Requirement of HE-PIXE at High Z Elements in Charnockite Matrix Composition

Abstract. The maximum of Proton Induced X-ray Emission analytical technique on metamorphic rocks in geology has used 3 MeV range proton beams for excitation of thick targets. Protons of such energies do not accurately excite K-X–rays for high Z elements in matrix geological compositions like charnockite. In this analysis, low-energy PIXE (LE-PIXE) uses K-X-rays of Low Z elements and L-X-ray series for high Z elements. The resulting spectra between K-X-rays of light elements and L-X-rays of heavy elements can require striping techniques to resolve overlap difficulties in matrix composition. The results high Z elements in charnockite are to be expected, as the cross section for K-shell ionization of high-Z elements have greater values in the proton energy range of greater than 3 MeV in case of charnockite matrix composition. It has been suggested that the overlap of these discrete, gamma-rays with the X-ray spectrum may be serious problem in charnockite high energy PIXE (HE-PIXE) work, sufficient to preclude its use as a viable analytical technique. The conclusion proves that for a very complex matrix charnockite material of unknown chemistry, a HE-PIXE analytical spectrum may contain various X-ray and gamma peaks, some of which may overlap, making the analysis of line identities and the evaluation of X-ray counts intractable. It does not however represent any intrinsic drawback in HE-PIXE, nor does it mean that HE-PIXE is any more or less intractable than many other nuclear analytical techniques. Alternatively, the same analytical tool use could be made of gamma-rays in HE-PIXE as in low energy analytical tools like PIGE, NRA or INAA to obtain the results of charnockite at high Z completely.