A new cold electron source is currently under development at the University of Manchester in collaboration with the Cockcroft Institute. We anticipate that this new source will have applications in diffraction imaging, such as Low Energy Electron Diffraction (LEED) studies of surface structures, and for new compact LINACs, such as a laser wakefield accelerator being designed at the Cockcroft Institute.

This cold electron source will use a high density ensemble of laser-cooled ⁸⁵Rb atoms held in a new type of trap invented in Manchester, the alternating current magneto-optical trap (AC-MOT). The AC-MOT allows precise control of low energy electron interactions with trapped atoms, by eliminating all magnetic fields at the time of the interaction. This technique allows the experiments to proceed >300 times faster than with conventional traps. A pulsed cold electron beam will be produced by selective near threshold photo-ionization of the cold atom ensemble using high resolution lasers, followed by electro-static extraction and focusing into a beam.

The cold atom source will consist of a collimated beam of rubidium emitted from an oven which feeds a Zeeman slower stage that rapidly loads a storage MOT. From here, atoms will be transferred to a µ-metal shielded interaction chamber containing the AC-MOT. The interaction chamber will also contain a low energy electron spectrometer to allow the resolution and flux of the electron beam to be optimised. This will be done by measuring negative ion resonances in the elastic scattering from He, Ne and Ar, since these resonances appear as sharp structures in the elastic cross-sections.

This presentation will provide a description of the new experiment, including details of the AC-MOT.