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TY - CONF AU - Wang, D. AU - Bane, K.L.F. AU - De Santis, S. AU - Li, D. AU - Luo, T.H. AU - Venturini, M. ED - Yamazaki, Yoshishige ED - Raubenheimer, Tor ED - McCausey, Amy ED - Schaa, Volker RW TI - The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project J2 - Proc. of NAPAC2019, Lansing, MI, USA, 01-06 September 2019 CY - Lansing, MI, USA T2 - North American Particle Accelerator Conference T3 - 4 LA - english AB - Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed. PB - JACoW Publishing CP - Geneva, Switzerland SP - 74 EP - 77 KW - impedance KW - wakefield KW - simulation KW - cavity KW - vacuum DA - 2019/10 PY - 2019 SN - 2673-7000 SN - 978-3-95450-223-3 DO - doi:10.18429/JACoW-NAPAC2019-MOZBA6 UR - http://jacow.org/napac2019/papers/mozba6.pdf ER -