Transient collisional excitation X-ray lasers with 1-ps tabletop drivers

Recent results are presented for I-ps driven X-ray laser amplification in N e-like and Ni-like transient collisional excitation research at the Lawrenc e Livermore National Laboratory, Plasma formation, ionization and collision al excitation are optimized using two laser pulses of 600- and I-ps duratio n at tabletop energies of typically 5 J or less in each beam. Gain of 35 cm (-1) and higher has been measured on the 147 Angstrom 4d --> 4p J = 0 --> 1 transition of Ni-like Pd and is a direct consequence of the nonstationary population inversion produced by the high intensity picosecond pulse. We re port the characterization of the X-ray laser properties including the trans ient gain lifetime and beam divergence for different Ne-like and Ni-like X- ray lasers.