Ways to discharge-based soft X-ray lasers with the wavelength λ<15 nm

Abstract

AbstractTwo basic ways to amplification of spontaneous emission in the soft X-ray region are described. The first is based on the electron-collisional recombination pumping scheme, which uses recombination of fully stripped ions into hydrogen-like ions to create (in the case of sufficiently fast cooling) a population inversion on energy levels belonging to the Balmer-alpha transition. We test this scheme on nitrogen, for which the lasing wavelength is 13.4 nm. The second way to amplification of spontaneous emission is based on the electron-collisional excitation pumping scheme: this uses for creation of population inversion a fast excitation of Ne- or Ni-like ions. However, for wavelength below 15 nm it is necessary to use Ni-like ions of some metal vapors. Feeding metal vapors into a capillary is difficult, and if being fed they deposit on the capillary wall and significantly reduce the capillary lifetime. That is why we prepare metal vapor plasma in a capillary with liquid wall – by wire explosion in water. For slowdown of the plasma-channel expansion a local-water-compression by linearly focused shock wave is being developed.