Soft-X-ray lasing in nickel-like barium at 9.2 nm using the grazing-incidence scheme

We report on the experimental demonstration of saturated X-ray lasing on the 4 d → 4p, J = 0–1 line of nickel-like barium (Ba, Z = 56) at a wavelength of 9.2 nm, using a main pulse energy of 9 J in a 1.5-ps duration pulse from a Nd:glass chirped-pulse amplification laser. Gain saturation was achieved by applying a triple-pulse scheme in which a weak (few-percent) prepulse, preceding the main pulse by 2.4 ns, is followed by a second, relatively intense (16%) prepulse ~ 50 ps before the main pulse. For handling convenience, compound targets of BaF2 were used, either in the form of windows or coated onto glass slides.