The Joint Accelerator Conferences Website (JACoW) is an international collaboration that publishes the proceedings of accelerator conferences held around the world.
TY - UNPB AU - Venturini, M. ED - Liu, Lin ED - Byrd, John M. ED - Neuenschwander, Regis T. ED - Picoreti, Renan ED - Schaa, Volker R. W. TI - Harmonic Rf Cavities and Instabilities in Electron Storage Rings 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 - Higher-harmonic rf cavities (HHC) are employed in several storage-ring light sources to lengthen the bunches and increase Touschek lifetime; their use is gaining further popularity in the new-generation machines as stronger intra-beam particle scattering is the unavoidable price to pay for higher brightness. Historically, HHCs were first introduced as a way to control certain collective instabilities. While often dubbed as "Landau cavities" (with reference to the damping potentially associated with the HHC-induced synchrotron-oscillation frequency spread), their effect on beam stability is, in fact, not necessarily always beneficial. Whether the HHCs help stabilize a beam, aggravate existing instabilities, or introduce new ones, is a complicated matter that depends on various circumstances. With focus on normal-conducting passive HHCs this talk will present some recent progress and revisit some older results on instability collective-mode theory illustrating aspects of the complex impact that HHCs have on beam dynamics. We will also review some open problems, making the case for the need of further theory development beyond conventional mode analysis. PB - JACoW Publishing CP - Geneva, Switzerland ER -