Gain Saturation Regime for Laser-Driven Tabletop, Transient Ni-Like Ion X-Ray Lasers

Abstract

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 $62{\mathrm{cm}}^{-1\mathrm{}}$ and gL product of 18 are determined on the $4d\to 4p$ transition for Ni-like Pd at 147 Å with an output energy of $12\mu \mathrm{J}$. 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.