Millimeter-wave phase-imaging interferometer for the GAMMA 10 tandem mirror

A millimeter‐wave phase‐imaging interferometer has been developed for the study of density profiles of the GAMMA 10 tandem mirror. The interferometer uses a 70‐GHz klystron oscillator and a quasi‐optical transmission system. The probe beam is expanded so as to fill an orthogonal view of a plasma cross section. The view is imaged onto a detector array. The detector array consists of beam‐lead GaAs Schottky barrier diodes bonded to antennas fabricated using photolithographic techniques on a fused‐quartz substrate. Two types of antennas, bow‐tie and Yagi–Uda antennas have been used in order to provide an effective matching to millimeter‐wave beams, and compared for the performance of an imaging system. The interferometers have been applied to the central‐cell and plug‐cell plasmas of GAMMA 10.