Bayesian optimization of the dynamic aperture in UVSOR-IV design study

Abstract

A lattice of a storage ring for the future plan of UVSOR synchrotron facility, UVSOR-IV, is designed at 1 GeV electron energy. The lattice of 12 compact double achromat cells conducts to an emittance of 4.2 nm at 1 GeV electron energy and 2.3 nm at 750 MeV electron energy in achromat condition, 82.5 m circumference, and six straight sections of 4 m long and six of 1.5 m long. The lattice requires strong sextupole magnets to compensate the natural chromaticity. To help deal with the challenge of dynamic aperture associated with the strong nonlinearities, we examined improving the dynamic aperture by optimizing the sextupole arrangement based on the Bayesian method. We have demonstrated optimizing the harmonic sextupole strength of four families with 100 iterations of running particle tracking simulation that is much faster than traditional methods such as complete parameter survey.