108 research outputs found
Unveiling the orbital angular momentum and acceleration of electron beams
New forms of electron beams have been intensively investigated recently,
including vortex beams carrying orbital angular momentum, as well as Airy beams
propagating along a parabolic trajectory. Their traits may be harnessed for
applications in materials science, electron microscopy and interferometry, and
so it is important to measure their properties with ease. Here we show how one
may immediately quantify these beams' parameters without need for additional
fabrication or non-standard microscopic tools. Our experimental results are
backed by numerical simulations and analytic derivation.Comment: 2 figures in text, 2 in supplementar
Spectral and spatial shaping of Smith Purcell Radiation
The Smith Purcell effect, observed when an electron beam passes in the
vicinity of a periodic structure, is a promising platform for the generation of
electromagnetic radiation in previously-unreachable spectral ranges. However,
most of the studies of this radiation were performed on simple periodic
gratings, whose radiation spectrum exhibits a single peak and its higher
harmonics predicted by a well-established dispersion relation. Here, we propose
a method to shape the spatial and spectral far-field distribution of the
radiation using complex periodic and aperiodic gratings. We show, theoretically
and experimentally, that engineering multiple peak spectra with controlled
widths located at desired wavelengths is achievable using Smith-Purcell
radiation. Our method opens the way to free-electron driven sources with
tailored angular and spectral response, and gives rise to focusing
functionality for spectral ranges where lenses are unavailable or inefficient
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