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Journal Article

Optical fiber-based photocathode

MPS-Authors
/persons/resource/persons136078

Casandruc,  Albert
Miller Group, Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free-Electron Laser Science (CFEL) and Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, Hamburg 22761, Germany;

/persons/resource/persons136038

Bücker,  Robert
Miller Group, Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free-Electron Laser Science (CFEL) and Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, Hamburg 22761, Germany;

/persons/resource/persons136033

Kassier,  Günther
Miller Group, Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free-Electron Laser Science (CFEL) and Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, Hamburg 22761, Germany;

/persons/resource/persons136024

Miller,  R. J. Dwayne
Miller Group, Atomically Resolved Dynamics Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Free-Electron Laser Science (CFEL) and Hamburg Centre for Ultrafast Imaging (CUI), Luruper Chaussee 149, Hamburg 22761, Germany;
Departments of Chemistry and Physics, University of Toronto, Toronto, Ontario M5S 3H6, Canada;

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Fulltext (public)

1.4962147.pdf
(Publisher version), 777KB

Supplementary Material (public)

supplementary.pdf
(Supplementary material), 478KB

Citation

Casandruc, A., Bücker, R., Kassier, G., & Miller, R. J. D. (2016). Optical fiber-based photocathode. Applied Physics Letters, 109(9): 091105. doi:10.1063/1.4962147.


Cite as: http://hdl.handle.net/11858/00-001M-0000-002B-60CE-7
Abstract
We present the design of a back-illuminated photocathode for electron diffraction experiments based on an optical fiber, and experimental characterization of emitted electron bunches. Excitation light is guided through the fiber into the experimental vacuum chamber, eliminating typical alignment difficulties between the emitter metal and the optical trigger and position instabilities, as well as providing reliable control of the laser spot size and profile. The in-vacuum fiber end is polished and coated with a 30 nm gold (Au) layer on top of 3 nm of chromium (Cr), which emits electrons by means of single-photon photoemission when femtosecond pulses in the near ultraviolet (257 nm) are fed into the fiber on the air side. The emission area can be adjusted to any value between a few nanometers (using tapered fibers) and the size of a multi-mode fiber core (100 μm or larger). In this proof-of-principle experiment, two different types of fibers were tested, with emission spot diameters of 50 μm and 100 μm, respectively. The normalized thermal electron beam emittance (TE) was measured by means of the aperture scan technique, and a TE of 4.0 π nm was measured for the smaller spot diameter. Straightforward enhancements to the concept allowed to demonstrate operation in an electric field environment of up to 7 MV/m.