Calibration of an electron cyclotron emission diagnostic system and electron temperature measurements on HT-7 tokamak

Recently, a broadband heterodyne radiometer has been installed on HT-7 tokamak to measure second harmonic X-mode electron cyclotron emission (ECE) at a frequency range 98 - 126 GHz, which is the only ECE detectable mode with optical depth greater than 1 in the present study. The high temporal resolution (4 mu s) diagnostic system is now operational with 16 detection channels separated by approximately 2 cm on the radial axis for measuring electron temperature (T-e) on the low-field side for typical machine operation at a toroidal magnetic field (B-T) of 1.0 - 2.5 T. The results of electron temperature measurements are presented along with the calibration of the diagnostic system. In order to cross calibrate the ECE system, the electron temperature data obtained have been compared to other Te measuring diagnostics, i.e. Thomson scattering and soft x-ray pulse height analysis (PHA). A radial electron temperature profile during the ohmic heating phase has been presented and analyzed. Future plans for the diagnostics of temperature fluctuations and measurements are also discussed.