Beam interactions with Materials&Atoms Nuclear Instruments and Methods in Physics Research B 130 (1997) 253-258 ELSEVIER Advances in 3D ion micro-tomography A. Sakellariou *, M. Cholewa ‘, A. Saint, G.J.F. Legge School c$ zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Physics, MARC. The Unicersiry zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGF of Mefbotme, Purkdle Vie. 3052, Ausiraiia Abstract A new method for three dimensional tomographic analysis of micro-samples is presented. The technique is capable of accurately calculating the mass density and composition distribution of a sample, using the data measured from a STIM and PIXE tomography experiment. The technique solves for the effects of the energy dependence of the proton stopping-power and X-ray production cross-section. It also incorporates X-ray attenuation for a cone geometry between the sample and X-ray detector. A priori information about low Z elements is easily incorporated into the technique. The reconstruction of the mass density and compositjon of a phantom is shown. zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFED 1. Introduction Ion microscopy can provide detailed quantitative information about microscopic samples. The large penetrating distance of the ion beam allows informa- tion from deep within the sample to be measured. A particularly useful technique for calculating the inter- nal properties of a sample is a tomographic experi- ment. With the use of Scanning Transmission Ion Mi- croscopy @TIM) and Particle Induced X-Ray Emis- sion CPIXE) data, mass density and elemental con- centrations of a sample can be calculated. Implemen- tation of these two techniques into a tomographic experiment should provide three dimensional distri- bution maps of most samples. Much investigation has gone into devising techniques to reconstruct * Corresponding author. Fax: + 61-3-9347-4783; emaii: a.sakel- ia~ou~physics.unimelb.edu.au ’ Permanent address: Institute of Nuclear Physics. Cracow, Poland. STIM and PIXE data into accurate tomograms of a sample [ zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPO 1- 121. Ion tomographic experiments involve non-linear processes which preclude accurate reconstruction of a sample using conventional techniques. In another paper [13], we showed that the data from a STIM tomography experiment could be very accurately reconstructed and that the accuracy of the solution was dependent only on how correctly the experiment is modelled. We also showed that the inherent noise associated with multiple iterations could be reduced by special discretisation. In this paper, we show that the Discrete Image Space Reconstruction Algorithm (DISRA) [ 141 can handle the complexities of cotn- bined STIM and PIXE three dimensional ion micro- tomography. At this stage, only the results for a phantom sample have been calculated. These results are shown for a geometric setup in which the X-ray detector subtends a solid angle of 30 mstr at the sample. A solid angle of up to 2rr steradians can be used. However, as the solid angle increases, the amount of computer resources required to reconstruct a tomo- 0168-583X/97/$17.00 0 1997 Published by Elsevier Science B.V. All rights reserved. PIIs0168-583x(97)00173-0 V. MICROPROBE ANALYTICAL TECHNIQUES