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Back-side emission from filtered gold targets

An investigation of the rapid rise time of incoherent x-ray emission from targets heated by an ultra-short pulse (USP) high-intensity optical laser was conducted for use as the x- ray source for inner-shell photo-ionized (ISPI) x-ray lasing. Previous studies considered front-side x-ray emission; however, ISPI x-ray lasing requires a filtered x-ray source. Modeling using the hydrodynamics/atomic kinetics code LASNEX of a 40 fs USP driving laser with an intensity of 1017 W/cm2 incident on a flat target of thin Au layered on a Be filter is presented. The filter has a modest influence on the x-ray emission of the Au via conduction cooling but has a large effect on the backside spectrum by removing low energy x-rays as the Au emission passes through the filter. The use of such a filtered source is shown to provide the needed x rays to achieve high gain in C at 45 angstrom.