Spark probability measurement for GEM for CBM (Summary of the beam - - PowerPoint PPT Presentation

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Spark probability measurement for GEM for CBM (Summary of the beam - - PowerPoint PPT Presentation

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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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SLIDE 1

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

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Outline of the talk

— Motivation — Test set-up — Analysis and Results — Summary and future plan

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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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Objective

— To 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 test

— 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

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SLIDE 6

Voltage distribution in GEM

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SLIDE 7

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

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SLIDE 8

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Set-up for Pion beam

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SLIDE 9

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Set-up for shower

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SLIDE 10
  • Ref. A. Senger

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Particle production during shower from FLUKA simulation

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SLIDE 11

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Comparison of shower number from measurement and simulation

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SLIDE 12

Current

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Current and GEM counting rate: Pion beam 300 kHz

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Current and GEM counting rate during Shower: Beam rate300 kHz

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Pion beam Pion beam with absorber

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Current as a function of rate for DM GEM

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Charge

  • Vs. current for DM GEM

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Pion beam Pion beam with absorber Slope: -1.38×10-12 Slope: -2.04×10-12

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SLIDE 17

Pion beam Pion beam with absorber

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Current as a function of rate for SM GEM

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SLIDE 18

Charge

  • Vs. current for SM GEM

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Pion beam Pion beam with absorber Slope: -1.35×10-12 Slope: -1.52×10-12

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SLIDE 19

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Efficiency

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SLIDE 20

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Efficiency during shower

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SLIDE 21

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Efficiency as a function of rate during shower

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SLIDE 22

Efficiency for pion beam

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SLIDE 23

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Efficiency vs. rate for pion beam

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SLIDE 24

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Spark probability measurement

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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)

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SLIDE 26

— 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 spill

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SLIDE 27

— 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 rate

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SLIDE 28

— 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 current

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SLIDE 29

— 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 spill

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SLIDE 30

Spark probability vs. global voltage for shower

Discharge probability:

  • No. of Discharge/ No. of incident particle

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SLIDE 31

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Spark probability vs. global voltage shower and pion beam

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Spark probability vs. gain shower and pion beam

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SLIDE 33

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Spark probability vs. global voltage SM and DM

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SLIDE 34

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Off spill spark rate as a function of global voltage

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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

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SLIDE 36

Future plan: test beam

— Optimized drift gap (3 mm) — Conditioned counters (SM and DM) — Pixel readout ?

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SLIDE 37

Acknowledgement

Thanks to the RD51 collaboration for their support in the beam test…. Thank you for your kind attention !

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Back up slides

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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.

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Pulse height distribution

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— 100 sample is taken — Difference of the

maximum and minimum value of the channel is taken as pulse height

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Method

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Resolution ~17.6%

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Fe55 spectrum @ 400-395-390 V

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For DM GEM at 400-395-390 with pion beam: Rate 300 kHz

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SLIDE 44

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For DM GEM at 415-410-405 during shower: Beam rate: 300 kHz

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SLIDE 45

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For SM GEM at 400-395-390 with pion beam: Rate 300 kHz

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SLIDE 46

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For SM GEM at 405-400-395 during shower: Beam rate: 300 kHz

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SLIDE 47

Geometry of the experimental set-up

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For SM GEM at 400-395-390 with pion beam: Rate 300 kHz

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SLIDE 49

Spill:

Rbeam <R*beam>

> 0.5 Spark: ¡

CGEM Cbeam <RGEM> <Rbeam>

< 0.2 Spill

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Definitions

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Gain as a function of global voltage for SM GEM

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Corrected voltage for GEM3

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— Discharge

probability:

  • No. of Discharge/ No.
  • f incident particle

Ref: S. Bachmann et al., NIM A 470 (2001) 548–561

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Discharge probability as a function of gain

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SLIDE 53

Spark rate as a function of global voltage

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