Evaluation of the heating effect in neutral beam injection experiments of the GAMMA 10 tandem mirror

Neutral beam injection heating has been studied for high-density mode plasma in the GAMMA 10 tandem mirror. During NBI heating, the increase in diamagnetism was found to be larger for the high-density mode plasma than the hot-ion mode plasma. A numerical model using zero-dimensional particles and energy balance equations was developed to investigate NBI heating in the central cell area. The evolution of total energy density was found to be consistent with that of diamagnetism in the low-density hot-ion mode. The initial ion temperature is a key parameter for enhancing beam heating. In high-density mode, discrepancies were found between the measured diamagnetism and the calculated total energy density. It is probably because that time behavior of the electron temperature is not suitable. (author)