W-Band Modular Antenna/Detector Array for the Electron Cyclotron Emission Imaging System in KSTAR

A design of a modular antenna/detector array for the electron cyclotron emission (ECE) imaging system at the Korea Superconducting Tokamak Advanced Research (KSTAR) is proposed. The modular antenna/detector array is based on a unit antenna/detector module, which consists of an elliptical mini-lens, a dual-dipole antenna, an antenna balun, a low-noise amplifier, and a metal frame. The proposed modular antenna/detector array resolves the problem in the conventional antenna/detector array where one faulty channel requires the entire array to be removed for the service. With the proposed modular array, each channel module can be easily and independently removed and replaced without interference to the rest of the array, thus minimizing the interrupted service time for maintenance. Moreover, the unit channel modules can be efficiently updated under a variety of the tokamak operation conditions. The antenna/detector modules are optimized to have improved performance, and are tested in a W-band test setup, and consistently provide the gain increase by 10~20 dB as compared with the conventional antenna/detector array. A set of the proposed modular antenna/detector array is currently installed and tested in the KSTAR ECE imaging system, and will consistently produce the improved ECE imaging to monitor MHD instability activities under various plasma operation conditions.