A quasi-linear formalism is developed for relativistic particles. It is self-consistent including spatial diffusion. An attempt is made to simulate the process of electron cyclotron resonant heating （ECRH） and electron cyclotron current drive （ECCD） for the HL-2A tokamak. Temperature oscillating regimes in Tore Supra diagnosed by MHD activity seem to be reproduced in the simulation. The special feature in this paper is to see the resonance in the long time scale for relativistic plasma.
The gas puffing performance plays a key role in repeatable discharges in the Sino- UNited Spherical Tokamak （SUNIST） experiments. In this paper, temporal evolution of the gas pressure in the vacuum vessel and the dependence of the repeatability of plasma discharges on different timing arrangements between the gas puffing pulse and the Ohmic field have been experimentally investigated. The results show that, after a fast rising phase, the gas pressure becomes quasi-stationary. In the regime of the discharges being started up when the gas pressure has already reached the quasi-stationary state for about 37 ms, an improved repeatability of the plasma discharges is achieved.
The tokamak plasma flows induced by the local radio frequency （RF） forces in the core region are analyzed. The effective components of local RF forces are composed of the momentum absorption term and the resonant parallel momentum transport term （i.e. the parallel component of the resonant ponderomotive forces）. Different momentum balance relations are em- ployed to calculate the plasma flows depending on different assumptions of momentum transport. With the RF fields solved from RF simulation codes, the toroidal and poloidal flows by these forces under the lower hybrid current drive and the mode conversion ion cyclotron resonance heating on EAST-like plasmas are evaluated.
Loss-cone instabilities are studied for linear fusion devices. The gyro-kinetic equation for such a configuration is rigorously constructed in terms of action-angle variables by making use of canonical transformation. The dispersion relation, including for the first time, finite bounce frequency is obtained and numerically solved. The loss-cone modes are found near ion-cyclotron frequency. The growth rates are greatly reduced and approaching zero with increasing beta value. The results suggest that loss-cone instabilities are unlikely to be threatening to linear fusion devices since a new longitudinal invariant is found and gives a constraint which helps confinement.
The spherical torus(ST)and compact torus(CT)are two kinds of alternative magnetic confinement fusion concepts with compact geometry.The ST is actually a sub-category of tokamak with a low aspect ratio;while the CT is a toroidal magnetic configuration with a simply-connected geometry including spheromak and field reversed pinch.The ST and CT have potential advantages for ultimate fusion reactor;while at present they can also provide unique fusion science and technology contributions for mainstream fusion research.However,some critical scientific and technology issues should be extensively investigated.
The ordinary–slow extraordinary–Bernstein（O-SX-B） mode conversion in the electron cyclotron range of frequencies（ECRF） is revisited in slab geometry. The analytical formula of the O-SX conversion efficiency by Mj？lhus is upgraded to include the magnetic field gradient, and the analytical expression of the SX-B conversion efficiency by Ram and Schultz is generalized for the case of oblique injection. Therefore, the conversion efficiency and optimal parallel refractive index for the whole O-SX-B conversion are obtained analytically and a shift of optimal parallel refractive index due to SX-FX loss is found. Full wave calculations are also presented to be compared with the analytical results.
