Light source at the hydrogen L-alpha wavelength for hot-plasma diagnostics

Results of experiments aimed at the development of an intense light source at the hydrogen L-alpha wavelength through the generation of the third harmonic of a laser beam are reported. The power level at the hydrogen L-alpha wavelength has been increased from that in earlier experiments (Batishchev et al., 1982) by improving the laser (increasing its power and reducing the beam divergence) and by using long-focus optics, which has allowed high-pressure operation. The maximum laser power at 364.8 nm was 10 to the 7th W, the pulse length was 20 ns, and the beam divergence was about 10 to the -4th. The maximum energy achieved at 121.6 nm was about 8 microjoules. The possibility of using this source to determine the density of atomic hydrogen is discussed.