PLASMA DIAGNOSTICS USING MILLIMETER-WAVE 2-DIMENSIONAL IMAGING ARRAY

A millimetre wave two-dimensional detector array has been newly develo ped for application to a phase-imaging interferometer installed in the GAMMA 10 tandem mirror. The interferometer consists of two sources an d a quasi-optical transmission system. The transmitted wave is mixed w ith the local oscillator (LO) wave to provide a 150 MHz intermediate f requency (IF) signal. The detector has 4 x 4 channels consisting of be am-lead GaAs Schottky barrier diodes bonded to bow-tie antennas fabric ated using photolithographic techniques on a fused quartz substrate of size 38.1 mm x 38.1 mm. The interferometer successfully measures the time evolution of line density profiles with a phase resolution of les s 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 app lied to the measurement of electron cyclotron emission (ECE) as a hete rodyne radiometer. The axial and radial dependence of the second-harmo nic ECE is observed simultaneously. The fluctuation spectra of the ECE signals are compared with those obtained from the interferometer. (C) 1997 Elsevier Science S.A.