Study of x-rays produced from debris-free sources with Ar, Kr and Kr/Ar mixture linear gas jets irradiated by UNR Leopard laser beam with fs and ns pulse duration

摘要

Experiments of x-ray emission from Ar, Kr, and Ar/Kr gas jet mixture were performed at the UNR Leopard Laser Facility operated with 350 fs pulses at laser intensity of 2 x 10(19) W/cm(2) and 0.8 ns pulses at an intensity of 1016 W/cm(2). Debris free x-ray source with supersonic linear nozzle generated clusters/monomer jet with an average density of >= 10(19) cm(-3) was compared to cylindrical tube subsonic nozzle, which produced only monomer jet with average density 1.5(-2) times higher. The linear (elongated) cluster/gas jet provides the capability to study x-ray yield anisotropy and laser beam self-focusing with plasma channel formation that are interconnecting with efficient x-ray generation. Diagnostics include x-ray diodes, pinhole cameras and spectrometers. It was observed that the emission in the 1-9 keV spectral region was strongly anisotropic depending on the directions of laser beam polarization for sub-ps laser pulse and supersonic linear jet. The energy yield in the 1-3 keV region produced by a linear nozzle was an order of magnitude higher than from a tube nozzle. Non-LTE models and 3D molecular dynamic simulations of Ar and Kr clusters irradiated by sub-ps laser pulses have been implemented to analyze obtained data. A potential evidence of electron beam generation in jets' plasma was discussed. Note that the described debris-free gas-puff x-ray source can generate x-ray pulses in a high repetition regime. This is a great advantage compared to solid laser targets. (C) 2016 Elsevier B.V. All rights reserved.