Basic and applied studies of field emission at microwave frequencies

The unique properties of field emission, as predicted by the Fowler-Nordheim theory [1], [2], have stimulated interest in the development of practical field emission cathodes. Recent work has yielded a more complete verification of the theory: pulsed emission densities above 108amp/cm2 [3], [4] agd d.c. emission densities above 107 amp/cm2 [5] have been, achieved and, with allowance made for space charge effects, found to be in accord with theory; also, recent careful measurements have reduced the observed energy spread of the field emitted electrons and brought it in excellent agreement with theory [6], indicating a beam noise temperature comparable to that of thermionic beams in the absence of beam area compression.