The Research on Matrix Effect and Correction Technology of Rock Sample in In-Situ Energy Dispersive X-Ray Fluorescence Analysis.

The mineral constituents of the rock sample can be analyzed with in-situ energy dispersive X-ray fluorescence analysis technology (In-situ EDXRF), the matrix effect of rock sample will effects on measurement results. The Monte Carlo simulation method is used to conduct fluorescence analysis spectrum with ideal measurement conditions, which provides analytical data for matrix effect research. The measured spectrum of seventeen kinds rock samples are being simulated, which has the same Cu content. Therefore, the influences with matrix effect of rock sample in in-situ EDXRF take Cu element for example. Based on correlation between Cu Kα X-ray intensity and spectral parameters, considering elements similarity of all kinds rock samples, it is found that the variation the Cu Kα X-ray intensity not only by the control of rock elements composition or rock classification. The matrix effect of rock samples must be classified according correlation between Cu Kα X-ray intensity and spectral parameters. After the matrix effect classification, fifteen kinds of rock samples, which belong to the same matrix effect, can be corrected more effective. Based on principal component analysis of similar matrix effect rock samples, it is found that the scattering background, target element K-series X-ray of X-ray tube and its incoherent scatter intensity can be a good description of Cu Kα X-ray intensity which is affected by rock matrix, thus it can be used to correct the Cu element measurement results. Certainly, this technology can also provide reference for matrix effect correction to other elements in rock.

[X-Ray Fluorescence Intensity Calculation for Micro-Particles via MCNPX and WDXRF Experiment].

In order to research the effect of X-ray fluorescence (XRF) analysis on the results in the sample's micro particles, MCNPX models had been established for an X-ray fluorescence analyzer in this paper. It had studied the characteristics of the samples with different particle sizes, the fluorescence peak counts, the peak to total ratios and the peak to source ratios. A micro particle analysis experiment had been designed for its verification. The results showed that: as for the relationship between the fluorescence intensity and the particle sizes, the MCNPX calculations were consistent with the theoretical, but contrary with the experimental results; the reason is that some hypotheses about samples in the MCNPX models were contrary with the actual states; the samples were crushed by grinding to small particles and tableting process, the MCNPX calculations and experimental results can be conversion; when the particle sizes of the samples reached the certain sizes, the fluorescence peak counts, the peak to total ratios and the peak to source ratios were stable value; within a particular size range, the influence of the particle size effects cannot be ignored, otherwise this influence can be ignored. The research methods and conclusions in this paper can provide a technical reference guide for X-ray analysis in practices.

[Study on Si-PIN and CdTe Detectors Used in Energy Dispersive X-Ray Fluorescence Measurements].

Semiconductor detector is widely used in energy dispersive X-ray fluorescence measurements due to its excellent performance. In this paper, Si-PIN and CdTe semiconductor detectors were studied, performances of the two detectors were compared in material properties, detection efficiency, energy resolution and other aspects. Focused on the performance of the detectors influenced by the thickness of detector sensitive area, energy of incident X-ray, shaping time of post-stage circuit, and analyzed the differences of energy spectrum caused by escape peaks and hole trailing. Aiming at the problem of incomplete hole collection in detector, a digital multi-channel analyzer (DMCA) based on FPGA with rise-time discriminator was designed, it could reduce the influence of hole trailing effectively and improve energy resolution. The experimentation results indicate that the detection efficiency of Si-PIN and CdTe is roughly equal when energy is below 15 keV while CdTe has much higher detection efficiency than Si-PIN when energy is above 15 keV. The optimum forming time of the Si-PIN detector is about 10 µs, and the CdTe detector is about 2.6 µs, so the CdTe detector is more suitable for the high count rate condition. Si-PIN detector has better energy resolution than CdTe detector for different energy incident X-ray. CdTe detector has obvious hole tailing effect and the energy resolution of CdTe detector is significantly improved by using DMCA with rise-time discrimination.

The Study of the Rescale Method of the Spectrum Shifting in X-Ray Fluorescence Well Logging.

