Self-absorption Correction Research Articles

Influence of chemical effects on the Li (i = 1–3) subshell X-ray spectra for 79Au compounds

The influence of chemical effects on intensity ratios i.e. ILi/ILα (i = l, β1, β15,2,3 and β5/2), ILα2/ILα1, ILj/ILβ1 (j = η, γ1 and γ5), ILk/ILγ4 (k = β6,4, β10,9/1 and γ2,3,6) and ILβ1/ILγ1 and chemical shift of Ll and Lγ1 X-ray emission peaks for 79Au compound has been investigated using polychromatic high resolution wavelength dispersive X-ray fluorescence (WDXRF). The measured intensity ratios of L X-ray emission spectra were corrected for spectrometers detector efficiencies and self-absorption correction factors. The experimental values of intensity ratios have been compared with the theoretical values evaluated using different set of available fractional emission rates, fluorescence and Coster-Kronig yields. The measurements also report significant energy shift (∼1–7 eV) in Ll and Lγ1 X-ray peaks of 79Au compounds relative to pure elemental form. The discrepancies in measured intensity ratios and shift in L X-ray emission spectra of 79Au compounds from the theoretical predicated values can be attributed to chemical effects due to core-valence exchange interactions and crystal effects of different ligands attached to central 79Au atom.

A method for improving the accuracy of calibration-free laser-induced breakdown spectroscopy by exploiting self-absorption

The existence of the self-absorption effect results in a nonlinear relationship between spectral intensity and elemental concentration, which dramatically affect the quantitative accuracy of laser-induced breakdown spectroscopy (LIBS), especially calibration-free LIBS (CF-LIBS). In this work, the CF-LIBS with columnar density and standard reference line (CF-LIBS with CD-SRL) was proposed to improve the quantitative accuracy of CF-LIBS analysis by exploiting self-absorption. Our method allows using self-absorbed lines to perform the calibration-free approach directly and does not require self-absorption correction algorithms. To verify this method, the experiment was conducted both on aluminium-bronze and aluminium alloy samples. Compared with classical CF-LIBS, the average errors (AEs) of CF-LIBS with CD-SRL were decreased from 3.20%, 3.22%, 3.15% and 3.01%–0.95%, 1.00%, 1.16% and 1.78%, respectively for four aluminium-bronze alloy samples. The AEs were decreased from 0.66%, 0.70%, 0.89% and 1.30%–0.43%, 0.61%, 0.77% and 0.33%, respectively for four aluminium alloy samples. The experimental results demonstrated that CF-LIBS with CD-SRL provided higher quantitative accuracy and stronger adaptability than classical CF-LIBS, which is quite helpful for the practical application of CF-LIBS.

Self-Absorption Correction in X-Ray Fluorescence- Computed Tomography With Deep Convolutional Neural Network

Data collected from the X-ray fluorescence-computed tomography (XFCT) is frequently reconstructed with algorithms proposed for X-ray transmission tomography. As these algorithms do not model the self-absorption effect inherent to XFCT, their capacity on accurately reconstructing the elemental distribution is limited. Although algorithms specialized for XFCT reconstruction have been developed, the majority of them impose strict requirements on the samples and the acquisition setup. To relax these prerequisites, a deep convolutional neural network is proposed to correct the self-absorption effect in the sinogram domain. Through quantitative evaluation, we conclude that the well-trained neural network can correct fluorescence sinograms affected by the self-absorption effect. Furthermore, we demonstrate that such corrections enable conventional algorithms to reconstruct the elemental distribution with high fidelity. As the only input required by the proposed neural network is the fluorescence sinogram, it is fully automatic and is applicable to different scan setups and samples.

