Quasi-stationary population inversion on Kalpha transitions.

In a search for an x-ray laser capable of operating in a quasi-cw mode, a suggested Kalpha-innershell scheme is examined using recently calculated rates. This scheme involves the decay of a K-shell vacancy followed by a more rapid (for certain elements) L-vacancy decay, which maintains the inversion. The present analysis indicates that the scheme is only marginally feasible unless a depletion of resonant absorbers is accomplished through line shifts associated with multiple ionization following K-vacancy production. The pumping requirements for overcoming photoionization losses in the beam and the associated gain conditions are estimated for three elements, namely silicon, calcium, and copper, and it is concluded that photoionization pumping in a selective energy band is required, with emission approaching the blackbody level. A multiline heavy-ion plasma source is suggested.