A superpowerful source of far-ultraviolet monochromatic radiation

Abstract

In several independent experiments investigating the interaction between the optical field of an intense laser pulse and a xenon cluster beam, we recorded an anomalously high quantum yield of the plasma radiation in the region 10–15 nm. In several cases, the conversion efficiency into the hemisphere reached 10% of the pumping pulse energy. The nature of this phenomenon has not yet been adequately explained. A high conversion efficiency is shown to be possible when producing a plasma with optimal parameters for the amplification of spontaneous radiation on Ni-like xenon transitions to be generated. In a collisional-radiative model, we performed detailed atomic-kinetic calculations of the gains and radiation spectra on the transitions with λ ≈ 4, 10, and 11.3 nm and in the region 13–13.9 nm. For each transition, we determined the time dependences of the gains on plasma parameters. The theoretical and experimental values of the optimal plasma parameters and energy yields of the radiation are in close agreement. Using a theoretical model, we propose possible plasma pumping schemes to achieve the maximum yield of the intense, narrowly beamed soft X-ray radiation. At a pumping pulse repetition rate of 10⁴ Hz, the output power for various Ni-like xenon transitions ranges from 100 to 5 × 10³ W.