Yield Optimization and Time Structure of Femtosecond Laser Plasma<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">K</mml:mi><mml:mi mathvariant="italic">α</mml:mi></mml:math>Sources

Abstract

The generation of femtosecond $K\ensuremath{\alpha}$ x rays from laser-irradiated plasmas is studied with a view to optimizing photon number and pulse duration. Using analytical and numerical models of hot electron generation and subsequent transport in a range of materials, it is shown that an optimum laser intensity ${I}_{\mathrm{opt}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}7\ifmmode\times\else\texttimes\fi{}{10}^{9}{Z}^{4.4}$ exists for maximum $K\ensuremath{\alpha}$ yield. Furthermore, it is demonstrated that bulk targets are unsuitable for generating sub-ps x-ray pulses: instead, design criteria are proposed for achieving $K\ensuremath{\alpha}$ pulse durations $\ensuremath{\le}100\mathrm{fs}$ using foils of $\ensuremath{\approx}2\ensuremath{\mu}\mathrm{m}$ thickness.