Cavity issues for Ni-like Ta x-ray laser

Lasing has been demonstrated at 44.83 angstroms in Ni-like Ta with a gain of order 3 cm-1 over a length of 3 cm. This wavelength is suitable for holography of biological specimens provided that sufficient energy is available. The duration of the x-ray laser pulse (FWHM of order 0.35 ns) allows the possibility of a second pass through the lasing medium to increase the output energy. The dependences of the output energy on the reflectivity of the multilayer mirror, the separation of the mirror from the lasing medium, and the duration of lasing are explored in this paper. The x-ray laser plasma is a strong source of x rays (energies up to 2 keV) that can damage the multilayer mirror. We examine the heating of the multilayer mirror as a function of the separation from the lasing medium. The effect of the mirror shape (radius of curvature and whether the surface is flat, concave, or convex) on the output energy and degree of coherence of the x-ray laser is given.