TRACE ELEMENT ANALYSIS IN AN OPTIMIZED SET-UP FOR TOTAL REFLECTION PIXE (TPIXE)

A newly constructed chamber for measuring with MeV proton beams at small incidence angles (0 to 35 mrad) is used to analyse trace elements on flat surfaces such as Si wafers, quartz substrates and perspex. This set-up is constructed in such a way that the X-ray detector can reach very large solid angles, larger than 1 sr. Using these large solid angles in combination with the reduction of bremsstrahlungs background, lower limits of detection (LOD) using TPIXE can be obtained as compared with PIXE in the conventional geometry. Standard solutions are used to determine the LODs obtainable with TPIXE in the optimized setup. These solutions contain traces of As and Sr with concentrations down to 20 ppb in an insulin solution. The limits of detection found are compared with earlier ones obtained with TPIXE in a non optimized setup and with TXRF results.