Directional couplers-polarimeters for high-power corrugated waveguide transmission lines

Compact directional couplers-polarimeters were developed for the circular corrugated waveguide transmission lines of the joint IFP-ENEA Electron Cyclotron Resonance Heating experiment at 140 GHz, 2 MW on the Frascati Tokamak Upgrade in Frascati. A linear array of cutoff holes was drilled in the mirrors of the quasi-optical miter bends. The radiated pattern preserves the symmetry and polarization of the waveguide mode in the plane of the array. The direction of propagation is preserved too. Two pairs of standard gain horns with detectors are placed in the plane of the array along the propagation axes of incident and reflected radiation to detect both linear components. The whole assembly is enclosed in a shielded anechoic box of suitable geometry.