New MRPC prototypes developed in Tsinghua Unversity Huangshan Chen (Tsinghua Unversity)

Outline  High rate MRPC modules  Performance of low resistivity silicate glass  Pad readout MRPC  Strip readout MRPC  MRPC module for STAR-MTD  Module structure  Cosmic-ray test setup and result  Beam test setup and result  Summary 2011/03/31STAR MTD Workshop, USTC, Hefei, China2

High rate MRPC modules 2011/03/31STAR MTD Workshop, USTC, Hefei, China3

FAIR – CBM TOF 2011/03/31STAR MTD Workshop, USTC, Hefei, China4 CBM Full TOF system:  Time resolution s T ~ 80 ps  Efficiency > 95 %  Rate capability < 20 kHz/cm 2  Acceptable cross-talk and charge-sharing.  Low power electronics (~ channels).  Sufficient space resolution Timing RPC :  Active area: A = 170 m 2  Counter time resolution: s T ~ 50 ps  Rate capability: R ~ kHz/cm 2  Granularity: DA ~ cm 2  Operation mode: free running

World map of MRPC’s rate capability 2011/03/31STAR MTD Workshop, USTC, Hefei, China5

Specification of low resistivity silicate glass 2011/03/31STAR MTD Workshop, USTC, Hefei, China6 Specifications: Maximal dimension: 50cm×50cm Bulk resistivity: ~10 10 .cm Standard thickness: 0.5mm--2mm Thickness uniformity:  0.02mm Permittivity : ~10 Surface roughness: <10nm DC measurement: very stable

Scanned images of low resistive silicate glass 2011/03/31STAR MTD Workshop, USTC, Hefei, China7 2-D image 3-D image L X Y Ry i  Ra=0.873 nm  Rq=1.10nm  Ry=9.30nm

8 Using low resistive silicate glass instead of common glass is an innovative way of improving the rate capability of Resistive Plate Chambers. Bulk resistivity: 3-4×10 10 Ωcm The accumulated charge was 1 C/cm 2, roughly corresponding to the CBM life-time over 5 year operation at the maximum counting rate. T = 28 C° HV = 1kV Low resistive silicate glass 2011/03/31STAR MTD Workshop, USTC, Hefei, China

Pad readout MRPC – MRPC #1 HV electrodeGraphite tape Readout pad31.5mm×60 mm×6 Glass typeLow resistive silicate glass Glass thickness0.7mm Gas gap0.22mm×6 2011/03/31STAR MTD Workshop, USTC, Hefei, China9 60mm 31.5mm 3mm

Pad readout MRPC – MRPC #2 HV electrodeGraphite tape Readout pad31.5mm×30 mm, 15.5mm×30mm Glass typeLow resistive silicate glass Glass thickness0.7mm Gas gap0.22mm× /03/31STAR MTD Workshop, USTC, Hefei, China10 30mm 31.5mm15.5mm 3mm

11 Tests were performed at GSI-Darmstadt under uniform irradiation by secondary particles stemming from proton reactions at 2.5 GeV. The higher rates can be obtained by moving the RPCs up closer to the main beam. Gas mixture: Freon/iso-butane/SF6 : 96.5%/3%/0.5% 2.5GeV Beam test setup at GSI-Darmstadt 2011/03/31STAR MTD Workshop, USTC, Hefei, China

12 The beam comes in spills. We take the mean of the PMT and MRPC measurements as a sound reference for rate estimation : PMT rate: 0.8~20 kHz/cm 2 MRPC rate: 2~30 kHz/cm 2 Mean rate: 1.4~25 kHz/cm 2 Counting rate 2011/03/31STAR MTD Workshop, USTC, Hefei, China

13 Time diff =T MRPC#1 -T MRPC#2 Time difference 2011/03/31STAR MTD Workshop, USTC, Hefei, China Resolution of time difference become worse with the raise of rate.

14 MRPC#2: 10-gap With rate increasing, the average charge decreases, which leads to a relativity lower efficiency. Charge distribution of MRPC#2 2011/03/31STAR MTD Workshop, USTC, Hefei, China

15  The efficiency is higher than 90% and the time resolution remains below 90ps once at the efficiency plateau.  By means of using more gas gaps, the 10-gap RPC shows a better performance. MRPC#1: 6-gap MRPC#2: 10-gap HV scan at 1.4kHz/cm /03/31STAR MTD Workshop, USTC, Hefei, China

16 90% 76% 110ps 85ps The efficiencies and time resolutions deteriorate with the counting rate. MRPC#2 yields much better results: 90% efficiency, 85ps resolution at the rate of ~25 kHz/cm 2. Rate scan 2011/03/31STAR MTD Workshop, USTC, Hefei, China

17 240mm 22mm interval: 3mm Strip readout module structure: MRPC#3 & MRPC#4 HV electrodecolloidal graphite Readout strip22mm×240 mm×3 Glass typeLow resistive silicate / common Glass thickness0.7mm Gas gap0.25mm× /03/31STAR MTD Workshop, USTC, Hefei, China

Surface resistivity distribution of electrode 2011/03/31STAR MTD Workshop, USTC, Hefei, China18 20 points: minimum: 2.9M  / □ maximum: 5.8M  / □ average: 4.3M  / □

Main beam Target  10 m PM12 PM34 Tsinghua RPC PM5 Silicon 19 MRPC#3 ： silicate glass MRPC#4: common glass Beam test layout 2011/03/31STAR MTD Workshop, USTC, Hefei, China

