Study of longitudinal energy-phase oscillation excited by RF phase deviation in low-\({\varvec{\beta}}\) proton and ion Linac

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- \(\beta\) $\beta$ proton/ion linac, significantly impacting operational safety.

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- \(\beta\) $\beta$ proton/ion linac. Comparison of BPM measurements with model predictions provides a method for monitoring the stability of beam operation.

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.