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Prototypes of high rate MRPC for CBM TOF. Jingbo Wang Department of Engineering Physics, Tsinghua University, Beijing, China. RPC-2010-Darmstadt, Germany. Outline. CBM TOF requirement Low resistive silicate glass Pad readout MRPCs Chamber Structure Test setup Test results

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Prototypes of high rate mrpc for cbm tof

Prototypes of high rate MRPC for CBM TOF

Jingbo Wang

Department of Engineering Physics, Tsinghua University, Beijing, China

RPC-2010-Darmstadt, Germany


Outline
Outline

  • CBM TOF requirement

  • Low resistive silicate glass

  • Pad readout MRPCs

  • Chamber Structure

  • Test setup

  • Test results

  • Strip readout MRPCs

  • Chamber Structure

  • Test setup

  • Test results

  • A prototype for CBM TOF


1 cbm tof requirement
1. CBM TOF requirement

  • Overall time resolution σT = 80 ps.

  • Space resolution ≤ 5 mm × 5 mm.

  • Efficiency > 95 %.

  • Pile-up < 5%.

  • Rate capability > 20 kHz/cm2.

  • Multi-hit capability (low cross-talk).

  • Compact and low consuming electronics (~65.000 electronic channels).

20 kHz/cm2


2 low resistive silicate glass
2. Low resistive silicate glass

3-4×1010Ωcm

  • The accumulated charge was 1 C/cm2, roughly corresponding to the CBM life-time over 5 year operation at the maximum counting rate.

T = 28 C°

HV = 1kV

  • Using electrodes made of semi-conductive glass is an innovative way of improving the rate capability of Resistive Plate Chambers.


3 pad readout mrpcs
3. Pad readout MRPCs

  • Chamber structure

  • Test setup

  • HV scan

  • Rate scan


Structure mrpc 1 6 gap
Structure: MRPC#1_6-gap

  • Parameters

  • Gap number: 6

  • Glass type: silicate

  • Gap width: 0.22mm

  • Glass thickness: 0.7mm

  • Gas mixture:

    Freon/iso-butane/SF6

    96.5%/3%/0.5%

Low-resistive silicate glass with a bulk resistivity of 3~4×1010Ωcm

Almost the same as the standard STAR module

63mm


Structure mrpc 2 10 gap
Structure: MRPC#2_10-gap

Positive HV

Negative HV

30mm

31.5mm

  • MRPC#2 has a similar structure and working conditions than MRPC#1 but with different dimensions of the pick-up pads.

  • Such a structure provides higher signal amplitudes and smaller fluctuations, which are expected to improve the detection efficiency as well as the time resolution.


Test setup
Test setup

  • 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.

2.5GeV


Counting rate
Counting rate

  • PMT rate: 0.8~20 kHz/cm2

  • MRPC rate: 2~30 kHz/cm2

  • Mean rate: 1.4~25 kHz/cm2

Top View

  • The beam comes in spills.

  • We take the mean of the PMT and MRPC measurements as a sound reference for rate estimates .


Time difference
Time difference

Timediff =TMRPC#1-TMRPC#2


Charge distribution of mrpc 2
Charge distribution of MRPC#2

MRPC#2: 10-gap

  • With rate increasing, the average charge decreases, which leads to a relativity lower efficiency.


Hv scan at 800hz cm 2
HV scan at 800Hz/cm2

  • The efficiency reaches above 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


Rate scan
Rate scan

90%

110ps

76%

85ps

  • The efficiencies and time resolutions deteriorate with the counting rate.

  • MRPC#2 yields much better results: 90% efficiency, 85ps resolution.

MRPC#1: 6-gap

MRPC#2: 10-gap


4 strip readout mrpcs
4. Strip readout MRPCs

  • Chamber structure

  • MRPC#3: silicate glass

  • MRPC#4: common glass

  • Test setup

  • HV scan

  • Position scan

  • Analysis with particle tracking


Structure mrpc 3 mrpc 4
Structure: MRPC#3 & MRPC#4

  • Glass type: silicate / common

  • HV electrode: colloidal graphite

  • Number of gaps: 10

  • Gap width: 0.25mm

  • Glass thickness: 0.7mm

  • Gas mixture:

    Freon/iso-butane/SF6

    96.5%/3%/0.5%

colloidal graphite

Guarding line

Diameter:1.5mm

Hole size:0.5mm

3mm

1.5mm

22mm

5mm

240mm

Width:0.508mm

Top and bottom layers


Test setup1
Test Setup

  • MRPC#3:silicate glass

  • MRPC#4: common glass

Target

Tsinghua RPC

Silicon

Main beam

PM12

PM5

PM34

 10 m


Hv scan
HV scan

Tdiff =T MRPC#3-T MRPC#4 ,

σMRPC#3 ≈ σMRPC#4 ≈ σdiff /sqrt(2)


Position scan

"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


Position resolution
Position resolution

T1

T2

DeltaT=(T2-T1)/2

  • Using the tracking, we get the signal propagation velocity:

    ~ 54ps/cm

  • Position resolution:

    ~ 1 cm


Efficiency correction with tracking
Efficiency correction with tracking

2×4 (cm2) 1×2 (cm2)

MRPC#3

MRPC#4

Efficiency: 95% 97%


Crosstalk mrpc 3 silicate
Crosstalk: MRPC#3_silicate

Rpcy (cm)

Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger)

3

2

1

10%

20%


Crosstalk mrpc 4 common
Crosstalk: MRPC#4_common

Rpcy (cm)

Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger)

3

2

1

2%

2%


5 a prototype for cbm tof
5. A prototype for CBM TOF

  • Chamber structure

  • Cosmic ray test system

  • HV scan


Structure mrpc 5
Structure: MRPC#5

  • Glass type: silicate

  • HV electrode: graphite

  • Number of gaps: 10

  • Gap width: 0.25 mm

  • Glass thickness: 0.7 mm

  • Pad dimension: 2*2 cm2

  • Gas mixture:

    Freon/iso-butane/SF6

    96%/3%/1%

2 cm

2 cm

For the inner region of the CBM TOF wall

13 cm


Cosmic ray test
Cosmic ray test

Cosmic ray


Hv scan1
HV scan

96%

~75ps

  • Beam test is needed!


Summary
Summary

  • CBM TOF requirement: 20kHz/cm2

  • Low resistive silicate glass: 3-4×1010Ωcm

  • MRPC#2: 10-gap, pad readout, silicate glass

  • HV scan at 800 Hz/cm2

    Efficiency>95%, Time resolution: <70ps

  • Rate capability: 25 kHz/cm2

    Efficiency: ~90%, Time resolution: ~85ps

  • MRPC#3: 10-gap, strip readout, silicate glass

  • Efficiency: ~97%,

  • Time resolution: ~75ps

  • Crosstalk: 20%, 10%? (further study is needed)

  • MRPC#5: 10-gap, 12 pads, silicate glass

  • Efficiency: ~96%,

  • Time resolution: ~75ps

  • Beam test is needed in the future!