Saturation in a Ni-like Pd soft-x-ray laser at 14.7 nm

Here we report on what is to our knowledge, the first achievement of satura ted output in a collisionally pumped, Ni-like Pd soft-x-ray laser at 14.7 n m (J=0-1 line). Using a single prepulse scheme and a 100-ps pulse duration we were able to observe the onset of saturated output and to measure a gain -length product of 15.8 (gain=8.3 cm(-1)) on flat slab targets. A systemati c investigation and discussion on beam divergence, deflection angle, and sp ace-resolved measurements is also presented. All these aspects lead to the evidence of the onset of saturation. The measured drive-irradiance threshol d for the x-ray laser emission was only 6.6 TW/cm(2) (approximate to 165 GW ) while the maximum used drive irradiance was only 12 TW/cm(2) (approximate to 300 GW). These. values correspond, respectively, to a pump energy of 16 .5 J and 30 J in 100 ps and demonstrate the realization of a real table-top soft-x-ray laser. A key role in the achievement of these results was playe d by the reduction in the roughness of the target surface, which greatly im proves the performances of the Pd x-ray laser. [S1050-2947(99)00502-8].