The generation of a population inversion in hydrogenic ions during rapid expansion and related cooling of plasma occurs during the cascade through the excited states following recombination into high-lying levels. Although it is relatively straightforward to generate a population inversion in a plasma produced by laser irradiation of solid targets, the production of sufficient gain to observe laser action places stringent conditions on the system to be used. A suitable arrangement to achieve small signal gain coefficients of ~10 cm−1 is obtained by irradiating a thin cylinder with a short laser pulse of appropriately matched characteristics. The relative ease with which thin carbon fibers can be constructed and their convenient match to present-day Nd:glass laser systems make this an attractive candidate to study such XUV laser systems with emission on its Ha line at 182 Å.
© 1982 Optical Society of AmericaPDF Article