The Sumy scanning nuclear microprobe: Design features and first tests

A new scanning nuclear microprobe based on a single-ended 2 MV Van de Graaff accelerator has recently been designed and constructed at the Sumy Institute of Applied Physics of the National Academy of Sciences of Ukraine. To achieve higher microprobe resolution the operating parameters of the accelerator were improved. By upgrading the ion source it was possible to increase the beam brightness by a factor of 4. The replacement of the charge belt and development of a new charging system for the high-voltage terminal provided more stable accelerator operation. The optimization calculations of the probeforming system optics were performed involving the maximum emittance criterion with allowance for the accelerator performance data. The assessment of various parametric multiplets of magnetic quadrupole lenses with two independent power supplies permitted a four-lens system with separated doublets of “Russian Quadruplet” type to be chosen. A special feature of the probeforming system is the use of a newly-designed magnetic quadrupole lens doublet made from a single piece of soft iron. The primary objective of the early tests was to investigate the focusing properties of the new doublets.