Optically self-photopumped x-ray laser at 13.4 nm in Ni-like tin (Sn 22+ )

A model of the source of monochromatic radiation with λ ~ 13.4 nm with a high conversion factor, intended for industrial nanolithography, is presented. The source is based on an x-ray laser (XRL) on the transition 4 f 5 / 2 [ J = 1] − 4 d 3 / 2 [ J = 1] of Ni-like tin ions (Sn 22+ ) in plasma formed during the interaction of a nanostructured tin target with an intense ultrashort pump laser ( I pump ~ 8·10 17 W cm −2 ). The inversion mechanism of the optically self-pumped laser is caused by photon reabsorption in optically dense plasma. Calculations of gains and quantum efficiencies of the XRL in Sn 22+ with λ ~ 13.4 nm under optimal plasma conditions are discussed.