The Research About The Relevant Technologies Involved In X-ray Fluorescence Analysis

X-ray fluorescence analysis is also called X-ray secondary emission spectrometry analysis,which is the method of Material composition analysis and chemical state research by using the original X-ray photons or other micro-particle to excitate atoms in the material under test, thus producing secondary characteristic X-ray. The first X-ray fluorescence analyzer was made by H.Friedmann and L.S.Birks in 1948. X-ray fluorescence analysis had been established in the field of analysis in 1960's. Modern X-ray fluorescence analyzer consists of the following components:X-ray generator(X-ray tube,high voltage power supply and stable stabilizing equipment),UV detection system(analysis of crystals,collimator and detector),counting record system(pulse radiation analyzer,meter calibration,timer,integrator and recorder).Different element has different characteristics of energy X-ray spectrum,and the fluorescence intensity of each spectrum is in a certain relationship with the concentration of elements.Thus, qualitative and quantitative analysis can be realized by measuring the energy and intensity of X-ray fluorescence spectrum of the material under test. This method has the advantages of simple lines, rapid analysis, multi-element measurement, carrying out simultaneous multi-element analysis and so on.It is one of the three widely used analytical tools in elemental analysis of atmospheric particulate matter(the others are neutron activation analysis and fluorescence analysis of proton).As an important part of the nuclear geophysical methods and application of nuclear technology, X-ray fluorescence method covers extremely broad area. In addition to the area of the geological exploration and evaluation of mineral resources with the first application and broad recognition,the method has been very widely used in the area of mineral processing, metallurgy, building materials, chemical, biomedical, oil, gas, environmental protection, industrial product inspection and testing precious metals, coatings research, cultural identification and so on. With the development of science and the improvement of X-ray fluorescence method,its applications will further increase the depth and scope.In this paper, the relevant technologies involved in X-ray fluorescence analysis has been studied in detail,including the research about the application of the energy-selected filter in the X-ray fluorescence analysis,about the impact of the X-ray tube's Voltage and current on the X fluorescence measurements,about the impact of the relative position relationship among the excitation source, sample and detector on the X fluorescence measurements. The research focuses on the application of the energy-selected filter in the X-ray fluorescence analysis. Based on the the law of X-ray absorption in the substance,we know that the same kind of material has different absorption coefficient on the different energy X-ray. The energy-selected filter was designed out of this basic principle. X-ray absorption in the material obeys the exponential law:.Thus, the transmittance of the X-ray photon passing through x thickness of material layer is . On the other hand, from the absorption curve of the material on the X-ray photon, we also know that it has the following three features:1.When the energy of the photon is greater than the K absorption limit of the element,the absorption of the same material on the low-energy photon is greater than on the higher-energy photon.2. Absorption curve makes a Sudden change in the absorption limit. The sudden change in the K absorption limit is very obvious. The ratio of its sudden change is andμ2 respectively represent the absorption coefficients of the high-energy side and the low-energy side to the absorption Limited. The ratio of the absorption sudden change of the different element gradually decreasing as the atomic number increases.3.The energy differences between adjacent elements (of the heavy elements can also be a similar element) in the K absorption limits is not obvious. Only 5% of the general, Their K absorption limit ratio of sudden change are almost equal. The variation law of the absorption coefficient curve in the energy region near the absorption limit are similar. Thus,we can design the following three commonly used X-ray filter according to need:1.Absorption coefficient filter:on the occasions of the low-energy photons, the absorption coefficient of the photon passing through substances vary widely with the photon energy.Lower photon energy, the greater absorption. So you can use a sheet of material(Its atomic number is smaller than the atomic number of the emission element filtering the X-ray). So high-energy photons can pass by easily , low energy photons not easily.We call the sheet of material as absorption coefficient filter.2.Absorption limited filter: on the both sides of the element absorption limit, in particular the K absorption limit,large absorption coefficient mutation, absorption coefficient has a great change. Therefore we can choose the filter material reasonably, the Absorption limit of which is just between the two adjacent X-ray energy, making high-energy photons pass by easily , low energy photons not easily. We call this kind of filter as absorption limit filter.3.Balance Filter: basic principle of balance filters is using the energy pass band formed by the differences between energy of the absorbing limit to measure the X-ray count rate between the energy pass band,enabling poor energy resolution detectors can also make adjacent elements X-ray clearly separated obviously.The research about the relevant technology involved in X-ray fluorescence analysis can greatly improve the precision of X fluorescence measurement.Thus, the X-ray fluorescence analysis can work better in Mineral exploration, oil and gas exploration, mineral processing, metallurgy, the detect of the hazardous substances in industrial products and other fields,and then bring about more social and economic benefits.