A general methodology to determine natural radionuclides by well-type HPGe detectors

This work aims to determine natural radionuclides (210Pb, 228,226Ra, 234,228Th and 40K) in NORM samples by well-type HPGe detectors because they are of vital importance in studies on environmental samples. For this, a novel methodology has been developed, based on obtaining a general function for the full-energy peak efficiency (FEPE) versus the sample apparent density and composition, keeping the sample height constant. To obtain the general FEPE function, a calibration in efficiency has been accomplished using certified standards provided by IAEA (RGU-1 and RGTh-1), and KCl. Besides, different self-absorption correction functions were compared for cylindrical geometry, where chemical compositions need to be known. Then, a study on using an anti-Compton system was done, getting a lower detection limit and allowing to propose gamma spectrometry as an alternative technique to alpha-particle spectrometry. Finally, the followed methodology to calculate the FEPE was subjected to internal and external validations, checking its validity range.

Analysis of Lakhra Coal by Calibration Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) and Comparison of Self-Absorption Correction Procedures

The analysis of Lakhra Coal to determine its total carbon content and ash content is reported by calibration-free laser-induced breakdown spectroscopy (CF-LIBS). The total carbon content and ash content in coal are key parameters for efficient energy u in sepower plants. The optical emission spectrum of coal contains spectral lines of Ca, Si, Fe, Ti, Mg, Na, K, Li, Al, and C together with traces of Ba and Sr. The excitation temperature and electron number density of the laser-produced plasma were estimated using a Boltzmann plot and Stark broadened Hα line, respectively. The self-absorption correction in the emission intensities of the spectral lines were performed using the internal reference self-absorption correction (IRSAC) and the density correction. The analysis of the coal was performed by CF-LIBS, CF-LIBS with IRSAC, and CF-LIBS with density correction which were then compared with the certified composition reported by the Lakhra Coal Development Company. The results revealed that IRSAC with a fixed slope is more easily applicable and reliable than the number density correction for analyzing the total carbon content, ash content, and trace elements.

DOSIMETRY MODELING AND EXPERIMENTAL VALIDATION FOR THE PETALE PROGRAM IN THE CROCUS REACTOR

The PETALE experimental program in the CROCUS reactor intends to provide integral measurements on reactivity worth and dosimetry measurement to constrain nuclear data relative to stainless steel heavy reflectors. The experimental setup consists in eight successive plates of pure iron, pure nickel, pure chromium, or nuclear-grade stainless steel set at the close periphery of the core. The plates are interleaved with up to nine dosimeters that consist of thin activation foils with different possible materials to be sensitive to different ranges of the neutron spectrum. A precise measurement with a good estimation of the uncertainties and correlations is required, especially when comparing reaction rates, e.g. transmission measurement and/or spectral indices. The present work focuses on the validation of the dosimetry technics developed in preparation of this experimental program. Different aspects are discussed: monitors, efficiency calibration, self-absorption correction, self-shielding and nuclear data uncertainties. The different sources of uncertainties for the experiment-calculation comparisons are characterized, taking into account all the correlation between the different dosimeters. These correlations are a mandatory element for the aimed Bayesian assimilation in order to avoir overfitting when considering dosimeter providing a similar information.

Self-absorption Correction Factors: Applying A Simplified Method to Analysis of Lead-210 in Different Environment Samples by Direct Counting of Low-energy Using HPGe Detector

This study aimed to determine the self-absorption correction factors of lead-210 (210Pb) in various Syrian environment samples. Seven sediments, five soils, and four plant samples were analysed by Gamma Spectroscopy using simple and direct analysis method called Cutshall. The method is based on measuring the penetration of gamma which emitted from a standard source, prepared in the laboratory by deposition of QCYB40 Standard Solution on stainless steel disk. The source was placed on top of the studied sample and the reference air sample during the measurement. The purpose was to study the self-absorption inside each sample by calculation of its self-absorption factors without knowing its chemical composition. The self-absorption correction results for the sediment samples SE3, SE6 and SE8 ranged between 36% and 45%, and 34% to 42% for the soil samples S5 and S1, respectively. Also, for the four plant samples, it recorded variance range from 4% to 18%. This is due to the difference in the density of the G4 sample, which appeared to be very low. However, the self-absorption correction factors CF were set for the different environmental samples, and the results show that the density factor of the sample is not the only influent factor in the CF values for low energies measurement, the sample chemical composition (sample matrix) is also more effective in addition to the samples’ particle sizes.

