Design and experimental research of a 28 GHz TE₀₁ mode 160° miter bend for electron cyclotron resonance ion source

In this paper, a 28 GHz TE₀₁ mode 160° miter bend employing two plane mirrors is proposed based on the quasi-optical technique and the coupled wave theory to realize high-efficiency transmission for the electron cyclotron resonance ion source. First, the TE₀₁ mode was converted to TE_0n hybrid modes with Gaussian beam characteristics by means of the designed mode converter. Second, the phase shift section was implemented to eliminate the phase difference of the hybrid modes. Then, upon reflection of two plane mirrors, the propagation direction of a wave beam is deviated by 160°. Finally, the hybrid modes were converted to the TE₀₁ mode using the same structures of the phase shift section and the mode converter. The simulation results reveal that the TE₀₁ mode transmission efficiency reaches 95.22% at the central frequency of 28 GHz. Additionally, the designed 160° miter bend has been fabricated, installed, and measured. The experimental results show that the power transmission efficiency reaches 98.54% including diffraction losses and ohmic losses.