The 500-MeV synchrotron of Argonne's Intense Pulsed Neutron Source operates at 30 Hz. Its beam spill must be locked to neutron choppers with a precision of ±0.5 us. A chopper and an accelerator have large and different inertias. This makes synchronization by phase lock to the 60-Hz power line extremely difficult. We solved the phasing problem by running both the Ring Magnet Power Supply (RMPS) of the synchrotron and the chopper motors from a common oscillator that is stable to 1 ppm and by

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... olling five quantities of the RMPS. The quantities controlled by feedback loops are dc current, injection current, ejection current* resonant frequency, and the phase shift between the synchrotron peak field and the chopper window.