LAUSR

We propose a novel algorithm to deal with the interaction of beam-cavity, which is convenient to be implemented on the platform of matlab supporting graphics process unit operations and can significantly improve the computational efficiency. Actually, this algorithm has been implemented and the corresponding code is named stable, which can be used to study the longitudinal beam dynamics of arbitrary filled bunches in electron storage rings. In this paper, the stable code is mainly used to evaluate the bunch lengthening produced by the passive higher harmonic cavity. We first carry out efficiency tests for stable and the results are satisfactory. We then benchmark the stable code against the semianalytical approach and elegant tracking for equilibrium and nonequilibrium cases, respectively, and the results are in good agreement. Furthermore, the stable code is applied to the case of Advanced Light Source upgrade (ALS-U) with distributed gaps, and the results firstly reveal a regular and periodic transient beam loading effect and thus show a nonequilibrium state for the overstretching case. As a second example, the stable code is also applied to the case of the Hefei advanced light facility (HALF) storage ring with uniformly distributed gaps, and the results show that the passive normal conducting harmonic cavities with a total $R/Q$ of $\ensuremath{\sim}200\text{ }\text{ }\mathrm{\ensuremath{\Omega}}$ will cause severe transient effects, thus being not suitable for Hefei advanced light facility.