Measurements of microwave transmission mode in HL-3 tokamak relevant ECH corrugated waveguides transmission line

• Published in: Fusion engineering and design Vol. 208; p. 114677
• Main Authors: Fan, Guoyao, Huang, Mei, Xia, Donghui, Chen, Cheng, Zhang, Feng, Chen, Xixuan, Zheng, Wanxin, Chen, Gangyu
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2024
• Subjects: Corrugated waveguide; Electron cyclotron heating; Mode analysis; Phase retrieval; Transmission line; Electron cyclotron heating; Transmission line; Corrugated waveguide; Mode analysis; Phase retrieval
• ISSN: 0920-3796
• DOI: 10.1016/j.fusengdes.2024.114677

•The work in the paper is the investigation of microwave transmission modes in the transmission line on HL-3 tokamak relevant the ECRH system.•A specific high power test platform with about 40-meter transmission line is established and the mode contents in the middle and the end of the transmission line are obtained through phase retrieval method from intensity measurement.•In the middle of the transmission line, the proportion of LP01 mode is about 97 % and other high-order modes contents are <3 %. In the end of the transmission line, the main mode purity is about 94 %.•The work indicates that the designed and machined corrugated waveguides transmission line, and the alignment method for long distance transmission line installation is highly useful for high-purity wave mode transmission for the ECRH system on HL-3.
The transmission modes of high-power millimeter wave in corrugated waveguides transmission line (TL) are crucial, especially for the long-pulse operation for long-distance TL. The microwave transmission mode in the TL on HL-3 tokamak relevant the electron cyclotron heating system are studied for the purpose according to the phase retrieval method based on intensity distribution measured by an infrared camera at several different locations away from the outlet of TL. A specific high power test platform with about 40-meter TL is established and the mode contents in the middle and the end of the TL are analyzed. In the middle of the TL, the proportion of main transmission mode LP01 mode is about 97 % and other high-order modes contents are <3 %. In the end of the TL, the main mode purity is about 94 %, and the high-order mode, LP11 even mode is excited about 4.6 %. These mode analysis results indicate that the high-power and long-pulse millimeter wave corrugated waveguides TL are designed and machined well, and the alignment method for long distance transmission line installation is highly useful for high-purity wave mode transmission.