Prompt Gamma-ray Activation Analysis Research Articles

Prompt gamma ray activation analysis for determining chemical composition of 3D printing and casting materials used in biomedical applications.

Three-dimensional printing and casting materials were analyzed by prompt gamma-ray activation analysis (PGAA) to determine their suitability as human tissue surrogates for the fabrication of phantoms for medical imaging and radiation dosimetry applications. Measured elemental compositions and densities of five surrogate materials simulating soft tissue and bone were used to determine radiological properties (x-ray mass attenuation coefficient and electron stopping power). When compared with radiological properties of International Commission on Radiation Units and Measurements (ICRU) materials, it was determined that urethane rubber and PLA plastic yielded the best match for soft tissue, while silicone rubber and urethane resin best simulated the properties of bone.

Structural Properties of Kerogens with Different Maturities.

The thermogenic transformation of kerogen into hydrocarbons accompanies the development of a pore network within the kerogen that serves as gas storage locations both in pore space and surface area for adsorbed gas within the source rock. Therefore, the successful recovery of gas from these rocks depends on the accessible surface area, surface properties, and interconnectivity of the pore system. These parameters can be difficult to determine because of the nanoscale of the structures within the rock. This study seeks to investigate the pore structure, surface heterogeneity, and composition of recovered kerogens isolated from source rocks with progressively increasing thermogenic maturities. Prompt gamma-ray activation analysis (PGAA), nitrogen and methane volumetric gas sorption, and small-angle neutron scattering (SANS) are combined to explore the relationship between the chemical composition, pore structure, surface roughness, surface heterogeneity, and maturity. PGAA results indicate that higher mature kerogens have lower hydrogen/carbon ratio. Nitrogen gas adsorption indicates that the pore volume and accessible specific surface area are higher for more mature kerogens. The methane isosteric heat at different methane uptake in the kerogens is determined by methane isotherms and shows that approximately two types of binding sites are present in low mature kerogens while the binding sites are relatively homogeneous in the most mature kerogen. The hysteresis effect of the structure during the adsorption and desorption process at different CD4 gas pressures are studied. An extended generalized Porod's scattering law method (GPSLM) is further developed here to analyze kerogens with fractal surfaces. This extended GPSLM quantifies the surface heterogeneity of the kerogens with a fractal surface and shows that kerogen with high maturity is chemically more homogeneous, consistent with the results from methane isosteric heat. SANS analysis also suggests a pronounced surface roughness in the more mature kerogens. A microporous region circling around the nanopores, which contributes to high surface roughness and methane storage, is shown to develop with maturity.

Comparison of PGAA and wet chemical analysis for determining major element contents in eucritic meteorites

Prompt gamma-ray activation analysis (PGAA) was applied to well homogenized meteorite samples initially prepared for the wet chemical analysis. By comparing the PGAA data with wet chemical analysis data in literatures, it was confirmed that PGAA can be alternative or even advantageous to wet chemical analysis in terms of the data reliability. Because the same sample can be analyzed by INAA followed by PGAA, data obtained by a combination of PGAA and INAA were proved to enable us to discuss the detailed chemical characteristics of meteorite samples represented by eucritic meteorites (eucrites).

Measurement of the 13C(n,gamma) thermal cross section via neutron irradiation and AMS

.Ampoules of amorphous 99.5% enriched 13C were irradiated at the PF1b neutron beam line at the high-flux ILL research reactor in order to produce 14C atoms. The precise ratio of 14C/13C was subsequently measured at the VERA Accelerator Mass Spectrometer, allowing the 13C(n, gamma)14C thermal cross section to be accurately determined. This is the first measurement of this cross section at sub-eV energies via this technique and the result of 1.52 pm 0.07 mb for the thermal cross section is in good agreement with other recent measurements which were performed via Prompt Gamma-ray Activation Analysis.

Trace anodic migration of iridium and titanium ions and subsequent cathodic selectivity degradation in acid electrolysis systems

The oxygen evolution reaction in acidic electrolyzers requires the presence of stable catalysts and current collectors at the anode. IrO2 catalysts and Ti current collectors are among the best in this regard. We show evidence of iridium and titanium corrosion and subsequent membrane crossover in long-term experiments of proton-exchange membrane electrolyzers for H2O2 production. The accumulation of trace iridium at the cathode was linked to degraded performance and increased cathodic current from hydrogen evolution. Detection of trace metal content at the cathode electrodes was enabled by prompt-gamma ray activation analysis and neutron activation analysis. These findings are not just relevant for H2O2 electrolyzers but to any system using iridium-based anode catalysts, including CO2 electroreduction.

