caa a22 4500 445305525 CHVBK 20180317142611.0 cr unu---uuuuu 170323e20110301xx s 000 0 eng 10.1007/s10762-010-9719-8 doi (NATIONALLICENCE)springer-10.1007/s10762-010-9719-8 High Efficiency Mode Converter for Low-Frequency Gyrotron [Elektronische Daten] [Ryutaro Minami, Tsuyoshi Kariya, Tsuyoshi Imai, Yoshika Mitsunaka, Keishi Sakamoto] A high efficiency quasi-optical (QO) mode converter for high-power, low-frequency gyrotron have been designed and tested. For low-frequency gyrotrons, the scales of the mode converter are comparatively small on the wavelength scale, thus causing significant diffraction losses. Over-1MW power gyrotron with TE8,3 cavity at 28GHz have been developed, which has a high efficiency mode converter designed by the use of numerical methods for launcher optimization. This calculation is sufficiently optimized to maximize the fractional Gaussian content of the far field. The total transmission efficiency from the mode converter to output window is 94.7%. For the experimental result of first tube, the output power of more than 1MW has been obtained with about 40% efficiency and output burn pattern agrees fairly with the calculated profiles, which imply the design appropriateness. Besides, the frequency dependence for diffraction loss is discussed, and these results give the guiding design principle of the mode converter for high-power, low-frequency and long-pulse gyrotrons. Springer Science+Business Media, LLC, 2010 Gyrotron nationallicence Mode converter nationallicence Low frequency nationallicence High power nationallicence Minami Ryutaro Plasma Research Center (PRC), University of Tsukuba, Ibaraki, Japan aut Kariya Tsuyoshi Plasma Research Center (PRC), University of Tsukuba, Ibaraki, Japan aut Imai Tsuyoshi Plasma Research Center (PRC), University of Tsukuba, Ibaraki, Japan aut Mitsunaka Yoshika Electron Tube Engineering Department, Toshiba Electron Tubes & Devices Co., LTD (TETD), Tochigi, Japan aut Sakamoto Keishi Plasma Heating Technology Group, Japan Atomic Energy Agency (JAEA), Ibaraki, Japan aut Journal of Infrared, Millimeter, and Terahertz Waves Springer US; http://www.springer-ny.com 32/3(2011-03-01), 311-319 1866-6892 32:3<311 2011 32 10762 https://doi.org/10.1007/s10762-010-9719-8 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10762-010-9719-8 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Minami Ryutaro Plasma Research Center (PRC), University of Tsukuba, Ibaraki, Japan aut NATIONALLICENCE 700 1- Kariya Tsuyoshi Plasma Research Center (PRC), University of Tsukuba, Ibaraki, Japan aut NATIONALLICENCE 700 1- Imai Tsuyoshi Plasma Research Center (PRC), University of Tsukuba, Ibaraki, Japan aut NATIONALLICENCE 700 1- Mitsunaka Yoshika Electron Tube Engineering Department, Toshiba Electron Tubes & Devices Co., LTD (TETD), Tochigi, Japan aut NATIONALLICENCE 700 1- Sakamoto Keishi Plasma Heating Technology Group, Japan Atomic Energy Agency (JAEA), Ibaraki, Japan aut NATIONALLICENCE 773 0- Journal of Infrared, Millimeter, and Terahertz Waves Springer US; http://www.springer-ny.com 32/3(2011-03-01), 311-319 1866-6892 32:3<311 2011 32 10762 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer