DEMONSTRATION OF X-RAY AMPLIFICATION IN TRANSIENT GAIN NICKEL-LIKE PALLADIUM SCHEME

We report experimental results of x-ray amplification of spontaneous e mission in a Ni-like transient collisional excitation scheme. The Ni-l ike plasma formation, ionization, and collisional excitation requires irradiation of a slab target by two laser pulses: a formation beam wit h 5 J energy of 800 ps duration and a pump beam of 5 J energy in 1.1 p s. A gain of 35 cm(-1) and a gL product of 12.5 are measured on the 4d --> 4p J = 0 --> 1 transition for Ni-like Pd at 147 Angstrom with an 8 mm line focus. The high efficiency of this scheme at ''table-top'' l aser energies is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse.