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R&D status of low resistive glass and high rate MRPC

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. Motivation. Heavy ion collision from 2-35Gev:

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R&D status of low resistive glass and high rate MRPC

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  1. 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

  2. Motivation Heavy ion collision from 2-35Gev: We can study phase structure of strongly interacting baryon rich matter. CBM Physics topics • Deconfinement / phase transition at high ρB • QCD critical endpoint • The equation-of-state at high ρB • Onset of chiral symmetry restoration at high ρB • 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 ρB.

  3. CBM-TOF requirement • 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

  4. CBM-TOF requirement Possible Solution: – Timing RPC with low resistivity glass ~1010 Ωcm – Center: pad-readout Outside: strip-readout 1 2 3 4 5

  5. Timing RPC world map

  6. Development of low resistive glass Thickness distribution Specifications: maximal dimension: 50cm×50cm bulk resistivity: ~1010.cm standard thickness: 0.5mm--2mm thickness uniformity: 0.02mm DC measurement: very stable surface quality: excellent

  7. Performance test of glass • Resistivity decreases with temperature • Resistivity is very stable in DC measurement This glass was applied with 1000V for about 32days, integrated charge: 1 C/cm2 --roughly corresponding to the CBM life-time over 5 years operation at the maximum particle rate.

  8. Prototype of high rate MRPC (pad-readout) + - FEE 2 cm 2 cm Colloidal graphite: 2M / Gas gap: 10×0.25mm 10×0.22mm Glass: 0.78mm,1mm resistivity: ～1010Ω.cm Working gas: 96% F134a+3% iso-butane+1%SF6 13 cm

  9. Cosmic ray test Cosmic ray test: Time resolution: ~80ps Efficiency: >95%

  10. Cosmic ray test 2mm 1st 2st 3st Trigger: 2cm*4cm 1st neighboring pad: charge sharing + crosstalk 2st and 3st: only crosstalk <5%

  11. Small high rate MRPC Carbon tape: 500k / Gas gap: 10×0.22mm Glass: 0.78mm resistivity: ～1010Ω.cm Working gas: 96.5% F134a+3% iso-butane+0.5%SF6 30 31.5

  12. 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

  13. 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

  14. Prototype of high rate MRPC (strip-readout) Colloidal graphite: 1M / Gas gap: 10×0.25mm Glass: 0.78mm,1mm resistivity: ～1010Ω.cm Gas mixture: Freon/iso-butane/SF6 96.5%/3%/0.5%

  15. Test Setup Target Tsinghua RPC Silicon Main beam PM12 PM5 PM34  10 m • MRPC#3：silicate glass • MRPC#4: common glass Source: 2.5GeV proton

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

  17. "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

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

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

  20. Position resolution T1 T2 DeltaT=(T2-T1)/2 • Using the tracking, we get the signal propagation velocity: ~ 54ps/cm • Position resolution: ~ 1 cm

  21. Conclusions • CBM TOF requirement: 20kHz/cm2 • Low resistive silicate glass: 3-4×1010Ωcm • 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/cm2 • Efficiency>95%, Time resolution: <70ps • Rate capability: 25 kHz/cm2 • Efficiency: ~90%, Time resolution: ~85ps • MRPC-strip readout: 10-gap, silicate glass • Efficiency: ~97%, • Time resolution: ~75ps • Crosstalk: <10% • Charge sharing + crosstalk: <20%

  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!

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