Magnets in the PEP Injection Lines

The electron and positron beams from the Stanford two-mile linear accelerator are brought to the PEP storage ring via two beam-transport lines, each about 225 meters in length. The beam pulses intended for PEP are switched out of the SLAC beam line by a pair of pulsed dipole bend magnets, which deflects them downward into a d.c. dipole magnet, where positron beams are bent into the south line and electrons into the north. See Figure 1. Each line beyond this common d.c. magnet contains 10 principal dipole magnets and 24 d.c. quadrupole magnets. The common "beam-splitter" magnet and the last dipole in each line are iron-septum ("Lambertson"-type) magnets, in which regions of strong and weak magnetic field are separated by thin iron septa. The other magnets are of a more conventional design but have design features with cost or size advantages.