Design of Longitudinal Gradient Bending Magnet of HALS

Hefei Advanced Light Source (HALS) is a diffraction limited light source, which was proposed and expected to be built in the next few years by National Synchrotron Radiation Laboratory (NSRL) of China. Just like other new light sources, longitudinal gradient bending magnet (LGB) will be adopted to suppress the beam emittance. The magnet consists of 7 modules with different magnet-ic field. Each module has yoke and poles with the same size but different amount of permanent magnet to gener-ate field gradient. FeNi alloy is used to shunt magnetic flux and thus improve the temperature stability. Correc-tor coil or movable wedge can be used to adjust the field. Impact of magnetization direction error of permanent magnet block and parallelism error of poles on multi-poles is also evaluated.