ECRH Launcher for Four-Beam Injection on HL-2A Tokamak

An Electron Cyclotron Resonance Heating (ECRH) launcher for four-beam injection has been installed on the HL-2A tokamak and used in plasma heating experiments. By the launcher, four EC wave beams can be injected into the tokamak through a Ø350 mm port, which are generated from 2 sets of 68 GHz/1 s and 2 sets of 68 GHz/1.5 s gyrotron tubes manufactured by GYCOM, with maximum output power of 500 kW for each. In this paper, the properties of the EC beam in the launcher and plasma are presented: at the centre of the cross section of the tokamak, the beam radius is 31.7 mm; thermal analysis of a 3D model indicates that the peak temperature increase would be only 30^oC at the mirror surface for a 500 kW/1 s pulse; ray-tracing calculation predicts satisfactory power deposition. In the plasma experiment, six beams including four beams from this launcher and two from another launcher have been injected simultaneously. Besides, obtaining ELM-y H-mode discharges, the ECRH system shows reliability and stability of the launcher functions.