The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The code is suitable for various auxiliary heating and current drive schemes in tokamak plasmas. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized. It is shown that, as an electrostatic force, the lower hybrid wave causes some of the trapped electrons to be untrapped and lose their energy, which can cut the LHCD efficiency by about 30%. The ITER scaling law is also used to estimate the trapped electron effects.
SMBI （supersonic molecular beam injection）, as an effective fueling method for fusion plasmas, has been widely used on the HL-2A tokamak and other fusion devices. Two different types of SMBI system are now installed on HL-2A. One is an electromagnetic valve injector on the low field side （LFS）, and the other is a pneumatic valve injector on the high field side （HFS）. A new electron density record nc = 4.7× 10^19 m ^-3 which exceeds both the Oreenwald density limit and the maximum density obtained by gas puffing （GP）, was obtained on HL-2A with single-null-divertor operation. The HFS injection system is still under test, however, its outstanding fueling characteristics have already been observed, e.g. it has higher fueling efficiency compared to the LFS system. This excellent feature is still preserved during the process of ECRH.
