Düsseldorf 2007 – wissenschaftliches Programm

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K: Fachverband Kurzzeitphysik

K 2: Poster I - Laseranwendungen

K 2.2: Poster

Montag, 19. März 2007, 16:30–18:30, Poster A

Development and Characterization of an Electron Source for Ultrafast Diffraction Experiments — •Ivan Rajkovic, Manuel Ligges, Ping Zhou, and Dietrich von der Linde — Universität Duisburg-Essen, Fachbereich Physik

Ultrafast electron diffraction (UED) is a new, promising technique for studying atomic motion on sub-picosecond timescales and has shown to be able to resolve fundamental processes in the fields of physics and chemistry [1,2].

In UED, ultrashort electron pulses are generated by illuminating a thin metal film with UV pulses generated by a frequency tripled Ti:Sa fs-laser. These photoelectrons are accelerated to several tens of keV, collimated and then diffracted on a thin film sample. Using an optical pump/electron probe geometry, the structural dynamics of the specimen can be observed.

However, due to the initial electron energy distribution and coulomb-forces between the single electrons, pulses are becoming longer in time. To minimize this pulse broadening, which limits the experimental temporal resolution, a careful design of gun electrodes as well as short pathways for the electrons are necessary.

Here we present our work on developing an electron gun suitable for ultrafast electron diffraction experiments. The electron pulses produced by the gun are characterized and different collimation methods used to obtain best quality diffraction pictures are compared.

[1] Siwick et al., Science 302, 1382 (2003)

[2] Ihee et al., Science 291, 458 (2001)