Wrong Selection Of X-ray Fluorescence Analysis

- Sep 19, 2017-

With the development of technology, more and more kinds of X-ray fluorescence Analyzer, the name of the commodity is also confusing, coupled with the user's knowledge of the relevant limited, making the user reasonable choice of the instrument greatly increased difficulty.

Emphasis on "fluorescence", many users mistakenly think that only the use of X-ray tube as excitation source of the tube excitation instrument is the X-ray fluorescence, blindly emphasize the so-called "fluorescence." In fact, as previously mentioned, both X-ray tubes and radioisotope sources are used as excitation sources, and as long as the X-rays are stimulated and the fluorescent x-rays emitted by the measured samples are used to obtain the chemical composition and content of the apparatus, they are X-ray fluorescence analyzers.

X-ray Fluorescence Analyzer

source excitation and tube excitation have advantages and disadvantages. The structure of the source excitation type is simple and compact, especially the X-ray emitted by radioisotope sources is a natural phenomenon and its strength is very stable. Although there is a natural attenuation, but this attenuation is to follow the description of the physical law, that is, we can accurately calculate, and as a commercial instrument selected isotope source half-life is relatively long, in a short period of time this attenuation is almost not reflected. The biggest weakness of a radioactive source is that it emits less intensity of X-rays and is not adjustable in energy distribution. Therefore, the types of elements are restricted, the geometrical arrangement of optical path must be very compact, the analysis time is relatively long, the spectral line processing and quantitative analysis is difficult.

The excitation source of tube-excited instrument is X-ray tube. Compared with radioisotope sources, the greatest advantage lies in its adjustable properties. By regulating the pipe flow and high pressure, the intensity and distribution of the output x-rays can be changed in a certain range, and then the excitation efficiency and the analysis ability of certain elements are selectively increased or reduced. Furthermore, the output intensity of X-ray tube is much higher than that of radioisotope source, and the geometrical arrangement of optical path is limited, which can be used to improve the performance of collimator, filter and slit. The biggest problem of using X-ray tube is stability, which provides high voltage power supply stability of X-ray tube must be under three out of 10,000, the X-ray tube itself needs to be cooled, and the environment temperature, power grid fluctuation and other factors will affect the stability of X-ray tube output X-rays. Therefore, in general, the requirements of the tube-stimulating apparatus for the use of environment and peripheral conditions are much higher than the source-excited instruments.