X-ray emission from high-Z mixture plasmas generated with intense blue laser light

A mixture plasma composed of high-Z elements is proposed as an efficient converter of laser light to x rays. It is shown theoretically that an energy band of small opacity for one element, corresponding to a partial cutout on its emission spectrum, can be enhanced with a large opacity band of another element so that the mean opacity for the mixture with an optimum mixing ratio becomes larger than the opacities of the individual elements. As a result, higher re-emission and efficient conversion to x rays can be expected for the mixture. Absolute x-ray emission from Au-Sm and Au-Tb mixture plasmas irradiated with a blue-laser pulse was measured for the first time. The results show a trend that the mixtures at the optimum mixing ratio give higher x-ray conversion efficiencies than their constituent materials.