Miter bend polarizers in CW ECRH systems: groove design, ohmic loss, and cooling in numerical analyses

Polarizer miter bends are important components in the transmission lines of electron cyclotron resonance heating systems, as they create a desired polarization for the electron cyclotron wave before coupling in the fusion plasma. Normally, a pair of grooved mirrors with different groove depths is enough to form a universal polarizer made of polarization twister and elliptical polarizer. The groove shape, and how the grooved mirror tolerates in a modern high-power system with continuous wave operation, can influence the entire operation of the system. This work contains various investigations on the grooved mirror including the parametric groove design, low ohmic loss, and effective cooling with an appropriate design of the cooling channel. Since the rounded trapezoidal grooves have some advantages over rectangular and sinusoidal grooves, the study is mainly dedicated to the trapezoidal grooves in both polarizer mirrors. The steady-state thermal analysis is carried out for 1 MW power at 110 GHz.