Plasma Diagnostics Using Millimeter-and Submillimeter-Wave Two-Dimensional Imaging Array

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1)During the period of this research project, a new phase imaging interferometer with frequency of 70 GHz has been developed. The system consists of the following components.i)Two-dimensional detector array was newly developed. The detector has 4x4 channels consisting of beam-lead GaAs Schottky barrier diodes bonded to bow-tie antennas monolithically fabricated on a fused-quartz substrate.ii)The interferometer consists of a quasi-optical transmission system and a heterodyne receiver with two separate oscillators. The beat frequency between the oscillators is stabilized by using a phase-lock-loop circuit. A double down-converted system(frequency tracking receiver)enabled us to use phase detectors with center frequency of 455kHz.2)The phase imaging interferometer has been to the plug cell of the GAMMA 10 tandem mirror. The spatial resolution of the interferometer is given by the aperture of the antenna array and the magnification of the optical system. The vertical resolution was estimat … More ed to be 2.7cm and horizontal one was 2.5cm, which were calibrated with a dielectric target. The phase resolution was less than 1/200 fringe, which equals to the line density of 2.5x10^<11>cm^<-2>. The system was successfully applied to the measurement of the line density profile during the operation of plug-potential formation.3)The imaging system has also been applied to the measurement of electron cyslotron emission(ECE)as a heterodyne receiver. From the ratio of the optically thin ordinary and extraordinary mode emission signals, we have determined the radial as well as axial profile of the warm and hot electron temperature of the plug-cell plasma. The temperature fluctuation were investigated from correlation study of two ECE signals. This was the first application to ECE imaging measurement.4)The detector was tested at the higher frequency of 90 GHz region. The sensitivity was similar to that at the frequency of 70 GHz. The monolithic imaging array with antennas and GaAs Schottky diodes completed on a substrate has been investigated for the application to millimeter to submillimeter wave. Less