Role of pre-pulse in gas-filled-capillary soft X-ray source

The pre-pulse should ensure that the main current pulse starts (due to skin effect) in a thin cylindrical layer near the capillary wall. Then an axially symmetrical compression (due to pinch effect) takes place that compresses the plasma into a thin, dense, hot, straight plasma fibre, in which there are favourable conditions for amplification of spontaneous emission in soft X-ray region and for lasing. We describe both passive and active generation of the pre-pulse and its influence on the waveform of the capillary discharge current, pinching process, and axial soft X-ray radiation. (author)