Effect of Grid Geometry on Transmittance of Retarding Field Analyzer:A Simulation Study

The ion-beam transport in triple-grid retarding field analyzer (RFA), installed in the lab-built Mirror with Axisymmetricity, was mathematically modeled and numerically simulated with software COMSOL for design optimization.The influence of the incident-angle/energy of ion beam and grid-structure on the RFA's transmittance was investigated.The simulated results show that the ion-beam properties and grid-structure all have a major impact.To be specific, as the ion beam energy increased, RFA's transmittance increased, approaching to the optical transmittance at a high energy because of significantly weakened inter-grids lens effect;RFA's transmittance depends on the incident angle of ion beam and on the properties of each grid, including the optical transmittance, mesh-shape, mesh-size and mesh-alignment.For example, a grid with circular-mesh has higher transmittance than that with square-mesh.Moreover, the ion incident angle should in 0°~10° range.