SPACE-CHARGE LIMITATION OF SECONDARY ELECTRON EMISSION CURRENTS PRODUCED BY HIGH ENERGY RADIATIONS.
Physical sciences research papers,
AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS
Pagination or Media Count:
Secondary electron emission is an important consideration in radiation hardening of electronics. Basic information on this phenomenon, its influence, and the factors that affect its magnitude are required. Space -charge effects on the low-energy, secondary-electron emission currents flowing within any evacuated, two-electrode, plane-parallel system bombarded by KeV or MeV electrons or photons are treated in this report. The secondary emission from each irradiated electrode is assumed to be representable by a Maxwellian distribution, as is done in thermionic electron emission. This permits the complete analytical solution for the thermionic problem to be carried over in its entirety to the secondary case. The principal objective is to determine the net current density between the electrodes J sub c, given the saturation current density J sub s, or vice-versa, under known geometrical and electrical conditions. It is found that d2 J sub o, where d is the electrode separation, is a useful parameter for characterizing space-charge effects in a parallel-plate geometry system. Generalized graphs employing this parameter are presented so that the results derived here can be readily applied to cases of interest they permit the determination of threshold voltage conditions for space-charge limitation and partial retardation effects in a diode configuration. Other graphs show the variation of d2 J sub c with applied voltage. These theoretical predictions are compared to data derived from some AFCRL experiments, in which foil electrodes of aluminum, tantalum and gold were irradiated by 60Co gamma-rays and 10 MeV electrons. Author
- Electricity and Magnetism