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TY - CONF AU - De Santis, S. AU - Baptiste, K.M. AU - Byrd, J.M. AU - Kwiatkowski, S. AU - Luo, T.H. AU - Marcellini, F. AU - Sanmateo, E.R. AU - Steier, C. AU - Swenson, C.A. ED - Petit-Jean-Genaz, Christine ED - Kim, Dong Eon ED - Kim, Kyung Sook ED - Ko, In Soo ED - Schaa, Volker RW TI - Multimodal Interaction in the ALS Longitudinal Feedback Kicker RF Cavity J2 - Proc. of IPAC2016, Busan, Korea, May 8-13, 2016 C1 - Busan, Korea T2 - International Particle Accelerator Conference T3 - 7 LA - english AB - RF cavities are essential components in particle accelerators not only for beam acceleration, but also for control purposes (bunch lengthening/shortening, deflecting and crabbing, transverse and longitudinal kickers) and for beam diagnostics (BPM). Normally, only a single resonating mode is actively used, although other modes can be excited by the circulating beam. Cavities used as feedback longitudinal kickers are designed with an axial mode which, appropriately excited, provides a kick to the circulating bunches for maintaining beam stability. To provide the necessary bandwidth this mode has to be strongly damped resulting in quality factors of just a few units. In the longitudinal feedback kicker cavity just installed on the ALS we have detected a second axial mode which, although a few hundreds of MHz below the 1.4 GHz design mode, is also strongly damped and has a shunt impedance high enough to be appreciably excited by the feedback amplifier coupling to the first mode. In this paper we show bench measurements on the cavity and with beam during its commissioning and discuss the interaction of the two modes resulting in a modulation of shunt impedance and phase response. PB - JACoW CP - Geneva, Switzerland SP - 2965 EP - 2967 KW - cavity KW - kicker KW - feedback KW - resonance KW - impedance DA - 2016/06 PY - 2016 SN - 978-3-95450-147-2 DO - 10.18429/JACoW-IPAC2016-WEPOW052 UR - http://jacow.org/ipac2016/papers/wepow052.pdf ER -