STAR Newsletter #87 December 2001
	Star Home Page			Editor: Howard Matis

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Contents

1. Spokesman's Column
2. STAR Operations
3. Detectors and Subsystems
4. Period Coordinators Report
5. Physics Working Groups (protected area) No contributions this month
6. People: Comings and Goings
7. Announcements and Notes
8. Employment Opportunities

Spokesman's Column (John Harris)

In the recent STAR Council Meeting, the Council elected Jay Marx to the new position of Council Chair. Jay will be in charge of STAR Council business and chair the Council for the next two years. The Council also approved the appointment of Rene Bellwied and Thomas Ullrich as Deputy Spokespersons for STAR. The Council was informed that in addition to Rene and Thomas, Mike Lisa will join the STAR Spokesman's Office as the STAR Physics Analysis Coordinator.

In other developments, Thomas Ludlam has agreed to serve as the Head of Upgrade Detectors and Additional Experimental Equipment for STAR, a post formerly held by Jay Marx. Tom Ludlam and Rene Bellwied will work together to lead STAR in the development of a Proposal for STAR Upgrade Detectors, due next Fall. Howard Wieman will continue in his role as Head of Technical Development in STAR and contribute to the STAR Upgrades proposal.

In other business last month, the STAR Council unanimously approved modifications to Sections II and III of the STAR Bylaws which include establishing Council elections for the Spokesperson and for the Council Chair. The Bylaws can be found on the STAR web site under organization. The Council Chair will arrange for an Council election of the STAR Spokesperson, to be held at the next Council Meeting.

The next STAR Collaboration meeting will be held at BNL starting Wednesday, February 6, through Sunday, February 10. There may be other smaller meeting associated with the Collaboration that take place just before or after the Collaboration Meeting, however the plenary sessions will be held between Wednesday and Sunday. The Council will meet on Friday, February 8.

At the Physics Working Group Convenor (PWGC) Meetings during the recent STAR Physics Analysis Meeting, the PWGC decided unanimously to institute a practice of having Principal Authors submit proposals for papers to the Spokesman for preview, once the analysis has been discussed in the PWG and agreed to be sound. It is expected that the proposal will include an abstract, the primary physics points of the paper, the proposed figures and tables, any other supporting or explanatory information (here a web page with all of this information would be best), and the journal to which this paper is intended to be submitted. The Physics Analysis Coordinator and the PWGC Group will be charged to discuss each proposal and make recommendations on the proposal to the Spokesman. The Spokesman will provide the PA's and PWG Convenors of the relevant PWG's with guidance on each proposal. This is intended to be a fast process. The intention of introducing this process is threefold:

to allow early examination of "papers" by a group with a broad physics perspective and a range of individual physics interests in STAR. This could include the merging of different types of analyses, specific figures, and possibly papers. This will rapidly become important for STAR as we attempt to correlate our results and better understand the physics from our data. We also anticipate that more "interpretive" papers, including a range of data and analyses from STAR, will become increasingly important. Such an early overview of proposals will help STAR prepare and publish better papers.

to provide early guidance on the journal for which each paper is targeted, and

to provide feedback and guidance to the PA's and PWG Convenors before the text and format of papers have been determined. Early examination is important to allow direction changes prior to any large investment of time and effort on the text of papers.

STAR Operations (Bill Christie)

No contribution this month.

Detectors and Subsystems

FTPC (from Volker Eckardt)

No contribution this month.

Slow Controls (from Mike Cherney)

Nothing broke.

EMC (from Alexandre Suaide)

No contribution this month.

TPC (from Blair Stringfellow)

The TPC completed the recent Au-Au running in very good shape. Gas was introduced on July 4 and removed on Nov. 26 and we had essentially 100% uptime for the entire run. The electronics was stable with >99% active channels. We experienced a minimal number of HV trips, usually beam related. My thanks to the usual hard working TPC crew - Leonid Kotchenda, Alexei Lebedev, Fabrice Retiere, Kai Schweda, Jim Thomas, Dennis Reichhold, Danny Padrazo, and Howard Wieman.

I would also like to thank all the dedicated Detector Operators who took great care in running the TPC and kept the after midnight calls to me to a minimum!

Level 3 Trigger (from the commissioning contingent)

No contribution this month.

Endcap EMC (from Will Jacobs)

After a few hitches (including returning half the lead sheet to remove "excess" material), production lamination of radiator plates began the first week of December. Separately, additional specification and fabrication discussion required the bid for the major Endcap structural elements to be updated (front plate, back plate and hub). The order should now finally clear purchasing and "start the clock" for work on this long lead time, critical path item required for both detector pre-assembly and calibration.

