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Spark probability measurement for GEM for CBM (Summary of the beam test at CERN SPS, October 2011). Saikat Biswas , A . Abuhoza , U . Frankenfeld , C. Garabatos , J. Hehner , T. Morhardt , C.J. Schmidt , H.R. Schmidt, J. Wiechula GSI Detector Laboratory.
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Spark probability measurement for GEM for CBM (Summary of the beam test at CERN SPS, October 2011) Saikat Biswas, A. Abuhoza, U. Frankenfeld, C. Garabatos, J. Hehner, T. Morhardt, C.J. Schmidt, H.R. Schmidt, J. Wiechula GSI Detector Laboratory RD51 Mini week, 13-15 June 2012, CERN
Outline of the talk • Motivation • Test set-up • Analysis and Results • Summary and future plan
GEM for CBM • Triple GEM as a precise tracking detector in the Muon Chamber (MUCH) under the extreme conditions of the CBM experiment
Objective • To measure the properties of GEM with shower and in particular Spark probabilities of Double mask and Single mask GEM
Detectors 2 Double mask GEM 1 Single mask GEM Measurement with Pion beam Pion beam with absorber: Shower Measured parameters Current Voltage Trigger and GEM Counts GEM signal Summary of beam test
Details of the set up • Gas mixture: Ar/CO2: 70/30 • 7 channel HVG210 power supply • 2 sum-up boards are used for signal (2×128 6×6 mm2 pads) for DM GEM • 4 sum-up boards are used for signal (4×128 4×4 mm2 pads) for SM GEM • PXI LabView based DAQ is used
Particle production during shower from FLUKA simulation Ref. A. Senger
Current and GEM counting rate during Shower: Beam rate300 kHz
Current as a function of rate for DM GEM Pion beam with absorber Pion beam
Charge Vs. current for DM GEM Slope: -2.04×10-12 Slope: -1.38×10-12 Pion beam with absorber Pion beam
Current as a function of rate for SM GEM Pion beam with absorber Pion beam
Charge Vs. current for SM GEM Slope: -1.52×10-12 Slope: -1.35×10-12 Pion beam with absorber Pion beam
Methods of Spark detection • Absence of signal • Drop in the counting rate of GEM signals • Data from sampling ADC • Detection of high current • Sudden increase in the Current (Slow) • Built in Trip checker in HVG210 Power supply (Fast)
No spark during a spill • Double Mask GEM with Fe Absorber • Gas: Ar/CO2 : 70/30, Gas flow rate: 5 lt/hr, Particle rate: ~300 kHz, Pion beam 415_410_405
Drop in GEM counting rate • Double Mask GEM with Fe Absorber • Gas: Ar/CO2 : 70/30, Gas flow rate: 5 lt/hr, Particle rate: ~300 kHz, Pion beam 415_410_405
Sudden increase in current • Double Mask GEM with Fe Absorber • Gas: Ar/CO2 : 70/30, Gas flow rate: 5 lt/hr, Particle rate: ~300 kHz, Pion beam 415_410_405
Two sparks during a spill 412 - 407 - 402 • Double Mask GEM with Fe Absorber • Gas: Ar/CO2 : 70/30, Gas flow rate: 5 lt/hr, Particle rate: ~300 kHz, Pion beam 415_410_405
Spark probability vs. global voltagefor shower Discharge probability: No. of Discharge/ No. of incident particle
Summary • SPS test line has good conditions for our purpose • 2 mm drift gap sub-optimal (3 mm standard!) • Efficiency • Rate dependency of efficiency observed • Pion (signal close to threshold!) • Shower (signal below threshold! Pick-up noise) • Spark probability • Spark measurement reliable also with noise (high thresholds) • Comparable spark probability for pion beam and shower (high rate) ! • Higher spark probabilities for lower intensities (shower) • SM GEM • Was in conditioning phase. • No indication for different performance
Future plan: test beam • Optimized drift gap (3 mm) • Conditioned counters (SM and DM) • Pixel readout ?
Acknowledgement Thanks to the RD51 collaboration for their support in the beam test…. Thank you for your kind attention !
Conclusion • The spark probability for pion beam is high. • May be the gain is not measured correctly!! • Effect of space charge !! • Investigated in different conditions. • to be understood the different spark probabilities.
Method • 100 sample is taken • Difference of the maximum and minimum value of the channel is taken as pulse height
Fe55 spectrum @ 400-395-390 V Resolution ~17.6%
Definitions Rbeam Spill: > 0.5 <R*beam> CGEM Cbeam < 0.2 Spark: <RGEM> <Rbeam> Spill