Correction for neutron self-shielding and gamma-ray self-absorption in prompt-gamma activation analysis for large and irregularly shaped samples

Prompt-gamma activation analysis (PGAA) has been extended and validated to measure large and irregularly shaped samples. The detailed sample geometry was implemented in the MCNP-model of the setup and accurate matrix-effect corrections were obtained.

NaI cubic detector full-energy peak efficiency, including coincidence and self-absorption corrections for rectangular sources using analytical method

Low activities of radionuclides in environmental and occupational samples demand for the lower detection limits of the measuring system, which can be achieved by minimizing the source-to-detector distance. Analytical technique to calculate full-energy peak efficiency and total efficiency, self-absorption of sources and a coincidence factor of the NaI cubic scintillation detector with rectangular cavity for rectangular source have been derived. The photon path length of the volumetric sources calculated and determined source self-absorption. The photon attention by rectangular sources and detector cap materials is also calculated. In the experiments gamma aqueous source containing Eu-152 radionuclide covering range from 121 to 1408 keV was used. By comparison analytical method for calculating the full energy peak efficiency and the corrected experimental efficiency values are in good a agreement.

Determination of correction factor of self-absorption for lead-210 in environment samples using spike method

In environment radiation measurement, calculation the correction factors are critical, especially for low energy measurement because of self-absorption phenomena. In this work the main purpose is to determination the self-absorption correction factors of lead-210 (210Pb) energy (46.5keV) in various environment samples (7 sediments, 5 soil) using an experimental method called Spike Method. The samples were collecting from different places in Syrian. They were prepared according to the laboratory producers starting from collecting, cleaning, drying, grounding, hemogenic and calculating the appearance density. Low-energy gamma spectroscopy HPGe was used for radiation analysis which available at the laboratories of the Protection and Safety Department - Syrian Atomic Energy Commission – Syria. The spike method depends on adding a quantity of a standard solution with a known activity which contains lead isotope 210Pb and added to the studied samples. Self-absorption correction factors (CF) calculated by the ratio of the count rate or activity of spiked and unspiked samples. The CF for sediment samples were between 29% to 54% and for soil samples, the CFs were between 38% to 56% recording correction higher than sediment samples. The results showed a relatively high self-absorption and CFs values because of the chemical composition changeable between the spiked and unspiked samples. For that, it is better to adopt other methods less expensive, give results faster, higher accuracy and do not make change in the chemical composition. The results were also showed the density factor is the most influential factor in self-absorption phenomena.

A general function for determining mass attenuation coefficients to correct self-absorption effects in samples measured by gamma spectrometry

This work is focused on obtaining a general function for calculating the mass attenuation coefficients of samples whose compositions are known such as waste, biota or NORM (Naturally Occurring Radioactive Materials) samples. After determining the general function, it is possible to assess the self-absorption effects by the self-absorption correction factor, which is really important to consider for samples measured by gamma spectrometry. In order to obtain a general function of the mass attenuation coefficients dependent on the gamma emission energy (Eγ) and the chemical elements (Zi) with their respective concentrations (xi), it was necessary to fit the tabulated values of the mass attenuation coefficients versus gamma energy in the range of 20 keV–2000 keV for each chemical element. This is the energy range for the majority of gamma emissions of natural radionuclides. Once those fittings for each chemical element, Z, from 1 (H) to 92 (U) were done, the parameters, that resulted from those fittings, were fitted versus the atomic number, Z. This provides a general function that allows to calculate the mass attenuation coefficient by knowing the gamma emission energy and the sample composition. Finally, both the general function for calculating the mass attenuation coefficient and the self-absorption correction factor, which is used in gamma spectrometry with coaxial Ge detectors, were validated by comparisons made with the values provided by databases for several samples with widely different known densities, compositions and activity concentrations.

Investigation of the mechanism and influence of laser wavelength and energy on laser opto-ultrasonic dual detection.

