Self-absorption Correction Research Articles

Gamma-Ray Self-Absorption Corrections in Stainless Steel 12Х18Н10Т for the Needs of Non-Destructive Isotopic Differentiation of Shielded Actinides

One of the main tasks of nuclear science and technology is related to the development of methods of countermeasures, circulation, non-proliferation, and safe use of shielded nuclear materials - actinides. To solve this problem, information about their isotopic and quantitative composition is necessary. One of the main methods of non-destructive differentiation of shielded actinides, which is constantly being developed, is based on the use of their characteristic or stimulated gamma rays. For its implementation, information on the self- absorption of gamma rays of a wide energy range in screens (combinations of the elements from which they are made) is required. The results of calculations of the dependence of the self-absorption values of gamma rays in stainless steel 12X18N10 on their energy (100 keV ÷ 3000 keV) at fixed values of the screen thickness (0.1 ÷ 20 mm) are presented in the article. It was established that the self-absorption of gamma rays has smaller values for the energy range of spectrometric measurements of stimulated gamma rays compared to the energy range of spectrometry of characteristic gamma rays during the differentiation of shielded actinides. The energy range of gamma rays from 1000 to 3000 keV was determined, which can be considered optimal for the spectrometry of stimulated gamma rays from shielded actinides during their differentiation.

Correction of self-absorption effect in laser-induced breakdown spectroscopy based on temperature iteration

Laser-induced breakdown spectroscopy (LIBS) is an ideal real-time on-line method for the detection of minor elements in alloy steel, but it needs to solve the undesired self-absorption effect in plasma. Since the plasma electron temperature (T), radiation particle number density and absorption path length (Nl) determine the degree of self-absorption and affect the corrected spectral line intensity, a new temperature iterative self-absorption correction method based on the plasma thermal equilibrium radiation model is proposed to continuously calculate and correct these two parameters. Compared with generally applied self-absorption correction methods, this method has obvious advantages of simple programming, high computational efficiency, and independence of the availability or accuracy of Stark broadening coefficients. The quantitative analysis results of Cu show that the linearity of calibration curves and the measurement accuracy of elemental content are significantly improved with the self-absorption correction. In addition, this method can directly obtain the accurate radiation particle number density and absorption path length, which benefits the plasma diagnostics and quantitative analysis.

A method for correcting self-absorption shown in fluorescence XAFS spectra

X-ray-absorption fine-structure (XAFS) measurement by the fluorescence-yield (FY) method can be applied to samples of various shapes and concentrations. However, it is known that XAFS spectra obtained by the FY method do not precisely reflect the original X-ray absorption of the sample due to the self-absorption effect. We therefore propose a method for correcting the self-absorption by using FY XAFS spectra of original and diluted samples. The proposed self-absorption correction method can be applied to samples with unknown compositions. The effectiveness of the correction method was evaluated by applying it to the FY XAFS spectra of several iron oxides and their mixtures. As a result, the corrected FY XAFS of Fe K-edge spectra were almost identical to the XAFS spectra obtained by the transmission method. The suppressed EXAFS oscillations of the FY XAFS spectra were also recovered. These results validate the effectiveness of the proposed correction method. They also demonstrate that the corrected XANES spectra can be applicable to linear combination fitting analysis.

Accuracy Improvement For Minor Elements Determination Using Modified Self-Absorption Correction And One-Point Calibration Laser-Induced Breakdown Spectroscopy

Accuracy Improvement For Minor Elements Determination Using Modified Self-Absorption Correction And One-Point Calibration Laser-Induced Breakdown Spectroscopy

Improvement of accuracy in radioactivity assessment of medical linear accelerator through self-absorption correction in HPGe detector

