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 amplification, tabletop laser. These results have been achieved at wavelengths from 139–203 Å using a total of 5–7 J energy in a traveling-wave excitation scheme. Strong amplification is also observed for Ni-like Sn at 119 Å. Gain of 62cm^-1 and gL product of 18 are determined on the 4d→4p transition for Ni-like Pd at 147 Å with an output energy of 12μJ. 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.