1. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University R&D status of low resistive glass and high rate MRPC Outline: Motivation and CBM-TOF requirement Development of low resistive glass High rate MRPC and beam test results Summary 1

2. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 2 Motivation Heavy ion collision from 2-35Gev: We can study phase structure of strongly interacting baryon rich matter. Particle ID  Hadrons: STS + TRD + TOF  Electrons: STS + MVD + TRD + TOF + ECAL  Muons: STS + MUCH + TOF A very good resolution of TOF is essential to get good PID at high ρ B. CBM Physics topics Deconfinement / phase transition at high ρ B QCD critical endpoint The equation-of-state at high ρ B Onset of chiral symmetry restoration at high ρ B

3. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 3  Full system time resolution  T ~ 80 ps  Efficiency > 95 %  Rate capability < 20 kHz/cm 2  Acceptable cross-talk and charge-sharing  Pile-up < 5%  Occupancy < 5 %  Spatial resolution CBM-TOF requirement

4. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 4 Possible Solution: – Timing RPC with low resistivity glass ~10 10 Ωcm – Center: pad-readout Outside: strip-readout CBM-TOF requirement 12345

5. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 5 Timing RPC world map

6. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 6 Development of low resistive glass Specifications: maximal dimension: 50cm×50cm bulk resistivity: ~10 10 .cm standard thickness: 0.5mm--2mm thickness uniformity:  0.02mm DC measurement: very stable surface quality: excellent Thickness distribution

7. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 7 Performance test of glass This glass was applied with 1000V for about 32days, integrated charge: 1 C/cm 2 --roughly corresponding to the CBM life- time over 5 years operation at the maximum particle rate.  Resistivity decreases with temperature  Resistivity is very stable in DC measurement

8. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 8 Prototype of high rate MRPC (pad-readout) 2 cm 13 cm Colloidal graphite: 2M  / Gas gap: 10×0.25mm 10×0.22mm Glass: 0.78mm,1mm resistivity: ～ 10 10 Ω.cm Working gas: 96% F134a+3% iso-butane+1%SF6 FEE + -

9. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 9 Cosmic ray test Cosmic ray test: Time resolution: ~80ps Efficiency: >95%

10. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 10 Cosmic ray test Trigger: 2cm*4cm 1 st 2 st 3 st 1 st neighboring pad: charge sharing + crosstalk 2 st and 3 st : only crosstalk <5% 2mm

11. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 11 Small high rate MRPC Carbon tape: 500k  / Gas gap: 10×0.22mm Glass: 0.78mm resistivity: ～ 10 10 Ω.cm Working gas: 96.5% F134a+3% iso-butane+0.5%SF6 31.5 30

12. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 12 Beam test for rate capability PMT: 0.8-20 kHz/cm 2 MRPC: 2-30 kHz/cm 2 Charge distributions of the 10-gap RPC for different particle fluxes at 2.64 kV/gap

13. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 13 Performance of high rate MRPC Efficiency and time resolution as a function of high voltage at a rate of about 800Hz/cm 2 When the particle flux increases every 5 kHz/cm 2, the efficiency decreases by 1% and the time resolution deteriorates by 4 ps.

14. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 14 Prototype of high rate MRPC (strip-readout) Colloidal graphite: 1M  / Gas gap: 10×0.25mm Glass: 0.78mm,1mm resistivity: ～ 10 10 Ω.cm Gas mixture: Freon/iso-butane/SF6 96.5%/3%/0.5%

15. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 15 Main beam Target  10 m PM12 PM34 Tsinghua RPC PM5 Silicon MRPC#3 ： silicate glass MRPC#4: common glass Test Setup Source: 2.5GeV proton

16. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 16 HV scan T diff =T MRPC#3 -T MRPC#4, σ MRPC#3 ≈ σ MRPC#4 ≈ σ diff / sqrt(2)

17. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 17 Position Scan 231 Rpcy -20-10010203040 0 20 40 60 80 100 "or" eff strip1 strip2 strip3 "and" eff Efficiency(%) Rpcy(mm) MRPC#3 MRPC#4

18. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 18 Crosstalk & charge sharing- doped glass 231 Rpcy (cm) 20% 10% Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger)

19. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 19 Crosstalk & charge sharing- common glass 231 Rpcy (cm) 2% Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger)

20. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 20 Position resolution T1T2 DeltaT=(T2-T1)/2 Using the tracking, we get the signal propagation velocity: ~ 54ps/cm Position resolution: ~ 1 cm

21. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 21 Conclusions CBM TOF requirement: 20kHz/cm 2 Low resistive silicate glass: 3-4×10 10 Ωcm MRPC-pad readout: 10-gap, 12 pads, silicate glass Efficiency>95%, Time resolution: ~80ps MRPC-pad readout: 10-gap, silicate glass HV scan at 800 Hz/cm 2 Efficiency>95%, Time resolution: <70ps Rate capability: 25 kHz/cm 2 Efficiency: ~90%, Time resolution: ~85ps MRPC-strip readout: 10-gap, silicate glass Efficiency: ~97%, Time resolution: ~75ps Crosstalk: <10% Charge sharing + crosstalk: <20%

22. 15 th CBM collaboration meeting, GSI, Darmstadt, Germany, April 12-16, 2010Wang Yi, Tsinghua University 22 Next steps Improve the production architecture of low resistive glass to increase the yield. Develop large prototype of high rate MRPC (pad or strip) Optimize the design of 1m long strip counter Beam test…. Thank You!