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 5 J energy of 800 ps duration and a pump beam of 5 J energy in 1.1 ps. A gain of 35cm^-1 and a gL product of 12.5 are measured on the 4d→4p J0ex0ex=0ex0ex0→1 transition for Ni-like Pd at 147 {} with an 8 mm line focus. The high efficiency of this scheme at ``table-top'' laser energies is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse.