Positron moderation experiment based on magnetic mirror

BackgroundSlow positrons have significant applications in the study of defects in thin-film materials, material surfaces, and interfaces. Slow positron beams are obtained by moderating conventional positron beams, where the moderation efficiency is currently a major factor limiting the development of slow positron beams.PurposeThis study aims to investigate methods for enhancing moderation efficiency by integrating a magnetic mirror with a tungsten foil moderator.MethodsA positron moderation device based on a 0.1 T magnetic mirror was designed and constructed, and corresponding moderation experiments were conducted. Then, the enhancement effect of the magnetic mirror on moderation efficiency was analyzed by measuring the slow positron count rate at the device terminal under different magnetic mirror configurations. Finally, the G4 beamline software was used for Monte Carlo simulation to explore the influence of the collimator inner diameter and position on the transmission performance, and the moderation efficiency of the device was subsequently calculated.ResultsThe experimental results demonstrate that the magnetic mirror can enhance the moderation efficiency of the device by nearly 90%. The measured experimental moderation efficiency is determined to be (0.059±0.005)%.ConclusionsThe findings of this study validate the feasibility of utilizing a magnetic mirrors to improve the moderation efficiency of such devices, providing a foundation for further optimization of positron moderation efficiency.