Optimization and characterization of the PGAI-NT instrument’s Neutron Tomography set-up at MLZ

The Prompt Gamma-ray Activation Imaging and Neutron Tomography (PGAI-NT) instrument at the PGAA facility of the Heinz Maier-Leibnitz Center (MLZ), provides a method to obtain and effectively visualize position-sensitive element abundances in samples by combining a three-dimensional extension of Prompt Gamma-ray Activation Analysis (PGAA) and Neutron Tomography (NT). Inspired by a proof-of-principle study, a cone-beam tomography set-up was designed, tested and installed. This article reports on the design of the new cone-beam tomography set-up and its optimization using neutron beam simulations and physical measurements. A new position-sensitive neutron detector with improved performance and instrument environment integration was designed, built and tested. The overall NT performance of the set-up is investigated in the course of a Quality Assessment for neutron tomography sites. Its stand-alone NT and all-in-one PGAI-NT suitability is determined.

Improving accuracy, precision, detection limits, and sample throughput in prompt gamma-ray activation analysis using cold and thermal neutrons and element ratios

A combination of thermal neutron (TN) and cold neutron (CN) prompt gamma-ray activation analysis (PGAA) has been used to lower analytical bias, to improve precision and detection limits, and to reduce sample throughput time. CNPGAA was used to measure element ratios relative to a comparator element, while TNPGAA was used to measure the comparator element. Low-Z elements with normally poor sensitivity (C, N, and S) were measured with expanded uncertainties of < 2% in coal and fuel oil using H as comparator element. Using the combined method, measurements can be made with good counting statistics in a fraction of the time needed for TNPGAA alone, with a 20–30-fold improvement in detection limits.

Archaeometry at the PGAA facility of MLZ – Prompt gamma-ray neutron activation analysis and neutron tomography

Instrumental neutron techniques such as Prompt Gamma-ray Activation Analysis and Neutron Tomography and their combination, are effective methods to obtain chemical compositions with good detection limits and visualize internal structures within a sample. As non-destructive analysis methods, they are especially suitable for the investigation of cultural heritage objects and are therefore attractive for the field of archaeometry. This article reports on the investigation of two ring-like Celtic burial gifts from the Bavarian region using these methods. In contrast to our initial presumption, the two rings were not made in the same way. Our results clearly show completely different compositions and internal structures.

Formation of Fe and Ni substituted LiMn2–XMXO4nanopowders and their crystal and electronic structure and magnetic properties

AbstractThe Pechini sol-gel method was applied to obtain LiMn2–xTxO4(T = Ni, Fe; x = 0.1 to 0.5) nanopowders. Crystal and electronic structures, chemical composition and magnetic properties of the materials were characterized by X-ray diffraction, XPS, SEM/EDX microscopy, prompt gamma-ray activation analysis (PGAA), Mössbauer spectroscopy and magnetic susceptibility, respectively. XRD measurements showed that the LiMn2–xNixO4were single phase for x = 0.1 and 0.2. Three samples with higher Ni content contained some addition of a second phase. Analysis of the oxidation state of the dopants by XPS revealed ionic Ni2+and Fe3+. Mössbauer spectroscopy also confirmed 3+ oxidation state of iron and its location in octahedral sites, which excluded the inverse spinel configuration. XPS examinations showed that Mn3+ions dominated in the iron substituted series whereas the Mn4+was dominant in the nickel series.

Assessment of PGAA capability for low-level measurements of H in Ti alloys.

The accuracy of low-level hydrogen measurements with prompt gamma-ray activation analysis (PGAA) depends on identifying and accounting for all background H signals, including interfering signals. At the cold-neutron (CN)PGAA facility at the NIST Center for Neutron Research, the sources of background H signals were investigated in the context of titanium-based matrices containing low-levels of H (<300 mg H per kg Ti) with the measurements of prepared standards (mixtures of polyvinyl chloride and titanium oxide) and Ti alloy (Ti6Al4V) samples. The sensitivity ratio, defined as the ratio of the H signal to the Ti signal per unit mass ratio of H in Ti, was determined (1) with the measurements of prepared standards and (2) based on partial gamma-ray production cross sections and full-energy detection efficiencies. The resulting calibrations from these two approaches agreed within experimental uncertainty. A series of Ti alloy NIST Standard Reference Materials (SRMs) previously certified for the H content (SRMs 2452, 2453, 2453a, 2454) were used as test cases, with the mass fractions determined based on the sensitivity ratios derived from method 1 and method 2, respectively. The results agreed with the certified values within experimental uncertainties, validating the analysis performed on the new instrument with newly-prepared standards at low H mass fractions (method 1), and with the standard-independent analysis (method 2). Various sample mounting improvements were made to lower the background H signal. Spectral interferences near the H peak were identified as potential sources of bias and as a limiting factor in the detection limit of H in Ti alloy samples.

