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The ion Bernstein wave (IBW) is launched into the JFT-2M tokamak plasma in order to investigate the antenna loading resistance and the heating effect. Antenna loading resistance increases as the scrape-off electron density increases, in the same manner as that of fast wave antennas. Although the hydrogen ion temperature increases due to the IBW, most of the wave power is absorbed by the peripheral electrons. This is mainly due to the antenna location, which is at an oblique angle to the midplane. Peripheral electron heating induces the enhanced radiation loss, and IBW power of only about 120 kW can be launched because of the radiation limit.

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.

Three plasma configurations have been compared for achieving an improved heating efficiency (H-mode) during the neutral beam injection phase. The H-mode plasmas are observed only in divertor configurations. The highly elongated divertor shape has achieved H-mode plasmas with the best heating efficiency. Required beam power for achieving these plasmas increases from ∼1 MW to ∼4 MW as the plasma current increases from 360 kA to 740 kA. The stored plasma energy increases as the plasma current increases and improves 50% over that in low heating efficiency (L-mode) at the best H-mode discharges.

A mass-separated neutral particle energy analyser able to carry out the simultaneous measurement of hydrogen and deuterium atoms emitted from a tokamak plasma was constructed. The analyser was calibrated for the energy and mass separation in the energy range from 0.4 keV to 9 keV. It was installed in the JFT-2 tokamak in order to investigate the behavior of deuterons and protons in a JFT-2 tokamak plasma heated by ion cyclotron wave and neutral beam injection. It was found that the energy spectrum could be determined with sufficient accuracy, and the ion temperature obtained from the energy spectrum was in good agreement with the ion temperature deduced from the Doppler broadening of the impurity ion line.

The dependence of spectral line-intensities on both the electron temperature and the partial pressure of gaseous contaminants in the scrape-off layer has experimentally been studied on the JFT-2M tokamak. The intensities of light-impurities increase with the electron temperature. On the other hand, the intensities are independent on the pressure of the contaminants such as CH4, CO, CO2 and H2O. The relation between the line-intensity and the impurity influx is simulated by using a one-dimensional impurity transport model. The cause of the light-impurity release relevant to physical and chemical sputterings is discussed.