Electron Bernstein Wave Experiments in the Low Aspect ratio Torus Experiment Device

Two kinds of EBW experiments have been done on LATE using 2.45 GHz microwaves obliquely injected using open circular waveguide launchers. The vacuum vessel is a cylinder with a diameter of 100 cm and a height of 100 cm, and an 11.4 cm center-post for center conductors for the Bt field with no central solenoid. In the first experiment we inject a relatively high power of 40-60 kW from three 20kW-magnetrons, which non-inductively starts up the discharge and finally maintains a toroidal current of 10 kA with a central plasma density 10 times the plasma cutoff density by EBW heating and current drive at the first propagation band. A wave injection with the optimal polarization for mode-conversion to EBW via one launcher (other two launchers being with usual linear polarization parallel to the mid-plane) improves plasma performance in terms of density and current. In the second experiment we investigate various basic characteristics of EBW, including the mode-conversion and subsequent propagation and absorption of EBW. Here, an 1.5 GHz microwave at 10 W is injected via OXB scheme into an ECR plasma maintained by a 2.45 GHz microwave at 1 kW. The wave field for 1.5GHz microwave is 2-dimensionally measured on the mid-plane using probes attached to a two-joint robot arm.