A FPGA-based high-order harmonic current control of resonant power supply system in rapid-cycling synchrotron

The rapid-cycling synchrotron (RCS) is a crucial device for proton beam acceleration at the China Spallation Neutron Source, operating at a repetition frequency of 25 Hz. The beam power was increased from 100 kW to 140 kW. This increase makes the on-orbit beam more sensitive to disturbances in various parts of the accelerator, including the RCS magnet power supply system. This paper presents a method for reducing the high-order harmonic current error in resonant power supplies for dipole magnets and examines its impact on the horizontal orbit offset of the beam. It adopts a control scheme that combines high-order harmonic current compensation with PI double-loop control of the resonant power supply. By utilizing the existing digital controller hardware in the RCS power supply system, this study demonstrates how to achieve precise control of the 50 Hz harmonic current output in a cost-effective manner. Ultimately, it enhances performance by reducing the current error by up to 50% and provides methodological support for future upgrades to the power supply system. Such improvements enhance the stability of the RCS, reducing the beam horizontal orbit deviation by at least 19.8%.