物理学报2026，Vol.75Issue(12)：61-71,11.DOI:10.7498/aps.75.20260113
1-10 MeV/u能区重离子在碳基薄膜表面的二次电子发射特性模拟
Simulation of secondary electron emission characteristics from carbon foils bombarded by 1-10 MeV/u heavy ions
摘要
Abstract
Secondary electron emission(SEE)is a fundamental surface phenomenon,but its accurate experimental characterization remains challenging due to high sensitivity to surface conditions and environmental factors.This study utilizes the Monte Carlo simulation method to investigate the SEE process induced by medium-and low-energy heavy ions incident on thin foils,aiming to provide theoretical guidance for the design and application of SEE-based beam diagnostic detectors in accelerator facilities.Taking the thin foil detector for the Xi'an 200 MeV Proton Application Facility(XiPAF)as the application background,we utilize the recently extended MicroElec module of Geant4 to quantitatively study the secondary electron yield(SEY),energy spectra,and angular distributions from carbon foils bombarded by heavy ions in the energy range of 110 MeV/u.The relationships between SEY and foil thickness,linear energy transfer(LET),and incident angle are systematically explored.Key findings are as follows: 1)The evolution of forward and backward SEY with foil thickness,as well as their asymmetry,is dominated by δ electron transport.Specifically,forward SEY increases rapidly with thickness up to～600 nm and then saturates,while backward SEY saturates at a smaller thickness(～300 nm),consistent with the different escape depths of δ electrons. 2)For a 100 nm carbon foil,the total SEY exhibits an approximately linear dependence on the incident ion's LET over three orders of magnitude(0.1-100 keV·cm2·μg-1).After normalizing the simulated yields with SRIM-calculated energy deposition,the fitted SEY-LET coefficient deviates by less than 30％from the experimental data compiled by Rothard et al.,which is well within the reported experimental uncertainty(a factor of two). 3)With increasing incident angle,both forward and backward SEY increase monotonically,but their sensitivities differ:power-law fitting yields f=0.95 for forward emission and f=1.12 for backward emission inγ(φ)=γ(0)(cos φ)-f.This disparity originates from the forward-peaked angular distribution of δ-electrons and their asymmetric transport in the foil,corroborated by the depth distribution of emitted-electron track vertices. The simulated electron energy spectra and angular distributions agree well with theoretical expectations.The energy deposition calculated by MicroElec shows a deviation from SRIM results(up to 23％for low-energy heavy ions),which is attributed primarily to the different effective-charge models adopted by the two codes. This study demonstrates that the Geant4-MicroElec module is an effective tool for simulating heavy-ion-induced SEE in the medium-and low-energy regime.The systematic data and physical insights obtained here provide valuable references for the design of thin-foil detectors,particularly for online monitoring of low-energy heavy-ion beams.关键词
二次电子发射/重离子/薄膜/蒙特卡罗模拟Key words
secondary electron emission/heavy ions/thin foil/Monte Carlo simulation引用本文复制引用
王迪,陈伟,丁泽军,马宗翔,宋朝晖,王敏文,王忠明..1-10 MeV/u能区重离子在碳基薄膜表面的二次电子发射特性模拟[J].物理学报,2026,75(12):61-71,11.基金项目
国家自然科学基金青年科学基金(批准号:12405182)资助的课题. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.12405182). （批准号:12405182）
