M. Sakaguchi

Electron Cyclotron / Bernstein Wave Heating and Current Drive Experiments using Phased‐array Antenna in QUEST

The phased‐array antenna system for Electron Cyclotron/Bernstein Wave Heating and Current Drive experiments has been developed in the QUEST. The antenna was designed to excite a pure O‐mode wave in the oblique injection for the O‐X‐B mode conversion experiments, and its good performances were confirmed at a low power level. The plasma current (<∼15 kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection in the low‐density operations. The long pulse discharge of 10 kA was also attained for 37 s. The new density window to sustain the plasma current was observed in the high‐density plasmas. The single‐null divertor configuration with the high plasma current (<∼25 kA) was attained in the 17 s plasma sustainment.

Electron Bernstein wave Emission diagnostics using phased-array antenna system in QUEST

The square waveguide phased-array antenna system has been developed for Electron Bernstein Emission diagnostics. The broadband orthomode transducer was prepared to measure the wave polarization. The measured fields were in good agreements with those evaluated from the Kirchhoff integral.

Differential-phase reflectometry using phased-array antenna system in QUEST

The differential-phase reflectometry has been developed to measure the density profile, concerning electron Bernstein Wave (EBW) heating and current drive in the QUEST. The Phased Array Antenna (PAA) system was proposed for the reflectometry to improve the ratio of signal to noise. The PAA was confirmed to be effective, as a launching antenna to receive the larger reflected-wave signal.

Quasi-Optical HE 11 -mode exciter for coupling into oversized circular corrugated waveguide

The Quasi-Optical (QO) HE11-mode exciter has been considered for mode coupling into the circular corrugated waveguides. It contained a feed antenna and QO mirror system. A fields radiated from the feed antenna were measured, and the mode contents was analyzed with irradiant waveguide modes.

Development of CW phased-array antenna system for electron Bernstein Heating and Current Drive experiments in QUEST

The CW phased-array antenna for the EBWH/CD has been developed in QUEST. The measured fields were in excellent agreement with those evaluated by the Kirchhoff integral. The thermal load and stress were analyzed. The phase array has been fast scanned to control the incident polarization and angle.

Phased-array antenna for electron bernstein wave heating and current drive in QUEST

The phased-array antenna has been designed for steady-state electron Bernstein wave heating and current drive at 8.2 GHz in the QUEST tokamak. The prototype antenna had rather large side-lobe components. In the new designed antenna the side-lobe components were reduced by modification of the antenna structure. For the steady-state operation, forced water-cooling and thermal stress were analyzed for the antenna component using the HFSS/ePhysics/ANSYS codes.

Design of phased array antenna system for electron Bernstein wave heating and current drive in QUEST

The phased array antenna system has been designed for electron Bernstein wave heating and current drive in the QUEST tokamak at 8.2 GHz. In order to control the launching polarization state, an orthomode transducer was designed to mix two orthogonal electric field components. The polarization state was arbitrarily controlled using phase difference and intensity ratio between the two field components. The fields radiated from the phased array antenna were evaluated using the Kirchhoff integral and HFSS codes. New designed phased array antenna steered a radiated beam to the desired launching-direction by the phased array.