Medical linear accelerators with an energy of 8 MV or higher are radiated owing to photonuclear reactions and neutron capture reactions. It is necessary to quantitatively evaluate the concentration of radioactive isotopes when replacing or disposing them. HPGe detectors are commonly used to identify isotopes and measure radioactivity. However, because the detection efficiency is generally calibrated using a standard material with a density of 1.0 g/cm3, a self-absorption effect occurs if the density of the measured material is high. In this study, self-absorption correction factors were calculated for tungsten, lead, copper, and SUS-303, which are the main materials of medical linear accelerator head parts, for each gamma-ray energy using MCNP 6.2 code. The self-absorption effect was more pronounced as the energy of the emitted gamma rays decreased and the density of the measured materials increased. These correction factors were applied to the radioactivity measurements of the in-built and portable HPGe detectors. Furthermore, compared to the surface dose rate measured by the survey meter, the accuracy of the measurements of radioactivity improved by an average of 124.31 and 100.53 % for in-built and portable HPGe detectors, respectively. The results showed a good agreement, with an average difference of 3.70 and 5.24 %.

Quantitative analysis method of laser-induced breakdown spectroscopy based on temperature iterative correction of self-absorption effect

Laser-induced breakdown spectroscopy (LIBS) is an ideal real-time on-line method of detecting minor elements in alloys. However, in the case of laser-produced high-density plasma, the self-absorption is usually an undesired effect because it not only reduces the true line intensity, leading the line intensity to become nonlinear with the increase of emitting species content, but also affects the characterization parameters of the plasma, and finally affects the accuracy of quantitative analysis. Since the plasma electron temperature <inline-formula><tex-math id="Z-20240228161235">\begin{document}$(T)$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231541_Z-20240228161235.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="5-20231541_Z-20240228161235.png"/></alternatives></inline-formula>, radiation particle number density and absorption path length (<i>Nl</i> ) determine the degree of self-absorption and affect the corrected spectral line intensity, a new self-absorption correction method is proposed based on temperature iteration. The initial <i>T</i> is obtained by using this method through spectral line intensity, and the self-absorption coefficient SA is calculated based on the initial <i>Nl</i> parameter to correct the spectral line intensity. Then a new <i>T</i> is obtained from the new spectral line intensity and the new SA is calculated to further correct the spectral line intensity. Through continuous calculation and correction of these two parameters, self-absorption correction is finally achieved. The experimental results of alloy steel samples show that the linearity of Boltzmann plot is increased from 0.867 without self-absorption correction to 0.974 with self-absorption correction, and the linear correlation coefficient <i>R</i><sup>2</sup> of the single variable calibration curve for Mn element increases from 0.971 to 0.997. The relative error of elemental content measurement is improved from 4.32% without self-absorption correction to 1.23% with self-absorption correction. Compared with the commonly applied self-absorption correction methods, this method has obvious advantages of simpler programming, higher computation efficiency, and its independence of the availability or accuracy of Stark broadening coefficients. Moreover, this method can directly obtain the radiation particle number density and absorption path length, which is beneficial to the diagnosis and quantitative analysis of plasma.

Self-absorption correction of NEXAFS spectra for intermediate sample thicknesses applied to organo-sulfur model compounds

We present a self-absorption correction for NEXAFS which is valid for any sample thickness. The corrected spectrum is recovered in a forward calculation by fitting a model spectrum to experimental data of samples with ideally different thicknesses.

Gross Alpha Activity Measurements: Investigating the Crucial Role of Self-Absorption Correction Factors

Gross Alpha Activity Measurements: Investigating the Crucial Role of Self-Absorption Correction Factors

Self-absorption correction method based on intensity self-calibration of doublet lines.

The self-absorption effect in an optically thick plasma seriously affects the spectral line intensity and the measurement accuracy of laser-induced breakdown spectroscopy (LIBS). In this work, a self-absorption correction method based on intensity self-calibration of doublet lines belonging to the same multiplet is proposed. The K/Δλ0 parameter and self-absorption coefficient (SA) of the doublet lines of the analytical element can be calculated based on the measured actual lines intensity ratio and the K parameters ratio. Compared with the generally applied self-absorption correction methods, this method can effectively reduce the influence of laser energy and plasma plume fluctuations and the non-uniformity distribution of the element in the plasma, and is independent of the availability of Stark broadening coefficients. So it has obvious advantages of high computation efficiency, high analysis accuracy and good applicability. Univariate quantitative analysis results of aluminum (Al) show that the correlation coefficient of calibration curves and the measurement accuracy of elemental content have been significantly improved with the self-absorption correction.

