Laser Cooled Atoms as a Focused Ion Beam Source


James L. Hanssen and Jabez J. McClelland

Electron Physics Group, National Institute of Standards and Technology, 100 Bureau Dr., Gaithersburg, MD  20899-8412


We describe a new method for creating a high quality focused ion beam using laser cooled neutral atoms in a magneto-optical trap[1] as an ion source.  We 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”.[2]   The beam quality is a result of a high brightness and a narrow energy distribution, both of which stem from the cold temperature (» 100 μK) 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 mono-energetic ions.  With the application of a potential gradient, the ions form a beam that can be focused via standard ion optical techniques.  We will discuss estimates based on the initial size of the ion cloud and the energy distribution, and show the resulting beam has a low emittance.  We will also present a realistic ray tracing analysis of a model focusing system and demonstrate that it is possible to focus the beam to a spot size of approximately 10 nm.  In addition, we will show our progress toward an experimental realization of this system using chromium ions.




Name:              James Hanssen

Mentor:            Jabez McClelland

Division:           Electron and Optical Physics (841)

Laboratory:      Physics

Building:           216

Room:              A247

Mail Stop:        8412

Telephone:        301-975-3768

Fax:                  301-926-2746


Sigma Xi:          not a member

Category:         Physics


[1] E. Raab, M. Prentiss, A. Cable, S. Chu, and D. Pritchard, Phys. Rev. Lett. 59, 2631 (1987).

[2] S.B. Hill and J.J. McClelland, Appl. Phys. Lett. 82, 3028 (2003).