ALGORITHM FOR FITTING XRF, SEM AND PIXE X-RAY-SPECTRA BACKGROUNDS

Existing background fitting of energy dispersive X-ray spectra (X-ray, electron or proton excited) algorithms (e.g. parabolas or polynomials ) are not universally applicable. Various limitations exist tying each algorithm to specific spectral shapes. This project aimed to find a g eneric algorithm which could reliably fit background independent of X- ray spectra source and form. A frequency differentiated non-linear dig ital filter ''rolling ball'' was chosen as a promising possibility. Th e algorithm is based on a square wave with an energy variable width as the structuring function, operated on by a gray scale morphological t ransformation. A wide range of spectra types have been successfully fi tted. This algorithm behaves equivalently to traditional polynomial ba ckgrounds in simple spectra e.g. PIXE aerosol spectra with funny filte r, and is considerably more robust for multiple overlapping peaks, rap idly varying backgrounds, and is independent of X-ray energy filter or excitation mode.