Operation of explosive-emission cold cathodes made from various materials was studied at a large number of pulses at current densities of approx. 104 A/cm2. The cathode voltage and the beam current were approx. 500 kV and 5 kA, respectively, with a pulsewidth of approx. 20 ns. At a small number of pulses (≤103), cathodes of like geometry (even made from different materials) demonstrated similar emission properties. For most of the materials tested, with a large number of pulses (≥103), the current risetime increased to the fullwidth of the voltage pulse and the maximum current of the vacuum diode decreased. When using a graphite cathode, the maximum current remained invariant until 108 pulses. Mass losses were measured for a series of cathode materials. The results obtained offered the possibility to realize long-lived operation of an X-band relativistic backward-wave oscillator with an almost invariant output power of 350-400 MW during 108 pulses at a pulse repetition rate of 100-150 p.p.s.
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Condensed Matter Physics