Effects of Vacuum Space Charge in Channel Multipliers

Abstract

Publisher Summary This chapter discusses effects of vacuum space charge in channel multipliers. The results obtained in the study are similar to those reported in the literature. It is important to stress that space charge saturation is independent of channel diameter. Furthermore, the analysis for a single channel should be valid for each channel of an array. The implications of these results for channel multiplier arrays in image intensifiers are that under continuous operation, space charge saturation of arrays of many channels cannot be achieved, but rather the output current will be limited at or below the conduction current, which in turn is limited by power dissipation to about the 10 –3 A/cm 2 region. If phosphor screen brightness is to be held constant, a 10 –3 A/cm 2 output current density is a drastic improvement over normal photocathode current density, and much lower voltages can be used from the array to a phosphor screen. This is especially helpful in reducing extraneous noise and breakdown if proximity focusing from the array to a phosphor screen is used. If normal voltage is used, the high output current density from the array would increase image brightness, yielding shorter exposure times for film-recording of the image.