PIXE Detection Limits for some Aerosol Collection Substrates by Excitation with protons and 4He2+ Ions from a 3 MV Tandem Accelerator

Comparisons of PIXE detection limits for K, X rays using 2-5 MeV protons and 7-8 MeV 4He2+ 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 4He2+ should be two to four times lower than for protons for equal vefoeity projectiles of equal numbers. However, the background in X-ray spectra arising from gamma-quanta being Compton scattered in the Si(Li) detector can strongIy affect the detection limits. The detection limits using protons and 4HeZ+ ions from a 3 MV electrostatic tandem accelerator are determined and discussed