Measurements of noise in image orthicons

Current fluctuations in the primary readout beam and fluctuations introduced by the secondary emission multiplier of several 5820 image orthicons were measured. The noise in the photocurrent leaving the photocathode was measured and found to be full shot noise. It was found that the primary beam noise is not suppressed by space charge but shows full shot noise. It was reconfirmed that the only dynode in the secondary multiplier chain contributing significantly to the noise at the multiplier output was the first.