Hyperbolic lens design of local oscillator optics system for electron cyclotron emission imaging on J-TEXT.

Abstract

An electron cyclotron emission imaging diagnostic system that contains two 16-antenna arrays is being developed on J-TEXT tokamak. In this heterodyne system, the mixers in the front microwave antenna are used to down-convert the electron cyclotron emission to a 2-12 GHz radio frequency. All of the 24 antenna mixers in the individual enclosure box are driven by shining local oscillator (LO) power via launching optics. The previous approach for LO optics was designed with spherical and cylinder lenses, which has limitations such as the inhomogeneity of the energy deposition on different channels and the difficulty of optics alignment. A new generation of LO optics has been designed and applied on J-TEXT with a hyperbolic lens for uniform power deposition across the entire antenna array. The robustness of the optical alignment will be significantly increased with three hyperbolic lenses. Furthermore, the simulation results and robustness analysis of these LO optics are discussed in this paper.