Prompt Gamma-ray Activation Analysis for Certification of Sulfur in Fuel Oil SRMs.

A combination of cold neutron prompt gamma-ray activation analysis (CNPGAA) and thermal neutron (TN) PGAA was used to determine sulfur in fuel oils to develop a method to provide values for certification. CNPGAA was used to measure S/H mass ratios, and TNPGAA to measure hydrogen mass fractions. Measurements were combined to determine sulfur mass fractions (with expanded uncertainties) of 2.159 % ± 0.072 % for SRM 1622e, 0.7066 % ± 0.0120 % for SRM 1619b, and 0.1266 % ± 0.0030 % for SRM 1617b, in agreement with certified values. The results validate the method as suitable for certification of sulfur at mass fractions ≥ 0.1 %.

Improved Ammonolytic Synthesis, Structure Determination, Electronic Structure, and Magnetic Properties of the Solid Solution Sn(x)Fe(4-x)N (0 ≤ x ≤ 0.9).

We report a synthetic and theoretical study of the solid solution Sn(x)Fe(4-x)N (0 ≤ x ≤ 0.9). A previously published ammonolytic synthesis was successfully modified to achieve the metastable nitrides in phase-pure quality out of many competing phases. As TG-DSC measurements show, the thermal stability of the nitrides increases with increasing tin content. The Sn(x)Fe(4-x)N series of compounds adopts an antiperovskite-like structure in space group Pm3̅m. Various experimental and theoretical methods provide evidence that the iron substitution by tin exclusively takes place at Wyckoff position 1a and leads to a Vegard-type behavior of the lattice parameter over the compositional range, with an expection for a small internal miscibility gap around Sn(0.33)Fe(3.67)N of unknown cause. For highly tin-substituted iron nitrides the composition was clarified by prompt gamma-ray activation analysis (PGAA) and determined as Sn(0.78(3))Fe(3.22(4))N(0.95(3)) evidencing a fully occupied nitrogen position. Magnetic measurements reveal a linear weakening of ferromagnetic interactions with increasing tin concentration.

Determination of Trace Concentration in TMD Detectors using PGAA

Transmutation detectors could be alternative to the traditional activation detector method for neutron fluence dosimetry at power nuclear reactors. This new method require an isotopically highly-sensitive, non-destructive in sense of compactness as well as isotopic content, precise and standardly used analytical method for trace concentration determination. The capability of Prompt Gamma-ray Activation Analysis (PGAA) for determination of trace concentrations of transmuted stable nuclides in the metallic foils of Ni, Au, Cu and Nb, which were irradiated for 21 days in the reactor core at the LVR-15 research reactor in Řež, is reported. The PGAA measurements of these activation foils were performed at the PGAA facility at Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRMII) in Garching.

Development and Test of a Neutron Imaging Setup at the PGAA Instrument at FRM II

We report on the developments of a neutron tomography setup at the instrument for prompt gamma-ray activation analysis (PGAA) at the Maier-Leibnitz Zentrum(MLZ). The recent developments are driven by the idea of combining the spatial information obtained with neutron tomography with the elemental information determined with PGAA, i.e. to further combine both techniques to an investigative technique called prompt gamma activation imaging (PGAI).At the PGAA instrument, a cold neutron flux of up to 6 x 1010 cm-2 s-1 (thermal equivalent) is available in the focus of an elliptically tapered neutron guide. In the reported experiments, the divergence of the neutron beam was investigated, the resolution of the installed detector system tested, and a proof-of-principle tomography experiment performed.In our study a formerly used camera box was upgraded with a better camera and an optical resolution of 8 line pairs/mm was achieved. The divergence of the neutron beam was measured by a systematic scan along the beam axis. Based on the acquired data, a neutron imaging setup with a L/D ratio of 200 was installed. The resolution of the setup was testedin combination with a gadolinium test target and different scintillator screens. The test target was irradiated at two positions to determine the maximum resolution and the resolution at the actual sample position. The performance of the installed tomography setup was demonstrated bya tomography experiment of an electric amplifier tube.

Determination of trace concentrations of transmuted stable nuclides in TMD detectors using PGAA

The capability of prompt gamma-ray activation analysis (PGAA) for neutron fluence dosimetry by means of transmutation detectors is reported. The metallic foils of Ni, Au, Cu and Nb and the small piece of Ge crystal, which were irradiated at the LVR-15 reactor at Řež for several days, were selected for analysis by PGAA technique. Concentrations of transmuted stable nuclides in these foils were measured using the PGAA facility installed at the research reactor FRM II in Garching.

