PROTON INDUCED X-RAY EMISSION
A PIXE (Proton Induced X-Ray Emission) set-up was calibrated by means of thin film standards, and improved by the introduction of a facility for in-situ change of external absorbers. Due to absorption in the Be window only elements with Z > 10 are measurable. For most elements uncertainties varied from 4 to 6%, increasing to about 20% for the lighter ones (Al, Si). For Cl and Na, in particular, uncertainties of 60% and 100%, respectively, were estimated due to difficulties in the production and characterization of the standards. For Z > 12 and energies above 0.5 MeV ionisation cross sections were predicted to within 30% by a semi-empirical, analytical expression from the literature. At the energies mostly used for PIXE analysis (1-2 MeV) the prediction was better than 15%. In contrast, the absorption in external Hostaphan foils was seriously underestimated on the basis of literature absorption coefficients. The detector solid angle could only be very roughly estimated geometrically, but was determined quite accurately from the present calibrations. Experimental calibration factors are listed for a number of K lines for the most commonly used external absorber (50 mum Hostaphan). For the estimate of further calibration factors only the measurement of the corresponding absorption in external absorbers is necessary.
Bibliographic Reference: IPP REPORT 9/55, 1985.
Record Number: 1989124053500 / Last updated on: 1987-01-01
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