https://doi.org/10.1140/epjp/s13360-025-05997-8
Regular Article
Source of instability in the rapid cycling synchrotron of the China spallation neutron source
1
Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, 100049, Shijingshan, Beijing, China
2
Spallation Neutron Source Science Center, No. 1, Zhongziyuan Road, 523803, Donguan, Guangdong, China
Received:
14
June
2024
Accepted:
10
January
2025
Published online:
26
January
2025
The rapid cycling synchrotron (RCS) of the China spallation neutron source accumulates 1.56 
protons and accelerates them from 80 MeV to 1.6 GeV at a repetition rate of 25 Hz, delivering a 100 kW proton beam to the target. Despite predictions that no instabilities would occur at high beam intensity, an unexpected coherent oscillation of the beam was observed during the beam commissioning. To confirm and address the instability, a series of systematic measurements and studies were conducted, revealing that the issue is a transverse coupled bunch instability and identifying a narrow-band impedance with a low frequency in the RCS. Further bench measurements confirmed that ceramic chambers with RF shields are the source of this impedance, which is consistent with the analysis of the experimental data. Based on these findings, a tune curve during the ramping process and chromaticity optimization have been implemented to completely mitigate the instability in the RCS at 100 kW.
© The Author(s) 2025
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
