Gain saturation regime for laser-driven tabletop, transient Ni-like ion x-ray lasers

We have demonstrated small signal gain saturation on several transient-gain Ni-like ion x-ray lasers by using a high-power, chirped-pulse amplificatio n, tabletop laser. These results have been achieved at wavelengths from 139 -203 Angstrom using a total of 5-7 J energy in a traveling-wave excitation scheme. Strong amplification is also observed fur Ni-like Sn at 119 Angstro m. Gain of 62 cm(-1) and gL product of 18 are determined on the 4d --> 4p t ransition for Ni-like Pd at 147 Angstrom with an output energy of 12 mu J. A systematic evaluation of the laser driver parameters yields optimum beam divergence and small deflection angles of 2-5 mrads, in good agreement with simulations.