Minutes of Oct/23/2001 highpt upgrade meeting.

["Susumu SATO" <ssato@bnl.gov>]

Dear high-pt upgraders.

 This is the minutes of Oct/23/2001 highpt meeting .
You can visit your interested sections from 5 sections.
 
     --0-- General  
     --1-- Updated results of bench tests. 
     --2-- Idea for short wavelength.
     --3-- Two ideas for scattering lights
     --4-- Two ideas for more photoelectrons
     --5-- Some more thought about KEK test.

The followings are www pages appearing in the minutes.
In http://www.phenix.bnl.gov/phenix/WWW/p/draft/ssato
(for Sec1)/upg2001oct/1018_2001_evgueni_highpt.PDF
(for Sec3)/upg2001oct/1024_2001_next_idea.PDF 
(for Sec5)/upg2001oct/1025_2001_pmt_position.PDF
(for Sec5)/upg2001oct/1025_2001_pi2_beam_line.PDF
              
In http://p25ext.lanl.gov/~hubert/phenix/aerogel/
(for Sec2) agel_01.html

(for Sec4)NIM-A315(1992)517-520.

Sincerely, Susumu SATO.



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    From here, the long minutes (till end of email).
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(0) 

  ---------  General  
 
Date: Oct/23/2001 
Place:  1008 conference room
The attendances:

  Selguei AFANASSIEV (JINR)
  Anatoli LITVINEKOV 
  Sean STOLL
  Evgueni MELNIKOV
  Susumu SATO
  Hubert van HECK
  Edouard KISTENEV
 

(1)       

    -------- Updated results of bench tests.

The test results by Evgueni and Sean are presented. 
The enhanced viewpoints from Sean's last measurement
are (i) comparison with 3 indices, and (ii) comparison with 
better white reflector, i.e., Tyvex.  The plots are at:
http://www.phenix.bnl.gov/phenix/WWW/p/draft/ssato
/upg2001oct/1018_2001_evgueni_highpt.PDF

page1: transmission through   20mm for n=1.02 and 1.015
page2: transmission through 105mm for n=1.02 and 1.015
page4: transmission through  15mm and 30 mm for n=1.007
page3: attenuation length for n=1.02 and 1.015
page6: attenuation length for(n=1.02 and 1.015)and 1.007

  -> n=1.02 gives longer attenuation length than n=1.015.
  -> n=1.007 gives similar attenuation length to n=1.02, 
                  but this might be due to the difference in 
                  condition in measurement. Namely, n=1.007 
                  uses much shorter depth (15 & 30 mm) for 
                  the evaluation of attenuation length  
                  than n=1.02 or 1.015 (10 & 105 mm).
 
 page5: difference between white paper (Tyvex, this 
           time) and black paper.                   
  ->  There is almost no difference between the reflector 
        used on both sides of aerogel. This is the same result
        as the last measurement where normal white paper
        is used for Tyvex white paper.
 
 
(2) 

     --------- Idea for short wavelength.

It is emphasized by HvH that in order to evaluate 
the attenuation length for the short wave length
it is useful to use thinner (e.g. 2mm or 5mm) 
sample of aerogel to eliminate the effect from 
scattering (note that at short wave length, the 
scattering length is getting smaller in lambda_input**4).
Simulation for the expected transmission% for the
thinner sample is posted by HvH at:
http://p25ext.lanl.gov/~hubert/phenix/aerogel/agel_01.html
Same study is also done by AnL, which support the
HvH's calculations. HvH has experiences to cut the
aerogel by a sheet of normal paper, or high-speed 
electrical saw (a note for the necessity of ventilator). 


(3) 

--------- Two ideas for scattering lights

There are other several suggestions for the next step in 
the bench test. Schematic drawings of the typical two are at
http://www.phenix.bnl.gov/phenix/WWW/p/draft/ssato
/upg2001oct/1024_2001_next_idea.PDF 

   Idea-(one) initiated by HvH. To evaluate the yield of 
transmission light, it is useful to see the angle dependence 
of  transmitted light, by using a collimator (drawn as a 
yellow tube, e.g. with a mm of diameter) of the 
transmitted light as well as another collimator (drawn
as a yellow plate, e.g. with a mm diameter of hole) 
of the input laser light. Drastic drop (like in logarithmic)
of yield is expected as the polar angle (to the input laser 
beam) increases. Non-zero polar angle is good evaluation
for the scattering light. We should note that the devices
we are using may accept non-zero polar angle because
the spherical integrator has relatively large input 
hole (about 1 inch in diameter). This require two 
collimators, one at the input (drawn as yellow plate) 
and the other at the output (drawn as yellow tube).
   -->Advantage compare to the original measurement 
at Tsukuba by Masui&Konno is: HvH's idea is NOT affected
by the attenuation due to the difference in PMT's position.

