Ray Fluorescence analysis

- Sep 19, 2017-

When the element is determined by the Pixe method, it is usually divided into absolute determination and relative determination method. For thin targets, the formula of absolute method is

The WJ, Nj, Aj and ΣXJ are respectively the content of the J-element, the characteristic peak count, the atomic weight, the producing section of the identification X-ray, ω is the probe's stereo angle, the ΕJ is the detector's X-ray detection efficiency of the J-element, the N0 is the Alpha constant, the n0 is the number of protons in the unit area of the target, T is the transmission rate of X-rays from the target. This method is difficult to be used in practice, and the results are affected by the change of experimental conditions and the instability of parameters. The relative determination method is often used in the work, and the internal standard method is used most. It is to put the elements of the known quantity into the target as the standard, to determine the content of the element to be measured by comparing with the known internal standard. The processing of measurement data is an important part in the work of Proton x fluorescence analysis. Computer on-line analysis is used.

Pixe method is absolutely sensitive, absolute detection limit up to 10 grams (refers to the area of a few square millimeter), the relative sensitivity can reach 10~10, so the sampling quantity is small; This method has good element-resolving ability, can be analyzed at the same time, even without destroying samples, suitable for rare archaeological samples, Analysis of biological samples and environmental samples. Due to the use of computer on-line data processing, analysis speed. The overall analysis of a sample takes only a few minutes. If the proton beam is focused into a thin beam with a diameter of several microns, and the sample is measured by point by spot, the spatial resolution of the element content map can be obtained, and the detection limit can be improved to 10~10 G. However, the Pixe method for the atomic number less than 11 elements, due to the detector window absorption and other reasons, the sensitivity is very poor.