DUAL-ENERGY TECHNIQUE FOR RAPID, HIGH-SENSITIVITY PIXE ANALYSIS OF AEROSOL SAMPLES COVERING ELEMENTS WITH ATOMIC NUMBERS DOWN TO Z=13

We have explored a dual-beam approach to external-beam PIXE analysis o f aerosol samples which allows a rapid change from one energy to the o ther. The aim was to achieve high sensitivity over a wide range of ele ments, including light elements with atomic numbers down to Z = 13. Th e quick change between a ''high'' energy of 2.6 MeV and a ''low'' ener gy of 1.3 MeV was accomplished by operating the accelerator at a fixed terminal voltage and by optionally passing the beam through an energy absorbing 57 mu m Kapton(T) foil. The detection limits thus obtained ranged from 5 ng for Al (Z = 13) to an optimum of 0.1 ng for atomic nu mbers around 30. Examples of the application of this procedure to PIXE analysis in current aerosol research projects are presented. Aging of the absorber foil is also discussed.