Space Charge Dynamics and Diffraction with Ultracold Electron and Ion Bunches

Professor Robert Scholten

The University of Melbourne, Australia

3:30 pm Friday, 17 April 2015, EN313 Lecture Theatre (EN Building), Hawthorn.

Space-charge driven expansion in charged particle beams is of critical importance for applications including electron and ion microscopy, mass spectrometry, synchrotrons and x-ray free electron lasers, and in electron diffraction where space-charge effects constrain the capacity to obtain diffraction information. Self-field effects are often difficult to observe because of thermal diffusion with conventional charged particle sources. Photoionisation of laser cooled atoms can generate very cold electron and ion bunches, such that subtle space-charge effects are apparent. The capabilities are illustrated by detailed investigation of complex ion bunch shapes, showing collective behaviour including high density caustics and shockwave structures arising from long-range interactions between small charge bunches. The insight allows formation of bunches shaped to allow the reversal of Coulomb-driven space-charge explosion and achieve ultrafast high-resolution electron diffraction.

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