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arXiv · 2605.19930

High resolution large working distance scanning helium microscopy

Sam M Lambrick·Nick A von Jeinsen·Alek Radić·David J Ward·John E Halpin·Donald A MacLaren·Andrew P Jardine
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Abstract

Scanning helium microscopy (SHeM) is attractive for imaging delicate and insulating surfaces because it combines a non-destructive neutral-atom probe with strong surface sensitivity. However, large-working-distance pinhole instruments have so far been limited in spatial resolution. Here we report sub-micron resolution in a large-working-distance pinhole SHeM, with an intrinsic beamwidth of 340nm achieved at working distances of 770 {\mu}m to 850 {\mu}m. This sixfold improvement over our previous long-working-distance configuration is enabled by constrained optimisation of the atom optics together with a redesigned high-resolution pinhole-plate, a reduced pinhole diameter, an increased source--pinhole distance and a larger detector aperture. Beamwidth measurements agree well with the modified optimisation model and show that geometric, source-size and diffraction terms now contribute on a similar footing, placing the instrument in a near-optimised regime. The resulting combination of sub-micron beam size, useful depth of field and practical sample access is demonstrated on bacterial specimens and eroded diamond. The work establishes large-working-distance pinhole SHeM as a viable sub-micron imaging platform and extends its usefulness for topographic imaging and micro-diffraction applications.

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Sam M Lambrick, Nick A von Jeinsen, Alek Radić, David J Ward, John E Halpin, Donald A MacLaren, Andrew P Jardine. 2026-05-19. High resolution large working distance scanning helium microscopy. https://arxiv.org/abs/2605.19930

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