New MRPC R&D in Tsinghua University

1. New MRPC R&D in Tsinghua University • Outline: • Introduction of MRPC • MRPC for RHIC STAR-TOF • LMRPC for STAR-MTD • High rate MRPC for CBM-TOF • Conclusions Wang Yi Department of Engineering Physics Tsinghua University

2. Introduction of MRPC Large area, high granularity Good time resolution<100ps High efficiency> 95% Low cost Was used or will be used in ALICE, STAR, FOPI, HADES HARP, CBM and NICA-MPD

3. Four kinds of MRPC prototypes • 4 gaps, used in HADEs-TOF • 10 gaps, used in ALICE-TOF Gap 6mm 3.8cm • 6 gaps, used in STAR-TOF 90cm • 6gaps, used in STAR-MTD

4. MRPCs used in hadron experiment 95/0/5 23040

5. QCD phase diagram The goal of hadron experiments are to search the QGP and find the origin of cosmology. Our goal is to develop high quality Time of Flight system for these hadron experiments! RHIC-STAR FAIR-CBM NICA-MPD JLAB upgrade project …..

7. MRPC used in STAR barrel TOF Long side view

8. Performance of STAR-TOF MRPC 6cm 3cm Readout pad Glass: ～4×1012.cm Carbon tape: 500k / Gas gap: 6×0.22mm Working gas: 95% F134a+5% iso-butane Time resolution: 70ps Efficiency >95% PID of TOF:  /k ~1.6 GeV/c (,k)/p ~ 3.0 GeV/c

9. 2007 2008 2006 1/2 3/4 5/6 7/8 11/12 1/2 3/4 5/6 7/8 1/2 3/4 5/6 7/8 11/12 9/10 9/10 Prod Start 132 MRPCs 768 MRPCs 1856 MRPCs 2944 MRPCs 4032 MRPCs MRPC production scheme MRPC production was finished in September of 2008. In Tsinghua: 3100 MRPC have been produced; 2951 Modules passed QA, yield >95% ; 2840 modules shipped to UT Austin . Great success! 9

10. STAR Muon Telescope Detector • A large area of muon telescope detector (MTD) at mid-rapidity, allows for the detection of • di-muon pairs from QGP thermal radiation, quarkonia, light vector mesons, possible correlations of quarks and gluons • as resonances in QGP, and Drell-Yan production • single muon from the semi- leptonic decays of heavy flavor • hadrons • advantages over electrons: no  conversion, much less Dalitz decay contribution, less affected by radiation losses in the detector • materials, trigger capability in Au+Au • trigger capability for low to high pT J/ in central Au+Au collisions • excellent mass resolution, separate different upsilon states • e-muon correlation to distinguish heavy flavor production from initial lepton pair production

11. Simulation: Hadron Rejection and Muon Trigger at STAR Iron bars • Muon penetrates iron bars, other particles are stopped • Good Time Resolution (60-70ps): rejects background greatly • 1 hit per 5 head-on Au+Au: Dimuon trigger • Large coverage: diameter of 7 meters 11

12. Concept of Design of the STAR-MTD            A detector with long-MRPCs covers the whole iron bars and leave the gaps in- between uncovered. Acceptance: 45% at ||<0.5 117 modules, 1404 readout strips, 2808 readoutchannels Long-MRPC detector technology, HPTDC electronics (same as STAR-TOF)           12

13. LMRPC for STAR-MTD

14. LMRPC for STAR-MTD Filter circuit • Readout strips: 3.8cm x 90cm x 12 • Inter-strip separation: 6 mm • Gas gaps: 0.25 mm x 6 • Outer glass:1.1 mm • Inner glass: 0.7 mm • HV electrode: colloidal graphite • ~4MΩ/ 1 2 3 Strip width: 3.8cm 4 5 6 Inter-strip separation:0.6cm 7 8 9 10 11 Strip length: 90cm 12

15. Surface resistivity distribution of electrode 20 points, average: 4.3M /□ minimum: 2.9M /□ maximum: 5.8M /□ 15

16. System layout of cosmic ray 1 2 5cm*5cm*20cm scintillators Above and below the module 3 2cm*2cm*4cm scintillators above and below the module PMT0 s0 4 5 PMT2 s1 PMT1 6 7 s3 PMT5 8 9 LMRPC 10 11 s4 PMT6 12 s2 PMT4 PMT3 Efficiency: determined by S3, S4, LMRPC Resolution: calculated with S0,S1, S2,LMRPC

