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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