Convergence map with action-angle variables based on square matrix for nonlinear lattice optimization

Autor: Li Hua Yu, Yoshiteru Hidaka, Victor Smaluk, Kelly Anderson, Yue Hao
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: Physical Review Accelerators and Beams, Vol 26, Iss 5, p 054002 (2023)
Druh dokumentu: article
ISSN: 2469-9888
DOI: 10.1103/PhysRevAccelBeams.26.054002
Popis: To analyze nonlinear dynamic systems, we developed a new technique based on the square matrix method. We propose this technique called the “convergence map” for generating particle stability diagrams similar to the frequency maps widely used in accelerator physics to estimate dynamic aperture. The convergence map provides similar information as the frequency map but in a much shorter computing time. The dynamic equation can be rewritten in terms of action-angle variables provided by the square matrix derived from the accelerator lattice. The convergence map is obtained by solving the exact nonlinear equation iteratively by the perturbation method using Fourier transform and studying convergence numerically. When the iteration is convergent, the solution is expressed as a quasiperiodic analytical function as a highly accurate approximation and hence the motion is stable. The border of stable motion determines the dynamical aperture. As an example, we applied the new method to the nonlinear optimization of the NSLS-II storage ring and demonstrated a dynamic aperture comparable to or larger than the nominal one obtained by particle tracking. The computation speed of the convergence map is 30 to 300 times faster than the speed of the particle tracking, depending on the size of the ring lattice (number of superperiods). The computation speed ratio is larger for complex lattices with low symmetry, such as particle colliders.
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