Electron cyclotron resonance heating system on tokamak Aditya

An Electron Cyclotron Resonance Frequency (ECRF) system has been installed and commissioned for operation on the Aditya tokamak. The system would serve the dual purposes of electron heating during a normal discharge and initial breakdown to help increase the operational window. The 200 KW gyrotron, VGA-8000AI9, operating at a frequency of 28 +/- 0.1 GHz is first commissioned into a dummy load for pulsed operation. The output power in TE-02 mode is measured by various techniques. A Matching Optics Unit is used to convert the TE-02 mode to a HE-II mode, which is then transmitted through an approximately 10 mt long transmission line. The total attenuation of the transmission line is measured to be less than 1.1 dB. Paper burn patterns at various locations of the transmission line confirm the mode structure. The transmission line terminates in a barrier window connected to the tokamak. Due to limitation of dc HV power supply of -60 kV, operation has been limited up to an output power of about 100 KW. Successful ECR breakdown of neutral gas at the center of the vacuum vessel has been achieved. The results obtained during the commissioning of the system on Aditya are reported. (Author)