Spark probability measurement for Spark probability measurement for GEM for CBM GEM for CBM (Summary of the beam test at CERN SPS, (Summary of the beam test at CERN SPS, October 2011)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
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Outline of the talkOutline of the talkMotivationTest set-upAnalysis and ResultsSummary and future plan
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GEM for CBM GEM for CBM Triple GEM as a precise tracking
detector in the Muon Chamber (MUCH) under the extreme conditions of the CBM experiment
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ObjectiveObjectiveTo measure the properties of
GEM with shower and in particular Spark probabilities of Double mask and Single mask GEM
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Summary of beam testSummary of beam testDetectors
◦ 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
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Voltage distribution in Voltage distribution in GEMGEM
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Details of the set upDetails of the set upGas mixture: Ar/CO2: 70/307 channel HVG210 power supply2 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 7
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Set-up for Pion beamSet-up for Pion beam
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Set-up for showerSet-up for shower
Ref. A. Senger 10
Particle production during Particle production during shower from FLUKA simulationshower from FLUKA simulation
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Comparison of shower number Comparison of shower number from measurement and from measurement and simulationsimulation
CurrentCurrent
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Current and GEM counting rate:Current and GEM counting rate:Pion beam 300 kHzPion beam 300 kHz
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Current and GEM counting rate Current and GEM counting rate during Shower: Beam rate300 during Shower: Beam rate300 kHzkHz
Pion beam Pion beam with absorber
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Current as a function of Current as a function of rate for DM GEMrate for DM GEM
Charge Vs. current for DM Charge Vs. current for DM GEMGEM
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Pion beamPion beam with absorber
Slope: -1.38×10-12
Slope: -2.04×10-12
Pion beam Pion beam with absorber
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Current as a function of rate for Current as a function of rate for SM GEMSM GEM
Charge Vs. current for SM Charge Vs. current for SM GEMGEM
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Pion beamPion beam with absorber
Slope: -1.35×10-12
Slope: -1.52×10-12
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EfficiencyEfficiency
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Efficiency during showerEfficiency during shower
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Efficiency as a function of rate Efficiency as a function of rate during showerduring shower
Efficiency for pion beamEfficiency for pion beam
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Efficiency vs. rate for pion Efficiency vs. rate for pion beambeam
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Spark probability Spark probability measurementmeasurement
Methods of Spark detectionAbsence of signal
◦Drop in the counting rate of GEM signals
◦Data from sampling ADCDetection of high current
◦Sudden increase in the Current (Slow)
◦Built in Trip checker in HVG210 Power supply (Fast)
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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
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No spark during a spillNo 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
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Drop in GEM counting rateDrop 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
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Sudden increase in Sudden increase in currentcurrent
Double Mask GEM with Fe Absorber
Gas: Ar/CO2 : 70/30, Gas flow rate: 5 lt/hr, Particle rate: ~300 kHz, Pion beam
412 - 407 - 402
415_410_405
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Two sparks during a spillTwo sparks during a spill
Spark probability vs. global Spark probability vs. global voltagevoltagefor showerfor shower
Discharge probability:
No. of Discharge/ No. of incident particle
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Spark probability vs. global Spark probability vs. global voltagevoltageshower and pion beamshower and pion beam
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Spark probability vs. gainSpark probability vs. gainshower and pion beamshower and pion beam
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Spark probability vs. global Spark probability vs. global voltagevoltageSM and DMSM and DM
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Off spill spark rate as a function Off spill spark rate as a function of global voltageof global voltage
SummarySummary 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
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Future plan: test beam Future plan: test beam Optimized drift gap (3 mm)Conditioned counters (SM and
DM)Pixel readout ?
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AcknowledgementAcknowledgement
Thanks to the RD51 collaboration for their support in the beam test….
Thank you for your kind attention !37
Back up slidesBack up slides
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ConclusionConclusionThe 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.
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Pulse height distributionPulse height distribution
100 sample is taken
Difference of the maximum and minimum value of the channel is taken as pulse height
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MethodMethod
Resolution ~17.6%
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FeFe5555 spectrum @ 400-395- spectrum @ 400-395-390 V390 V
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For DM GEM at 400-395-390 For DM GEM at 400-395-390 with pion beam: Rate 300 kHzwith pion beam: Rate 300 kHz
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For DM GEM at 415-410-405 For DM GEM at 415-410-405 during shower: Beam rate: 300 during shower: Beam rate: 300 kHzkHz
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For SM GEM at 400-395-390 For SM GEM at 400-395-390 with pion beam: Rate 300 kHzwith pion beam: Rate 300 kHz
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For SM GEM at 405-400-395 For SM GEM at 405-400-395 during shower: Beam rate: 300 during shower: Beam rate: 300 kHzkHz
Geometry of the experimental set-Geometry of the experimental set-upup
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For SM GEM at 400-395-390 with For SM GEM at 400-395-390 with pion beam: Rate 300 kHzpion beam: Rate 300 kHz
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Spill:Rbeam
<R*beam> > 0.5
Spark:
CGEM
Cbeam
<RGEM>
<Rbeam>
< 0.2
Spill
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DefinitionsDefinitions
Gain as a function of global voltage Gain as a function of global voltage for SM GEMfor SM GEM
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Corrected voltage for Corrected voltage for GEM3GEM3
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Discharge probability:
No. of Discharge/ No. of incident particle
Ref: S. Bachmann et al., NIM A 470 (2001) 548–561
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Discharge probability as a Discharge probability as a function of gainfunction of gain
Spark rate as a function of Spark rate as a function of global voltageglobal voltage
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