Lifetime advantage and failure mechanism of a metal-ferroelectric cathode

The lifetime of explosive emission cathodes is important for high power microwave generators operating in the repetitive regime. For normal metallic cathodes, micropoints on the cathode surface with large field enhancement factors may be gradually consumed in explosive electron emission, which will lead to a limited lifetime. In this paper, a metal-ferroelectric cathode made of stainless steel and BaTiO3 is manufactured. Under voltage close to 1MV and current near 10 kA, this cathode presents a much longer lifetime than the normal stainless steel cathode, demonstrating the lifetime advantage of the metal-ferroelectric cathode. Nevertheless, in the lifetime experiment of 1.28 x 10(5) pulses, this metal-ferroelectric cathode also presents obvious lifetime phenomena, one of which is the microwave duration generated by a relativistic backward wave oscillator decreasing from 27 ns to 19 ns. Observation of the cathode surface morphology shows that the emission property deterioration of the metal-ferroelectric cathode may originate from severe ablation of the ferroelectric ceramic layer, which leads to shortening of the ceramic layer relative to the metallic layer. Therefore, choosing the metallic material properly and decreasing the blade thickness of the metallic layer moderately may suppress the relative shortening of the ceramic layer and thus can further lengthen the lifetime of the metal-ferroelectric cathode. Published by AIP Publishing.