Development of Prototype High Gradient Small Aperture Quadrupole Magnets for HEPS-TF

A test facility named HEPS-TF for new storage-ring-based high energy photon source with low beam emittance is now under construction in China. Two prototype quadrupole magnets with small aperture and high field gradient are important devices in HEPS-TF. The bore diameters of the prototypes are both 25 mm, and the field gradients are 80 and 90 T/m, respectively. A lot of effort was spent to obtain an optimized pole shape, which meets the stringent field quality requirement, the mechanical boundary condition, and is also convenient to be machined. The influence of magnetic property nonuniformity of the core material on the field quality was studied. The design and manufacture of these prototype quadrupole magnets are finished. The field measurement results show that the field quality of these prototypes meets the specifications. The detailed two-dimensional (2-D) and 3-D magnetic design, field simulation, and field error analysis of the two prototypes are presented, and field measurement results are also described.