Minimizing the fluctuation of resonance driving terms in dynamic aperture optimization

• Published in: Physical review. Accelerators and beams 2023-08, Vol.26 (8), p.084001, Article 084001
• Main Authors: Wei, Bingfeng, Bai, Zhenghe, Tan, Jiajie, Wang, Lin, Feng, Guangyao
• Format: Article
• Language: English
• ISSN: 2469-9888; 2469-9888
• DOI: 10.1103/PhysRevAccelBeams.26.084001

Dynamic aperture (DA) is an important nonlinear property of a storage ring lattice, which has a dominant effect on beam injection efficiency and beam lifetime. Generally, minimizing both resonance driving terms (RDTs) and amplitude dependent tune shifts is an essential condition for enlarging the DA. In this paper, we study the correlation between the fluctuation of RDTs along the longitudinal position and the DA area with double-bend and multibend achromat lattices. The fluctuation of one RDT is quantitatively represented by the average RDT at the positions of nonlinear magnets. It is found that minimizing the RDT fluctuations is more effective than minimizing the commonly-used one-turn RDTs in enlarging the DA, and thus can serve as a very powerful indicator in the DA optimization. It is also found that minimizing low-order RDT fluctuations can also reduce both higher-order one-turn RDTs and higher-order RDT fluctuations, which also indicates that even higher-order RDTs can also be controlled due to the reduction of higher-order RDT fluctuations. This could be the underlying physics behind the strong correlation between minimizing the RDT fluctuations and enlarging the DA. And this also suggests that controlling lower-order RDT fluctuations in the DA optimization can avoid the need for calculating higher-order RDTs to a large extent, which are not only more computationally complicated but also more numerous. Besides, the effectiveness of controlling the RDT fluctuations in enlarging the DA confirms that the local cancellation of nonlinear effects used in some diffraction-limited storage ring lattices is more effective than the global cancellation.