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

RPC in aluminum box

FEE (PADI III)

DPG-Frühjahrstagung Münster, 21 - 25.03.11

Ingo Deppner 5

Experimental Setup

test beam time @ COSY Jülich in Nov. 2010

proton – beam

1st. Scin.

+ PMT 1,2

1st. Sili.stage

2nd. Scin. + PMT 3,4

3rd. Scin. + PMT 5,6

2nd. Sili.stage

HD- RPC

Buc. – MRPC

rear viewfront view

Beam parameter:Beam: protonsMomentum: 3 GeV/cExtraction time: 5 minRate: 10 Hz/cm2 – 40 kHz/cm2 Beam diameter: 6 cm

Trigger and DAQ:

TDC: CAEN 1290V

DPG-Frühjahrstagung Münster, 21 - 25.03.11

Ingo Deppner 6

Results

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

DPG-Frühjahrstagung Münster, 21 - 25.03.11

Ingo Deppner 12

thank you for your attention

CBM-TOF Group Contributing institutions:Tsinghua Beijing,NIPNE Bucharest,GSI Darmstadt,USTC Hefei,PI Heidelberg,KIP Heidelberg,INR Moscow,ITEP Moscow,IHEP Protvino,FZD Rossendorf,KU Seoul,RBI Zagreb.

DPG-Frühjahrstagung Münster, 21 - 25.03.11

Ingo Deppner 13

Backup

reflectometer measurementsTypical RPC signal at 11 kV

(from one pickup electrode)

signal properties: amplitude 5 – 30 mV rise time ~ 250 ps FWHM ~ 500 ps – 1 ns

Scope: LeCroy Wavepro 7300, 3 GHz, 10GS/s