prototypes of high rate mrpc for cbm tof jingbo wang department of engineering physics, tsinghua...
TRANSCRIPT
Prototypes of high rate MRPC for CBM TOF
Jingbo WangDepartment 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
• Strip readout MRPCs Chamber Structure Test setup Test results
• A prototype for CBM TOF
2/27
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).
3/27
20 kHz/cm2
2. Low resistive silicate glass
4/27
0 200 400 600 800 10001E8
1E9
1E10
1E11
Applied voltage(V)
Bulk
resis
tivity(
cm
)
20°C 30°C 40°C 50°C 60°C 70°C
0 5 10 15 20 25 30 35
1
2
3
4
5
67
Current(A)
Bulk resitivity(1010cm)
Time(days)
Curr
ent(A
)
2
3
4
5
678910
Bulk
resis
tivity(1
010
cm)
• Using electrodes made of semi-conductive glass is an innovative way of improving the rate capability of Resistive Plate Chambers.
• 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
3-4×1010 Ωcm
3. Pad readout MRPCs
• Chamber structure
• Test setup
• HV scan
• Rate scan
5/27
Structure: MRPC#1_6-gap
627
63mm
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%
Almost the same as the standard STAR module
Low-resistive silicate glass with a bulk resistivity of 3~4×1010 Ωcm
Structure: MRPC#2_10-gap
7/27
30mm
31.5mm
Negative HV
Positive HV
• 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
8/27
• 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
9/27
• 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
10/27
Timediff =TMRPC#1-TMRPC#2
Charge distribution of MRPC#2
11/27
MRPC#2: 10-gap
• With rate increasing, the average charge decreases, which leads to a relativity lower efficiency.
2.3 2.4 2.5 2.6 2.7 2.870
75
80
85
90
95
100
Efficiency(%)Time resolution(ps)
Applied voltage(kV/gap)E
ffici
ency
(%)
50
60
70
80
90
100
110
120
130
140
150
Tim
e re
solu
tion(p
s)
HV scan at 800Hz/cm2
12/27
2.2 2.3 2.4 2.5 2.6 2.740
50
60
70
80
90
100
Efficiency(%) Time resolution(ps)
Applied voltage(kV/gap)
Effi
cien
cy(%
)
60
70
80
90
100
110
120
130
140
150
Tim
e re
solu
tion(p
s)
MRPC#1: 6-gap MRPC#2: 10-gap
• 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.
0 5 10 15 20 2550
60
70
80
90
100
6-gap MRPC
10-gap MRPC
Effi
cien
cy(%
)
Counting rate (kHz/cm2)
Rate scan
13/27
90%
76%
110ps
85ps
MRPC#1: 6-gap
MRPC#2: 10-gap
• The efficiencies and time resolutions deteriorate with the counting rate.
• MRPC#2 yields much better results: 90% efficiency, 85ps resolution.
0 5 10 15 20 2560
70
80
90
100
110
120
130 diff/210-gap
6-gap
Tim
e re
solu
tion(p
s)Counting rate (kHz/cm2)
4. Strip readout MRPCs
14/27
• 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
15/27
1.5mm5mm
Diameter:1.5mmHole size:0.5mm
Width:0.508mmTop and bottom layers
240mm22mm
3mm
Guarding line
• 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
Test Setup
Main beam
Target
10 m
PM12
PM34
Tsinghua RPC
PM5
Silicon
16/27
• MRPC#3 : silicate glass
• MRPC#4: common glass
HV scan
17/27
5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.220
30
40
50
60
70
80
90
100
Eff: MRPC#3 Eff: MRPC#4
diff/2
Applied voltage(kV)
Effi
cie
ncy(%
)
60
70
80
90
100
110
120
130
140
Tim
e r
esolu
tion(p
s)
Tdiff =T MRPC#3-T MRPC#4 ,
σMRPC#3 ≈ σMRPC#4 ≈ σdiff / sqrt(2)
Position Scan
18/27
2 3 1
Rpcy
-20 -10 0 10 20 30 400
20
40
60
80
100 "or" eff
strip1
strip2
strip3
"and" eff
Effi
cien
cy(%
)
Rpcy(mm)-20 -10 0 10 20 30
70
80
90
100
110strip1
strip2
strip3
Tim
e re
solu
tion(
ps)
Rpcy(mm)
-20 -10 0 10 20 30 400
20
40
60
80
100 "or" eff strip1 strip2 strip3 "and" eff
Effici
ency
(%)
Rpcy(mm)
MRPC#3
MRPC#4
19/27
T1 T2
DeltaT=(T2-T1)/2
Position resolution
• Using the tracking, we get the signal propagation velocity:
~ 54ps/cm• Position resolution: ~ 1 cm
Efficiency correction with tracking
20/27
2×4 (cm2) 1×2 (cm2)
Efficiency: 95% 97%
MRPC#3 MRPC#4
5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2
40
50
60
70
80
90
100
110
Eff_tracking(%) Eff_original(%)
Effi
cien
cy (%
)
High voltage (kV)
5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2
40
50
60
70
80
90
100
110
Eff_tracking(%) Eff_original(%)
Effi
cien
cy (%
)
High voltage (kV)
-1.5 -1.0 -0.5 0.0 0.5 1.00
10
20
30
40
50
60
70
80
90
100
Cha
rge(
ch)
Efficiency_2(%)
Crosstalk_3(%)
Charge_3(ch)
Effi
cien
cy(%
)
Rpcy(cm)
0
100
200
300
400
500
600
700
800
900
1000
Crosstalk: MRPC#3_silicate
21/27
2 3 1
Rpcy (cm)
-1.5 -1.0 -0.5 0.0 0.5 1.00
10
20
30
40
50
60
70
80
90
100
Efficiency_2(%)
Crosstalk_1(%)
Charge_1(ch)
Effi
cien
cy(%
)
Rpcy(cm)
0
200
400
600
800
1000
Cha
rge(
ch)
20%
10%
Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger)
-1.5 -1.0 -0.5 0.0 0.5 1.00
10
20
30
40
50
60
70
80
90
100
Rpcy(cm)
Cha
rge(
ch)
Effi
cien
cy(%
)
Efficiency_2(%)
Crosstalk_3(%)
Charge_3(ch)
0
200
400
600
800
1000
Crosstalk: MRPC#4_common
22/27
2 3 1
Rpcy (cm)
-1.5 -1.0 -0.5 0.0 0.5 1.00
10
20
30
40
50
60
70
80
90
100
Efficiency_2(%)
Crosstalk_1(%)
Charge_1(ch)
Cha
rge(
ch)
Effi
cien
cy(%
)
Rpcy(cm)
0
200
400
600
800
1000
2%2%
Crosstalk_1=counts(T2>0 && T1>0) / counts(trigger)
5. A prototype for CBM TOF
23/27
• Chamber structure
• Cosmic ray test system
• HV scan
Structure: MRPC#5
24/27
2 cm2 cm
13 cm
• 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%
For the inner region of the CBM TOF wall
Cosmic ray test
25/27
Cosmic ray
HV scan
26/27
• Beam test is needed!
96%
~75ps
Summary CBM TOF requirement: 20kHz/cm2
Low resistive silicate glass: 3-4×1010 Ωcm 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!
27/27
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