X-ray laser using lithium-like recombination scheme: effects of plasma inhomogeneity

A number of experiments in various laboratories, particularly in the LULI at Palaiseau, have shown that the lithium-like recombination scheme is a good candidate for pumping soft x-ray lasers with a moderate pumping power. However, some difficulties arise for maintaining large gain coefficients in plasma columns longer than 1 - 2 cm. Several types of phenomena can be invoked to explain the deleterious consequences of the plasma column lengthening. In this paper, we discuss mainly the role of plasma non-uniformity along the amplification path, due to inhomogeneities of the pumping optical laser. Large scale and small scale inhomogeneities will be considered.