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GridPix studies at Saclay

RD51. GridPix workshop, Feb . 22, 2012. GridPix studies at Saclay. Avalanche fluctuations. D. Attié , A. Chaus , P. Colas, M. Titov. On- going work at Saclay. Until now in LCTPC (EUDET, AIDA)

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GridPix studies at Saclay

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  1. RD51 GridPix workshop, Feb. 22, 2012 GridPixstudiesat Saclay Avalanche fluctuations D. Attié, A. Chaus, P. Colas, M. Titov

  2. On-goingworkat Saclay • Untilnow in LCTPC (EUDET, AIDA) • Concept of digital TPC: single-electronsensitivityyieldsultimateresolution and cluster countingdE/dx • If a light higgsisdiscovered, the emphasismightturn to a standard pad TPC • In this case, CAST with X-ray focus or directionaldarkmattersearchmightbecome the driving application

  3. On-goingworkat Saclay • Untilnow in LCTPC (EUDET, AIDA) • Concept of digital TPC: single-electronsensitivityyieldsultimateresolution and cluster countingdE/dx • If a light higgsisdiscovered, the emphasismightturn to a standard pad TPC • In this case, CAST with X-ray focus or directionaldarkmattersearchmightbecome the driving application

  4. Send to a Friend or Friends • Tool for fundamentalstudies of gases • Ionization • Counting of X-ray inducedelectrons, Fano factor measurements • Avalanche fluctuations • Octopuce: 8-chip

  5. TPC at 1T • He/Iso 80/20 • Vmesh = 400V • Time mode LCTPC WP phone meeting #119

  6. The Octopuce module at DESY (Nikhef-Saclay)

  7. Electron counting and avalanche statistics • M. Lupberger’sDiplomathesis (2009-2010, Saclay and Freiburg) • Nowbeingcontinued by Andrii Chaus (PhDstudentsupervised by M. Titov)

  8. Electron counting Direct access to Fano fluctuations

  9. Avalanche fluctuations Avalanche size fluctuatesaccording to a distribution. The rms of this distribution is an important ingredient to single electronefficiencyand resolution of a position-sensitive detector. Common parametrization: polya

  10. Avalanche fluctuations Time over threshold calibration

  11. Direct measurement of avalanche size distribution using TOT

  12. Efficiency for single electrondetection

  13. December 15, 2011 : good news, Yevgen Bilevytch came with 3 boxes of 16 good InGrids on TimePix chips, done by wafer-scale post-processingat IZM Berlin. Boxes sharedbetween Bonn, Nikhef and Saclay Tested by Harry van der Graaf et al. before Christmas.

  14. At Saclay webonded 5 chips on boards. At first theyhad a wrongconnection to HV Aftercorrectingthis, a 1st chip worked for 1-2 days, and suddenlydiedat the highest voltage in Ar Isobutane 5% A second chip lookedunstable and wasdiscarded A 3rd chip isnowtaking good data in our new, optimizedgas box (Heinrich Schindler, Rob Veenhof). Calibration, electroncounting, efficiency vs threshold, avalanche fluctuations, are ongoing

  15. Threshold calibration using 10 -> 50 mV on a capacitor Thresholdcanbe set as low as 500 electrons (used to be 700) WORK RE-STARTED AND IN PROGRESS !

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