1 STAR TPC The STAR TPC Status and Issues A brief report to the STAR Council Jim Thomas

2 STAR TPC The TPC is alive and well and taking data, pp 500 The last time I spoke to the STAR Council, we were in the middle of an education and documentation project It has been reasonably successful. The TPC is up and running Goal: Plug and Play people – try to avoid singleton experts Three people know how to run the gas system (sort of …) –Alexei Lebedev –Dana Beavis –Jim Thomas

3 STAR TPC pp 500 is more demanding of the TPC … Beam currents are up compared to previous pp runs –Peak luminosity at the very end of run 8 was 2 * –Peak luminosity today is 3.8 * 10 31, and still going up –pp 500 goals are to achieve 4x higher luminosity Significantly more tripping than in previous years –Carl has taken to calling them “our old friend 18-4” –Speculation as to why this may be true –This may be due to holes in our shielding in the tunnel leading to hotspots in the TPC (consistent with Carl’s observations) –It may merely be due to increased background that goes with increased beam currents –Perhaps the TPC is getting older (aka ‘aging’) or has faults This is happening even though trigger rates are being held at about 100 Hz –A higher trigger rate means more charge travels to the anode wires; in proportion to a background rate + the trigger rate –We have tested up to 400 Hz. Rate limiter prevents exceeding 750 Hz.

4 STAR TPC Anode Currents in Run 8 Our tradition has been to keep the anode currents low to avoid damage to the TPC and to avoid aging the anode wires

5 STAR TPC Anode currents on the outer sector in Run 9 The radiation load on the TPC sectors ~ 1/r 2 so the outer sectors see less load

6 STAR TPC Inner Sector: Normal operation – GG triggered Last night at 2:20 AM To be fair, the alarm limits are set at our discretion and we haven’t changed the alarm limits on these screens compared to last year. We are debating whether it is wise … or not.

7 STAR TPC We are exploring new territory … Trigger rates could go up by a factor of 3 compared to last year The luminosity is already up a factor of 2 compared to last year and will climb higher as the run progresses pp 500 multiplicities are up a factor of 1.25 compared to pp 200 So the radiation load on the TPC could go up by almost an order of magnitude this year Here we go … –pp 500 operation is very stressful on the TPC … more stress than HI –High rate running cause the TPC anode wires to age rapidly –How much is too much … we don’t know –Peter Braun-Munzinger is concerned and raised the issue at the Science and Technology review last summer and even challenged the assumptions underlying our previous estimates of aging in the TPC

8 STAR TPC Upcoming TPC Review – report due by end of May Evaluate the seriousness of the aging problem Evaluate the impact on the physics programs Evaluates possible ways to predict and/or mitigate the problem The STAR Collaboration has recently upgraded the Time Projection Chamber readout electronics so the TPC can take data at ~1 kHz rates. The collaboration is also planning to install several new detectors whose installation will coincide, in time, with a significant increase in the luminosity of the beams at RHIC. These upgrades will allow the collaboration to continue to do compelling physics for many more years but the usefulness of these new detectors will depend on excellent performance from the TPC. Therefore, it is important to know if the TPC can meet the requirements of the experimental program in the high luminosity era at RHIC and if there are intrinsic lifetime or aging issues for the TPC that might affect how, or how long, it can run. The committee is requested to assess the performance of the TPC in the high luminosity environment which will be encountered at RHIC II, for both pp and HI collisions. The benchmark values of the luminosity for 2013, and beyond, are: Au-Au (200 GeV/N) L avg = 80 x cm -2 sec -1 pp (200 GeV) L avg = 6 x cm -2 sec -1 pp (500 GeV)L avg = 15 x cm -2 sec -1 The committee should also review the manpower commitments that are devoted to the operation of the TPC.

9 STAR TPC More Challenging Than Ever … TPC calibrations are more challenging than ever –Yesterday’s low luminosity run (12x12) was not low luminosity –Usually we try to get a very low luminosity run to calibrate our calibrations –This year we will have to calibrate the calibration run –Not to mention that the magnitude of the distortions in the physics runs will be larger than ever before The TPC is supposed to last another 10 years –One constraint: HFT takes its first data in Run 14 –Data taking sequence is 3-5 years long … run 14, 15, 16, 17,18 At some point we, as a collaboration, may decide that it is prudent to manage the luminosity of the beams –Manage the luminosity –Manage the trigger rates –Not an exact science What happens if we run the TPC until it melts? –The anode wires are the most likely component to wear out –We can replace them –Not clear that we can predict, in advance, if and when this will be necessary

10 STAR TPC Winding new grids Approximate Cost and schedule 6 technicians 1 year 1 million dollars The STAR TPC should last a long time. However, the option to replace the wire grids on the endcaps of the TPC is an extremely valuable contingency for us in case of pre-mature aging of the anode wires or other worst case scenarios.

11 STAR TPC End

12 STAR TPC TPC Manpower - Hardware Hardware –Alexei (BNL), Dana (BNL), Jim (LBL), Howard Wieman (The Temple Mount) –Blair does answer … but is anxious to preserve his retired status Gas System –Leonid Kotchenda (MePhi) [Alexei, Dana, Jim … in training for Lite duty] Interlocks –Jim Water –CAD, Alexei, Soja (BNL) Slow controls & Computers –Yuri Gorbunov (Creighton) & Wayne Betts(BNL) Electronics –STSG – Padrazo + Crew, Tonko, Jeff Landgraf, Bob Scheetz (BNL) Laser –Alexei

13 STAR TPC TPC Manpower - Software Pad Monitor –Jo Schambach (UT) has plans to upgrade the old pad monitor –Will require continuing support: new features, formats change … –Jeff arranged a test last year, Blair was able to see DAQ1000 files Bad Pad/Gain file –Tonko, Jeff Calibrations for Drift Velocity, dE/dx, etc. –Richard Witt (Naval Academy), Yuri (BNL), Patricia Fachini (BNL) Calibrations for Grid leak, Space Charge, Shorts etc. –Gene (BNL), Jim, Hao Qiu New Fast Tracker for Fast Offline –Hao Qiu (Lanzhou & BNL) + Zhangbu + Yuri

14 STAR TPC Manpower Issues Same old faces … some are wearing out –Many of these folks would like to move on to new frontiers New faces –Nu has been very good about recruiting students (esp. for calibration work) –We also need some senior faces, and people who don’t rotate so fast Slow Controls –DAQ 1000 is only one of the new systems joining STAR this year –STAR is always under-staffed in this category. Creighton does heroic work … but its only a small group … additional manpower would help ensure STAR’s future Pad Monitor –Who upgrades and maintains the new pad monitor for DAQ 1000? –Hopefully Jo Schambach is willing to do this … but unknown

15 STAR TPC New TPC Projects Possible new gated grid system and new pulser –Based on ALICE driver, depends on performance (& failure) of old drivers –R&D should proceed now Fast tracking with fast offline event pool –Hao Qiu has made an excellent start in this direction TPC Calibrations –There is always something … –Usually driven by increasing luminosity … but hardware failures are possible, too. Explore aging of the TPC wire grids –PBM challenged us at the last S&T review. Must report again. Wind new grids for the TPC –pp 500 GeV running will be very stressful on the TPC … kaput in 2 years? –Preserve capabilities, document procedures, R&D

16 STAR TPC Inner Sector: Beam Background – GG Closed The background rate is 10-20% of the total load on the anodes