Abstract
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.
Highlights
Thermonuclear fusion technology has been actively explored for generating safe, abundant, and radioactive-free green energy
The proposed modular antenna/detector array is based on the unit antenna/detector module, which can be independently tuned and installed on the array frame
In case of performance failure due to a specific channel, the corresponding channel module can be removed and replaced without interference to the rest of the array, minimizing the interrupted time used for maintenance
Summary
Thermonuclear fusion technology has been actively explored for generating safe, abundant, and radioactive-free green energy. The intensity measurement of the ECE radiation in various frequency bands allows for the identification of the radially localized electron temperature fluctuation [12,13]. In KSTAR, the antenna/detector array was designed with various RF components (e.g., antenna, diode, etc.) especially optimized to measure W-band (75 to 110 GHz) signals out of the wide spectrum of ECE radiated frequencies. A conventional-type ECE imaging system, which uses an array of a dielectric lens integrated with an antenna and a Schottky diode, may still serve as a practical ECE imaging system for most tokamak devices as long as the intensity of the plasma-radiated ECE signal is not so weak for the measurements. Each unit antenna/detector module, which is mounted in an array frame, is composed of an elliptical mini-lens, a dual-dipole antenna, a Schottky diode, an ultra-wideband balun, a low-noise amplifier (LNA), and a unit frame. This study is the first published work that discusses in detail about the improved antenna/detector array for the ECE imaging system at KSTAR
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