|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.