The differential PIXE set-up at the Van de Graaff laboratory in Florence

PIXE analysis performed with protons of different energies makes it possible to obtain information about the depth sequence of different elements within the analysed sample. In this paper we report on the differential PIXE set-up installed at the external-beam facility of the KN3000 accelerator in Florence. In order to change beam energy on the sample. our choice was to insert energy degraders between beam exit window and sample. 25 mum Upilex foils are used to degrade the beam: with 3 MeV protons, the energy loss is about 500 keV: higher energy losses are obtained by sandwiching more foils. Measurements of lateral beam profiles and of energy loss and straggling after the Upilex foils are reported, compared to those obtained with other materials such as aluminium and copper, We also investigated the possible damage to the foil due to beam irradiation. Preliminary applications of this set-up to the stratigraphic analysis of samples of archaeometrical interest are described.