The X-ray fluorescence well logging technology is a significant method that can make quantitative analysis orsemi-quantitative analysis on the wellface. This method is very important to mineral exploration. The spectrum shifting is often observed in the X-rayfluorescence well logging because the temperature in the well changes acutely. The hardware is used to release the spectrum shifting and the software method is used to rescale the tiny spectrum shifting. There are too manyspectra to be rescaled in a well logging task by manually. In this paper, an auto method to rescale spectrum shifting, via the expert system model which is based on the special process to rescale spectrum shifting in manual, is presented. The symmetric zero-area conversion method, which is not sensitive to the changes of the baseline, is used to research the peaks. And then, the characteristic peaks will be identified by the standard errors, automatically. The prior knowledge (the last energy scale) and the gauss probability density function are used to analyze the peaks qualitatively and confirm the energy of characteristic peaks. Then the least square method is applied energy calibration. The singular deviation point, away from the calibrationline, will be rejected and the energy ratio will be obtained again. This method is applied for rescaling spectrum shifting in 322 spectra and obtains a satisfactory achievement.

[Influence of the Experiment Energy Dispersive X-Ray Fluorescence Measurement of Uranium by Different Excitation Source].

Aiming at the self-excitation effect on the interference of measurements which exist in the process of Energy dispersive X-ray fluorescence method for uranium measurement. To solve the problem of radioactive isotopes only used as excitation source in determination of uranium. Utilizing the micro X-ray tube to test Self-excitation effect to get a comparison of the results obtained by three different uranium ore samples--109 Cd, 241 Am and Mirco X-ray tube. The results showed that self-excitation effect produced the area measure of characteristic X-ray peak is less than 1% of active condition, also the interference of measurements can be negligible. Photoelectric effect cross-section excited by 109 Cd is higher, corresponding fluorescence yield is higher than excited by 241 Am as well due to characteristics X-ray energy of 109 Cd, 22.11 & 24.95 KeV adjacent to absorption edge energy of L(α), 21.75 KeV, based on the above, excitation efficiency by 109 Cd is higher than 241 Am; The fact that measurement error excited by 241 Am is significantly greater than by 109 Cd is mainly due to peak region overlap between L energy peaks of uranium and Scattering peak of 241 Am, 26.35 keV, These factors above caused the background of measured Spectrum higher; The error between the uranium content in ore samples which the X-ray tube as the excitation source and the chemical analysis results is within 10%. Conclusion: This paper come to the conclusion that the technical quality of uranium measurement used X-ray tube as excitation source is superior to that in radioactive source excitation mode.

[Analyzer Design of Atmospheric Particulate Matter's Concentration and Elemental Composition Based on ß and X-Ray's Analysis Techniques].

Monitoring atmospheric particulate matter requires real-time analysis, such as particulate matter's concentrations, their element types and contents. An analyzer which is based on ß and X rays analysis techniques is designed to meet those demands. Applying ß-ray attenuation law and energy dispersive X-ray fluorescence analysis principle, the paper introduces the analyzer's overall design scheme, structure, FPGA circuit hardware and software for the analyzer. And the analyzer can measure atmospheric particulate matters' concentration, elements and their contents by on-line analysis. Pure elemental particle standard samples were prepared by deposition, and those standard samples were used to set the calibration for the analyzer in this paper. The analyzer can monitor atmospheric particulate matters concentration, 30 kinds of elements and content, such as TSP, PM10 and PM2.5. Comparing the measurement results from the analyzer to Chengdu Environmental Protection Agency's monitoring results for monitoring particulate matters, a high consistency is obtained by the application in eastern suburbs of Chengdu. Meanwhile, the analyzer are highly sensitive in monitoring particulate matters which contained heavy metal elements (such as As, Hg, Cd, Cr, Pb and so on). The analyzer has lots of characteristics through technical performance testing, such as continuous measurement, low detection limit, quick analysis, easy to use and so on. In conclusion, the analyzer can meet the demands for analyzing atmospheric particulate matter's concentration, elements and their contents in urban environmental monitoring.

[Rapid Determination of Cu and Zn in PM2.5 with Wavelength Dispersive X-Ray Fluorescence Spectrometry].

This paper proposes the analyzing method of adopting wavelength dispersive X-ray fluorescence spectrometry to measure the content of Cu and Zn in PM2.5. PTFE membrane is used to prepare standard samples and atmospheric particulate samples; a research into sample cup's structure，using polypropylene film of 6.7 µm to help to improved sample cup to package atmospheric particulate samples. The improved sample cup is used to measure the content of Cu and Zn in atmospheric particulate, which can obviously reduce background, improve peak/background ratio and decrease detection limit to target element; discussion is made on the measurement condition of Cu and Zn in PM2.5: taking Kα line as analysis line of Cu and Zn, selecting PX10 as analyzer crystal, using 300 µm pitch collimator, adopting scintillation detector for the Kα of Zn, applying the integrating of flow-gas proportional counter and closed-end proportional counter to the Kα of Cu, setting 50 kV, 50 mA as operating voltage and current. The prepared Cu and Zn standard sample is used to set up working curve, the results show that their linear correlations are better, accuracy are higher, relative standard deviations of Cu and Zn are 2.43% and 2.00%(n=8), detection limit are 0.028 and 0.021 µg·cm-2respectively, and analysis of the single sample only need 60 s. To sum up, this method can quickly and accurately analyze the content of Cu and Zn in PM2.5, and provide scientific basis for study the element content characteristics and source apportionment.

