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Micromegas Performance and Ageing studies

Micromegas Performance and Ageing studies. David Attié MPGD. Towards an R&D Collaboration, CERN – 10 September 2007. Summary. Gain measurements Energy resolution Ion feedback Ageing Conclusion. Gain measurements. Goals : find a gas mixture with comfortable gain margin

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Micromegas Performance and Ageing studies

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  1. Micromegas Performance and Ageing studies David Attié MPGD. Towards an R&D Collaboration, CERN – 10 September 2007 MPGD. R&D Collaboration, CERN – September 10, 2007

  2. Summary • Gain measurements • Energy resolution • Ion feedback • Ageing • Conclusion MPGD. R&D Collaboration, CERN – September 10, 2007

  3. Gain measurements • Goals: • find a gas mixture with comfortable gain margin • know as much as possible the maximum gain (to avoid spark) • Description: • “Standard” 50 mm mesh of • 10 cm x 10 cm size • Gas mixing system with • triple mixture available MPGD. R&D Collaboration, CERN – September 10, 2007

  4. Mixtures of gases containing argon: gain curves iC4H10 CO2, CH4 C2H6 Micromegas Mesh : 50 mm gap of 10x10 cm² size MPGD. R&D Collaboration, CERN – September 10, 2007

  5. Ar/CH4: simulation vs. measurements Good agreement: measurements are consistent with simulations MPGD. R&D Collaboration, CERN – September 10, 2007

  6. Ar/iC4H10: simulation vs. measurements : Agreement with the slope at low fields but not with the absolute gain and the photons effects UV photons ? Penning effect MPGD. R&D Collaboration, CERN – September 10, 2007

  7. Energy resolution vs. gain Argon/Isobutane • Best RMS for a gain • between 3.103 & 6.103 • Degradation increase in inverse • proportion to the quencher MPGD. R&D Collaboration, CERN – September 10, 2007

  8. Energy resolution • Micromegas standard 10 cm x 10 cm • 55Fe source in Argon/iC4H10 (95:5) • Escape line at 3 keV • Kα at 5.9 keV • Kβ at 6.4 keV • Obtain easily a monochromatic source by filtering the Kβ line at 6,4 keV • 10 μm of Chromium foil (Center for X-Ray Optics) • Chromium K-edge (Center for X-Ray Optics) σE/E = 7.0 % FWHM = 16.6 % 2/ndf = 19 σE/E = 8.0 % FWHM = 18.8 % 2/ndf = 112 Pressure = 1 atm, thickness = 10 μm Transmission (%) Photon energy (keV) MPGD. R&D Collaboration, CERN – September 10, 2007

  9. Energy resolution Cr foil source Drift cathode mesh MPGD. R&D Collaboration, CERN – September 10, 2007

  10. Energy resolution • Energy resolution using a « microbulk » • Argon/Isobutane (95:5) • Chromium foil σE/E = 5.7 % FWHM = 13.5 % 2/ndf = 1.36 55Fe MPGD. R&D Collaboration, CERN – September 10, 2007

  11. Energy resolution • Energy resolution using an Ingrid (gap: 50 μm; picth: 32 μm; Ø: 14 μm) • Argon/Methane (90:10) • Chromium foil σE/E = 5.0 % FWHM = 11.7 % 2/ndf = 1.35 55Fe MPGD. R&D Collaboration, CERN – September 10, 2007

  12. Ion feedback • Measurement concept: X-rays generator Idrift I0 • I0: primary current • Idrift: cathode current • Imesh: amplification current -500 V Imesh -300 V MPGD. R&D Collaboration, CERN – September 10, 2007

  13. Ion feedback • Pitch: 58 μm; Ø: 31 μm • Pitch: 20 μm; Ø: 10 μm MPGD. R&D Collaboration, CERN – September 10, 2007

  14. Ageing • X-rays gun (40 kV, 20 mA) • Micromegas “Bulk” (T2K-like) • Gas mixture: • Argon/Isobutane (95:5) • Argon/CF4/Isobutane (95:3:2) MPGD. R&D Collaboration, CERN – September 10, 2007

  15. Ageing Normalized unit • Mesh current Ar/CF4/Iso (95:3:2) 16,1 C / cm² ~ 20 LHC years Time (d) MPGD. R&D Collaboration, CERN – September 10, 2007

  16. Ageing Normalized unit • Mesh current • Temperature • Pressure Time (d) MPGD. R&D Collaboration, CERN – September 10, 2007

  17. Ageing 11 cm 11 cm • Gain ~4000 • Mesh current ~ 5 μA during 5 days inside 10 cm² • New measurement procedure with an other bulk: Hole 2cm x 5cm Absorber 200 mm of Al 2cm x 2cm MPGD. R&D Collaboration, CERN – September 10, 2007

  18. Ageing Current (mA) • Mesh current Ar/Iso (95:5) 0,17 C/cm² ~ 2 LHC years Time (d) MPGD. R&D Collaboration, CERN – September 10, 2007

  19. Ageing MPGD. R&D Collaboration, CERN – September 10, 2007

  20. Conclusion • The choice of the gas mixture could be adapted to the needs • The energy resolution can easily reach 5 % RMS (11,7 % FWHM) • The ion feedback is depending of the geometry and achieve 10-3 • Until now, no ageing has been observed clearly • The studies continue following the technology developments… MPGD. R&D Collaboration, CERN – September 10, 2007

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