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TY - CONF AU - Torgasin, K. AU - Kii, T. AU - Masuda, K. AU - Morita, K. AU - Nagasaki, K. AU - Ohgaki, H. AU - Suphakul, S. AU - Zen, H. ED - Kuzin, Maxim ED - Schaa, Volker RW TI - Coaxial Quarter Wavelength Impedance Converter for Coupling Control of Triode Cavity J2 - Proc. of RuPAC2016, St. Petersburg, Russia, November 21-25, 2016 C1 - St. Petersburg, Russia T2 - Russian Particle Accelerator Conference T3 - 25 LA - english AB - A quarter wavelength coaxial cavity has been developed for triode-type thermionic RF gun. The triode-type RF gun is a modification of present 4.5 cell thermionic RF gun of KU-FEL (Kyoto University Free Electron Laser) facility with aim to mitigate the back'bombardment effect. Thereby a coaxial quarter wavelength cavity with cathode material shall be added to the main 4.5 cell accelerating body. The coaxial cavity has the function of pre-buncher to control the injection phase and power of electron bunches into the main accelerating body*. Transient tests have demonstrated the quarter wavelength cavity to be undercoupled. However, for operation at high beam loading conditions overcoupled conditions are required. In order to control the coupling we have developed an external air side coaxial quarter wavelength impedance converter. The design of the impedance converter enables operation at high RF power (<20 kV) without changing the cavity geometry. In this work we present our design and performance of quarter wavelength impedance converter as applied to quarter wavelength triode cavity. PB - JACoW CP - Geneva, Switzerland SP - 689 EP - 691 KW - impedance KW - cavity KW - coupling KW - electron KW - gun DA - 2017/02 PY - 2017 SN - 978-3-95450-181-6 DO - 10.18429/JACoW-RuPAC2016-THPSC067 UR - http://jacow.org/rupac2016/papers/thpsc067.pdf ER -