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Ultracold Electron Source for Single-Shot, Ultrafast Electron Diffraction

Published online by Cambridge University Press:  03 July 2009

S.B. van der Geer ,
M.J. de Loos ,
E.J.D. Vredenbregt  and
O.J. Luiten
S.B. van der Geer*
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
M.J. de Loos
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
E.J.D. Vredenbregt
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
O.J. Luiten
Affiliation:
Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
*
Corresponding author. E-mail: [email protected]
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Abstract

Ultrafast electron diffraction (UED) enables studies of structural dynamics at atomic length and timescales, i.e., 0.1 nm and 0.1 ps, in single-shot mode. At present UED experiments are based on femtosecond laser photoemission from solid state cathodes. These photoemission sources perform excellently, but are not sufficiently bright for single-shot studies of, for example, biomolecular samples. We propose a new type of electron source, based on near-threshold photoionization of a laser-cooled and trapped atomic gas. The electron temperature of these sources can be as low as 10 K, implying an increase in brightness by orders of magnitude. We investigate a setup consisting of an ultracold electron source and standard radio-frequency acceleration techniques by GPT tracking simulations. The simulations use realistic fields and include all pairwise Coulomb interactions. We show that in this setup 120 keV, 0.1 pC electron bunches can be produced with a longitudinal emittance sufficiently small for enabling sub-100 fs bunch lengths at 1% relative energy spread. A transverse root-mean-square normalized emittance of εx = 10 nm is obtained, significantly better than from photoemission sources. Correlations in transverse phase-space indicate that the transverse emittance can be improved even further, enabling single-shot studies of biomolecular samples.

Type
Special Section: Ultrafast Electron Microscopy
Information
Microscopy and Microanalysis , Volume 15 , Issue 4 , August 2009 , pp. 282 - 289
Copyright
Copyright © Microscopy Society of America 2009

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References

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