Design of the longitudinal-gradient dipole magnets for HEPS

The High Energy Photon Source (HEPS) is the fourth generation light source with high brilliance and low emittance. The lattice of the storage ring consists of five different dipoles with longitudinal gradients. The longitudinal-gradient dipoles (BLGs) are permanent magnets. This paper presents the construction of BLGs and the magnetic field results using OPERA3D. By optimizing the shape of the polar surface, the magnetic field uniformity is optimized to about 2 × 10 −4 . With some adjustable screws, the magnetic field is controlled accurately. Some temperature compensation shunt sheets are arranged to make the temperature stability of magnets better than ± 50 ppm/ °C. At last, the mechanical tolerances of the magnets are studied.