Design of a compact and integrated vortex field-emission electron source

Abstract

Vortex electron beams in the energy range of 100–300 keV have been widely demonstrated in electron microscopy. However, the experimental realization of higher-energy vortex beams remains a major challenge. To enable the coupling of vortex electron sources with electron accelerators, this study proposes and designs a compact vortex field-emission (FE) electron source that integrates a field emitter, an electrostatic lens, and a nanoscale grating. In this new design, the field emitter is fabricated via the electrochemical etching method with tip radii of 40–60 nm, and the lens geometry is systematically optimized to precisely control the local electric field and beam dynamics. In contrast to electron microscopes, the employed electrostatic lens enables near-parallel beam propagation over a distance of 60 mm, with a divergence angle of approximately 2.3 mrad. Based on the van Cittert–Zernike theorem, the transverse coherence length is estimated to exceed 15 μm. Under these conditions, the proposed vortex FE electron source is capable of generating vortex beams. This compact design offers a viable technical pathway for the generation and application of high-energy vortex electron beams.