HOLISTIC DESIGN OF A SCANNING NUCLEAR MICROPROBE

A scanning nuclear microprobe (SNM) has been designed to focus high flux densities of protons to 1 mu m in vacuum and to 25 mu m in air or controlled atmospheres. The design was constrained by demanding that the market price of a commercial SNM, including end-station, scanner, automated control and data acquisition system, be less than or equal to 1 million US dollars. This goal can be achieved with a single-ended electrostatic accelerator delivering proton and alpha beams up to 1.5 MeV. The holistic design not only substantially reduces the cost of the overall system but allows all elements in the system - ion source, velocity selector, accelerator, magnetic focusing and scanner - to be optimized. We find that it should be possible to obtain 2 nA of 1.5 MeV protons in a 1 mu m target spot; i.e. an order of magnitude improvement over existing systems. Such beam densities will make the SNM a versatile tool for studies in the few hundred nanometer range.