MWPC Commissioning: A Status Report What the MWPC’s do and how Data taking Jan-Feb 2000 Results from the Analysis

Timeline of MWPC Installation Spring 99: Installation of MWPC FEE Cards Aug-Sep 99:Installation of MWPC Sector Controller boards, Cabling Jan-Feb 2000:First tests with STAR Trigger. Noise, Pulser, and Cosmic ray Data March 2000:Analysis of the data

What do the MWPC ’s do? – Read out the response of the TPC anode wires each RHIC beam crossing, 1/105nsec. RHIC beam crossing, 1/105nsec. – Measure the multiplicity of charged particles passing through the endcaps of the TPC. through the endcaps of the TPC.

Numerology and Definitions Inner SectorOuter Sector 170 Wires 172 Wires160 with MWPC FEE Cards 10 Orphans12 Orphans Good web documentation by R. Bossingham (STAR TPC Group pages) Each FEE is connected to 20 wires. This gives 16 FEE cards per super-sector. (In reality, only 15. The innermost connector is smaller.) The FEE cards are divided into groups of 4 cards (innermost group has only 3). Such a group is called a Sub-sector.

More Definitions Each wire returns 0 or 1 (hit or miss). No ADC Info. MWPC Multiplicity  # of wires hit Sensitivity of wires determined by adjustable discriminator threshold. 1 threshold set for the entire TPC. Read-out granularity: Trigger Level 0: Currently 1 value  summed MWPC multiplicity. Possible upgrade to 4(  ) x 4(  ) = 16 bins. Trigger Level 1 or 2: Improved granularity, 12(  ) x 8(  ) = 96 bins. 1 value per Sub-sector (4 FEE’s, 80 wires).

Noise Data Random Trigger: Read every trigger token. No Pulser, No cosmic trigger, Threshold at 70 mV. – Non-statistical noise, more probable that entire FEE cards fire than just a few wires. – Could be a pick-up + grounding problem. – Some sectors/sub-sectors worse than others.

Cosmic Ray Data Trigger: 1 CTB hit (ADC>5) +  1 MWPC Wire Used one side of the TPC, noisiest sectors disconnected, 5 active sectors (1,4,6,9,10). Took 8 runs with varying thresholds ( mV) ,000 events/run

Trigger Rate Expected rate from cosmics: Hz Noise threshold  150 mV

Meaning of threshold Intrinsic electronic noise <5 mV Noise threshold in lab (at Berkeley) 60 mV (Chin Vu) Noise threshold in Wide Angle Hall mV Min. Ionizing Particle (Calc.) mV (Spencer)

Hit Distributions – Each bin corresponds to 1 sub-sector – 80,81  Sector 9, Subsectors 1,2 – 2/3 of events in these to bins!

Correlation MWPC  TPC Tracks Select “golden” events: 1 TPC Track, 1 MWPC SubSector Hit Why are Sect 9, SubSect 1,2 more efficient than the others? This is an unsolved mystery! Could be difference in timing (CTB/MWPC) or threshold distribution.

MWPC hits  incident angle I mV threshold - As expected, more wires are likely to be hit at large incidence angles

MWPC hits  incident angle II mV threshold

Timing MWPC vs. CTB The CTB/MWC path lengths have not yet been optimized. They could be off by 1-2 RHIC Clocks! The trigger preserves the information in the 5 RHIC clocks preceding and following the triggered event. From this information it seems that MWC are lagging the CTB. An offset in timing would affect the efficiency CTB MWCFEE/RDORCVR optical fiber DSM CDBDSM

Time distribution of MWPC hits - Seems shifted toward later times. - There is a bias. There has to be an entry in bin 0, otherwise no trigger.

MWPC Slow Simulator I Vladimir Morozov Sensitive volume: gating grid  pad plane (  300ns) This corresponds to a drift time of 2-3 RHIC Clocks The shaping time of the FEE pre-amplifier is  170ns

MWPC Slow Simulator II What it will do: - Correctly model the space and time distribution of the MWPC signal - Find the optimal relation between number of wires hit  multiplicity - Simulate the electronic noise __________________________________________ Understand and correct for the trigger acceptance and efficiency.

SummarySummary The MWPC Works! Hit pattern correlated with the TPC tracks in a reasonable way (for part of the system). Outstanding issues to be solved: — High noise levels (pick-up) — non-statistical noise (entire FEE cards fire) — Timing: Synchronization of CTB and MWPC Next Cosmic Run: Need more statistics 10,000+ Events/sampleNext Cosmic Run: Need more statistics 10,000+ Events/sample