STAR MRPC TOF: Project Overview

1
STAR MRPC TOF Project Overview
BNL January 26, 2006
Geary Eppley Rice University
2
Design considerations

• The integration space available for TOF in STAR
  is that currently occupied by the CTB.
• The space is about 2.2m from the beam line
  requires precision time measurement.
• The clearance between the TPC and EMC is about 10
  cm.
• The space has a uniform 0.5T magnetic field
  parallel to the beam.
• There is limited space for nearby electronics
  outside the magnet steel.

3
MRPC development

• Multigap glass RPCs developed in the late 1990s
  at CERN, C. Williams, et.al.
• STAR TOF group designed STAR-specific MRPC
  modules that would fit existing CTB trays and
  tested them at CERN in 2000 2001.

4
MRPC prototypes in STAR

• One tray of MRPC modules has been installed in
  STAR for Runs 3, 4, 5.
• An improved tray design each year but some
  modules have been installed for all 3 years.
• Runs 3 4 used CAMAC electronics.
• Prototype HPTDC based electronics used in Run 5
  and Run 6

5
Electronics integral to tray

• 95 of the electronics resides on the tray inside
  the cover
• 4 external electronics boxes located on the
  magnet steel connect the 23k-channel system to
  STAR trigger and DAQ

6
Tray specifications

• There are 32, 6-channel modules per tray.
• The active area covers about 87 of -0.9ltetalt0.9
• Occupancy in central AuAu is 12.
• HV provides -7 kV.
• Gas mixture 95 r134a, 5 isobutane.
• Average noise rates are 15 Hz/channel with
  greater than 100 correlation.
• Detection efficiency is 95.

7
Time measuring

• Absolute times are recorded and buffered by the
  HPTDC for all hits above threshold.
• A single 40 MHz oscillator provides the clock for
  the 2882 HPTDCs in the system.
• Both start and stop detectors use the HPTDC to
  record times eliminating systematic uncertainty
  from the choice of counter.
• Each HPTDC has a 21 bit clock counter providing
  a 51 us clock period. The HPTDCs are reset by a
  signal with a common origin at the beginning of
  each run giving each HPTDC a different phase that
  may be learned from the data.
• Since this phase is always the same, the phase
  becomes a powerful tool to monitor the integrity
  of the data through buffering, trigger matching,
  event building, transmission to DAQ, and global
  event building.

8

Total time resolution from Run 5
62GeV CuCu, 124ps
200GeV CuCu, 105ps
9
Time resolution by channel
10
Timing results, Runs 3, 4, 5
11
STAR TOF publications

• Physics
• Open charm yields in dAu collisions STAR
  Collaboration, Phys.Rev.Lett. 94 (2005) 062301.
• Cronin effect of identified particle at RHIC
  STAR Collaboration, Phys.Lett.B 616 (2005) 8.
• Technical
• B. Bonner et al., Nucl.Instr.Meth.A 478 (2002)
  176.
• M. Shao et al., Nucl.Instr.Meth.A 492 (2002) 344.
• W.J. Llope et al., Nucl.Instr.Meth.A 522 (2004)
  252.
• F. Geurts et al., Nucl.Instr.Meth.A 533 (2004)
  60.
• J. Wu et al., Nucl.Instr.Meth.A 538 (2005) 243.
• Y. Wang et al., Nucl.Instr.Meth.A 538 (2005) 425.
• Y.E. Zhao et al., Nucl.Instr.Meth.A 547 (2005)
  334.

12
Organization chart
13
Manufacturing overview

• Module production and test, electronics
  production and test, and tray assembly and test
  each have a duration of 2.2 years.
• Module production begins 3 months before the
  start of tray assembly and electronics production
  1.5 months before the start of tray assembly.
• Modules are thoroughly tested in China with
  integral HV wire and signal cables.
• Electronics cards are tested in groups of 17, 1
  tray, with their integral cables and sent to the
  tray assembly site as a set.
• Modules are assembled into trays, the electronics
  added, and tested for 2-4 weeks as a complete
  detector unit.
• Tested trays are shipped to BNL as complete
  detector units ready for insertion into STAR.
• Trays are re-tested at BNL HV current, noise
  rates, gas leak test
• Test beam at BNL for selected trays?

14
Gantt chart
15
TOF system functional requirements
16
Current project status

• Cosmic ray testing of the TINO front-end board is
  ongoing.
• Automated TINO board production has been
  achieved.
• Upgraded 38-channel start detector under
  construction.
• Based on a recommendation from the review, the
  China TOF project built a few new modules with
  highly resistive electrodes. Due to difficulties
  involved with the manufacturing process, the
  China groups decided to stick with the
  graphite-tape electrodes.
• Layout of the first prototype THUB is underway.
• The project started officially January 1. We hope
  to get the university accounts open before the
  end of February.

17
TOF Gas system

• The TOF system will operate on a gas mixture of
  90 parts r134a and 5 parts isobutane.
• The system will vent 12 pounds r134a per day
  during STAR operations
• The system will be sealed but not operate during
  shutdown periods.
• The isobutane/r134a ratio is set by the factory
  calibration of the mass flow meters. It will also
  be monitored by an isobutane analyzer.
• The aggregate gas circulation rate through the
  trays is 450 l/h.
• The gas is re-circulated and dried maintaining
  H2Olt20 ppm, O2lt30 ppm.
• The system is interfaced to STAR slow controls
  through a shared disk. Isobutane content is
  alarmed to insure non-flammable gas. Gas flow is
  alarmed to maintain safe operation of the trays.

18
TOF gas system schematic
19
DOE review recommendation

• Investigate using SF6 or C4F10 Improves MRPC
  operational characteristics.
• Our reply Our AGS 11-week test run data confirms
  this SF6 greatly extends the HV plateau from
  lt500v to gt1000v.
• Using SF6 will allow running at a higher voltage
  and improve timing resolution.
• We will investigate
• Developing standards for gas-tight integrity
• Adding gas leak SF6 detectors
• Adding positive air flow in the TOF tray area