Compact plasma focus soft x-ray source with high repetition and high intensity

We have developed two Compact Plasma Focus (CPF) devices operating in neon with high repetition rate capacity to be used as a repetitive pulse soft x-ray (SXR) source for lithography. A single capacitor module 1-1-1 (7.85 mu F) was used to test high repetitive rate capability and was observed to produce soft x-rays in the wavelength range of 0.8-1.4 nm at up to 10 Hz. The discharge current rises in 1.2 us to peal; value of 140 kA at 15 kV charge. The soft x-ray yield varies with the pressure of working gas, the value and polarity of voltage applied to capacitor. On the basis of this module we have designed a four module test system for SXR designated as the NX1. The peak discharge current is 270 kA when the capacitor bank (7.8 mu F x4) is charged to 12kV. It produces 100J of soft x-ray per shot in single shot mode, in the wavelength range of 0.8 to 1.4nn and a spot size of below 1mm viewed end on. With a repetitive rate of up to 3Hz this gives 300W of average SXR power. The NX2 is a second system that has been designed and constructed. It will be operated at peak currents in excess of 300kA into water-cooled electrodes at repetitive rates up to 20Hz to produce 300W SXR in burst durations of up to 5 minutes. It is estimated that with such a SXR yield into a well designed beamline and a reasonably sensitive resist an exposure could be made in less than 10 seconds. Pushing such x-ray sources further to 2 kW output will make their intensity sufficient for SXR lithography with reasonably high throughput to be of industrial interest.