[Determination of 22 Elements in Herb Tea by X-Ray Fluorescence Spectrometry].

N, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Ba and Pb in herb tea were determined by X-ray fluorescence spectrometry with pressed powder pellets. The measuring conditions of target elements were investigated, including how to select its analytical line. In addition to Ba and Pb using L line, Kalpha line was selected for the rest. When the Compton scattered radiation of Rh Kalpha was measured, The X-ray tube voltage should be appropriately reduced, and the appropriate tube current should be selected. The matrix effect was corrected by empirical coefficient method and using scattered radiation (the Rayleigh scattered radiation of Rh Lalpha, the scattered background of 0.1876 nm wavelength position and the Compton scattered radiation of Rh Kalpha) as internal standard, and the spectral overlapping interference of some elements (N, Na, Ca, Ti, Mn, Sr and Ba) was corrected. For the target elements, the detection limit of this method was low, and its accuracy and precision were high. The results showed that there were abandon of elements in herb tea, of which different kinds had different components, even the same kind of herb tea with different source had some difference in element and content more or less, however, there was a lot of similarity between the features of its components. In a word, this method could achieve multi-element determination of herb tea, and it was simple in operation, low cost, rapid, and accurate.

[The Study of Advanced Fundamental Parameter Method in EDXRFA].

The X-ray Fluorescence Analysis(XRFA) is an important and efficient method on the element anylsis and is used in geology, industry and environment protection. But XRFA has a backdraw that the determination limit and accuracy are effected by the matrix of the sample. Now the fundamental parameter is usually used to calculate the content of elements in XRFA, and it is an efficient method if the matrix and net area of characteristic X-ray peak are obtained. But this is invalide in in-stu XRFA. Also the method of net area and the "black material" of sample are the key point of the fundamental parameter method when the Energy Dispersive X-ray Fluorescence Analysis(EDXRFA) method is used in the low content sample. In this paper a advanced fundamental parameter method is discussed. The advanced fundamental parameter method includes the spectra analysis and the fundamental parameter method, which inserts the overlapping peaks separation method into the iteration process of the fundamental parameter method. The advanced method can resolve the net area and the quantitative analysis. The advanced method is used to analyse the standard sample. Compare to the content obtained from the coefficient method, the precision of Cu, Ni and Zn is better than coeffieciency method. The result shows that the advanced method could improve the precision of the EDXRFA, so the advanced method is better than the coefficient method.

[Analyse Output Specurum in Miniature Transmission X-Ray Tube of Aluminum Window and Silver Target by MC Simulation].

The miniature transmission X-ray tube is widely used in energy dispersive X-ray Fluorescence Analysis (EDXRFA). The miniature transmission X-ray tube with a small, low power consumption, X-ray emission efficiency that can be made the excitation source of handheld X-ray energy dispersive fluorescence analyzer. Beryllium (Be) is the most commonly used X-ray window material. But beryllium is expensive and toxic. At the same time set filtering window by aluminum (Al) to reducing low-energy scattering rays. This paper be adopted Al for exit window material of miniature transmission X-ray tube, achieve high-energy rays transmission and low-energy scattered radiation shielding, at the same time reduce production cost and difficulty. The present paper simulate the X-ray tube output spectrum of silver (Ag) target and aluminum window with different thickness by MCNP5. We consider the X-ray of low energy part is completely shielded when aluminum windows thickness is greater than 1.5 mm. We can conclude that 2 µm and 0.8 mm are the best combination of target thickness and aluminum windows through comparative analysis of existing research results. Then we can get flux of high energy part is big and low energy part is small when the target is 2 µm thick Ag and the window is 0.8 mm thick Al.

[Application of the racial algorithm in energy dispersive X-ray fluorescence overlapped spectrum analysis].

