Experimental investigations of double-pass amplification of an x-ray laser in Ne-like germanium were carried out at the Shengguang laser facility (of the High Power Laser and Physics Laboratory, Shanghai, China). In these experiments a molybdenum-silicon multilayer mirror was used at normal incidence, and a flat-field grating spectrograph was used to measure the intensities of the laser lines. We observed double-pass emission intensity in Ne-like Ge at 23.2 and 23.6 nm that was five times larger than that of the single-pass amplified spontaneous emission. The damage of the multilayer mirror irradiated by laser plasma was measured simultaneously, the lifetime of Mo-Si multilayer mirror was about 440–700 ps. In addition, we measured the beam divergence of the lasing beam; the results showed that the beam divergence in the vertical direction was about 22 mrad and in the horizontal direction about 12 mrad. Also, the beam optics of the double-pass signal was observed.

• Received 6 August 1991

DOI:https://doi.org/10.1103/PhysRevA.46.1610