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TY - CONF AU - Yamaguchi, T. AU - Naito, D. AU - Sakanaka, S. AU - Takahashi, T. AU - Yamamoto, N. ED - Liu, Lin ED - Byrd, John M. ED - Neuenschwander, Regis T. ED - Picoreti, Renan ED - Schaa, Volker R. W. TI - Optimization of the Parasitic-Mode Damping on the 1.5 GHz TM020-type Harmonic Cavity J2 - Proc. of IPAC2021, Campinas, SP, Brazil, 24-28 May 2021 CY - Campinas, SP, Brazil T2 - International Particle Accelerator Conference T3 - 12 LA - english AB - Bunch-lengthening harmonic cavity is one of the essential tools to mitigate the intrabeam scattering in the 4th-generation synchrotron light sources. For this purpose, we proposed a normal-conducting 1.5 GHz harmonic cavity* of TM020-type**. Thanks to its low R/Q (68 ohms) and high unloaded Q (34, 000), bunch gap transient in the harmonic cavity can be reduced to ~20% as compared to that in a typical TM010 cavity. Furthermore, harmful parasitic modes in this cavity can be heavily damped by installing ferrites where no magnetic fields of TM020-mode exist. However, some of the parasitic modes, e.g. TM021 and TM120 modes, are difficult to damp because their field patterns are similar to that of the TM020 mode. To damp such modes effectively, we optimized the cavity inner shape by tailoring the curvature at the cavity equator, the shape of the nose cones, and introducing "bumps" on the inner wall. Our goals of the coupling impedances are fxR < 2.4[kohm GHz] and RT < 23 kohm/m in the longitudinal and the transverse planes, respectively. As a result of optimization, we almost achieved these goals. To confirm our simulation results, fabrication of a low-power test cavity is in progress. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1064 EP - 1067 KW - cavity KW - damping KW - impedance KW - coupling KW - simulation DA - 2021/08 PY - 2021 SN - 2673-5490 SN - 978-3-95450-214-1 DO - doi:10.18429/JACoW-IPAC2021-MOPAB343 UR - https://jacow.org/ipac2021/papers/mopab343.pdf ER -