Development of a secondary-electron ion-microscope for microbeam diagnostics

We describe a novel secondary-electron ion microscope (SEIM), designed for diagnostics of the upcoming sub-micron Columbia University charged-particle microbeam. This secondary-electron ion microscope allows much higher resolutions, at higher single particle detection efficiencies, than previously available, for rapid and accurate diagnostics of sub-micron charged-particle beams. Based on ion electron-emission microscopy (IEEM) and photo-electron microscopy (PEM), the SEIM involves conversion of the incident projectiles on a secondary-electron emitting film. The ejected electrons are focused using a unipolar electrostatic lens and conical electrostatic mirror to form a magnified image on a microchannel plate (MCP). The flight path of the electrons includes two 45° bends; this “folded” geometry results in lower aberrations than a “straight” design, and enables efficient beam imaging down to 100 nm resolution with >50% single electron transfer efficiency.