In this last month, material orders went out for the special pre- (5mm Bicron BC400) and post-shower (5 mm Kuraray SCSN-81) layers of the calorimeter. Meanwhile, production of the layer 3-23 megatiles continues at a good pace and has reached 20% (30%) of the tiles needed for first Endcap half (4 sectors).

Final PMT and MAPMT box locations, now allowing for the additional laser splitters and other diagnostic devices, has been defined. Detailed fiber tray locations in the services gap, including movement of existing obstructions where they occur, has been agreed to with STOG. Additionally, during the recent pp shutdown, Styrofoam fiber tray dummies were mounted and tested for tray size and possible obstruction (and destruction!) during poletip removal. This combination of events allowed finalizing of the clear fiber runs, and an order for the fiber material to readout the lower Endcap half was placed.

Also during the recent pp shutdown, a 12-tube tower PMT box, complete with tubes, housings, internal fiber harness and a LED pulsing system, was successfully mounted on the back of the STAR west poletip near the 4 o'clock position. Arrival of the HVSys controller and CW bases at the last possible moment (a combination of lengthy Russian and American customs delays) resulted in a rather tight review and installation schedule - a "big" thank you for everyone's help. In the next weeks, temperatures in the box will be monitored along with the performance of the tubes in the STAR "environment" (magnetic field on/off, etc.). The effectiveness of the box/housing magnetic shielding will be determined and a strategy for box cooling and heating will be devised.

Physics Working Groups - (See the protected area)

No contribution this month.

This section contains summaries of the status of the physics working groups. These articles are in a protected area for STAR collaboration members only. This link uses the standard STAR account and password for physics results. If you do not have this information, please contact your council representative.

People

	Transitions Milestones

Announcements and Notes

Some notes on a talk by Wolfram Fisher on the status of RHIC (Spencer Klein)

Wolfram Fisher (BNL) gave an excellent talk on "RHIC Operations in 2001" on December 6th at LBNL's Center for Beam Physics. He said a lot that hasn't been presented elsewhere, and I thought some notes might be of general interest.

In 2001, RHIC reached it's instantaneous design luminosity, but the average luminosity is below expectations, largely because of the short beam lifetime and low machine reliability.

Wolfram was very honest about the machine reliability problem. He listed it as the first item limiting current machine performance. He had a plot showing what broke when, and said that they would look intensively at the top 6-8 problems (specific items, like an individual quench link interlock) that really stuck out, and fix them, but that the 40-60 other problems would receive less attention, seemingly due to manpower limitations.

The short beam lifetime (1 1/2 hours) is due to emittance growth, not loss of beam particles. The longitudinal emittance growth is understood, but the transverse is not. The problem is most likely due to non-linearities (higher order corrections) in the magnets around the IR's (the DX magnets?), but the non-linearities are very hard to model, and also hard to fix. They could add high (up to 10th?) order correction coils, but the effect of a single coil is subtle enough that it's hard to even be sure it's wired correctly.

One manifestation of the non-linearities comes from a ~ 10 Hz (many lines with similar frequencies) modulation of the beam due to mechanical vibrations in the DX magnets. This causes a slight (.03 sigma) movement of the collision point at the same 10 Hz rate.

At high beam currents, the machine vacuum breaks down. If there is too much current in the machine at a time when losses are high (injection or transition), then the vacuum will rise suddenly, eventually (at 10^-7 Torr) triggering a beam dump. This is most likely due to ion desorption in the warm sections of the beam pipe.

In the long term, intra-beam scattering will limit the RHIC luminosity. The cure for this is electron cooling (i.e., the lead-in to eRHIC). Inter-beam scattering is less important.

Some significant changes were made in 2001. As we've heard, the 200 MHz RF system was commissioned, shortening the bunches from 35 ns (as provided by the 28 MHz RF system that is used for capture and acceleration) to 5 ns They also used a new method to get through transition quickly. In 2000, they had jumped through transition by increasing the energy quickly by changing the beam radius. In 2001, they used a new method where they ramped the beam energy linearly, but, near transition, suddenly changed the magnet configuration to reduce the transition energy; the two energies matched only briefly. [For non-enthusiasts, this energy, about 28 GeV per nucleon for gold at RHIC marks the transition from the low energy, non-relativistic operation to high-energy relativistic operation.]

Except for the electron cooling, he didn't really discuss future luminosity increases. The emittance growth problem is very difficult, and the vacuum breakdown is not yet well understood. He seemed to regard RHIC as pretty far down the road to routine operation, with thoughts turning toward longer-term upgrades (mostly the electron cooling). One other possible upgrade is raising the machine energy to 120 GeV/nucleon (for gold), which is possible by replacing the DX magnets.

Spencer circulated these notes to the LBNL RNC group. I thought that they were of general interest to the STAR collaboration, so I asked him for permission to include this in our newsletter - Editor

Employment Opportunities

No contribution this month.