Temporal evolution of micro-plasma in a low-current, repetitive vacuum spark soft X-ray source

Temporal evolution of micro-plasma and soft X-ray emission in a short vacuum gap, operated with a repetitive low-current (/spl sim/100 A) discharge was investigated. The device consists of two resonant circuits having different resonant frequencies for energy storage. Micro-plasma of diameter less than 1 mm is formed during spark phase with a very high-frequency (VHF) voltage, and electrodes are heated by successive high-frequency (HF) current. Thermo-field electrons are accelerated by an electric field in a cathode sheath that is formed after arc extinction. Soft X-rays were emitted mainly in the period between arc extinction and subsequent breakdown.