Wide spectral range soft x-ray lasing with Ni-like ions

We present a review of the recent Ni-like soft x-ray laser experiments performed at the Institute of Laser Engineering by the multiple pulse pumping scheme with curved slab targets. We have demonstrated amplification in the Ni-like ions of Ag(Z=47), Te(Z=52), La(Z=57), Ce(Z=58), Pr(Z=59), Nd(Z=60), Sm(Z=62), Gd(Z=64), Tb(Z=65) and Dy(Z=66) at the wavelengths of 6-14 nm where Z is the atomic number. A gain coefficient of 3 cm⁻¹ and a gain-length product of 8 have been observed at 7.9 nm with Nd with a pumping laser energy of 250 J on a 2.5 cm length target. The estimated output energies of these x-ray lasers are a few μJ. We describe the direction for optimizing the pumping conditions based on the modeling analysis. A properly configured preformed plasma should be pumped by non-thermal electrons driven by an intense short laser pulse. We also report evidence for the induced emission from various high Z elements up to Ta (Z=73). The measured wavelengths are precisely compared with those calculated with the relativistic atomic physics code which will contribute to the atomic physics of highly ionized high atomic number ions.