Demonstration of large amplification in multipulse-pumped lithiumlike aluminum soft-x-ray lasers

We report on a demonstration of a gain-length product greater than five for recombination-pumped Li-like soft-x-ray lasers, using a long plasma length of 3.3 cm. Slab aluminum targets are irradiated by a multipulse Nd:glass laser pump at an intensity of 1 TW/cm². A time-integrated small-signal gain coefficient of 1.7 cm^-1 and a gain-length product of 5.6 are observed for the 154.7 Å Li-like Al laser. Space-resolved observations reveal a gain region width of 200 μm full width at half maximum, which is found to be wide enough for saturated amplification experiments.