Abstract: An X-ray laser apparatus (100) for generating X-rays (1) comprises an excitation laser device (10) arranged to generate re) driving laser pulses (2), and a converter material source device (20) arranged to provide a droplet-shaped converter material, which is capable of generating X-rays (1) by non-linear frequency conversion in response to an irradiation with the driving laser pulses (2), wherein the excitation laser device (10) is arranged for a focused irradiation of the droplet-shaped converter material and the converter material source device (20) is configured to provide superfluid Helium droplets (3), which provide the converter material. Furthermore, a method for generating X-rays (1) is described, wherein superfluid Helium droplets (3) are utilized as a converter material.