Alpha–electron and alpha–photon coincidences in high-resolution alpha spectrometry

Photons and electrons emitted in coincidence with an alpha particle distort the ideal peak shape and may lead to spurious identifications and incorrect activity estimation. Simulations are used here to establish the role of coincidences in high-resolution alpha spectrometry using 241Am as an example. The coincidence summing between an alpha particle and an electron may then account for 20–50% of the peak area when the source-to-detector distance is 15 mm or less. A few percent of the peak area is produced by alpha–photon coincidences. These numbers strongly depend on the measurement geometry and the nuclide in question. The peak-shape distortion should be taken into account in unfolding the spectrum. Comparison with measured spectra confirms the reliability of the simulated spectra.