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A Brief Report on Characteristic Studies of Micromegas

Applied Nuclear Physics Division Saha Institute of Nuclear Physics, Kolkata, India. A Brief Report on Characteristic Studies of Micromegas. RD51 Collaboration Meeting CERN, 14-17 October, 2013. MPGD Laboratory at SINP, Kolkata. RD51 Activities . Experiment Test bench setup

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A Brief Report on Characteristic Studies of Micromegas

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  1. Applied Nuclear Physics Division Saha Institute of Nuclear Physics, Kolkata, India A Brief Report on Characteristic Studies of Micromegas RD51 Collaboration Meeting CERN, 14-17 October, 2013

  2. MPGD Laboratory at SINP, Kolkata RD51 Activities • Experiment • Test bench setup • Characterization of MPGDs • Upgrade for new measurements • Explore other applications • Simulation • Development of neBEM • Interface with Garfield • Upgrade and maintenance • Simulation of MPGDs • Plan for interface with Garfield++ 12th. RD51 Collaboration Meeting

  3. Test Bench Setup • Stainless steel test box • Gas distribution system with 4-channel mixing-unit • Electronics with single-parameter data acquisition system • Fe55 source 12th. RD51 Collaboration Meeting

  4. Supplementary Facilities Residual Gas analyser Digital microscope 12th. RD51 Collaboration Meeting

  5. Schematic Setup Purification System Gas Cylinder Residual Gas Analyzer Gas Mixing System Power Supply (High Voltage) (N471A) Gas Flow In Pressure Gauge Gas Chamber & Detector Gas Flow Out Pre-Amp (ORTEC 142IH) Filter MCA (AMTEK 8000A) Amplifier (ORTEC 672) Oscilloscope 12th. RD51 Collaboration Meeting

  6. Characterization Studies Micro-bulk Micromegas Bulk Micromegas Electron transparency Electron gain Energy resolution Ion back flow Electron transparency Electron gain Energy resolution Experiment Experiment Simulation Experimental studies on GEM and triple-GEM have been initiated !! 12th. RD51 Collaboration Meeting

  7. Bulk Micromegas Mesh Hole ~ 45m Pitch ~ 63m • Specifications • Active area: 15x15 cm2 • Amplification gap: 64 /128 / 192 / 220 m • SS wire diameter: 18 m, pitch 63 / 78 m • Spacer diameter: 400 m, pitch 2 mm Spacer Diameter ~ 400m Pitch ~ 2 mm 12th. RD51 Collaboration Meeting

  8. Estimate of Electron Transparency Experiment: Electron transparency at a given drift field value (d): where: signal amplitude at the given drift field (d) : maximum signal amplitude (keeping amplification field constant) Simulation: Drift of electron from randomly distributed points in drift region using microscopic tracking method Estimate the fraction of electron arriving in amplification region 12th. RD51 Collaboration Meeting

  9. Electron Transparency for Different Gaps Better transparency can be obtained with larger gaps at lower drift field although it worsens with increase in drift field. However, smaller gap shows better transparency at higher drift field !! 12th. RD51 Collaboration Meeting

  10. Electron Transparency for Different Pitches Smaller pitch shows better transparency at lower drift field whereas it is larger pitch which helps at larger values !! 12th. RD51 Collaboration Meeting

  11. Estimate of Electron Gain Experiment: Electron gain at a certain field configuration : where : total number of electrons : primary electrons : constant dependent on electronics : peak position Simulation: Effective electron gain : where : electron transparency : multiplication factor of electrons in their trajectories 12th. RD51 Collaboration Meeting

  12. Electron Gain for Different Amplification Gaps Higher gain can be achieved with larger amplification gap at safer operating regime. Slightly higher transfer rate is required to make the simulation agree with experiment which needs further verification !! 12th. RD51 Collaboration Meeting

  13. Electron Gain for Different Mesh Pitches Higher voltage is required for larger pitch to obtain same gain as of smaller pitch !! 12th. RD51 Collaboration Meeting

  14. Estimate of Energy Resolution Experiment: Energy resolution at a certain field configuration : where : r.m.s of the pulse height distribution : peak position Simulation: Energy resolution : where : fano factor : relative variance of gain distribution : transparency : number of primary electrons 12th. RD51 Collaboration Meeting

  15. Energy Resolution for Different Gaps Smaller gap shows better resolution at higher drift field. In all cases, the resolution seems to worsen at higher field beyond a limit of 1kV/cm !! 12th. RD51 Collaboration Meeting

  16. Energy Resolution for Different Pitches Larger pitch shows better resolution at higher drift field. Simulation needs further investigation as there is still a substantial disagreement with experiment!! 12th. RD51 Collaboration Meeting

  17. Estimate of Ion Back Flow Experiment: Ion back flow : where : number of backflowing ions : number of total ions produced in avalanche : current on drift cathode : primary current on drift cathode (referred to primary ionization) : current on micromesh Simulation: Ion back flow : where : mesh pitch FR: field ratio (amplification field/drift field) : transverse diffusion 12th. RD51 Collaboration Meeting

  18. Experimental Setup for IBF Measurement • X-ray tube (XRG 3000) for delivering photons with variable intensity • Currents on drift and mesh planes measured from HV supply (CAEN N471A) • Second drift placed 1 cm above the first at same voltage 12th. RD51 Collaboration Meeting

  19. Comparison of Experiment & Simulation Use of double drift improves the result !! 12th. RD51 Collaboration Meeting

  20. Micro-Bulk Micromegas Specifications: Amplification Gap: 50 micron 25 micron 30 micron (with rim) 50 micron 12th. RD51 Collaboration Meeting

  21. Electron Transparency 12th. RD51 Collaboration Meeting

  22. Electron Transparency 12th. RD51 Collaboration Meeting

  23. Electron Gain 12th. RD51 Collaboration Meeting

  24. Energy Resolution 12th. RD51 Collaboration Meeting

  25. Energy Resolution 12th. RD51 Collaboration Meeting

  26. Energy Resolution 12th. RD51 Collaboration Meeting

  27. Future Plans • Upgrade of cosmic-ray bench for efficiency measurement • Procurement of multi-parameter data acquisition system for measuring space resolution and time resolution • Use of existing X-ray source for more detailed characterization studies including IBF and ageing • Detailed setup for IBF measurement with precise pico-ammeter (already procured) • Expecting microbulk detectors from CERN for a long time! • Experimental measurement on triple-GEM characteristics • Procurement of gases to initiate various gas compositions Group Members: SINP: Purba Bhattacharya, Sudeb Bhattacharya, NayanaMajumdar, SupratikMukhopadhyay CEA-Saclay: Paul Colas, David Attie, Wenxin Wang Acknowledgement: Rui de Oliviera, CERN and MPGD Workshop RD51 Collaborators and IFCPAR / CEFIPRA Scientific Assistants at SINP AbhikJash, Deb Sankar Bhattacharya (PhD students) 12th. RD51 Collaboration Meeting

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