APD photodetectors in the Geiger photon counter mode.

International audienceThe best detector in Cerenkov experiments still remains the PM tube, thanks to its characteristics of sensitivity and speed. But its disadvantages are its low quantum efficiency and its cost. We are currently working on solid state silicon detectors, used in the Geiger photon counter mode. We have conducted a series of tests using standard APD, but with an electronic circuitry to raise the polarisation towards the Geiger mode. The photodiode is polarized over its own breakdown bias, one single photon passing through it may start an electron avalanche resulting in about 106 electrons collected. After that, the diode should recover as soon as possible to be available for the next photon. This process is under modelization: electrical diagrams (PSPICE), differential equations (VHDL-AMS) and components physics equations (SABER) are needed to reproduce closely the physical processes and to allow optimisation and improvement of the electronics both for triggering and for the readout of the detectors. Our most promising results will be presented