Utilising Portable Laser-Induced Breakdown Spectroscopy for Quantitative Inorganic Water Testing

At present, the majority of water testing is carried out in the laboratory, and portable field methods for the quantification of elements in natural waters remain to be established. In contrast, portable instruments like portable X-ray fluorescence (pXRF) analysis and portable laser-induced breakdown spectroscopy (pLIBS) have become routine analytical methods for the quantification of elements in solids. This study aims to show that pLIBS can also be used for chemical compositional measurements of natural waters. Bottled mineral waters were selected as sample materials. A surface-enhanced liquid-to-solid conversion technique was used to improve the detection limits and circumvent the physical limitations in liquid analysis. The results show that low to medium mineralised waters can be analysed quantitatively for their ions using the documented method. For more highly concentrated samples, typically above an electrical conductivity (EC) of 1000 µS/cm, further adjustment is required in the form of self-absorption correction. However, water with a conductivity up to this limit can be analysed for the main cations (Li+, Na+, Mg2+, K+, Ca2+, and Sr2+) as well as the main anions (SO42− and Cl−) using the documented method. This study demonstrates that there is significant potential for developing field-based pLIBS as a tool for quantitative water analysis.

Estimation of self-absorption correction coefficients for gross-alpha activity measurements

Optimizing the sample volume is an important consideration while preparing planchets for measuring gross-alpha activity in environmental water samples. A higher sample volume results in increased thickness, which has a significant impact on gross-alpha activity measurements due to self-absorption in the samples. Moreover, while evaporating water samples on planchets to dryness, necessary precautions must be taken to prevent the loss of sample mass due to excessive heating. The present study represents a preliminary effort to estimate self-absorption correction coefficients and the efficiency of the detector, corrected for self-absorption, for estimating gross-alpha activity. The self-absorption correction coefficient versus sample volume is determined by performing gross alpha counting of different volumes of IAEA reference water samples. This is achieved through planchet preparations using varying quantities of water samples (ranging from 1 ml to 5 ml in steps of 1 ml, and from 10 ml to 20 ml in steps of 5 ml). The study also examines the effect of sample volume on the detector's efficiency for gross-alpha activity measurements. Additionally, the study highlights the impact of different drying methods in planchet preparations on gross-alpha activity measurements. The study reveals that the self-absorption correction coefficient decreases with increasing sample volume, indicating that larger sample volumes require more corrections for efficiency. Furthermore, it is observed that the efficiency, corrected for self-absorption, decreases with an increase in sample volume, as expected.

Extension of the Boltzmann plot method for multiplet emission lines

The Boltzmann plot method is widely used to determine the temperature of laser induced plasma. It involves the use of individual lines that are not easy to find in complex spectra and/or in the spectral range available. If the number of such lines is not enough to build a reliable Boltzmann plot, overlapping lines are often used, which are separated by software. However, line separation is a rather imprecise procedure, which, in addition, requires significant computational costs. This study proposes an extension of the Boltzmann plot method that allows a specific group of unresolved lines to be included in a Boltzmann plot without the need to separate them. This group of lines are multiplets, lines of the same element with similar upper and lower transition states. The multiplet lines along with the individual lines are included in the algorithm, which also includes a correction for self-absorption and is used to determine the plasma temperature. The algorithm is tested on synthetic spectra which are consistent with the model of a homogeneous isothermal plasma in local thermodynamic equilibrium and is shown to be superior to the standard Boltzmann plot method both in more accurate determination of the plasma temperature and in a significant reduction in the computational time. The advantages and disadvantages of the method are discussed in the context of its applications in laser induced breakdown spectroscopy.