17. Efficiency and time resolution @7.5kV, 4000 events, time is 65ps 95%Freon/5%iso-butane : efficiency>90% @ 7000V, time resolution <100ps 94%Freon/5%iso-butane/1%SF6 : efficiency>90% @ 7200V, time resolution ~ 75ps

18. Noise rate Noise < 0.4 Hz/cm^2 @ 7200V

19. Uniformity 94%Freon/5%iso-butane/1% SF6 @ 7500V Efficiency ~ 95% Time resolution 60~80ps Not bad uniformity!

20. Beam-test area in IHEP

21. Detector system at experiment area position Trigger and PID T0(trigger) and MRPC MRPC C0 MRPC MWPC PMT3&4 PMT1&2

22. Efficiency & time resolution for proton Efficiency > 95% @ 6600V Time resolution ~ 70ps

23. Trigger scan -- vertical 9 Trigger: 2cm x 4cm Move trigger: 5mm/step@7200V 10 11 12 Time resolution Efficiency

24. Trigger scan -- horizontal 9 10 Move trigger: 5cm/step@6800V 11 12 Efficiency ~ 99% Time resolution ~ 55ps Good uniformity!!

25. Signal propagation velocity Charge at two ends of one strip @ 6800V T_diff/2 = x0+dx/v 1/v = 56 ps/cm Good linearity

26. LMRPC manufacture milestones 2011 2012 Plan 1/2 3/4 5/6 7/8 9/10 11/12 1/2 3/4 5/6 11/12 7/8 9/10 Start 20 LMRPCs 40 LMRPCs 60 LMRPCs 80 LMRPCs 100 LMRPCs 115 LMRPCs Tsinghua : 65 USTC: 50 We want to duplicate STAR-TOF’s success!

27. FAIR-CBM TOF • Full system time resolution sT ~ 80 ps • Efficiency > 95 % • Rate capability ~ 20 kHz/cm2 • Acceptable cross-talk and charge-sharing • Pile-up < 5% • Occupancy < 5 % • Spatial resolution CBM

28. CBM-TOF requirement 20kHz/cm2 8kHz/cm2 3.5-8kHz/cm2 1.5-3.5kHz/cm2 0.5-1.5kHz/cm2 Possible Solution: – Timing RPC with low resistivity glass ~1010 Ωcm – Center: pad-readout Outside: strip-readout 1 2 3 4 5 28

29. World map of MRPC’s rate capability

30. Performance of low resistivity glass Specifications: Maximal dimension: 50cm×50cm Bulk resistivity: ~1010.cm Standard thickness: 0.5mm--2mm Thickness uniformity: 0.02mm Dielectric constant: ~10 Surface roughness: <10nm DC measurement: very stable

31. Scanned images of glass 3-D image 2-D image

32. MRPCs with different structure 2 cm 2 cm 2.5cm Gap 4mm 13 cm 97cm

33. Beam test for rate capability PMT: 0.8-20 kHz/cm2 MRPC: 2-30 kHz/cm2 Charge distributions of the 10-gap RPC for different particle fluxes at 2.64 kV/gap

34. Performance of high rate MRPC When the particle flux increases every 5 kHz/cm2, the efficiency decreases by 1% and the time resolution deteriorates by 4 ps. Efficiency and time resolution as a function of high voltage at a rate of about 800Hz/cm2

35. HV scan (strip readout module) • Tdiff =T MRPC#3-T MRPC#4 , • σMRPC#3 ≈ σMRPC#4 ≈ σdiff /sqrt(2)

36. "or" eff 100 strip1 strip2 80 strip3 "and" eff 60 Efficiency(%) 40 20 0 -20 -10 0 10 20 30 40 Rpcy(mm) Position Scan MRPC#3 3 2 1 Rpcy MRPC#4

37. Crosstalk & charge sharing- doped glass Rpcy (cm) Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger) 3 2 1 10% 20%

38. Crosstalk & charge sharing- common glass Rpcy (cm) Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger) 3 2 1 2% 2%

39. Position resolution T1 T2 DeltaT=(T2-T1)/2 • Using the tracking, we get the signal propagation velocity: ~ 61ps/cm • Position resolution: <5 mm

40. Conclusions • Development of 6-gap MRPC for STAR-TOF, time resolution<70ps, efficiency>95% • 3100 MRPCs were assembled for STAR-TOF, yield>95% • Development of LMRPC for STAR-MTD, time resolution • <70ps, efficiency>95%, noise rate<1Hz/cm2 • Development of low resistive glass with resistivity ~ 1010Ωcm • Development of pad- and strip- readout high rate MRPCs, rate capability>25kHz/cm2, time resolution<80ps • Application in NICA-MPD and Jefferson lab, .…

41. Thanks for your attention!