Design and performance of the PEP-II B-Factory HER QDA quadrupole magnet

The High Energy Ring (HER) in Stanford Linear Accelerator Center`s PEP-II B-Factory employs two high field quality quadrupole magnets, labeled QD4, for final horizontal beam de-focusing at a gradient of {approximately}75.65 kG/m. An asymmetric, septum quadrupole design is required for QD4. Due to space constraints, the magnetic field is shaped with both the iron and the coil. Each coil has fifteen conductors. A perturbation analysis was performed using the Poisson code in order to locate the ideal position of the individual conductors. Manufacturing and assembly tolerances of +/- 0.5 mm of each conductor were required to maintain an integrated field quality of multipole content of b{sub n}/b{sub 2}{le}0.0001 for n=3-15 at a radius of 59.0 mm. The steel core of the magnet is 1.425 m long and is comprised of 1.5 mm thick laminations. A cut out in the steel core is required to allow the Low Energy Ring beam to pass through the side of the magnet. A double shield is in place to allow the LER beam to remain field free. The pole tip shape is a simple hyperbola without any end contours. The design and performance of the QD4 magnet is presented.