The change of heavy metal content in water environment, soil and plant can reflect the change of heavy metal pollution in ecological environment, and it is important to monitor the trend of heavy metal pollution in eco-environment by using water environment, soil and heavy metal content in plant. However, the content of heavy metals in nature is very low, the background elements of water environment, soil and plant samples are complex, and there are many interfering factors in the EDXRF system that will affect the spectral analysis results and reduce the detection accuracy. Through the contrastive analysis of several heavy metal elements detection methods, it is concluded that the EDXRF method is superior to other chemical methods in testing accuracy and method feasibility when the heavy metal pollution in soil is tested in ecological environment.
In order to improve the performance of X ray geometric imaging, the key factors of size and image of X ray focus and
geometric clarity as well as imaging quality of real time imaging system were studied by using software simulation.
Analyze the reasons and factors that affecting the X - ray focus size and blurred image, evaluated the performance of X
ray geometric imaging through the relationship between the relationship of X-ray focus size and image geometric
definition. It provides a low cost and high efficiency solution for the selection of X-ray tube in the system design.
In order to improve the imaging quality of X-ray and reduce the effects of X-ray and scatter line on image, the adoption
of X-ray collimator is the most effective method. MCP collimator in parallel structure can effectively reduce the ratio of
X-ray and scatter line to reach on image plane, and reduce the atomization degree of images, so as to improve the image
contrast. Through the establishment first-order radiation transmittance model of MCP collimator, test the performance of
MCP collimator, it is prove that the MCP collimator can be used in the imaging system that consists of proximity of
X-ray image intensifier, first-order radiation transmittance calculation formula of MCP absorption type collimator in
parallel structure is reduced, obtain the transmittance distribution non cosine curve distribution of MCP collimator
In the proximity of X-ray imaging systems based on X-ray image intensifier, pixel matching and noise suppression are
important methods to improve image quality. This paper analyzes CCD parameters’ impact on imaging quality and the
relations with, proposes pixel matching degree is a critical factor to restrict the performance of imaging system, and
verified by experiments, the CCD refrigeration can effectively suppress the image noise, which adopts the extension of
integration time method and obtains favorable signal-to-noise ratio, it also provides a simple and low cost solution for
high quality X-ray real-time imaging of static objects.
Based on the imaging features of the original image intensifier of X-ray, the light halo caused by X-ray projective halation is analyzed, the result shows the stray X-ray energy is lower than the direct X-ray energy. The screen brightness generated by the image intensifier of X-ray stimulated by the stray X-ray energy is weaker than that generated by the direct X-ray energy. In addition the projector facula reflected from the direct X-ray is focused on the central region of X-ray image intensifier, therefore a toroidal ring similar to the solar halation is formed around the projector halation. The results of the theoretical analysis and experimental discovery show this phenomenon caused by X-ray tube on X-ray image intensifier can not be eliminated and in the system of X-ray size detection composed of them the X-ray halation will reduce the detection accuracy resulting in measurement results’ deviation dispersion under given conditions. This kind of nonlinear system error can not be canceled out by the segmented modification of coefficient compensation but it can be restrained through the adjustment of correction coefficients. After the physical testing and comparison of the physical normal size the accuracy of 0.1mm of the compensated X-ray measurement results after the adjustment of correction coefficient has been reached. The results are highly reproducible and the method of the segmented coefficient compensation has been improved.
To analyze the effect of ion barrier film in micro-channel plate on the performance of proximity focusing low-light-level
image intensifier, the noise characteristics of ion barrier film are studied. The transmission electrons’ distribution for
those have transmitted ion barrier films is determined by simulating the collision interaction between the incident
electrons and ion barrier film with Monte Carlo method. Furthermore, the relationship model of the incident electrons
and transmission electrons are established by time differential method. We simulate how the incident electron energy and
ion barrier film thickness affect the noise factor of ion barrier film. The simulation analysis results reveal that the noise
factors gradually decreased with the increase of incident electron energy (0.1 KeV - 2.0 KeV) and decreasing of film
thickness (1 to 8 nm). So the tendency of simulation results is accordant with the actual devices. The smaller noise factor
means the better image quality for low-light-level image device, and the simulation results suggest how to realize the ion
barrier film in low light level image intensifier with low noise factor. Therefore, the study of ion barrier film’s noise
characteristics provides theoretical and technical support for optimization of the
three generations low-light-level device’s performance.