Apparatus and method for generating X-rays by laser irradiation of superfluid helium droplets

An X-ray laser apparatus, being configured to generate coherent X-rays, comprising

• an excitation laser device arranged to generate driving laser pulses having a pulse duration in a range from 1 fs to 5 ps, and
• a converter material source device arranged to provide a droplet-shaped converter material, which is capable of generating the coherent X-rays by non-linear frequency conversion in response to an irradiation with the driving laser pulses, wherein
• the excitation laser device is arranged for a focused irradiation of the droplet-shaped converter material, and
• the converter material source device is configured to provide superfluid Helium droplets, which provide the droplet-shaped converter material, wherein the Helium has physical state conditions wherein the Helium is in a superfluid state and the Helium has a viscosity equal to zero, wherein
• the non-linear frequency conversion is represented by a coherent process of separating electrons from Helium atoms of the superfluid Helium droplets by the irradiation with the driving laser pulses, accelerating the electrons in the light field of the driving laser pulses and recombination of the electrons with atomic Helium nuclei.