Simulation verification of longitudinal acceptance measurement for low-energy superconducting linacs

Controlling longitudinal beam loss is crucial for ensuring the stable operation of superconducting linacs. Measuring and optimizing longitudinal acceptance are effective methods to reduce longitudinal beam loss. The SNS has reported research results on measuring longitudinal acceptance in a high-energy accelerator. Compared to high-energy accelerators, low-energy accelerators exhibit stronger space charge effects and nonlinearities, larger beam sizes, and more significant impacts from errors. Therefore, the measurement and optimization of longitudinal acceptance are more essential for beam loss control in low-energy superconducting linacs. This paper systematically investigates the measurement of longitudinal acceptance in low-energy superconducting linacs and validates the longitudinal acceptance measurement based on phase and energy acceptance scans through numerical simulation on the CAFe superconducting linac. Additionally, the impact of errors under actual operating conditions on the longitudinal acceptance is comprehensively analyzed. The research results indicate that conducting experiments to measure the longitudinal acceptance of a low-energy superconducting linac is highly feasible.