In summary, we have demonstrated intense x-ray lasing from nickel-like plasmas of Mo, Pd, Ag, and Sn by utilizing a short (8 ps) prepulse irradiating the target at a grazing angle of incidence of 22.5°, i.e., collinear with the 3 J, 8 ps main pulse. Saturated lasing has not been proved yet, but comparison with signal levels achieved in previous work suggests that saturation has well been reached in these experiments. This is supported by the fact that a large range of prepulse energies and time intervals gives rise to intense x-ray lasing, as has been demonstrated in the case of Pd. References 1. Yu.V. Afanas'ev and V.N. Shlyaptsev: 'Formation of a population inversion of transitions in Ne-like ions in steady-state and transient plasmas', Sov. J. Quant. Electron. 19, 1606, 1989. 2. M.P. Kalashnikov et al.: 'Saturated operation of a transient collisional x-ray laser', Phys. Rev. A 57, 4778, 1998; J. Dunn et al.: 'Gain saturation regime for laser-driven tabletop, transient Ni-like ion X-ray lasers', Phys. Rev. Lett. 84, 4834, 2000. 3. V.N. Shlyaptsev et al.: “Numerical study of transient and capillary x-ray lasers and their applications”, Proc. SPIE, Vol. 5197, 221-228, 2003; R. Keenan et al., “Efficient pumping scheme for high-average brightness collisonal x-ray lasers”, ibid., 213-220.
