604x288 electron-bombarded CCD image tube for 2D photon counting

Abstract

A hybrid intensified CCI) tube, based on a moulded thinned backside-bombarded CC'!) sensor (604x288 pixels) has been achieved for applications of very low light level imaging and twodimensional photon counting. The CCD is a modiflcd version of the Philips NXA 101 1 FT sensor, moulded in a ceramic/glass material before thinning, so that the sensitive area remains flat, frontside supported and thermally stahilized. Materials are fully compatible with ultra-vacuum technological constraints and with the presence of alkalis incorporated during the photocathodc growing process. In this paper, the main results of electron detection experiments with thinned CCI)'s are displayed, both obtained in scaled tubes and in a Scanning Electron Microscope (SEM) equipment : electronic gain vs incident energy, gain fluctuations and noise behaviours, pulse height distributions under multielectron bombardment, and image homogeneity. In SEM, at 20 keV and at room temperature, the signal to noise is so high that it is possible to count up to 6 electrons in a single pixel. Thanks to the realization of stable tube prototypes, we have Used such a device in a photocounting astronomical experiment.