RF Experiments on TST-2

RF experiments were performed on the TST-2 spherical tokamak (R= 0.38 m, a = 0.25 m, B$_{t}$ = 0.3 T, I$_{p}$ = 0.1 MA) with up to 5 kW of power at 2.45 GHz and up to 400 kW of power at 21 MHz. In HHFW electron heating of inductively produced plasmas, parametric decay instability was often observed. The spatial distribution measured by RF magnetic probes located at different toroidal locations indicated wave propagation effects as well as nonlinear effects. Spontaneous formation of the ST configuration was studied. Sustainment of the ST configuration was accomplished by low frequency (21 MHz) RF power alone for the first time. LHCD and I$_{p}$ ramp-up experiments are in preparation using up to 400 kW of power at 200 MHz. This experiment will be carried out at B$_{t}$ = 0.3 T, and the density of the EC produced plasma will be kept low during I$_{p}$ ramp-up by LHCD. Status of preparation and results of calculations will be presented.