RESULTS OF RADIATION TESTS PERFORMED ON THE ISOCAM INFRARED DETECTOR ARRAY

Extensive radiation tests have been performed on the long wavelength infrared detector array, developed at CEA for the ISOCAM camera, to be launched on the ISO European satellite. Transient and memory effects, induced by gamma-rays, protons, and heavy ions have been investigated. Each time a pixel is traversed by a particle, an ionization pulse (a "glitch") is generated. The results of different "deglitching" techniques have been compared; among them, the "half Gauss" method seems to be the best. In addition to the transient effect, a memory effect is induced by the radiation: an increase of the photoconductive gain is observed. For 2 rad, the raise in responsivity is about 60%. The relaxation time is of the order of 1 h. The relativistic Fe ions present in cosmic rays have been simulated by Argon ions of 70 MeV/nucleon energy. These very heavily ionizing particles induced a large responsivity change, not only in the pixels directly hit by the particles, but also in their neighbors. No permanent damage was observed after irradiation: the initial characteristics were recovered after a few hours and the noise remained unaffected.