Gamma Radiation Induced Noise in a CCD Imager

In this paper, measurements of gamma well filling and noise generation in 100 × 100 pixel CCD imagers with bulk and reduced photosite collection volumes will be reported. The measurements were made at dose rates from 1.5 to 35 rad(Si)/sec which produce signals from 8 to 90% of well saturation in the 0.1 sec integration time. The rate of well filling in the 9 to 12 micrometer thick devices was only 25% of that in the 200 micrometer thick bulk device. Noise values from 55 to 60 times the optical shot noise were measured in the thin devices and described using a previously developed noise model. A value of 35 was measured in the thick device. The lower than expected gamma induced noise in the thick device was modeled using a diffusion-recombination mechanism.