Demonstration of X-Ray Amplification in Transient Gain Nickel-like Palladium Scheme

We report experimental results of x-ray amplification of spontaneous emission in a Ni-like transient collisional excitation scheme. The Ni-like plasma formation, ionization, and collisional excitation requires irradiation of a slab target by two laser pulses: a formation beam with 5J energy of 800ps duration and a pump beam of 5J energy in 1.1ps. A gain of 35 cm{sup {minus}1} and a gL product of 12.5 are measured on the 4d{r_arrow}4p J=0{r_arrow}1 transition for Ni-like Pd at 147{Angstrom} with an 8mm line focus. The high efficiency of this scheme at {open_quotes}table-top{close_quotes} laser energies is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse. {copyright} {ital 1998} {ital The American Physical Society}