Millimeter-wave two-dimensional imaging array for the GAMMA 10 tandem mirror

Abstract

A millimeter-wave two-dimensional imaging array has been fabricated in order to diagnose the plug-cell plasma of the GAMMA 10 tandem mirror. The heterodyne system with two separate sources enables the measurement of density and electron cyclotron emission (ECE) in one plasma shot. The interferometer successfully measures the time evolution of the axial and radial line-density profiles with phase resolution less than 1/200 fringe and spatial resolution of 16 mm in the vertical direction and 5 mm in the horizontal one. It is shown that the Abel-inverted density profiles are changed due to the injection of electron-cyclotron-resonance heating at the plug/barrier cells and central cell. The axial and radial dependence of the second-harmonic ECE emitted from hot electrons produced in barrier region is observed simultaneously. The fluctuation spectra of the ECE signals are compared with those obtained from the far-forward scattering diagnostic system.

Advancements of microwave diagnostics in magnetically confined plasmas

“…An FIR laser interferometer with a 20-element micro-bolometer array has been applied to tokamak plasma [2]. A millimeter-wave phase-imaging interferometer using a 4 × 4 Schottky barrier diode array has been applied to the GAMMA 10 tandem mirror [3].…”

Heterodyne methods in millimetre wave plasma diagnostics with applications to ECE, interferometry and reflectometry

“…At the GAMMA 10 mirror experiment two independent free-running sources at 70 GHz are used for LO and probing signal generation. An array of beam lead GaAs Schottky diodes integrated on a fused silica substrate is used (Oyama et al 1997). For the MICROTOR tokamak the probing signal was generated by a free-running carcinotron, whereas the LO signal was obtained by Dopplershifting the carcinotron signal on a rotating grating.…”

Development and Application of Millimeter-Wave Imaging Radar.

“…In a collaboration between the University of Tsukuba, Sanyo Electric Co., and Tohoku University, 1-D arrays with bow-tie and Yagi-Uda antennas [1] and a 2-D array with bow-tie antennas [3] have been developed for both imaging interferometry and electron cyclotron emission imaging (ECEI) on the GAMMA 10 tandem mirror. Figure 1 shows a 4 × 4 array of GaAs beam-lead Schottky diodes bonded onto bow-tie antennas monolithically fabricated on 38.1-mm square fused-quartz substrates.…”

“…This technique uses a single set of optics and a multichannel detector array instead of a multichannel optical path with a single author's e-mail: mase@astec.kyushu-u.ac.jp detector for each chord. We have developed both hybrid and monolithic detector arrays for use in plasma imaging applications [1,3,5].…”

“…Imaging Array Millimeter-wave imaging diagnostics have been developed for the measurements of density and temperature profiles and their fluctuation components in magnetically confined plasmas [1][2][3][4][5]. This technique uses a single set of optics and a multichannel detector array instead of a multichannel optical path with a single author's e-mail: mase@astec.kyushu-u.ac.jp detector for each chord.…”