Heterodyne detection of ruby laser light scattered in a theta pinch plasma

Ruby laser light scattered by a 1016 cm-3, 5 eV deuterium theta pinch plasma is detected and its frequency and wavelength spectra measured by heterodyne techniques using a vacuum photodiode as a mixer, stray light radiation as the local oscillator and a UHF communications receiver as a frequency analyser. Scattered light comes predominantly from k vectors parallel to the magnetic field. Frequency and wavelength distributions showed maxima at 680 MHz and 4 x 10-3 respectively, consistent with scattering by an ion acoustic wave corresponding to plasma temperature 8 eV. The temperature deduced from the plasma diamagnetism is 4.8 eV. (author)