Optimization of a vacuum spark discharge for soft-X-ray emission

A 1-kJ vacuum-spark device has been developed as a pulsed X-ray source for applications in the field of microlithography, microscopy, flash radiograph y, etc. The optimization works for the pulsed soft-X-ray emission are prese nted. The optimization was made in two steps: 1) X-ray emission maximizatio n and 2) X-ray emission reproducibility. For the X-ray emission maximizatio n, the changed parameters were the main capacitor energy, the anode-cathode geometry, the anode material, and the trigger pulse amplitude. The best co mbination is 1 kJ for the main capacitor energy, a conical shape for the an ode, 6-12 mm anode-cathode separation, iron for the anode material, and 14- 15 kV for the trigger pulse amplitude. In these conditions, energies of up to 10 J per pulse are obtained in the 3-40 keV range for the X-ray pulses. In order to have a good reproducibility, a high-power, very fast, high-volt age trigger pulse is required. To fulfill these conditions, a pulse transfo rmer and an air spark gap were added to the initial triggering device (a ma gnetic pulse compression circuit). With the new trigger pulse (20 J per pul se, 50-ns rise-time, 22-kV amplitude in an open circuit), an acceptable X-r ay emission reproducibility was obtained.