Résumé du preprint DAPNIA-04-347

The detection of single electrons by means of a Micromegas-covered Medipix2 pixel CMOS readout circuit
M. Campbell, M. Chefdeville, P. Colas, A.P. Colijn, A. Fornaini, Y. Giomataris, H. Van der Graaf, E.H.M. Heijne, P. Kluit, X. Llopart, J. Schmitz, J. Timmermans,J.L. Visschers
A small drift chamber was read out by means of
a MediPix2 readout chip as direct anode.
A Micromegas foil was placed 50 $\\mu$m above the chip, and electron multiplication
occurred in the gap. With a He/Isobutane 80/20 mixture, gas multiplication factors
up to tens of thousands were achieved, resulting in an efficiency for detecting
single electrons of better than 90\\% . We recorded many frames containing 2D
images with tracks from cosmic muons.
Along these tracks, electron clusters were observed, as well as $\\delta$-rays. 


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