70 GHz Electron Cyclotron Resonance Heating System for Heliotron J SHIDARA Hiroyuki. NAGASAKI Kazunobur, SAKAMOTO Kinzor.

A 70 GHz electron cyclotron resonance heating (ECRH) system has been constructed in Heliotron J, a helical-axis heliotron device, in order to rcalize localized heating and current drive experiments. This ECRH system consists of a gyrotron, a matching optics unit (MOU), a waveguide transmission line with the HE,1 mode, polarizers, a barrier window and a launching system. The low power transmission test shows lhat the beam radius of the focused Gaussian beam is 22 mm at the magnetic axis, which is small enough compared to the averaged minor plasma radius (170 mm), and the launching system covers a wide steering range which is necessary for controlling the power localization in the three-dimensional helical-axis configuration. In the high power transmission test, the transmission efficiency of the comrgated waveguide of 20 m in length is 92 Vo, and the available output power to the vacuum vessel is up to 0.4 MW. Keywords: ECH, Fteliotron J, localized heating, current drive, Gaussian beam, transmission efficienc