X-ray laser on the relativistic ion and pump laser beams

In this paper, the possibility of lasing in the X-ray domain by means of a relativistic high-density ion beam and a counter-propagating pump laser field in a high-gain regime is investigated. This deliberation is based on the self-consistent set of Maxwell and relativistic quantum kinetic equations describing the X-ray generation process at which a pump wave resonantly couples two internal ionic levels and the necessity of initial inverse population for lasing vanishes.