Tracking simulation of longitudinal beam dynamics in a triple RF system for electron storage rings

For diffraction-limited storage rings, a triple RF system scheme has been proposed, aimed at achieving longer bunch lengthening or meeting the specific requirements of longitudinal injection. In such a system, the choice of RF cavity parameters plays a critical role in the longitudinal beam dynamics, which typically requires precise analysis through macroparticle tracking simulations. This paper extends STABLE code [T. He et al., Phys. Rev. Accel. Beams 24, 104401 (2021)] to investigate the longitudinal dynamics of the triple RF system proposed for the Hefei Advanced Light Facility (HALF) storage ring. The simulation results reveal that two key factors limit bunch lengthening.