Application of a grating polarizer to the 106.4 GHz ECH system on Heliotron‐E

A grating polarizer with rectangular grooves is designed for the 106.4 GHz electron cyclotron heating (ECH) system on the Heliotron‐E helical device. The polarizer is installed on mirrors of waveguide miter bends. In oversized waveguides, the HE11 mode can be treated by the plane wave theory. The polarization of the reflected wave is calculated as a function of the groove parameters and the mirror rotation angle. When launching the ECH power to fusion devices with moderate or strong magnetic shear such as heliotron/torsatron configurations, we should take into account the change of the wave polarization through the plasma. The effect of the magnetic shear can be investigated by using the polarizer. The dependence of the absorbed power on the mirror rotation angle is presented.