Operating modes of a pulsed 50-GW diode

Operational characteristics of a 50-GW high-field-emission diode are discussed in detail. The diode is shown empirically to have two distinct modes of operation, with corresponding impedances, which depend on the diode aspect ratio, pressure, and total voltage and current. The first mode indicates rectilinear electron flow, with impedance shown to be about ½ that predicted by the Child-Langmuir Law for pressures ranging from 5 × 10^-3to 10^-5torr. The second mode displays a pressure-dependent "funneling" phenomenon in the gap region with radial compression of the electrons. For this condition the diode impedance is ≤ Child-Langmuir predictions. Theoretical models by Friedlander and de Packh for estimating the occurrence of funneling conditions are verified. Experimental evidence of funneling is presented for values of v/γ, (measured) above 80 percent of v/γ, (critical).