Soft X-ray effects upon silicon-diode arrays aged in camera tubes

The rate of dark current increase of silicon-diode-array camera- tube targets has been found to be as high as 10 nA/h when operated with electrode potentials as high as 1000 volts. Irradiation of the target by soft X-rays is shown to cause the fast-state density at the silicon-silicon dioxide interface to increase. The increased fast-state density is largely responsible for the increased dark current. The X-rays are generated by the impact of the returning electron beam upon high-potential tube electrodes. Several means for reducing the X-ray flux at the target are discussed. The most effective means is a reduction in tube electrode potentials to low values where dark current aging rates as small as 0.001 nA/h have been achieved.