  Idea-(two) initiated and repeatedly emphasized by EK .
To evaluate the yield of transmission, it is useful to 
measure the position dependence in transverse 
direction (See the red both-sided arrow on the PMT 
in the pdf schematic drawing). This dependence would 
immediately tell the maximum size of the aerogel 
segmentation, which we need for the practical design.
  -->AnL's raise a worry about the effect of attenuation
due to the difference in PMT's position (i.e. the same 
worry mentioned in above Masui&Konno measurement,
while EK's case differs in transverse direction).  EK 
promptly got a better idea to that. Another PMT (shown
as a red PMT_backward with a dotted both-sided arrow 
in the schematic drawing) at the input side of the laser 
can normalize the effect.
  -->AnL has another worry about the effect of angle
(of PMT itself) dependence (,which is schematically 
drawn as a thin both-sided arrow on PMT). This effect
might be small, because the light is already multiply 
scattered.    


(4) 

 ----------- Two ideas for more photoelectrons

Idea-(three)  initiated by AnL and improved by HvH.
It will help to use the wave length shifter (or optical 
fiber) putting inside the aerogel. This immediately 
raise a worry about large emission of scintillation
light in the fiber. HvH showed the NIM paper to
overcome this worry. The idea is to put the very 
thin wave length shifter in parallel to the beam 
direction. The paper is:
NIM-A315(1992)517-520.
"The aerogel Cherenkov counters with wavelength 
shifters and phototubes" by KEDR experiment.           
  
Idea-(four) initiated by HvH. It might help to
use POPOP on/in the reflector. A paper he
refers (so far, he needs to re-find the 
article's ID) tells ca.40% of increase in light yield 
by POPOP-doped reflector, while they used 
liquid media to contain POPOP, i.e. the reflector 
seems not to be thin. FYI the typical wavelength
of POPOP is 350-360 nm for absorption, and
410 for re-emission. The authors use 
para-Terphenyl as well in order to save much 
shorter wavelength (FYI the typical wavelength
of para-Terphenyl is 280nm for absorption, and
350-360 nm for re-emission, which is followed
by the POPOP's absorption-reemission). 
(a Tip) People might want to dope POPOP directly 
to aerogel, but think of density of aerogel ! The  
thought might result in e.g. 10 times more POPOP 
than aerogel itself !! Anyway we like HvH to 
re-find the article. Another wavelength shifter
called "Koumarine" is reminded. 

(5)

  --------- Some more thought about KEK test.

  EK likes to see the effect of mirror for the light collection.
HvH has made mirror and its support (,which also 
support PMT and aerogel) in CERN. The schematic
drawing of the support is at:
http://www.phenix.bnl.gov/phenix/WWW/p/draft/ssato
/upg2001oct/1025_2001_pmt_position.PDF
If the PMT is allowed to be positioned in 
the case-2-position in the schematic drawing,
the difference between case1 and case2 gives
the idea for the light collection by mirror.
HvH will check the capability of case2 by the 
existing support (or its drawing). But we should note
that the support is designed for the ring imaging
type of cherenkov counter (we ourselves are aiming
threshold type of the Cherenkov counter).
 
  A question is raised how parallel the 
KEK-"pi2"-beam is. The beam is almost 
parallel, namely, 0.6 degree as polar angle. 
(Please note that the 6 degree mentioned 
during the meeting is a simple mistake of 
calculation. Just after the meeting, I got the
correction.) FYI, the carbon copy of handbook 
for KEK-"pi2" beam line is at: 
http://www.phenix.bnl.gov/phenix/WWW/p/draft/ssato
/upg2001oct/1025_2001_pi2_beam_line.PDF
(Top figure) The hatched region in pink is 
the area for the counters.  The point (F1) in 
pink is beam focused point. 
(Bottom figure) The beam profile of 
the "pi2" beam line along the magnets.
top curve is horizontal profile in [cm], 
and the bottom curve is the vertical 
profile in [cm]. the beam goes from 
0[m]  to beam bump through 
the "F1"-focused point at ca.28 [m].
Please have the idea of area size
by eye-comparison between two 
figures. 

Those could be all as meeting minutes, I think.
Thank you for patience, this time too !  :-)  

----- end of minutes and end of email----

******************************************
Susumu SATO.   
Japan Society for the Promotion of Science (JSPS)
Fellowship for Research Abroad.
Email: ssato@bnl.gov , Mail:BNL 510c,Upton,NY11973.
Tel: 1-631-344-2679 , Pager: x-5614.
******************************************