Development of a 140 GHz Steerable Launcher for the HL-2A ECRH System

A new electron cyclotron resonance heating and current drive (ECRH/ECCD) launcher system has been designed and installed on the HL-2A tokamak to inject four beams and enable continuous millimeter-wave beam scanning independently in the toroidal and poloidal directions for ECRH/ECCD experiments. The launcher is connected to four mm-wave lines capable of transmitting high power up to 3 MW with two 1 MW/140 GHz/3 s and two 0.5 MW/68 GHz/1 s beams. Based on ray tracing simulation using the TORAY-GA code, the scanning range of wave beams is -15 degrees similar to 15 degrees in the toroidal direction and 0 degrees similar to 10 degrees in the poloidal one for 140 GHz beams, which could cover half of the cross section of plasmas and can satisfy the requirements of advanced physical experiments. The beam radii in the plasma is 17.1 mm and 20 mm for the two 140 GHz beams and 29.5 mm for the two 68 GHz beams, respectively, allowing a very high localization of the absorbed power. The performance of the steering system was proven to be reliable and the linearity is perfect between the displacement of drive shaft and rotate angle of mirror. Additionally the injection performance of the wave beams was optimized by simultaneously setting the injection angle and the polarization to realize desirable pure O- or X-mode injection.