Multi-objective optimization of the dynamic aperture for the Swiss Light Source upgrade

Abstract: The upgrade of the Swiss Light Source, called SLS 2.0, is scheduled for 2023-24. The current storage ring will be replaced by one based on multi-bend achromats, allowing for about 30 times higher brightness. Due to the stronger focusing and the required chromatic compensation, finding a reasonably large dynamic aperture (DA) for injection, as well as an energy acceptance for a sufficient beam lifetime, is challenging. In order to maximize the DA and prolong the beam lifetime, we combine the well-known tracking code tracy with a massively parallel implementation of a multi-objective genetic algorithm (MOGA), and further extend this with constraint-handling methods. We then optimize the magnet configuration for two lattices: the lattice that will be used in the commissioning phase (phase-1), and the lattice that will be used afterwards, in the completion phase (phase-2). Finally, we show and further analyze the chosen magnet configurations and in the case of the phase-1 lattice compare it to a pre-existing, manually optimized solution.