In the energy dispersive X-ray fluorescence spectrum analysis, scintillation detector such as NaI (Tl) detector usually has a low energy resolution at around 8%. The low energy resolution causes problems in spectral data analysis especially in the high background and low counts condition, it is very limited to strip the overlapped spectrum, and the more overlapping the peaks are, the more difficult to peel the peaks, and the qualitative and quantitative analysis can't be carried out because we can't recognize the peak address and peak area. Based on genetic algorithm and immune algorithm, we build a new racial algorithm which uses the Euclidean distance as the judgment of evolution, the maximum relative error as the iterative criterion to be put into overlapped spectrum analysis, then we use the Gaussian function to simulate different overlapping degrees of the spectrum, and the racial algorithm is used in overlapped peak separation and full spectrum simulation, the peak address deviation is in +/- 3 channels, the peak area deviation is no more than 5%, and it is proven that this method has a good effect in energy dispersive X-ray fluorescence overlapped spectrum analysis.

[Research on spectral characteristic of miniature X-ray tube and determination of beryllium window thickness].

Applying Monte Carlo method, the present paper simulates the emitted X-ray spectrum of miniature X-ray tube with thirteen thickness of beryllium window in the range from 50 to 500 microm. By analyzing the characteristic of the spectrums, the reasonable choice of thickness of beryllium window relies on the application and for the beryllium window it is not the thinner the better. Taking in-situ EDXRF as an example, though the emission X-ray intensity is higher as the thickness of the beryllium window becomes thinner, the proportion of useless low-energy X-ray (<5 keV) intensity to all energy X-ray intensity also is higher (>20%). The accuracy of in-situ EDXRF will be reduced when the high-throughput low-energy X-ray enters the detector. Therefore, this paper puts forward several parameters as judgment index for beryllium window thickness, which is described as follows: 1)The intensity ratios of the K-series X-ray to middle-energy (5-25 keV) bremsstrahlung and middle-high-energy (5-50 keV) bremsstrahlung (F1 and F3); 2)The intensity ratios of useless low-energy X-ray (<5 keV) to middle-energy (5-25 keV) X-ray and middle-high-energy (5-50 keV) X-ray (F2 and F4), it can reflect the relative intensity of useless low-energy X-ray. The simulation results demonstrate that with the increase in the beryllium window thickness, the value of F1 (F3) improves slowly, and the value of F2 (F4) decreases rapidly. In addition to the judgment index discussed above, and considering the X-ray shielded by beryllium window, the beryllium window of miniature X-ray tube can be determined. Based on simulation analysis, the thickness of around 250 microm is appropriate to miniature X-ray tube applied in the in-situ EDXRF. Comparing the emitted spectrum with 50 microm-thick beryllium window, 71.66% of low-energy X-rays are shielded, only 21.31% of X-rays with energy from 5 to 50 keV is shielded, the intensity ratio of low-energy X-ray to total energy X-ray is less than 10%, and the intensity proportion of K-series X-ray to middle-high energy X-ray maintains a high level. In other words, when the mobile X-ray source with 250 microm beryllium window is used in the in-situ EDXRF, proportion of effective signal is higher, and effect of energy resolution of the detection is least; Moreover, the relative intensity of the excitation spectral scattering background, which is obtained by detection for specimen excitation analysis, will remain at low level, thus to ensure the precision of the result of element analysis. For the beryllium window in the application of radiation therapy, the thicker the better. At this time, low-energy X-ray flux maintains a high level, and it can ensure that radiation dose is concentrated on treatment tissue.

[Theoretical calculation and simulation research on micro X-ray tube target thickness and spectra].

The present paper established a mathematical model, according to the structure of the end-window transmission micro X-ray tube anode. And we discussed the relationship between the average thickness of electron beam targeting and the high voltage. Also we obtained the spectral intensity distribution characteristics of the emitted X-ray on the angle, meanwhile by the use of Monte Carlo, the authors simulated the intensity distribution characteristics of the spectrum in the direction of 2pi. The results show that the average thickness of the micro X-ray tube anode target is about 2 microm, and we can get much better single-energy spectrum in the vertical direction of the incident electron beam within a few degrees. These conclusions have some theoretical significance for the structural design of the micro X-ray tube and the emitted spectrum monochrome applications.

[Application of in situ micro energy dispersive X-ray fluorescence analysis in mineralogy].

