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.