Simulations of hard X-ray generation by hot electrons in a silver target

Abstract

A semi-analytical model is developed for the generation of X-ray bremsstrahlung in metallic targets with the inclusion of hot electron recirculation (refluxing). The hard bremsstrahlung and characteristic X-ray yields are calculated in relation to the thickness of a silver target for an s-polarised subpicosecond laser pulse intensity of 2 × 1019 W cm–2. The effect of hot electron recirculation in thin foils is shown to significantly improve the Kα radiation and bremsstrahlung yields in a photon energy of 10 – 100 keV. By contrast, the 0.1 – 1 MeV bremsstrahlung photon yield from thin foils with hot electron recirculation corresponds approximately to the highest photon yield from those targets in which recirculation is insignificant. We make a comparative analysis of the highest laser-to-X-ray energy conversion efficiencies obtained to date.