Techniques for measuring the alpha-particle distribution in magnetically confined plasmas

Methods are proposed for measuring the alpha-particle distribution in magnetically confined fusion plasmas using neutral-atom doping beams, ultraviolet spectroscopy, and neutral particle detectors. In the first method single charge exchange reactions, A0 + He++ → A+ + (He+)*, are used to populate the n = 2 and n = 3 levels of He+. The ultraviolet photons from the decaying excited states are Doppler shifted by 5 to 10 Angstroms from those produced by the thermalized alpha-particle ash. In the second method double charge exchange reactions, A0 + He++ → A++ + He0, enable fast neutralized alpha-particles to escape from the plasma and be detected by neutral particle analyzers. These methods are distinguished from similar techniques of observing plasma impurities in that they allow a determination of the dependence of the distribution function on energy and pitch angle, as well as spatial position