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Micromegas detectors for the CLAS12 central tracker

Micromegas detectors for the CLAS12 central tracker. CERN experiment: results. Brahim Moreno (for the Saclay group). CLAS12 central detector meeting : 2 december 2009. Cea Saclay. Micromegas detectors for the CLAS12 central tracker. CERN experiment: results. Introduction

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Micromegas detectors for the CLAS12 central tracker

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  1. Micromegas detectors for the CLAS12 central tracker CERN experiment: results Brahim Moreno (for the Saclay group) CLAS12 central detector meeting : 2 december 2009 Cea Saclay

  2. Micromegas detectors for the CLAS12 central tracker CERN experiment: results • Introduction • Experiment at CERN • Results • Conclusions and outlook

  3. Introduction • Micromegas and CLAS12 • What is a spark?

  4. Micromegas and CLAS12 Several points to be adressed before micromegas implementation in CLAS12 Experiment at CERN bMM: bulk micromegas cbMM: curved bluk micromegas * bMM and cbMM showed the same behaviour

  5. What is a spark? (1) Ionizing particle (MIP) Drift electrode 600V conversion e- 400V Mesh amplification PCB Signal amplified Charge collected on the strips

  6. What is a spark? (2) Ionizing particle (hadron) Drift electrode 600V conversion 0V 400V Mesh Discharge amplification PCB Discharge blinds MM detector because it sets mesh HV to ground High charge density Recovery time depends on Protection circuit (~1 ms) Spark = discharge in amplification gap

  7. Experiment at CERN Description • Experimental set-up • Data acquisition • Running conditions and data

  8. Experimental set up (1) Main goal: evaluating sparks rate in presence of or without magnetic field Goliath y 5 4 3 2 1 x z Beam Region a magnet y Scintillator paddles coupled to PMTs Region b z Pitch: region a → 400μm region b → 1000μm x 10 cm Distance between strips: 100μm Gaz: 5% Isobutane/Ar

  9. Experimental set up (2) Main detectors characteristics

  10. Experimental set up (3) Magnet Upper coil Beam 1.77 m

  11. Experimental set up (4) Detectors Beam Electronics

  12. Data acquisition (1) Spark monitoring Data file Mesh HV filter Amplifier MM Detector Computer Labview based monitoring Discriminator • Same principle for all detectors • All detectors monitored simultaneously Scaler VME

  13. Data acquisition (2) Spark monitoring: user interface Goes red if one detector is sparking Clock: +1 every 5s Goes red if detector 4 is sparking Total number of spark Spark list display Total number of coincidences Total number of spark VS time Associated derivative Display updated at the clock frequency

  14. Data acquisition (3) Spark monitoring: data format Text file Total number of coincidences Clock Timestamp Total number of spark: a column for each detector

  15. Running conditions and data • Beam Characteristics: • Nature: pion or muon • Energy: 150 GeV • Spill duration: 9s • Time between spill: 1mn • Particle/spill: ~106 part/spill Experiment: Oct the 23rd – Nov the 3rd ~210 runs Measurements at: 0, 0.28, 0.56, 0.7, 0.84, 1.12 and 1.4 T

  16. Results Sparks • Spark probability • Magnetic field effect

  17. Spark probability (1): as a function of gain No sizeable different behaviours between classic and bulk micromegas

  18. Spark probability (2): transparency effect Transparency : probability for a primary electron to get through the mesh Transparency decreases (at fixed mesh HV) as drift HV increases Stainless steel drift electrode Less electron getting through mesh at 1500V than at 600V Increasing drift HV requires to increase the gain in order to compensate the loss in transparency Drift HV: 1500V Lower spark probability Drift HV: 600V HV mesh (V)

  19. Spark probability (3): magnetic field effect Classic MM: HV 380/1500 Y Bulk : HV 380/1200 X Bulk : HV 380/1500 No sizeable (transverse) magnetic field effect High HV drift lowers Lorentz angle

  20. Conclusions and outlook Conclusions: -Bulk micromegas behaves the same as classic micromegas -No strong magnetic field effect observed Outlook: -Analysis still ongoing: new results expected -New experiment next year to perform gaz mixture optimization -CERN experiment: 150 GeV beam 1.5T magnet extrapolation to CLAS12 experimental conditions not straightforward (hadron ~1 GeV, 5T)

  21. Back up slides

  22. Micromegas and CLAS12 (2) Use:alternative/complement to silicon vertex tracker (for  @ 0.6 GeV/c ,  = 90°) Flat bulk micromegas A mixed solution combines advantages of both the silicon (SI) and micromegas (MM) detectors Curved bulk micromegas

  23. Basic principles of a micromegas detector ~100 mm thin gap

  24. Basic principles of a micromegas detector: bulk-micromegas Drift electrode Conversion Micromesh Strips Amplification • Advantages: • Detector built in nearly one process • Geometry (flexible PCB) Same principle as « classic » micromegas Difference lies in construction process: mesh embedded on the PCB

  25. Description (2) Oct the 23rd – Nov the 3rd Detectors Electronics Beam

  26. Description (4): measurements Hadron beam 150 GeV Measurements at: 0, 0.28, 0.56, 0.7, 0.84, 1.12 and 1.5 T -Mesh high voltage variation with fixed drift HV -Drift HV variation at fixed mesh HV

  27. Preliminary results: Gain Estimated with Fe source

  28. Preliminary results: sparks rate Classic MM (5 mm drift gap) bMM (2 mm drift gap, alumized mylar) bMM with Y strips (5 mm drift gap) bMM (5 mm drift gap, inox) bMM (5 mm drift gap) Total number of sparks Detector was off Time (s)

  29. Preliminary results: sparks (2) Hadron beam 150 GeV 2 mm drift gap 5 mm drift gap Number of sparks Number of sparks X-strips X-strips HT mesh: 370V HT drift: 600V Number of sparks normalized to PMs coincidences (~106 c/spill) Spill number Spill number 5 mm drift gap 5 mm drift gap X-strips Y-strips Number of sparks Number of sparks Sparks rates stable over time ~10-5 sparks/particle Spill number Spill number

  30. Preliminary results: beam profile (1) Beam profile (classic MM) X strips Muon beam (~150 GeV) Online monitoring X (mm) Beam profile (bMM 5mm drift gap) Beam profile (bMM 2mm drift gap) X strips Y strips Beam profiles Run with beam spread in Y X (mm) Y (mm)

  31. Preliminary results: beam profile (2) Correlation 1-3 (XX) X3 (mm) Online monitoring X1 (mm) Correlation 1-2 (XY) Y2 (mm) 2D beam profiles Run with beam spread in Y Muon beam (~150 GeV) 1 = classic MM (X-strips) 2 = bMM (Y-strips) 3 = bMM (X-strips) X1 (mm)

  32. Preliminary results: tracking Residual Only the small pitch region (400 μm) is taken into account Before alignment correction σ< pitch/(12)1/2 ΔX (strip) ΔX (strip) = difference between expected and measured hit position

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