J-PARC RCS; High-order field components inherent in the injection bump magnets and their effects on the circulating beam during multi-turn injection

發知 英明; 原田 寛之; 高柳 智弘

Proceedings of 10th International Particle Accelerator Conference (IPAC '19) (Internet), p.2009 - 2012, 2019/06

https://doi.org/10.18429/JACoW-IPAC2019-TUPTS033

In the J-PARC RCS, we investigated the influences of high-order field components inherent in four sets of injection bump magnets (dipole magnets) on the circulating beam during multi-turn injection. Ideally, the injection bump fields including the high-order field components are cancelled out with each other through the integration over the four injection bump magnets. But, in the RCS, such a field compensation is incomplete owing to the effects of magnetic interferences and feed-down fields. The residual high-order field components, not cancelled out, have a significant influence on the circulating beam via the excitation of high-order random betatron resonance. In this paper, we discuss the detailed mechanism of emittance growth and beam loss caused by the high-order field components of the injection bump magnets including their correction scenario, on the basis of numerical simulation and experimental results.