No abstract

The transverse broadband impedances of major components in the BRing (booster ring) of HIAF (High Intensity Heavy-ion Accelerator Facility) are estimated using the analytical formulas or the wakefield solver in the CST Studio Suite. At low frequency, the transverse broadband impedance model of BRing is Z H 1 ðωÞ ¼ −417.14i kΩ=mðhorizontalÞ and Z V 1 ðωÞ ¼ −530.19i kΩ=mðverticalÞ, which are larger than the threshold impedance for the transverse mode-coupling instability. The ceramic rings in the vacuum chamber are the primary source of impedance. With a goal of mitigating the instability by reducing the impedance of ceramic rings, a high conductivity coating is discussed in detail. In addition, a prototype of ceramic rings-loaded thin-wall vacuum chamber is manufactured and the impedance measurements are performed. When ceramic rings are coated by 2 μm-copper, the CST simulation and experiment results show that the transverse broadband impedance of ceramic rings-loaded thin-wall vacuum chamber can be reduced from Z H 1¼ −291.69i kΩ=m and Z V 1 ðωÞ ¼ −352.37i kΩ=m to Z H 1 ðωÞ ¼ −46.16i kΩ=m and Z V 1 ðωÞ ¼ −64.56i kΩ=m. Furthermore, in this case the transverse broadband impedance model of BRing is reduced by more than 50% to Z H 1 ðωÞ ¼ −171.61i kΩ=m and Z V 1 ðωÞ ¼ −242.38i kΩ=m.