Gamma-ray Spectrometry and X-ray Fluorescence Analysis for Natural Radioactivity Evaluation Associated with Radiation Hazard in Construction Materials

Abstract: This paper had threefold objectives: 1) to evaluate the natural radioactivity using the gamma spectrometry technique, 2) to correct the gamma self-absorption using the transmission method, and 3) to perform mineralogical analysis using the X-ray fluorescence (XRF) analyzer in seven different types of construction materials. The transmission method was used to measure the linear attenuation coefficient µ(E) of the samples as well as their standards at different energetic points. Next, the µ(E) coefficients were used to calculate the self-absorption correction factors (Cauto), and then they were introduced in a simplified formula to correct the fraction of the attenuated gamma radiation inside the traveled medium. Moreover, the quantitative assessment of natural radioactive elements (238U, 232Th, and 40K) was done in different geological matrices. The results have shown that the mean absorbed dose and the annual average dose received by these materials are 40.65 nGy.h-1and 0.2 mSv.y-1, respectively. According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the obtained values in no way pose a risk to human health. For compositional analysis, the X-ray fluorescence (XRF) analyzer was used to determine the concentrations of the major oxides (SiO2, CaO, CO2, and Al2O3) along with other oxides in all collected samples. The compositional results show that the self-absorption correction factors varied depending on the density and chemical composition of a sample. The XRF data shows that the mineralogical compositions are within their recommended limit. Thus, from a health safety perspective, the composition of the minerals does not pose any significant risks. Keywords: Gamma Spectrometry, Natural Radioactivity, Construction Materials, Radiological Hazard, Self-Absorption. PACS NaI(Tl): Sodium iodide (NaI) detector activated by thallium (Tl), XRF: X-Ray Fluorescence.

Single-Slice XRF Mapping of Light Elements in Frozen-Hydrated Allium schoenoprasum via a Self-Absorption-Corrected Hyperspectral Tomographic Reconstruction Approach.

3D and 2D-cross-sectional X-ray fluorescence analysis of biological material is a powerful tool to image the distribution of elements and to understand and quantify metal homeostasis and the distribution of anthropogenic metals and nanoparticles with minimal preparation artifacts. Using tomograms recorded on cryogenically prepared leaves of Allium schoenoprasum, the cross-sectional distribution of physiologically relevant elements like calcium, potassium, manganese, and zinc could be tomographically reconstructed by peak fitting followed by a conventional maximum-likelihood algorithm with self-absorption correction to reveal the quantitative cross-sectional element distribution. If light elements such as S and P are located deep in the sample compared to the escape depth of their characteristic X-ray fluorescence lines, the quantitative reconstruction becomes inaccurate. As a consequence, noise is amplified to a magnitude where it might be misinterpreted as actual concentration. We show that a tomographic MCA hyperspectral reconstruction in combination with a self-absorption correction allows for fitting of the XRF spectra directly in real space, which significantly improves the qualitative and quantitative analysis of the light elements compared to the conventional method as noise and artifacts in the tomographic reconstruction are reduced. This reconstruction approach can substantially improve the quantitative analysis of trace elements as it allows the fitting of summed voxel spectra in anatomical regions of interest. The presented method can be applied to XRF 2D single-slice tomography data and 3D tomograms and is particularly relevant for, but not limited to, biological material in order to help retrieve self-absorption corrected quantitative reconstructions of the spatial distribution of light elements and ultra-trace-elements.

Self-absorption correction on 2D X-ray fluorescence maps

X-ray fluorescence mapping (XRF) is a highly efficient and non-invasive technique for quantifying material composition with micro and nanoscale spatial resolutions. Quantitative XRF analysis, however, confronts challenges from the long-lasting problem called self-absorption. Moreover, correcting two-dimensional XRF mapping datasets is particularly difficult because it is an ill-posed inverse problem. Here we report a semi-empirical method that can effectively correct 2D XRF mapping data. The correction error is generally less than 10% from a comprehensive evaluation of the accuracy in various configurations. The proposed method was applied to quantify the composition distribution around the grain boundaries in an electrochemically corroded stainless steel sample. Highly localized Cr enrichment was found around the crack sites, which was invisible before the absorption correction.

