Determination of the ion temperature in a hot plasma from the scattering of fast atoms

The possibilities of a method proposed some time ago for local measurements of the ion temperature in a hot plasma from the scattering of fast atoms (injected as a narrow, monoenergetic beam) are analyzed. Factors affecting the choice of the energy and species of the probing atoms and the choice of the scattering angle are discussed. The requirements imposed on the properties of the injected beam and the detectors are also discussed. In an experimental test of the method, a beam of 8-keV helium atoms with a current density approx.10 mA/cm2 and a pulse length 100 μs was used. The scattering angle was 90; the spatial resolution was 1 cm in the direction across the beam and 9--10 cm in the direction along the beam. The results found for the ion temperature agree well with measurements by other particle-diagnostic methods: a method which makes use of the energy distribution of the atoms emitted by the plasma and a method in which an artificial target for ion charge exchange is used