ECE-imaging work on GAMMA 10 and LHD

Millimeter-wave two-dimensional (2-D) imaging array in the frequency range of 70 GHz has been developed for the application to the GAMMA 10 tandem mir ror at the University of Tsukuba. It is installed in the plug cell, and suc cessfully measures time evolutions of three-dimensional (3-D, radial and ax ial) profiles of line density and the second-harmonic electron cyclotron em ission (ECE). The ECE imaging is also being applied to large helical device (LHD) at the National Institute for Fusion Science. In order to cover the frequency range of ECE on LHD, the novel detector using monolithic microwav e integrated circuit (MMIC) technology is designed and fabricated. The dete ctor consists of the integration of a bow-tie antenna, a down-converting mi xer using a Schottky barrier diode, and hetero-junction bipolar transistor (HBT) amplifiers on a GaAs substrate. The response of the detector is compa red with that of the previous hybrid-type detector. The heterodyne response up to 10 GHz was confirmed at 70-140 GHz for the monolithic-type detector. The imaging system using the monolithic detector has been applied to the m easurement of ECE from GAMMA 10 and compact helical system (CHS) plasmas. ( C) 2001 Elsevier Science B.V. All rights reserved.