Laser opto-ultrasonic dual (LOUD) detection, which uses laser irradiation of samples to generate spectral and ultrasonic signals simultaneously, can perform multimodal detection of element composition and structural property. As such, it has been applied to the detection of additive manufacturing (AM) components. Further, optimized parameters lead to better detection results. To the best of our knowledge, however, there is no study on the effect of laser properties on LOUD detection. Therefore, we studied the mechanism and influence of laser wavelength and energy on LOUD detection. In this work, the intensity, signal-to-noise ratio (SNR), and stability evolution of the laser excitation spectrum and ultrasonic signals at different wavelengths and energies were analyzed. It was found in the plasma evolution that high electron number density means a large amount of ablated mass generated, which was favorable for laser ultrasonic excitation and can produce higher SNR and a more stable signal. However, it also led to more atoms of the ground-state, which resulted in the self-absorption effect and reduced spectrum intensity in the spectrum analysis. Therefore, with self-absorption correction, better stability, and higher signal intensity, an SNR of spectral and ultrasonic signals can be obtained using 355 nm laser excitation at optimal energy. As a result, in the quantitative analysis of Cu and Si elements by LOUD detection, the determination coefficients (R2) were higher than 0.995, and the average relative errors were less than 2.5%, the limit of detection could reach the order of 100 ppm. Further, the defect size of 0.55 mm in the wire +arc additive manufacturing sample was detected by LOUD detection, and the average relative error was 5.59% compared with the digital radiography results, which indicate that laser wavelength and laser energy affect the intensity and stability of spectral and ultrasonic signals in LOUD detection, which means selecting appropriate laser parameters is important to obtain a high precision detection.

Developing a software for self-absorption correction for gamma spectrometry of soil and water samples based on MCNP5 Monte Carlo simulations

Gamma spectroscopy using HPGe is one of the most effective methods in determining the concentration of gamma emitting radionuclides in environmental samples. The purpose of this study is obtaining the efficiency calibration curves for the HPGe detector using MCNP5 Monte Carlo code, and designing appropriate software for correction of self-absorption caused by changes in density, height, and geometry of different samples. For this purpose the detector was simulated using MCNP5 Monte Carlo code, and the detector calibration curves were obtained for different geometries and heights, and appropriate software was designed for efficiency calibration. The results obtained in this study, show that changing the height, geometry, and density of the samples have significant effects on the detector efficiency because of the changes in self-absorption of the samples. Comparison of the self-absorption correction using the software, and the results of simulations show that designed software can predict the calibration curves for the new samples in different energies with error much less than 1%.

Experimental and Simulation Results of the Self-Absorption Correction Factors of Some Chemical Fertilizers in the Energy Range from 80 to 1332 keV

The purpose of this study is to calculate self-absorption correction factors of some chemical fertilizers used in Antalya in Turkey. Eight different types of chemical fertilizers with densities varying from 1.043 to 1.485 g cm–3 were investigated by Monte Carlo simulations and experimentally using the Transmission Method. Self-absorption correction factors of some chemical fertilizers were calculated experimentally using point sources which are 133Ba, 137Cs, 22Na and 60Co in the energy range from 80 to 1332 keV. The point source emissions were counted for 1000 seconds using a high purity germanium (HPGe) detector. Spectra were analyzed using computer software. Self-absorption correction factors versus energy graphics were obtained and compared with those of air and ultrapure water. The self-absorption correction factor versus energy graphics were obtained and fitted. Experimental and simulation results of the self-absorption correction factors of some chemical fertilizers were obtained and compared in the energy range from 80 to 1332 keV.

Effects of element composition in soil samples on the efficiencies of gamma energy peaks evaluated by the MCNP5 code

In this work, self-absorption correction factor related to the variation of the composition and the density of soil samples were evaluated using the p-type HPGe detector. The validated MCNP5 simulation model of this detector was used to evaluate its Full Energy Peak Efficiency (FEPE) under the variation of the composition and the density of the analysed samples. The results indicates that FEPE calculation of low gamma ray is affected by the composition and the density of soil samples. The self-absorption correction factors for different gamma-ray energies which was fitted as a function of FEPEs via density and energy and fitting parameters as polynomial function for the logarithm neper of gamma ray energy help to calculate quickly the detection efficiency of detector. Factor Analysis for the influence of the element composition in analysed samples on the FEPE indicates the FEPE distribution changes from non-metal to metal groups when the gamma ray energy increases from 92 keV to 238 keV. At energies above 238 keV, the FEPE primarily depends only on the metal elements and is significantly affected by aluminium and silicon composition in soil samples.

