Plasma diagnostics using millimetre wave two-dimensional imaging array

A millimetre wave two-dimensional detector array has been newly developed for application to a phase-imaging interferometer installed in the GAMMA 10 tandem mirror. The interferometer consists of two sources and a quasi-optical transmission system. The transmitted wave is mixed with the local oscillator (LO) wave to provide a 150 MHz intermediate frequency (IF) signal. The detector has 4 × 4 channels consisting of beam-lead GaAs Schottky barrier diodes bonded to bow-tie antennas fabricated using photolithographic techniques on a fused quartz substrate of size 38.1 mm × 38.1 mm. The interferometer successfully measures the time evolution of line density profiles with a phase resolution of less than 1/200 fringe and a spatial resolution of 16 mm in the vertical direction and 5 mm in the horizontal direction. The system is also applied to the measurement of electron cyclotron emission (ECE) as a heterodyne radiometer. The axial and radial dependence of the second-harmonic ECE is observed simultaneously. The fluctuation spectra of the ECE signals are compared with those obtained from the interferometer.