PIXE detection limits for some aerosol collection substrates by excitation with protons and 4He 2+ ions from a 3 MV tandem accelerator

Comparisons of PIXE detection limits for K _α X rays using 2-5 MeV protons and 7-8 MeV ⁴He ²⁺ ions as projectiles have been performed. The comparisons have been made for common aerosol backings. According to simple theoretical considerations regarding X-ray production cross sections and the production of background radiation, detection limits for ⁴He ²⁺ should be two to four times lower than for protons for equal velocity projectiles of equal numbers. However, the background in X-ray spectra arising from γ quanta being Compton scattered in the Si(Li) detector can strongly affect the detection limits. The detection limits using protons and ⁴He ²⁺ ions from a 3 MV electrostatic tandem accelerator are determined and discussed.