Ultracold electron source for single-shot diffraction studies

Department of Applied Physics, Eindhoven University of Technology - P.O. Box 513, 5600 MB Eindhoven, The Netherlands, EU

^a e.j.d.vredenbregt@tue.nl

Received: 21 January 2010
Accepted: 10 August 2010

Abstract

Ultracold electron sources, which are based on near-threshold photo- and field-ionization of a cloud of laser-cooled atoms, offer the unique combination of low emittance and extended size that is essential for achieving single-shot, ultrafast electron diffraction of macromolecules. Here we present measurements of the effective temperature of such a pulsed electron source employing rubidium atoms that are magneto-optically trapped at the center of an accelerator structure. Transverse source temperatures ranging from 200 K down to 10 K are demonstrated, controllable with the wavelength of the ionization laser. Together with the 50 μm source size, the achievable temperature enables a transverse coherence length of ≈20 nm for a 100 μm sample size.