Design of the HEPS booster lattice

The high energy photon source (HEPS) is a diffraction-limited storage ring light source being built in China. Along with the deeper studies of booster and the evolution of the lattice design and injection scheme of the storage ring, four versions of the booster lattices have been proposed from the project proposal stage. Unlike the design of the storage ring, in the booster design, more effort was made to realize stable and reliable operation rather than advanced performance. A FODO structure lattice and the “high-energy accumulation” scheme was adopted in the HEPS booster design. To find the ultimate performance of the lattice, a multi-objective genetic algorithm (MOGA) and particle swarm optimization (PSO) were used to optimize the emittance and the dynamic aperture. In the latest booster lattice design, the emittance was reduced to 16.3 nm rad. At the same time, the single-bunch charge limit was increased by minimizing the average vertical beta function and reducing the chromaticity. Through multi iterations with the hardware system, the current lattice was basically frozen and can be used as a basis for related physics studies, hardware and engineering design of the booster. In the future, more detailed physical studies will be performed based on this lattice.