Correlating the fissile mass of standard uranium samples with delayed gamma rays from fission products

The Japan Atomic Energy Agency and the European Commission Joint Research Centre are collaborating to develop delayed gamma-ray spectroscopy (DGS) for nuclear materials for safeguards verification in reprocessing plants. In this paper, we describe DGS interrogation using the Pulsed Neutron Interrogation Test Assembly with standard samples of different 235U enrichments. By analyzing gamma-ray spectra, we reveal a linear correlation between the sample mass and both the total counts above 3.3 MeV and the peak counts of specific high-energy gamma-ray. We were able to observe, qualify and quantify specific gamma rays peak down to the depleted uranium (0.5 g 235U) mass sample. Based on this, we demonstrate that our technique is able to estimate the total fissile mass with a statistical uncertainty <2% when taking into account self-shielding and gamma self-absorption corrections. Using integrated counts above 3.3 MeV we were able to reduce the mass-dependent bias for the higher enrichments (∼3 to 4%) to <4%.

Electron number density conservation model combined with a self-absorption correction methodology for analysis of nanostructure plasma using laser-induced breakdown spectroscopy.

We studied laser ablation and plasma property evolution for a nickel (Ni) doped tin (Sn) oxide nanostructures target using laser-induced breakdown spectroscopy (LIBS). The transition metal Ni doped tin oxide nanostructures were synthesized by co-precipitation and hydrothermal methodologies. The size of prepared nanoparticles was verified by X-ray diffraction and transmission electron microscopy techniques. A frequency-doubled pulsed Nd:YAG laser with a wavelength of 532 nm was used to produce ablated plasma nanostructures. Ablation of doped and undoped nanostructures revealed salient-enhanced spectral emissions compared with their bulky counterparts. The emission lines of the constituent elements of doped material were used to find plasma parameters. The plasma temperature was estimated from a Boltzmann plot, and the electron number density was determined from the Saha-Boltzmann equation. The self-absorption effect has been observed in tiny plasma of nanostructures. The affected profiles of spectral lines of Ni and Sn nanoparticles due to self-absorption in LIBS spectra were corrected by the internal reference self-absorption correction (IRSAC) methodology. After correction of emitted line intensities by IRSAC, the electron number density (END) conservation approach was applied for quantitative analysis of doped nanostructures. In the END conservation approach, quantitative analysis of samples was carried out using electron number densities. Quantitative results derived from the END conservation approach at high and low concentrations exhibited good correlation when these were compared and validated with results from a conventional calibration free approach and the standard recognized energy dispersive X-ray technique.

Correction of self-absorption effect in calibration-free laser-induced breakdown spectroscopy(CF-LIBS) by considering plasma temperature and electron density

The self-absorption effect due to optical thickness characteristics greatly affects the measured spectral intensity, which in turn affects the accuracy of CF-LIBS quantitative analysis. In this paper, the emission spectra of laser induced 303 stainless steel plasma are obtained, a new self-absorption correction method that takes into account plasma temperature and electron density is proposed. In order to eliminate the influence of the self-absorption effect, the spectral line intensity is first corrected using an internal reference line that neglects the self-absorption effect, and then the line broadening is determined by calculating the electron density, and spectral line intensity is corrected for the second time. The results show that after calibration, the accuracy of Mn, Cr, Ni and Fe by CF-LIBS is improved 15.4 %, 14.2 %, 2.9 % and 0.7 % respectively, which are much superior to those without self-absorption correction. This method can improve the accuracy of CF-LIBS and facilitate the quantitative analysis of alloy samples. It can be applied to fields such as metallurgy and material composition determination.

