Dual-aperature dipole with 2nd harmonic

Two-rapid-cycling accelerator rings are arranged in one magnet-iron structure. There are two sets of coils, one located in each ring, which are connected in series and excited with a first-harmonic frequency. One dc bias coil and one second-harmonic coil are common to both rings. The second harmonic reduces B during acceleration by 33% as compared to single-frequency operation. The features of this economical arrangement are described and compared to more-conventional systems. This system is especially suitable for combined-function magnets