Thirteen rock samples were collected for studying the variation of element content in the mineral during the alteration process from Xinjiang, China. The IED-6000 in situ micro energy dispersive X-ray fluorescence developed by CDUT was applied to get chemical and physical data from minerals. The non-destructive spectrometer is based on a low-power Mo-anode X-ray tube and a Si-PIN peltier cooled X-ray detector. The unique design of the tube's probe allows very close coupling of polycapillary and makes the use of micro-area measurement feasible and efficient. The spectrometer can be integrated into any microscope for analysis. The long axis diameter of beam spot is about 110 microm. According to micro-EDXRF measurement, the tetrahedrite was corrected to pyrite, improving the efficiency and accuracy of the mineral identification. The feldspar of mineralized rock sample is rich in Cu and Zn which can be used as prospecting indicator elements. Element content of Cr, Mn and Co shows negative correlation with the degree of mineralization.

[Study on the effect of target thickness on output spectrum in transmission anode micro X-ray tube by MC method].

The transmission anode micro X-ray tube is a key component of energy dispersive X-ray Fluorescence Analysis (EDXRFA) as exciting source. So in EDXRFA we hope to get the primary X-ray spectrum which is simply distributed. In the present paper, the authors used the Monte Carlo (MC) method to study the spectrum character of the transmission anode micro X-ray tube with different thickness of target. We cut the spectrum into high energy (5keV-50keV) part and low energy (< 5 keV) part and compared them to each other. The result showed that the flux of high energy part is big and the flux of low energy part is small when the electron energy is 50 keV and the target is 4 microm thick Ag. This is better for EDXRFA.

[Research on the application of principal component analysis and improved BP neural network to the determination of Fe and Ti contents in geological samples].

Aiming at forecasting elemental contents in geological samples accurately, a principal component analysis and improved BP (PCA-BP) neural network theory is proposed in the present work. The samples from west Tianshan were measured through X-ray fluorescence measurement method, and the X-Ray fluorescence counts of each element such as Fe, Ti, V, Pb, Zn, etc. were input to the PCA-BP neural network as input variables to forecast Fe and Ti contents in uncertified geological samples quantitatively. The results show that the PCA-BP neural network can give an ideal result, and the relative error between the forecast data and chemical analysis data is less than 3%. This method provides a new and effective approach to forecasting elemental contents in geological samples.

[Research on the peak search method based on improved simulated annealing model for x-ray fluorescence spectrum].

In energy dispersive X-ray fluorescence analysis technical analysis, the spectrum information processing has been being the focus of researches, spectrum smooth, peak-search, and peak area processing are the top priority, tA peak search method is based on simulated annealing algorithm principle, and to establish a new search peak model algorithm, this algorithm uses the advantages of the global convergence properties of simulated annealing and the Metropolis criterion is used as a peak valley judgment basis. A new decision criteria on peak valley array is used in this method, too. At the same time, convergence is taken from both ends of the spectrum channel address, it ends up when convergence reaches to the same optimal solution. This paper compared the algorithm with the simple comparison method, third derivative method, and the contrast experiment results, showing that this algorithm has a strong ability on X-ray fluorescence spectrum peak-search and a certain value in the actual production.

[Research on the application of improved M-P neural network to the determination of lead and zinc ore element contents by energy disperse X-ray fluorescence analysis].

Because of different constraints (such as different kinds of measurable elements, characteristic X-ray energy, changes in matrix composition, etc.), usually it's not easy to get accurate information of elements, resulting in mistakes in later data analysis of energy disperse X-ray fluorescence measurement. The method is based on McCulloch-Pitts neural network (M-P neural network), according to matrix effect, to establish a new neural network model for quantitative forecasting of Zn by taking the data of X-ray fluorescence measurements of Cu, Fe, Pb, etc in lead-zinc mine in western Tianshan as the training sample. The relative error between predicted value and measured value is less than 5%. This method can be more accurate and rapid for X-ray fluorescence; it provides a new approach to correcting information of X-ray fluorescence.

Study of a full-digital multi-waveform nuclear pulse signal generator.

The traditional nuclear pulse signal generator outputs the nuclear pulse signal of specific waveform according to the input pulse amplitude probability distribution and counting rate, following the signal output laws of radiation detector in both pulse amplitude and time interval. However, the output waveform is generally regulated by an analog circuit, with the single waveform and difficult parameter adjustment. In this study, the digital C-R and R-C filters were explored, a cascading digital C-R or R-C filter algorithm was proposed, realizing multiple pragmatic nuclear pulse signal outputs through the serial or parallel connection of multiple digital filters. The actual test results show that the nuclear pulse signal generator constructed by this algorithm can simulate the nuclear pulse signals under different detectors and counting rates, thus expanding the scope of application and improving the flexibility of digital nuclear pulse signal generators.