Particle emission of discharge-based soft S-ray lasers

Discharge-based lasing is traditionally achieved in pulsed, high- current capillary discharges on the wavelength of 46.9 nm of Ne-like Ar line. Despite this wavelength is not very convenient (due to strong absorption in any material, and in any residual atmosphere) it has already found its practical application in cases, either where high resolution is required (e.g. for dense plasma diagnostics {shadowgraphy, interferometry}, for X-ray nano-patterning, ...), or where high quantum energy is needed (e.g. for radiation damage). Unfortunately, soft X-ray emission is accompanied by a stream of primary, scattered primary, and secondary particles, which can leave traces of impacts on the exposed target and complicate the measurement evaluation. Moreover, in other experiments these particles can damage expensive mirrors and diagnostic devices. The present paper shows that the primary particles arrive to the target at a distance of ~1 m from the discharge with the delay of a few miliseconds (time-of-flight) and can be removed by a distant, sufficiently fast shutter. On the other hand the secondary particles - birthed at interaction of soft X-ray radiation with an obstacle (thin foil filter, diaphragm, above mentioned fast shutter, ...) cannot be removed (esp. if this obstacle is in vicinity of the investigated target), but only reduced (by suitable choice of obstacle material). The scattered primary particles must be treated very carefully, because they have randomly distributed velocity vector and impacts from any direction must be expected. As a result of all measures we expect reduction of particle impacts on the target/mirror/diagnostic device.