Assessment of the Soil Self-Attenuation Correction Factor to Determine the Efficiency of a High-Purity Germanium Detector

The experimental attenuation coefficient of ten soil samples was measured for a 661.66 keV photon belonging to 137Cs. The chemical composition of the samples was determined by XRF method, and according to the results, the mass attenuation coefficient was calculated using MCNP software. For each sample, a hypothetical elementary compound based on the experimental attenuation factor was presented. HPGe efficiency was calculated using MCNP software based on the elemental composition measured by XRF and hypothetical method. The result was compared with the experimental value, which showed good agreement. In this study, self-absorption correction was determined in gamma-ray spectrometry of environmental samples.

Angular distribution of characteristic X-ray emission from Fe and V following photoionization

&lt;sec&gt; The de-excitation process of vacancy in the inner shell of the target atom caused by collision ionization produces the characteristic X-ray or Auger electrons. The precise measurement of ionization cross sections plays an important role in many basic research fields, as well as in practical fields, such as chemical analysis of Particle Induced X-ray Emission (PIXE), atomic and nuclear processes, and X-ray fluorescence (XRF) spectroscopy. As we know, when ionization cross sections are measured precisely, whether the emission of X-ray is isotropic in collision process must be considered. However, there have been few experimental results for angular dependence of &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;β&lt;/sub&gt;/&lt;i&gt;K&lt;/i&gt;&lt;sub&gt;α&lt;/sub&gt; intensity ratios in the literature until now. Therefore, this study aims to verify that the &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;α&lt;/sub&gt; and &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;β&lt;/sub&gt; X-rays originated from filling of the &lt;i&gt;K&lt;/i&gt; shell vacancies with total angular momentum quantum number 1/2 (&lt;i&gt;J&lt;/i&gt; = 1/2) are isotropic.&lt;/sec&gt;&lt;sec&gt; In this work, the typical &lt;i&gt;K&lt;/i&gt;-shell X-ray spectra for Fe and V, which induced by bremsstrahlung with central energy of 13.1 keV, have been measured at emission angles varied from 120° to 170° at intervals of 10°. The characteristic X-ray spectra obtained by the detector are fitted by Gauss function, where the absorption of incident X-rays by the detector, the absorption of emitted X-rays by the atmosphere and the self-absorption correction factor of incident and emitted X-rays by the target are all taken into account.&lt;/sec&gt;&lt;sec&gt; The experimental results of &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;β&lt;/sub&gt;/&lt;i&gt;K&lt;/i&gt;&lt;sub&gt;α&lt;/sub&gt; intensity ratio in this experiment coincide with those of theoretical calculation, as well as the Ertuğral’s experimental result. The experimental results show that the intensity ratio of &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;β&lt;/sub&gt;/&lt;i&gt;K&lt;/i&gt;&lt;sub&gt;α&lt;/sub&gt; is a constant at different detection angles. Therefore it can be concluded that the emission of &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;α&lt;/sub&gt; and &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;β&lt;/sub&gt; is isotropic in the detection range. Since the &lt;i&gt;K&lt;/i&gt; shell has no sub-shell, there is no Coster-Kronig transition in the collision ionization process. In the process of photoionization, the vacancies in the &lt;i&gt;K&lt;/i&gt; shell are produced by direct ionization. As a result, the cross section ratio of &lt;i&gt;K&lt;/i&gt; shell X-ray generation is independent of the &lt;i&gt;K&lt;/i&gt; shell photoionization cross section. In addition, the experimental results show that the &lt;i&gt;K&lt;/i&gt;&lt;sub&gt;β&lt;/sub&gt;/&lt;i&gt;K&lt;/i&gt;&lt;sub&gt;α&lt;/sub&gt; characteristic X-ray intensity ratio of target Fe is 8% higher than that of target V, which are consistent with the theoretical analysis results that the characteristic X-ray intensity ratio depends on the target atomic number &lt;i&gt;Z&lt;/i&gt;.&lt;/sec&gt;