20 T diff =T MRPC#3 -T MRPC#4 HV scan Eff MRPC#3 ≈ Eff MRPC#4 > 95%, σ MRPC#3 ≈ σ MRPC#4 ≈ σ diff / sqrt(2) < 80ps 2011/03/31STAR MTD Workshop, USTC, Hefei, China

Rpcy "or" eff strip1 strip2 strip3 "and" eff Efficiency(%) Rpcy(mm) MRPC#3 MRPC#4 Position Scan 2011/03/31STAR MTD Workshop, USTC, Hefei, China

22 Position resolution 2011/03/31STAR MTD Workshop, USTC, Hefei, China T1T2 DeltaT=(T2-T1)/2 Using the tracking, we get the signal propagation velocity: ~ 61ps/cm Position resolution: <5 mm

23 2×4 (cm 2 ) 1×2 (cm 2 ) Efficiency: 95% 97% MRPC#3MRPC#4 Efficiency correction with tracking 2011/03/31STAR MTD Workshop, USTC, Hefei, China

MRPC module for STAR-MTD 2011/03/31STAR MTD Workshop, USTC, Hefei, China24

Module structure 2011/03/31STAR MTD Workshop, USTC, Hefei, China25 Strip length: 900mm Strip width: 38 mm Interval: 6 mm HV electrodecolloidal graphite ~5 MΩ/ Readout strip38mm x 900 mm x 12 Interval6mm Glass typeFloat Glass Glass thickness0.7mm(inner), 1.1mm(outer) Gas gap0.25mm x 6

Cosmic-ray test system layout 2011/03/31STAR MTD Workshop, USTC, Hefei, China26 2cm*2cm*4cm scintillators above and below the module cm*5cm*20cm scintillators Above and below the module Gas mixture: 95%Freon/5%iso-butane Or 94%Freon/5%iso-butane/1%SF6 Gas flow: 50ml/min

Efficiency and time resolution 95%Freon/5%iso-butane : 96.3kV/cm (HV=±7.22 kV), time resolution <100ps 94%Freon/5%iso-butane/1%SF6 : 98.3 kV/cm (HV= ±7.37 kV ), time resolution ~ 75ps 2011/03/31STAR MTD Workshop, USTC, Hefei, China27

Noise level 2011/03/31STAR MTD Workshop, USTC, Hefei, China28 Filter circuit Having a filter circuit on HV electrode, the noise is reduced to a very low level! Most of noise level are smaller than 1.0 Hz/cm 2. 94%Freon/5%iso-butane/1% SF6, E=104 kV/cm (HV=±7.8kV)

Noise level 2011/03/31STAR MTD Workshop, USTC, Hefei, China29 94%Freon/5%iso-butane/1% SF6 95%Freon/5%iso-butane Noise < 0.6 Hz/cm (HV=±7.2kV, eff~95%)Noise < 0.6 Hz/cm (HV=±7.4kV, eff ~95%)

Uniformity 94%Freon/5%iso-butane/1% 100 kV/cm (HV=±7.5 kV) Efficiency ~ 95%Time resolution :60~80psNot bad uniformity! 2011/03/31STAR MTD Workshop, USTC, Hefei, China30

Beam-test area at IHEP, BEIJING 2011/03/31STAR MTD Workshop, USTC, Hefei, China31 Particle e+, e-,  +,  -,p momentum e200MeV/c~1.3GeV/c  400MeV/c~900MeV/c p500MeV/c~1GeV/c rate3~4Hz

Detector system at experiment area 2011/03/31STAR MTD Workshop, USTC, Hefei, China32 C0 MWPC MRPC PMT1&2 PMT3&4 MRPC Gas mixture: 150ml/min T0(trigger) and MRPC position Trigger and PID

Beam 2011/03/31STAR MTD Workshop, USTC, Hefei, China33 Trigger = SC1+SC2-C0+T0   + p (600MeV) Rate ~ 1-20/min Distinguish between pion and proton using the charge spectrum of PMTs

Efficiency & time resolution for proton 2011/03/31STAR MTD Workshop, USTC, Hefei, China34 Efficiency > ~87 kV/cm (HV= ±6.525 kV)Time resolution ~ 70ps

Trigger scan -- vertical 2011/03/31STAR MTD Workshop, USTC, Hefei, China Move trigger: 96kV/cm (HV=±7.2kV) EfficiencyTime resolution

Trigger scan -- horizontal 2011/03/31STAR MTD Workshop, USTC, Hefei, China Move trigger: kV/cm (HV= ±6.8 kV) Efficiency ~ 100% Time resolution ~ 55ps T_diff/2 = t0+dx/v 1/v = ps/cm

Summary  High rate MRPC modules  Low resistive silicate glass  ~10 10 .cm, <10nm, stable DC measurement  MRPC #2 (10-gap, pad readout, silicate glass)  >95%, < kHz/cm 2 ; ~90%, ~85 25 kHz/cm 2  MRPC #3 (10-gap, strip readout, silicate glass)  ~97%, ~75 ps, <5mm  MRPC module for STAR-MTD  >95%, ~75 ps in cosmic-ray test; ~100%, ~70 ps in beam test  Low noise level  Good uniformity across the different strips and along the strip 2011/03/31STAR MTD Workshop, USTC, Hefei, China37 That’s all! Thank you!