Measurement of germanium escape peaks in PIXE spectra recorded using high purity Ge (HPGe) detector

This paper deals with studies on Ge Kα and Kβ escape peaks in particle induced X-ray emission (PIXE) spectra recorded by a high purity germanium (HPGe) detector. A knowledge of the energies and intensities of these escape peaks is desirable for accurate qualitative as well as quantitative analysis of elements by PIXE. The spectral interferences caused by Ge K escape peaks in the determination of Fe in U by PIXE are highlighted for illustration. A simple theoretical approach based on the production of Ge K X-rays inside the Ge crystal of the detector during the process of detection of the incident characteristic X-rays and the subsequent escape of a fraction of the produced radiations from the crystal, is described to calculate the intensity ratio of the Ge escape peak to its parent characteristic X-rays. The calculated values are in agreement with the experimental values and those estimated using the formulation provided in GUPIX software for PIXE. The Ge K escape peaks are very prominent; the intensities of Ge Kα escape peaks, from bromine to silver, range from 15% to 6% of those of their respective Kα X-rays. These intensities are, in general, considerably higher compared to those of Si escape peaks in spectra recorded by Si(Li) detector. Ge K escape peaks therefore may give rise to severe interferences. The present approach provides a precise (∼8%) determination of the intensity of an escape peak and thereby facilitates a reliable PIXE analysis. (author)