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

R&D Collaboration, CERN – September 10, Summary Gain measurements Energy resolution Ion feedback Ageing Conclusion

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

R&D Collaboration, CERN – September 10, Mixtures of gases containing argon: gain curves iC 4 H 10 CO 2, CH 4 C2H6C2H6 Micromegas Mesh : 50  m gap of 10x10 cm² size

R&D Collaboration, CERN – September 10, Ar/CH 4 : simulation vs. measurements Good agreement: measurements are consistent with simulations

R&D Collaboration, CERN – September 10, Ar/iC 4 H 10 : simulation vs. measurements : Penning effect UV photons ? Agreement with the slope at low fields but not with the absolute gain and the photons effects

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

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

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

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

R&D Collaboration, CERN – September 10, Energy resolution Energy resolution using an Ingrid (gap: 50 μm; picth: 32 μm; Ø: 14 μm) Argon/Isobutane (95:5) Chromium foil 55 Fe σ E /E= 5.0 % FWHM= 11.7 %  2 /ndf= 1.35

R&D Collaboration, CERN – September 10, Ion feedback Measurement concept: -500 V -300 V I drift I0I0 I mesh I 0 : primary current I drift : cathode current I mesh : amplification current X-rays generator

R&D Collaboration, CERN – September 10, Ion feedback - Pitch: 58 μm; Ø: 31 μm - Pitch: 20 μm; Ø: 10 μm

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

R&D Collaboration, CERN – September 10, Ageing Normalized unit Time (d) - Mesh current Ar/CF 4 /Iso (95:3:2) 16,1 C / cm² ~ 20 LHC years

R&D Collaboration, CERN – September 10, Ageing Time (d) Normalized unit - Mesh current - Temperature - Pressure - Mesh current - Temperature - Pressure

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

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

R&D Collaboration, CERN – September 10, Ageing

R&D Collaboration, CERN – September 10, 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 Until now, no ageing has been observed clearly The studies continue following the technology developments…