier
explosive molecules. Samples of trace explosives were initially
loaded in liquid phase, contained in solutions of acetonitrile,
methanol, and/or ethanol, but difficulties in distinguishing explosive
absorption lines from solvent absorption lines prompted using a
different method. Sample solutions were poured into a small copper
cup and evaporated over several days to leave only the solid residue
of the explosive material. We believe that we have located unique
rotational and vibrational spectra for TNT and PETN. At least three
consistent and readily identifiable absorption lines for TNT are
noted, and new lines appear at higher temperatures, which suggests
molecular fragmentation. Some uncertainty remains due to system
contamination, however. Sample vapors may condense onto fiberglass
heating cables inside the spectrometer and emerge again later during
other tests when the temperature of the cables increases. We believe
that the contaminant species, if present, can be identified and
distinguished from the sample species, but prudence would dictate
redesigning the spectrometer -- such that all fibers and materials
that could potentially trap sample vapors lay outside the stainless
steel tubes -- before continuing with data collection.
We Control the Phonons: Coherent Control of Surface Phonons with a Picosecond
Pulse Laser. RYAN LEWIS (Whitman College, Walla
Walla, WA, 99362) DAVID HURLEY (Idaho National Laboratory, Idaho
Falls, ID, 83415)
All over the
world, scientists use lasers to produce very high frequency sound
waves, often using a pump and probe beam to produce and detect
the phonons. In this experiment, we shine our pump beam onto a
semiconductor sample (either Si or GaAs) beneath an Al grating-thusly
generating a coherent surface acoustic wave. Furthermore, we employ
a Michelson interferometer to produce a second, time-delayed pump
pulse, which produces a second surface acoustic wave. With fine
tuning of the micrometer, we achieve both constructive and destructive
interference of the waves. Such coherent control will be useful
in piezoelectric eddy current imaging, as well as managing the
induced strain on quantum structures.
