Active Beam Scattering Method for Measurement of Ion Temperature in JFT-2 Tokamak Plasma

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Abstract
The capability of determining ion temperature by neutral beam scattering was investigated, and the ion temperature of an ohmically-heated JFT-2 tokamak was determined using a neutral beam scattering system. In the scattering experiment, a continuous beam of 15 keV hydrogen atoms was used with a scattering angle of 4°C. The ion temperature obtained by this method agreed with that deduced from measurement of passive charge-exchange neutrals. The influence of impurities on the scattering spectrum was investigated, and it was found that the difference between the intensity estimated from Rutherford scattering theory and the observed intensity increased with the atomic number of the target particle. It was established that the fact that impurity ions did not contribute to the scattering intensity arose from the ionization of the neutral beam by collision with impurity ions.