An overview of TRIAM-1M experiments is presented. The current status of issues related to steady state operation is presented with reference to the achievement of super-ultra-long tokamak discharges sustained by LHCD for over 2 h. The importance of control of the initial phase of theplasma, the avoidance of high heat load concentration, wall conditioning and the avoidance of abrupt termination of long discharges are discussed as the crucial issues for the achievement ofsteady state operation of the tokamak. A high ion temperature (HIT) discharge fully sustained by 2.45 GHz LHCD with both high ion temperature and steep temperature gradient was successfully demonstrated for longer than 1 minin the limiter configuration. The HIT discharges can be obtained in a narrow window of density and position. The avoidance of heat load concentration on a limiter is the key point for the achievement and long sustainment of the HIT discharge. As the effective thermal insulation between the wall andthe plasma is improved for the single null configuration, HIT discharges with peak ion temperature > 5 keV and a steeper temperature gradient of up to 85 keV/m can be achieved through the fine control of density and position. Plasmas with high κ ≈ 1.5can also be demonstrated for longer than 1 min. The current profile is also well controlled for a time about 2 orders of magnitude longer than the current diffusion time using combined LHCD. The serious damage to the material of thefirst wall caused by energetic neutral particles produced by charge exchange is also described. As the neutral particles cannot be affected bya magnetic field, this damage by neutral particles must be prevented by a new technique.
Confinement and turbulence study in the Frascati Tokamak Upgrade high field and high density plasmas