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Saikat Biswas , A . Abuhoza , U . Frankenfeld , C. Garabatos ,

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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Saikat Biswas , A . Abuhoza , U . Frankenfeld , C. Garabatos ,

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  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

  2. Outline of the talk • Motivation • Test set-up • Analysis and Results • Summary and future plan

  3. GEM for CBM • Triple GEM as a precise tracking detector in the Muon Chamber (MUCH) under the extreme conditions of the CBM experiment

  4. Objective • To measure the properties of GEM with shower and in particular Spark probabilities of Double mask and Single mask GEM

  5. 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

  6. Voltage distribution in GEM

  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

  8. Set-up for Pion beam

  9. Set-up for shower

  10. Particle production during shower from FLUKA simulation Ref. A. Senger

  11. Comparison of shower number from measurement and simulation

  12. Current

  13. Current and GEM counting rate:Pion beam 300 kHz

  14. Current and GEM counting rate during Shower: Beam rate300 kHz

  15. Current as a function of rate for DM GEM Pion beam with absorber Pion beam

  16. Charge Vs. current for DM GEM Slope: -2.04×10-12 Slope: -1.38×10-12 Pion beam with absorber Pion beam

  17. Current as a function of rate for SM GEM Pion beam with absorber Pion beam

  18. Charge Vs. current for SM GEM Slope: -1.52×10-12 Slope: -1.35×10-12 Pion beam with absorber Pion beam

  19. Efficiency

  20. Efficiency during shower

  21. Efficiency as a function of rate during shower

  22. Efficiency for pion beam

  23. Efficiency vs. rate for pion beam

  24. Spark probability measurement

  25. 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)

  26. 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

  27. 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

  28. 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

  29. 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

  30. Spark probability vs. global voltagefor shower Discharge probability: No. of Discharge/ No. of incident particle

  31. Spark probability vs. global voltageshower and pion beam

  32. Spark probability vs. gainshower and pion beam

  33. Spark probability vs. global voltageSM and DM

  34. Off spill spark rate as a function of global voltage

  35. 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

  36. Future plan: test beam • Optimized drift gap (3 mm) • Conditioned counters (SM and DM) • Pixel readout ?

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

  38. Back up slides

  39. 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.

  40. Pulse height distribution

  41. Method • 100 sample is taken • Difference of the maximum and minimum value of the channel is taken as pulse height

  42. Fe55 spectrum @ 400-395-390 V Resolution ~17.6%

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

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

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

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

  47. Geometry of the experimental set-up

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

  49. Definitions Rbeam Spill: > 0.5 <R*beam> CGEM Cbeam < 0.2 Spark: <RGEM> <Rbeam> Spill

  50. Gain as a function of global voltage for SM GEM

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