Radiation damage of mylar foils by a nuclear microprobe
Mylar foils have been irradiated under typicalPIXE conditions using the Bochum nuclear microprobe. The induced radiation damage was investigated with theHEIS technique for studies of the chemical composition and theSTIM technique for studies of the extent of axial and lateral damage. The data show that the current density of the microbeam influences the extent of axial and lateral damage in the foils, while the fluence of the microbeam causes changes in chemical composition: more than one-half of the originalH andO abundances are lost, while theC abundance — after a 15% drop within the first few seconds — increases slowly with fluence. Furthermore, the thickness of the foil affects the final chemical composition of the sample only at large fluences. The results indicate that some caution is necessary in the interpretation of PIXE analyses of trace elements in biological or medical samples using nuclear microprobes.