Enhanced Field Bending Magnet for the APS

An enhanced field bending magnet (EFBM), a pie-shaped dipole magnet that produces a peak field of about 1.2 T at the center of its gap of 4.9 cm, was recently designed for Sector 2 at the Advanced Photon Source (APS). The By field is maximized and its multipole components over X and Y are minimized by introducing two different chamfers on each edge of the iron poles. The calculated roll-off fields around the gap center in the region of ±1.5 cm in X and ± 1.8 cm in Y are 1.4 × 10^-4 and 8.3 × 10^-5, respectively, at the center of the EFBM length in Z. This is a different idea as compared to shaping the top surface of iron poles by changing the gap size over the horizontal direction to get a good roll-off field, as was done for the standard APS dipole. The peak field at the center of the gap of the EFBM as a function of the current shows there is no magnetic saturation on the iron poles up to a field of 1.2 T.