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DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 1
A differential MRPC prototype for CBM
Outline:• Motivation and CBM-ToF Requirements• Conceptional Design of CBM-ToF • MRPC Design• Experimental Setup (@ COSY)• Results • Summary
Ingo Deppner for the CBM-TOF Group
Physikalische Institut Uni. Heidelberg
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 2
Kaon acceptance depends critically on TOF resolution
CBM-ToF Requirements
full system time resolution T ~ 80 ps
Efficiency > 95 %
Rate capability 25 kHz/cm2
Acceptable cross-talk and charge-sharing.
Polar angular range 2.5° – 25°
Low power electronics (~75.000 channels).
Pile-up < 5%
Occupancy < 5 % (for Au-Au(central) at E=25 GeV/A)
Motivation
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 3
Conceptional Design
Timing RPC with: active area: A = 120 m2
counter time resolution: T ~ 50 ps rate capability: R ~ 0.5 – 25 kHz/cm2
granularity: A ~ 6 – 50 cm2
operation mode: free running HK55.3
44 SM (55%) have a rate < 1 kHz/cm2
Rate profile (Au-Au(minimum bias) at E=25 GeV/A)
kHz/cm2
A. Kiseleva, P.-A. Loizeau
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 4
Strip-MRPC Design
Fully differential Strip MRPC developed at Physikalische Institut Uni. Heidelberg
Counter is designed for an impedance of 100 strip size ~ avalanche size
active area 28 x 16.5 cm2
strips 16strip / gap 7 / 3 mmglass thickness 0.55 mm floatnumber of gaps 8gap width 220 mgas: Reclin/SF6/iso-But 85/10/5 pickup electrode
A proper threshold is important for a low occupancy
cluster := group of neighboring strips with signals generated by a single avalanche
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 7
Results
2RPC := 2
sys – (ref/2)2
ref = 0.5*( 4 PMT_i )1/2
At this time resolution level the TDC non-linearity corrections become important
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 8
Results
At a higher threshold bigger signals with steeper rise times are discriminated which leads typically to a better time resolution
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 9
Results
hits in the RPChits in the trigger PMTsEfficiency := Control of threshold is very important
for a high and uniform efficiency
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 10
Results
DPG-Frühjahrstagung Münster, 21 - 25.03.11
Ingo Deppner 11
Summary
Summary With a threshold of 30 mV at nominal working voltage (11.7 kV) an efficiency of
about 94 % is obtained Cluster size is between 1.4 (thr. = 50 mV) and 1.6 (thr. = 30 mV)
at nominal working voltage
occupancy can be reduced by setting the proper threshold Cross talk is less 3 % Time resolution is in the order of 50 ps and depends also on threshold A rate capability of 1 kHz/cm2 is not achievable with this prototype (float glass)
warming up the counter can help fulfilling this criterion
Next steps testing the rate capability of this prototype in a high rate environment at
GSI in a warm up condition building and testing a full size prototype (active area 25 x 32 cm2, 32
channels and semi conducive glass) until end of May next iteration of PADI (V) with individual threshold settings is ready in the next month