AbstractMillimeter-wave two-dimensional (2-D) imaging array in the frequency range of 70 GHz has been developed for the application to the GAMMA 10 tandem mirror at the University of Tsukuba. It is installed in the plug cell, and successfully measures time evolutions of three-dimensional (3-D, radial and axial) profiles of line density and the second-harmonic electron cyclotron emission (ECE). The ECE imaging is also being applied to large helical device (LHD) at the National Institute for Fusion Science. In order to cover the frequency range of ECE on LHD, the novel detector using monolithic microwave integrated circuit (MMIC) technology is designed and fabricated. The detector consists of the integration of a bow-tie antenna, a down-converting mixer using a Schottky barrier diode, and hetero-junction bipolar transistor (HBT) amplifiers on a GaAs substrate. The response of the detector is compared with that of the previous hybrid-type detector. The heterodyne response up to 10 GHz was confirmed at 70–140 GHz for the monolithic-type detector. The imaging system using the monolithic detector has been applied to the measurement of ECE from GAMMA 10 and compact helical system (CHS) plasmas.
Electron cyclotron emission imaging system for 2D electron temperature fluctuation measurements in WEST