Monte Carlo simulation of PGNAA system for determining element content in the rock sample

The element content in rock sample can be determined by prompt gamma ray activation analysis technology. The neutron distributions under the conditions with different moderating materials, moderator size and distance from neutron source to lead-out hole were simulated using Monte Carlo method, and then the optimal structure parameters to get the highest thermal neutron flux was obtained. The PGNAA system with optimal parameters based on 252Cf neutron source was founded. In addition, the rock and element standard samples were irradiated by thermal neutron in this system. Moreover, the element content was calculated by processing gamma ray spectroscopy recorded, and it is in agreement with result of XRF method.

Optimization of a prompt gamma setup for analysis of environmental samples

A thermal neutron capture-based Prompt Gamma ray Activation Analysis setup has been designed to analyze the elemental concentration of environmental bulk samples using a D(d,n) reaction-based portable neutron generator. The performance of the setup was tested through mercury concentration measurements in Hg-contaminated water samples using a large volume cylindrical bismuth germinate (BGO) gamma ray detector. Excellent agreement of experimental count rate of 2.64, 3.19 + 3.29 and 4.67–5.05 MeV Hg prompt gamma rays with theoretical count rate obtained through Monte Carlo simulations, indicates excellent performance of the newly designed portable neutron generator-based PGNAA setup.

Preparation and Certification of Hydrogen in Titanium Alloy Standard Reference Materials

A series of three hydrogen in titanium alloy Standard Reference Materials (SRMs 2452, 2453, and 2454) was prepared with hydrogen mass fractions bracketing the hydrogen specification limit of 125 mg/kg. Commercial titanium alloy Ti6Al4V (6 pct aluminum and 4 pct vanadium) was heated under vacuum in a furnace to remove native hydrogen, then it was doped with a measured quantity of hydrogen. Prompt gamma-ray activation analysis was used to determine hydrogen in the degassed material and finished SRMs. A combination of preparation data and PGAA measurement was used to certify the hydrogen mass fraction of each. The certified hydrogen mass fractions are 62.5 mg/kg ± 1.6 mg/kg for SRM 2452, 114 mg/kg ± 5 mg/kg for SRM 2453, and 211 mg/kg ± 4 mg/kg for SRM 2454.

Comparison of IUPAC k 0 values and neutron cross sections to determine a self-consistent set of data for neutron activation analysis

Abstract Independent databases of nuclear constants for Neutron Activation Analysis (NAA) have been independently maintained by the physics and chemistry communities for many year. They contain thermal neturon cross sections σ 0, standardization values k 0, and transition probabilities P γ . Chemistry databases tend to rely upon direct measurements of the nuclear constants k 0 and P γ which are often published in chemistry journals while the physics databases typically include evaluated σ 0 and P γ data from a variety of experiments published mainly in physics journals. The IAEA/LBNL Evaluated Gamma-ray Activation File (EGAF) also contains prompt and delayed γ-ray cross sections σ γ from Prompt Gamma-ray Activation Analysis (PGAA) measurements that can also be used to determine k 0 and σ 0 values. As a result several independent databases of fundamental constants for NAA have evolved containing slightly different and sometimes discrepant results. An IAEA CRP for a Reference Database for Neutron Activation Analysis was established to compare these databases and investigate the possibilitiy of producing a self-consistent set of σ 0, k 0, σ γ , and P γ values for NAA and other applications. Preliminary results of this IAEA CRP comparison are given in this paper.

Local ordering and magnetism in Ga 0.9Fe 3.1N

Prior investigations of the ternary nitride series Ga 1– x Fe 3+ x N (0≤ x≤1) have indicated a transition from ferromagnetic γ′-Fe 4N to antiferromagnetic “GaFe 3N”. The ternary nitride “GaFe 3N” has been magnetically and spectroscopically reinvestigated in order to explore the weakening of the ferromagnetic interactions through the gradual incorporation of gallium into γ′-Fe 4N. A hysteretic loop at RT reveals the presence of a minority phase of only 0.1–0.2 at%, in accord with the sound two-step synthesis. The composition of the gallium-richest phase “GaFe 3N” was clarified by Prompt Gamma-ray Activation Analysis and leads to the berthollide formula Ga 0.91(1)Fe 3.09(10)N 1.05(7). Magnetic measurements indicate a transition around 8 K, further supported by Mössbauer spectral data. The weakening of the ferromagnetic coupling through an increasing gallium concentration is explained by a simple Stoner argument. In Ga 0.9Fe 3.1N, the presence of iron on the gallium site affects the magnetism by the formation of 13-atom iron clusters.