Using laser-cooled atoms as a focused ion beam source

Abstract

The authors describe a new method for creating a high quality focused ion beam using laser-cooled neutral atoms in a magneto-optical trap as an ion source. They show that this new technique can provide spot resolutions and brightness values that are better than the state of the art in focused ion beams. The source can be used with a range of different ionic species and can be combined with laser cooling techniques to exert unprecedented control over the ion emission, for example, producing single ions “on demand.” The beam quality is a result of a high brightness and a narrow energy distribution, both of which stem from the cold temperature (≈100μK) of the atoms. The ions are produced by subjecting the cold neutral atoms to a photoionization laser, after which they become a compact source of nearly monoenergetic ions. With the application of a potential gradient, the ions form a beam that can be focused via standard ion optical techniques. They discuss estimations based on the initial size of the ion cloud and the energy distribution and show that the resulting beam has a low emittance.