Calibration of the KSTAR ECE system

Abstract

Summary form only given, as follows. An electron cyclotron emission (ECE) diagnostic system on KSTAR tokamak was built in last year. The ECE system consists of quasi-optical light collection optics and a heterodyne radiometer. The ECE heterodyne radiometer operates in a single side band and has an eight-channel power divider and filter banks to cover a frequency range of 72 to 84GHz. The heterodyne radiometer measures the electron temperature and its profiles of the initial plasma (B/sub T/=1.5T, R/sub O/=1.6m, a=0.3m) of KSTAR. It is very important to calibrate the ECE radiometer absolutely with a high accuracy because there are no diagnostic tools comparing electron temperature data with the results of the ECE radiometer in initial operation period of KSTAR. The operation frequency range of the ECE radiometer is in E-band, so we can use a commercial noise source for relative calibration between channels of the ECE radiometer, which has an advantage of high temperature 20 times higher than other calibration sources. For absolute calibration of the ECE system including quasi-optical light collection optics, we use a temperature controlled calibration source that has a maximum temperature of 900/spl deg/K. We use a chopper system and a precision digital voltmeter for data acquisition. The calibration error is less than 10%.