A timing-reference generator for power-grid-synchronized neutron-spallation facilities

Accelerator-based neutron-spallation facilities often derive their internal timing reference from the AC-power grid. Because the grid-frequency fluctuates, there is an inherent conflict between the performance of accelerator systems and neutron choppers. An optimal solution to this problem is to provide a phase-locked timing-reference signal with enough coupling to the grid to meet accelerator demands and enough de-coupling to meet chopper requirements. This paper describes the design and operation of a LANSCE-12-developed DSP-based timing-reference generator suitable for grid-synchronized facilities. It outputs a phase-locked, nominal 120-Hz pulse train. The amount of grid coupling or output pulse-to-pulse filtering can be set by the user to any of 10 discrete levels. The paper also includes a description of the real-time dual-loop control algorithm running in the DSP, how different loop parameters are used at each control point and performance results.