Principles and present state of capillary-discharge-pumped soft x-ray lasers

The article reviews the progress in the development of discharge-pumped soft X-ray lasers. Especially the results of the last decade proved that discharge created plasmas in capillaries are sufficiently uniform to allow for soft x-ray amplification. Amplification conditions and population inversion mechanisms are briefly reviewed. Then the activities in individual fields are summarized with emphasis on the gas filled capillaries which obey electron-collisional excitation pumping. Namely these capillaries can work as an efficient, table-top, high average power soft X-ray lasers capable to produce millijoule-level laser pulses at a repetition rate of several Hz, with a corresponding spectral brightness. Finally, some of tested applications are also briefly mentioned.