TTPIXAN - THE 4TH GENERATION

During the past six years the computer code TTPIXAN [I. Orlic et al., NIMB 49 (1990) 166] went through many changes and developments. From i ts infant stage when it was developed for a simple quantitative broad beam PIXE analysis, through a more sophisticated version [K.K. Loh et al., NIMB 77 (1993) 132] suited for applications in Nuclear Microscopy (NM). At present, the program is finally reaching, its mature stage o r its 4th metamorphosis [S.C. Liew et al., NIMB 104 (1995) 222]. It is now capable of not only simulating NM elemental images but also perfo rming quantitative analysis and reconstruction of a complex 3D element al composition encountered in NM applications. From a given initial 3D elemental distributions the program calculates exact elemental maps, compares them with the corresponding measured maps and by using a very efficient iterative Maximum-Likelihood Expectation-Maximisation (MLEM ) algorithm, it calculates a new 3D elemental distributions. Energy lo ss of the incident particles and attenuation of the X-ray photons are incorporated into the reconstruction algorithm by using the most up-to date data base. The reconstruction algorithm has been successfully te sted on several samples such as thin tungsten wire coated with paint, integrated circuits, and single aerosol particles. The computer code i s briefly described and future plans outlined. (C) 1997 Elsevier Scien ce B.V.