Perveance of a planar diode with a multipoint cathode

The I–V characteristics of a planar diode with a multipoint explosive emission cathode are studied under the conditions when the impedance of the diode is matched to the output resistance of the nanosecond generator. The experiments are carried out on the TÉU-500 (350–500 keV, 60 ns, 250 J per pulse) high-current electron accelerator. The perveances of the diodes with a spike (140 spikes) cathode, multipoint copper cathode, and cathode made of carbon felt are measured in the course of electron beam generation. Comparison is performed between the I–V characteristics of the diodes with multipoint and continuous cathodes made of the same material. It is found that the electron current of the diode is described well by Child’s law with regard to the shrinkage of the anode-cathode gap and an increase in the emissive surface due to the expanding plasma (formfactor). When the cathode is made of carbon felt or is multipoint, the space-charge-limited electron current mode sets in even 5–10 ns after the voltage is applied.