Miniature plasma cathode for high-power terahertz sources

Efforts to improve efficiency in terahertz vacuum electronic sources such as backward-wave oscillators (BWO) have motivated studies of cathodes capable of generating high-density electron beams so that various interaction circuits may be driven closer to saturation. Preliminary results from experiments on a miniature plasma cathode demonstrate that current densities of up to 1 kA/cm² in a 100-micron diameter beam have been achieved. Initial analysis of a 850-GHz, slotted slow-wave structure show that the circuit could be driven at 3-4 times the starting current and that efficiencies of a few percent could be realized. Tests on a gridded plasma cathode show that stable beams of 200 mA at a pulse length of 100 μsec and repetition frequencies of up to 200 Hz were generated.