A low-frequency normal conducting cavity with higher-order mode damping for fourth-generation synchrotron radiation sources

Jun-Yu Zhu; Xiao Li; Jie-Bing Yu; Zhi-Jun Lu; Chun-Lin Zhang; Wei Long; Sheng-Yi Chen; Yang Liu; Sheng-Hua Liu; Bin Wu; Xiang Li; Jian Wu

doi:10.1063/5.0169598

A low-frequency normal conducting cavity with higher-order mode damping for fourth-generation synchrotron radiation sources

Rev Sci Instrum. 2023 Dec 1;94(12):123304. doi: 10.1063/5.0169598.

Authors

Jun-Yu Zhu^{1

2}, Xiao Li^{1

2}, Jie-Bing Yu^{1

2

3}, Zhi-Jun Lu^{1

2}, Chun-Lin Zhang^{1

2}, Wei Long^{1

2}, Sheng-Yi Chen^{1

2}, Yang Liu^{1

2}, Sheng-Hua Liu^{1

2}, Bin Wu^{1

2}, Xiang Li^{1

2

3}, Jian Wu^{1

2

3}

Affiliations

¹ Spallation Neutron Source Science Center, Dongguan, Guangdong 523803, China.
² Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
³ University of Chinese Academy of Sciences, Beijing 100049, China.

PMID: 38117197
DOI: 10.1063/5.0169598

Abstract

The utilization of a low-frequency (<200 MHz) RF system in storage facilitates the attainment of ultra-low emittances in synchrotron light sources through on-axis injection. This paper focuses on the development of a low-frequency normal conducting (NC) cavity with higher-order mode (HOM) damping for fourth-generation synchrotron light sources. We propose a novel approach to achieve efficient HOM damping in a NC cavity by optimizing the lowest frequency HOM and implementing a beam-line absorber. Notably, unlike conventional NC cavities, the presence of a large beam tube for the beam-line absorber does not compromise the accelerating performance in a coaxial resonant cavity, enabling effective HOM damping while maintaining a high shunt impedance. Through simulations, the prototype design of a 166.6 MHz HOM-damped cavity demonstrates a fundamental mode impedance of ∼8 MΩ, with longitudinal and transverse HOM impedances below 2.0 and 50 kΩ/m, respectively.