The physics of heavy metal X-ray fluorescence in polymers: Model and measurement.

摘要

The analysis of plastics using energy dispersive x-ray fluorescence (EDXRF) differs from the traditional analysis of metal alloys in several key ways. Because polymers are mainly composed of light elements, the x-ray mass attenuation depth is higher. Polymer analysis requires a physical model with greater fidelity than Sherman's model: (1) infinite sample thickness is no longer valid and the incident and outgoing beams cannot be modeled as parallel beams, rather they exhibit substantial divergence, and (2) the overlap of the source beam and the detector acceptance angle where primary fluorescence occurs is no longer a simple plane at the surface but a more complicated volume and very sensitive to energy dispersion and beam angle geometry.; This thesis presents theoretical two-dimensional calculations that modify the existing Sherman formulations for application to polymer analysis. In addition, measurements of reference polymers are compared to the theoretical calculations.