Study of longitudinal energy-phase oscillation excited by RF phase deviation in low-β proton and ion Linac

Background In accelerator operations, some phase drifts in the reference signals of low-level radiofrequency (LLRF) control systems and analog components can hardly be detected and corrected by the LLRF itself, leading to phase deviations in the cavity and exciting sustained longitudinal energy-phase oscillations of the beam during subsequent acceleration. This phenomenon is particularly pronounced in low-β proton/ion linac, significantly impacting operational safety.
Methods The longitudinal oscillations of the beam eventually manifest in the measurements of overall beam position/phase monitors (BPM) with a distinct pattern. In this paper, the effects of cavity phase deviations on the particle accelerating process are simulated and analyzed using a trace model, and beam experiments are performed at an upgraded Chinese ADS front-end demo facility (CAFe2) to demonstrate the morphologies and characteristics of longitudinal oscillations in the low-β proton/ion linac. Comparison of BPM measurements with model predictions provides a method for monitoring the stability of beam operation.
Results and conclusion Beam experiments on CAFe2 support the results of relevant simulations and confirm the unique correspondence between beam phase oscillation trajectories and phase-deviated cavities, validating the feasibility of a method for detecting and correcting cavity phase anomalies based on longitudinal measurements.