Optimized design considerations for hybrid undulator

The hybrid undulator, is optimized in beam direction based on transverse optimization developed in ESRF. The thickness of the magnet and the pole is optimized at the ratio of 16∶9 for the maximized peak field. The analytical equations for designing the hybrid undulator are listed and discussed. One prototype hybrid undulator with 25mm period length is being constructed with NdFeB magnets and vanadium permendur poles by the optimized results. The magnet gap of the hybrid undulator can be tunable in 10~300mm. At 10mm magnetic gap, the undulator peak field can reach 0.648T with only the main magnet. It can be enhanced to 0.722T and 0.773T by further adding the side magnet and top magnet. The field resolution is better than 10-4T with 1μm gap tuning system driven by servomotor. All optim