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In this paper, three Monte Carlo codes were tested for electron transport in various materials. MCNPX (version 2.4.0), Penelope (version 2003) and EGSnrc codes were used for modeling simple problems. These problems were focused on bremsstrahlung, energy deposition in matter, electron ranges and production of secondary electrons by gamma radiation. The electrons were primary particles, except in the last exercise, where photons were used. Various materials, e.g., water, lead and tungsten were used. The energy of the primary particles was within the energy range from 20 to 450 keV. The simulation results were compared with each other., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Abstract The aim of this paper is to introduce an easily feasible procedure for data evaluation in X-ray fluorescence analysis that enables to identify stratified structure of an investigated object and to determine the approximate amount of an element and its mean depth under the surface. This technique is based on a Kα/Kβ diagram describing the relation of Kα/Kβ ratio versus Kα count rate for various depth distributions of a certain element. Such calibration was performed for NITON XL3t GOLDD Plus analyzer as a typical example of nowadays very popular handheld analyzers that enable in-situ measurements and have many users worldwide. Kα/Kβ diagrams for iron, copper, nickel and titanium were drawn by means of combination of measurements and Monte Carlo simulations and then applied to the determination of approximate structures of several objects. The advantages and also some disadvantages of this technique in connection with the handheld analyzers are summarized in this article. Highlights • MCNP model for NITON XL3t GOLDD Plus analyzer was prepared and validated. • The principle and creation of Kα/Kβ diagrams for individual elements were introduced. • The approximate structures of investigated objects were determined with Kα/Kβ diagrams. [ABSTRACT FROM AUTHOR]

This article describes the method for the estimation of depth distribution of radionuclides in a material with gamma-ray spectrometry, and the identification of a layered structure of a material with X-ray fluorescence analysis. This method is based on the measurement of a ratio of two gamma or X-ray lines of a radionuclide or a chemical element, respectively. Its principle consists in different attenuation coefficient for these two lines in a measured material. The main aim of this investigation was to show how the detected ratio of these two lines depends on depth distribution of an analyte and mainly how this ratio depends on density and chemical composition of measured materials. Several different calculation arrangements were made and a lot of Monte Carlo simulation with the code MCNP – Monte Carlo N-Particle ( Briesmeister, 2000 ) was performed to answer these questions. For X-ray spectrometry, the calculated Kα/Kβ diagrams were found to be almost independent upon matrix density and composition. Thanks to this phenomenon it would be possible to draw only one Kα/Kβ diagram for an element whose depth distribution is examined. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes surface effects in microscopic X-ray fluorescence analysis, including the Monte Carlo simulations of the production and the detection of characteristic radiation. A new data analysis technique is also introduced. It enables us to make improved calculations of element concentrations and to determine the shape of the surface in an analyzed spot. Finally, reliefs of two scanned objects are presented. Good results were achieved, especially for a metallic object containing chemical elements only measurable with X-ray fluorescence analysis. [Copyright &y& Elsevier]

Abstract: This paper deals with difficulties in making a quantitative evaluation with the use of in-situ X-ray fluorescence analysis. Incorrect sample positioning and some properties of the surface of the sample have a negative effect on quantitative analyses. Monte Carlo simulations with the MCNPX code were used for classifying the disturbing effects that must be taken into account in-situ X-ray fluorescence analysis. The relation between the count rate and variations in the geometrical arrangement has been studied. The Monte Carlo calculations provide an interpretation of effects that had been ascertained experimentally and also imply the range of uncertainties in the count rates. The results enable us to find an optimal set-up for a given in-situ measurement. [Copyright &y& Elsevier]

Abstract: This paper shows how the Monte Carlo N-Particle eXtended (MCNPX) computer code can easily be applied to calculate the Kα/Kβ ratios of elements distributed heterogeneously in an analyzed specimen. Experiments were performed on specimens made of thick substrates covered by one or two mono-elemental layers (Ti, Ni, and Cu) of intermediate thickness. The Kα/Kβ ratios of the elements present in a substrate and in the layers were measured and then compared with the ratios obtained with the MCNPX computer code and with simple analytical calculations. Good correspondence was achieved between the experimental and calculated values. It was demonstrated that the MCNPX code makes it possible to predict the Kα/Kβ ratios for a specimen composed of layers and a substrate. This code can be applied for recognizing sample homogeneity or the depth heterogeneity of a specimen. In addition, the depth distribution of elements can be estimated and then the coating thicknesses in layered samples can also be determined. [Copyright &y& Elsevier]

Abstract: Monte Carlo simulations enable us to improve the applicability of analytical techniques based on emission of characteristic radiation. In particular, the MCNP4C2 code was tested for interpretation of measured data obtained with the use of energy dispersive X-ray fluorescence analysis. This paper describes MCNP outputs and compares them with the results of analytical calculations or experiments. Then the application of Monte Carlo simulations to the prediction of measurement results is shown, and the MCNP results are verified. [Copyright &y& Elsevier]

Abstract: Two methods enabling depth heterogeneity to be recognized and taken into account in quantitative analysis have been elaborated and then applied to various samples. The first method involves predicting the Kα/Kβ (or L lines) ratios for all identified elements. The second method is based on comparing the spectra measured on different geometric arrangements. In particular, sample tilting makes identification of depth heterogeneities possible. If the sample is heterogeneous, the heights of some peaks in the X-ray spectra change according to the depth distribution of the corresponding elements. Monte Carlo simulations with the MCNP4C2 code can be used to predict these changes and interpret the experimental results. [Copyright &y& Elsevier]

X-ray tubes belong among the most important sources of ionizing radiation and are used in various applications and methods, i.e. investigation of materials, diagnostics in medicine, irradiation, etc. For such applications, the exact properties of X-ray sources or their X-ray beams need to be known, as well as when Monte Carlo simulations of experimental setups are considered with the aim of optimization or calibration of X-ray systems. These properties include X-ray spectra, beam profiles, divergence and homogeneity of beams. Properties of low power X-ray tubes with the maximum voltage up to 50 kV were investigated in this study. These devices included a small laboratory X-ray tube with collimated X-ray beam and a microfocus X-ray tube with polycapillary focusing optics. Beam shape features were reconstructed using a silicon pixel detector. The pixel detector was inserted into X-ray beams at different distances from X-ray sources. Beam 2D profiles were obtained and since the pixel detector worked in a single event detection mode, approximate energy of individual photons could be measured as well as their position. In this way, detailed information about the beam properties was obtained. • X-ray beam parameters are mapped by a pixel detector. • The beam shape and energy distribution of the emitted photons are assessed. • The size of the irradiated point and the quality of the collimators are determined. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations with the MCNP code were applied to evaluation of X-ray fluorescence (XRF) data obtained with two laboratory XRF devices. The aim of this investigation was to test an iterative Monte Carlo procedure used for quantitative analysis of copper alloys which were analyzed alone or they were overlapped with a covering layer. The iterative procedure consists of the performance of several Monte Carlo calculations with varying properties of a simulated object to obtain the best agreement of measured and calculated X-ray count rates of identified elements. The attention was paid to high efficiency of the Monte Carlo simulation to achieve shorter time for computing than for XRF measurements. The robustness of the quantitative MC procedure was tested for situations when the experimental conditions are not known exactly. • Quantitative XRF analysis with the data evaluation based on iterative Monte Carlo procedure with the MCNP code was introduced. • Composition of copper alloys was successfully determined for all major elements. • Computing time can be less than couple of minutes depending on desired uncertainty. • Robustness of the quantitative MC procedure in relation to inaccurately known experimental conditions was demonstrated. [ABSTRACT FROM AUTHOR]