Arbitrarily shaped high-coherence electron bunches from cold atoms

• Published in: Nature physics 2011-10, Vol.7 (10), p.785-788
• Main Authors: McCulloch, A. J., Sheludko, D. V., Saliba, S. D., Bell, S. C., Junker, M., Nugent, K. A., Scholten, R. E.
• Format: Article
• Language: English
• Subjects: Atomic; Atoms & subatomic particles; Biological; Brightness; Classical and Continuum Physics; Coherence; Cold atoms; Complex Systems; Condensed Matter Physics; Coulomb friction; Electron sources; Electrons; Explosions; letter; Mathematical and Computational Physics; Molecular; Nanostructure; Optical and Plasma Physics; Optics; Particle physics; Physics; Physics and Astronomy; Theoretical
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys2052

The potential to generate pulsed electron beams with charge distributions tailored in all three dimensions could revolutionize high-speed electron diffraction. A demonstration of a highly coherent pulse electron beam that can be arbitrarily tailored in two dimensions is a step towards this goal. Ultrafast electron diffractive imaging of nanoscale objects such as biological molecules 1 , 2 and defects in solid-state devices 3 provides crucial information on structure and dynamic processes: for example, determination of the form and function of membrane proteins, vital for many key goals in modern biological science, including rational drug design 4 . High brightness and high coherence are required to achieve the necessary spatial and temporal resolution, but have been limited by the thermal nature of conventional electron sources and by divergence due to repulsive interactions between the electrons, known as the Coulomb explosion. It has been shown that, if the electrons are shaped into ellipsoidal bunches with uniform density 5 , the Coulomb explosion can be reversed using conventional optics, to deliver the maximum possible brightness at the target 6 , 7 . Here we demonstrate arbitrary and real-time control of the shape of cold electron bunches extracted from laser-cooled atoms. The ability to dynamically shape the electron source itself and to observe this shape in the propagated electron bunch provides a remarkable experimental demonstration of the intrinsically high spatial coherence of a cold-atom electron source, and the potential for alleviation of electron-source brightness limitations due to Coulomb explosion 6 .