Study of the matrix composition effect on gamma spectrometry analysis using Monte Carlo simulation: application for soil to crop transfer factor determination

Abstract Self-absorption effect has a significant impact on gamma spectrometry measurement for the highly precise determination of the radionuclides activity. Among the main factors affecting the self-absorption effect especially at low gamma energies is the matrix composition of the sample. For this purpose, we studied the matrix composition effect on the self-absorption correction for plant and soil matrices using a Monte Carlo simulation model, composed of High Purity Germanium (HPGe) detector and a cylindrical geometry source. The simulated configuration model was validated by comparison of simulated full energy peak efficiency (FEPE) values with the experimental ones using a standard radioactive solution, covering large interval gamma energies in the range of 59.54–1836.12 keV. The results show that the FEPE values of low gamma energies are affected by the matrix composition, where in the soil matrix the FEPEs decreased by 36% and only by 1% in the plant matrix. The Monte Carlo results were applied in order to accurately calculate the transfer factor of the environmental radionuclides 226Ra, 232Th and 40K from soils to several crops, mustard, artichoke and fennel through their specific activities.

Determination of Self-absorption Correction Factors of Some Algae Samples: An Experimental study

The purpose of this study to examine experimentally self-absorption correction factors (SACFs) of some algae samples using gamma-ray spectrometry. Various algae samples were collected from Boğaçay in Antalya, Turkey. Collected algae samples were dried, and masses of the samples were calculated. Then densities of the samples were calculated. Each of algaes was counted with and without point sources which are 22Na, 60Co, 133Ba, and 137Cs about 1000 seconds using high purity germanium detector. The SACFs of algae samples were calculated between 80 keV and 1332 keV gamma-ray energies. As a result, SACFs of studied algae samples generally reduce as gamma-ray energy enhances. SACFs of some algae samples are nearly steady because of the densities and elemental contents of the studied algaes.

Study of the effect of photon self-absorption on the detection efficiency of HPGe detector in measurements of an activated uranium sample

The photon self-absorption effect of uranium on the full-energy peak (FEP) efficiency calibration of high purity germanium (HPGe) detector was studied as a function of energy using an activated uranium sample has a thickness of 1 mm. The absolute efficiencies of the detector were obtained with the use of gamma standard sources and gamma rays of radionuclides created by irradiating the uranium sample with secondary neutrons. The measurements were carried out with the use of a Planar HPGe detector. MCNP simulation code was used to verify the experimental results. The comparison of the empirical results with the simulation results showed a good agreement. To interpret the efficiencies, the reaction rates were calculated using two methods: (1) - the use of the efficiency curve from the standard sources combined with the self-absorption correction of the uranium material and (2) - the use of the efficiency curve obtained from gamma rays in the sample.

Investigation of a method for the correction of self-absorption by Planck function in laser induced breakdown spectroscopy

Self-absorption correction of LIBS spectra using the Planck function or equivalently the plasma temperature.

Self-absorption correction method for one-point calibration laser-induced breakdown spectroscopy.

As an important variant of calibration-free laser-induced breakdown spectroscopy (CF-LIBS), one-point calibration LIBS (OPC-LIBS) corrects the Boltzmann plot of the unknown sample by using one known sample and obtains higher quantitative accuracy than CF-LIBS. However, the self-absorption effect restricts its accuracy. In this work, a new self-absorption correction (SAC) method for OPC-LIBS is proposed to solve this problem. This method uses an algorithm to correct the self-absorption and does not require the calculation of the self-absorption coefficient. To verify the effectiveness of this SAC method, Ti, V, and Al elements in two titanium alloys were determined by classical OPC-LIBS and OPC-LIBS with SAC. The average relative errors (AREs) of all elements in the two samples were decreased from 8.78% and 9.28% to 8.07% and 7.56%, respectively. The results demonstrated the effectiveness of this SAC method for OPC-LIBS.