The Application Of Monte Carlo Method In EDXRF Analysis

This subject is derived from :①National 863 Program Project named"Development of Seabed in-situ X-Ray Fluorescence Probe System",②China Geological Survey Program named"Research of X-Ray Fluorescence Well-logging Technology".It chiefly studies the simulation of Monto Carlo method associated with such sample characteristic X rays of Fe, Cu, Zn and other elements excited by 241Am and 238Pu source.In the design of the detecting system via X rays of X-ray fluorescence well-logging instrument and seabed X ray probe, the geometry dispose between samples exciting source and detector can derectly affect the factor of excited efficiency and the ratio of peak-back of characteristic X-ray. Well the best value of these coefficients can influent the precision and low detect limit in in-situ X ray fluerescence analysis. In fact, we chiefly rely on the peak value of spectrums to judge spectrums and this requires analysis of lots of acturally tested spectrums in the experiment. In fact, we chiefly rely on the peak value of spectrums to judge spectrums and this requires analysis of lots of acturally tested spectrums in the experiment, and finally it must be taken seriously considering about the radiation safety of people and protection problems.Considering the most difficutlt problem of the designation of X ray fluorescence detecter above, and in combination of the features of Monte Carlo Method, this paper has established an application procedure based on Monte Carlo Method and uses this method to simulate deposition energy spectrum of X-ray in Sin-PIN dectector. X-ray featured byγray samples released from non-point source is taken as the target of research to analyze the entire process of transmission of photons reacted and recorded by the detector since they are emitted from radiation source Based on the physical model of Monte Carlo, computer programming is used to generate the random number to simulate the reaction tracks of single or multi photons which re-present the statistic law of particle transmission. Self-designed Montel Carlo simulation software is used to simulate the entire process of photon transmission and display the featured X-ray enegy spectrum recorded by the detector.According to this article, Monte Carlo method can be applied to adjust the angle of the source for placement at will and that the self-compiled program can judge the peak value of any angle and whether the source-angle shown is the best or not. Main research contents and achievements are as follows:(1) This paper was base on the compound research of national and international infermation, and it chiefly discussed the basic theory of energy dispersive X ray fluorescence analysis method, as well as the basic method of Monte Carlo to simulate the transmition of photons.(2) The random sample model and photons transmit process of position, energy, angle, freedom distance and so on were proposed in this paper.(3) This paper combined with the demand of geometry design of X ray well-logging detector and source and detecter to simulate such characteristic X rays as samples of 241Am and 238Pu source stimulating Fe, Cu and Zn. The best geometry position of sample-source-detecter was achieved. And, the relation of flourescence peak area count and sample contant, medium thickness was achieved by the theory analysis of simulation results, especially the change of characteristic X ray peak area under different logging liquid thickness.(4) A Monte Carlo simulation software was developed by myself, and it has the function of simulating the spectrum as well as to simulate such characteristic X rays as samples of 241Am and 238Pu source stimulating Fe, Cu and Zn as well as the sedimentary spectrums in the Si-PIN detector;(5) The reliable and veracity of simulation was validated by the comparation between real sample measurment and simulate results.(6) In the light of actual needs of X-ray fluorescence logging the detector should be used in detecting mineral samples at the bottom of the sea. This article has taken into consideration the water and B window between the detector and samples.In this article, the comparison between characteristic X rays and actual spectrums simulated by applying Monte Carlo method is of considerable compatibility. Corresponding parameters in the adjustment procedure make a success of demonstrating the change of fluorescence counts along with the change of parameters, hence playing a very good role of theoretical guidance to the design of the detecting system of X fluorescence analysis.