Schonland Research Centre for Nuclear Sciences

Ion-Beam Microprobe

Tomographic STIM imaging of biological specimens

University of the Witwatersrand, SRCNS : SH Connell, RD Maclear, BP Doyle, IZ Machi, JPF Sellschop, E Sideras-Haddad
Lawrence Livermore National Laboratory : , G Bench,
Sandia National Laboratory : A Antolak, D Morse
SPM Unit, Oxford : MHB Breese

Micro-probes oriented to biological samples (which contain volatiles) use STIM to measure sample surface densities in order to calibrate micro-PIXE trace element distributions and obtain absolute concentrations. This concept has been extended at SRCNS to tomography of multiple STIM images. In addition, the heavy- ion capability of the Tandem accelerator is exploited to tune the energy loss of the STIM projectile to the sample composition and geometry. In an initial project, tomographic images of a fungi spore were acquired with both proton and 12C beams, to demonstrate clearly the increased contrast in heavy-ion imaging. The tomograms were reconstructed at the Lawrence Livermore National Laboratory. The method is non-destructive and extremely efficient in acquisition time. 3-D density maps (ion beam radiography) may be rapidly acquired for samples of the order of 10-100 mm diameter. The beautiful images of the internal structure of the micro-spores, obtained non-destructively, is, like the laser was originally, a technique demonstrating physics but without application. We will be marketing STIM microtomography to the potential users in the next research period. Meanwhile, work continues with further refinements to sample preparation, manipulation, and detector performance.

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                                                                                                                                Last updated: 5 October 1998