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Abstract  

Developing a better understanding of xenon transport through porous systems is critical to predicting how this gas will enter the atmosphere after a below ground nuclear weapons test. Radioxenon monitoring is a vital part of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) International Monitoring System. This work details the development of prompt gamma activation analysis for measuring the diffusion rates of xenon and argon gases through a porous medium. The University of Texas at Austin maintains a prompt gamma activation analysis facility with a peak neutron flux of ~1.5 × 107 cm−2 s−1 and a beam diameter of 1 cm. Due to the relatively large prompt gamma cross sections of many stable xenon isotopes at thermal and sub-thermal neutron energies, prompt gamma activation analysis is a suitable technique for in situ non-destructive analysis of natural xenon. A test chamber has been designed and constructed to utilize prompt gamma activation analysis to measure xenon and argon diffusion through geological materials (e.g., sand, soil, etc.). Initial experiments have been conducted to determine the detection limits for stable gas measurements. The results from these experiments will be utilized to benchmark parts of a xenon transport model that is being used to determine diffusion coefficients for xenon and argon.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: L. Cao, J. Hattrick-Simpers, R. Bindel, B. Tomlin, R. Zeisler, R. Paul, L. Bendersky, and R. Downing

Abstract  

Cold neutron prompt gamma activation analysis (PGAA) was used to determine the mass of hydrogen in Mg hydride thin films with varying hydrogenation times. The results suggest that hydrogenation of the Mg thin films remains unsaturated even after 48 h of treatment, contrary to the indications of inferential hydrogen measurement methods. To demonstrate PGAA as an effective combinatorial methodology for hydride thin films, a continuously varying composition gradient of thin MgyTi(1−y) hydride film with y ranging from 0.65 to 0.94 was prepared and analyzed by both PGAA and instrumental neutron activation analysis (INAA). The variation in the molar ratio of Mg, Ti, and H was obtained for nine 5 mm wide segments of the film.

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Abstract  

The Budapest Research Reactor’s Prompt Gamma Activation Analysis (PGAA) and Neutron-Induced Prompt gamma Spectroscopy (NIPS) facilities were significantly upgraded during the last few years. The higher neutron flux, achieved by the partial replacement and realignment of the neutron guides, made feasible the automation and specialization of the two experimental stations. A new neutron flux monitor, computer-controlled beam shutters and a low-level counting chamber have been put into operation to assist with in-beam activation experiments. An automatic sample changer has been installed at the PGAA station, while the NIPS station was redesigned and upgraded with a Compton suppressor to use for the non-destructive analysis of bulky samples. In the near future the latter setup will be completed with a neutron tomograph and a moving table, to turn it into a Neutron Radiography/Tomography-driven PGAA equipment.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: D. Perry, G. English, R. Firestone, K. Leung, G. Garabedian, G. Molnar, and Zs. Revay

Abstract  

Prompt gamma activation analysis (PGAA) has been used to analyze metal ion oxyanion materials that have multiple applications, including medicine, materials, catalysts, and electronics. The significance for the need for accurate, highly sensitive analyses for the materials is discussed in the context of quality control of end products containing the parent element in each material. Applications of the analytical data for input to models and theoretical calculations related to the electronic and other properties of the materials are discussed.

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Abstract  

Two methods are presented for the prompt gamma activation analysis (PGAA) of samples in relatively thick containers. In the “Invisible container” method, the prompt gamma-radiation from the activated parts of the container can be suppressed in the spectrum. The target can be analyzed simultaneously with the shielding material, when the target signal in the spectrum is stronger. Uranium containing compounds were analyzed in lead capsules.

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Abstract  

A Prompt Gamma Activation Analysis (PGAA) facility is being developed at The University of Texas at Austin (UT). The UT-PGAA facility will utilize a focused cold-neutron beam from the Texas Cold Neutron Source (TCNS). the TCNS consists of a cold source cryostat and a curved neutron guide. the use of a guided focused cold-neutron beam will provide a high capture reaction rate and low background. The UT-PGAA facility will be used in the nondestructive determination of B, Cd, Gd and S in biological and environmental samples.

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Abstract  

The off-line γ-counting of in-beam activated radionuclides has been explored to extend the detection capabilities of prompt gamma activation analysis (PGAA). Such combination of the prompt measurement with a subsequent decay-counting is feasible if radionuclides with half-lives of minutes or hours are produced in the sample during neutron irradiation. Thanks to the simpler spectrum and the higher counting efficiency of decay counting, both selectivity and sensitivity can be improved. The pros and cons of the proposed method have been demonstrated on a series of industry-related measurements.

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Abstract  

Applying thek 0 standardization method to prompt-gamma activation analysis (PGAA) offers similar benefits as in instrumental neutron activation analysis. It has been demonstrated that under constant flux conditionsk 0-factors obtained by normalizing to a titanium comparator, measured separately, yield consistent analytical sensitivity ratios. The ratio method has been generalized by using stoichiometric compounds for the determination ofk 0-factors. Since chlorine forms compounds with essentially everyelement and it also serves as a detector efficiency standard,k 0 values have been determined relative to chlorine as an internal standard for several analytically important elements in two reactor facilities: the thermal guided beam at the BRR in Budapest and the cold-neutron beams at the NBSR at NIST.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: H. Chen-Mayer, V. Sharov, D. Mildner, R. Downing, R. Paul, R. Lindstrom, C. Zeissler, and Q. Xiao

Abstract  

A neutron lens has been constructed to focus cold neutrons from the exit of a58Ni neutron guide, which delivers a beam to the Prompt-Gamma Activation Analysis (PGAA) station at the NIST Cold Neutron Research Facility. The lens compresses a neutron beam of cross section 50 mm× 45 mm onto a focal spot of diameter 0.53 mm (fwhm) wich an average gain of 80 in neutron current density. PGAA measurements have been performed to demonstrate the enhanced sensitivity and detection limits for various elements and the spatial resolution in one transverse dimension. For the two test particles (a gadolinium glass bead and cadmium metal of sizes less than 0.5 mm), the gain in the -count rate with the lens is a factor of 60, and the detection limit is improved by a factor of 20. The system can be used for two-dimensional mapping of samples on a sub-millimeter scale to complement other analytical techniques such as neutron depth profiling (NDP).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: G. Molnár, T. Belgya, L. Dabolczi, B. Fazekas, Zs. Révay, Á. Veres, I. Bikit, Z. Kiss, and J. Östör

Abstract  

Prompt gamma-activation analysis (PGAA) is an important complementary technique to conventional instrumental activation analysis that can be successfully used in a number of cases when INAA is not applicable. Therefore, a PGAA facility has been constructed at the recently refurbished and upgraded Budapest Research Reactor. It occupies the end position of a new curved themal guide of 30 m length and 2.5×10 cm2 cross section which provides a clean beam of low energy neutrons. The sophisticated HPGe-BGO -ray spectrometer system can be operated in Compton-suppression and pair-spectrometer modes simultaneously. The octal splitting of the main BGO improves efficient pair mode operation when coincidences between pairs of opposite segments and the HPGe detector are required separately. Gamma-gamma coincidence measurements will also be possible when the new multiparameter data acquisition system is completed. One of the main tasks at the new facility will be the accumulation of new spectroscopic data for detector calibration and standardisation, as well as for the construction of a more accurate prompt -ray library for the chemical elements. Various applications are planned, such as the determination of hydrogen in fullerenes and of toxic trace elements in environmental samples.

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