Development of advanced millimeter-wave plasma diagnostics

This paper reports on the recent results of two types of millimeter-wave plasma diagnostics, reflectometry and imaging, applied to a tandem mirror plasma. The ultrafast-sweep broadband and ultrashort-pulse reflectometry provide reliable density profiles under the existence of density fluctuations. The combination of high performance system and advanced data analysis methods are necessary for automatic evaluation of density profiles. A millimeter-wave imaging array in the frequency range of 60-90 GHz has been successfully applied for measurements of line-density and electron cyclotron emission (ECE) profiles. It is being installed in Large Helical Device (LHD). In order to cover the frequency range of the second harmonic ECE on LHD (120-180 GHz), a new detector using MMIC technology has been designed and fabricated.