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多元素中子俘获瞬发γ射线分析方法的研究 总被引:2,自引:0,他引:2
进一步提出被测元素瞬发γ射线特征峰的面积与其含量的关系式。经实验证明对各常见元素的仪器分析回归值与化学分析值的均方根偏差皆小于0.5wt%。在铁矿石的分析实验中发现了慢化体的作用,它可明显地提高分析灵敏度。该套中子俘获瞬发谱仪对H瞬发γ峰(2.223MeV)的FWHM为3keV。 相似文献
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Jean-Louis Pinault Jose Solis 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(7):1139-1148
The uncertainty of the elemental analysis is one of the major factors governing the utility of on-line Prompt Gamma Neutron Activation Analysis (PGNAA) in the blending and sorting of bulk materials. In this paper, a general method applicable to Gamma spectra processing is presented and applied to PGNAA in mineral industry. Based on the Fourier transform of spectra and their de-correlation in the Fourier space (the improvement of the conditioning of the correlation matrix), processing of overlapping of characteristic peaks minimizes the propagation of random errors, which optimizes the accuracy and decreases the detection limits of elemental analyses. In comparison with classical methods based on the linear combinations of relevant regions of spectra the improvement may be considerable, especially when several elements are interfering. The method is applied to four case stories covering both borehole logging and on-line analysis on conveyor belt of raw materials. 相似文献
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To characterize legacy radioactive materials, it is necessary to determine both the radioactive and, in the case of carrier-based materials, the stable, non-radioactive chemical constituents. Reputable process knowledge may afford some insight but, absent such information, gamma spectroscopy and (non-destructive) prompt gamma activation analysis (PGAA) cover essentially all of the analytical needs, with the former addressing most radionuclides with the exception of the pure β−-emitters and the latter addressing the stable chemical constituents. This paper integrates both methods into a general analytical protocol based upon radioanalytical work performed at Lawrence Berkeley National Laboratory (LBNL) and PGAA work performed collaboratively by the various groups. A new LBNL-developed neutron generator is also discussed. 相似文献
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E. Alvarez S. Landsberger 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,262(2):333-339
Prompt gamma activation analysis (PGAA), available at The University of Texas at Austin (UT), has been employed for the direct determination of hydrogen content in a series of metal oxide materials typically used as cathodes in lithium ion battery systems. Special attention was given to the experimental setup including potential sources of error and system calibration for the detection of hydrogen. Spectral interference with hydrogen arising from cobalt was identified and corrected for. Limits of detection as a function of cobalt mass present in a given sample are also discussed. PGAA has proven to be a novel and precise technique for the determination of hydrogen in metal oxides. This type of investigation could provide valuable insight regarding the factors that limit the practical capacities of lithium ion oxide cathodes. 相似文献
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《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1998,143(3):414-421
The performance of the prompt gamma neutron activation analysis (PGNAA) facility at the MIT Research Reactor has been improved by a series of modifications. These modifications have increased the flux by a factor of three at the sample position to 1.7 × 107 n/cm2 s, and have increased the sensitivity, on average, by a factor of 2.5. The background for many samples of interest is dominated by unavoidable neutron interactions that occur in or near the sample. Other background components comprise only 20% of the total background count rate. The implementation of fast electronics has helped to keep dead time reasonable, in spite of the increased count rates. The PGNAA facility at the MIT Research Reactor continues to serve as a major analytical tool for quantifying 10B in biological samples for Boron Neutron Capture Therapy (BNCT) research. The sensitivity for boron-10 in water is 18 750 cps/mg. The sensitivity for pure elements suitable for PGNAA analysis is reported. Possible further improvements are discussed. 相似文献
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K. Kasviki I.E. Stamatelatos E. Yannakopoulou J. Kalef-Ezra 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,263(1):132-135
A prompt gamma neutron activation analysis (PGNAA) facility has been developed for the determination of nitrogen and thus total protein in large volume biological samples or the whole body of small animals. In the present work, the accuracy of nitrogen determination by PGNAA in phantoms of known composition as well as in four raw ground meat samples of about 1 kg mass was examined. Dumas combustion and Kjeldahl techniques were also used for the assessment of nitrogen concentration in the meat samples. No statistically significant differences were found between the concentrations assessed by the three techniques. The results of this work demonstrate the applicability of PGNAA for the assessment of total protein in biological samples of 0.25-1.5 kg mass, such as a meat sample or the body of small animal even in vivo with an equivalent radiation dose of about 40 mSv. 相似文献
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J.L. Gräfe F.E. McNeill S.H. Byun D.R. Chettle M.D. Noseworthy 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(15):2451-2457
Gadolinium (Gd)-based contrast agents are a valuable diagnostic aid for magnetic resonance imaging (MRI). The amount of free Gd deposited in tissues following contrast enhanced MRI is of toxicological concern. The McMaster University in vivo prompt gamma neutron activation analysis facility has been adapted for the detection of Gd in the kidney, liver, and the leg muscle. A simple model of the HPGe detector used for detection of the prompt γ-rays following Gd neutron capture has been created using Monte Carlo simulation. A separate simulation describing the neutron collimation and shielding apparatus has been modified to determine the neutron capture rate in the Gd phantoms. The MCNP simulation results have been confirmed by experimental measurement. The deviations between MCNP and the experiment were between 1% and 18%, with an average deviation of 3.8 ± 6.7%. The validated MCNP model is to be used to improve the Gd in vivo measurement sensitivity by determining the best neutron moderator/reflector arrangement. 相似文献
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J. Grinyer J. Atanackovic S.H. Byun D.R. Chettle 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,263(1):262-265
Prompt gamma neutron activation analysis is a means of non-invasive monitoring for occupational exposure to toxic heavy metals such as Cd and Hg. Preliminary kidney detection limits from previous phantom studies at McMaster were 13.6 ± 0.2 ppm for Cd (125 mL phantom) and 315 ± 24 ppm for Hg (125 mL phantom) using the 238Pu-Be neutron source and 0.88 ± 0.01 ppm for Cd (125 mL phantom) and 16.91 ± 0.05 ppm for Hg (30 mL phantom) using the thermal neutron beam port at the McMaster Nuclear Reactor. The detection limits vary greatly between the two methods due to differences in experimental set-up, neutron energy spectra and a difference in dose by more than a factor of 100. The Hg detection limit from preliminary data is much higher than expected for both neutron source types. In order to explain the apparent detection limit discrepancy, measurements of Hg and Cd phantoms were performed using the 238Pu-Be neutron source. The results were compared to phantom measurements of Cl, a well-known neutron activation element. 相似文献
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M.N. Nasrabadi M. Jalali 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,263(2):473-476
In this work thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing materials is studied using bulk sample prompt gamma neutron activation analysis (BSPGNAA) with the MCNP code. The code was used to perform three dimensional simulations of a neutron source, neutron detector and sample of various material compositions. The MCNP model was validated against experimental measurements of the neutron flux performed using a BF3 detector. Simulations were performed to predict thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing solutes. In practice, the MCNP calculations are combined with experimental measurements of the relative thermal neutron flux over the sample’s surface, with respect to a reference water sample, to derive the thermal neutron self-shielding within the sample. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the average thermal neutron flux within the sample volume is required. 相似文献
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The proton-capture reactions 14N(p,γ)15O and 15N(p,αγ)^12C have been studied to determine their applicabilities to the analysis of materials for 15N enrichment,It is true that precision of the measurement concerned in these techniques cannot compete with mass spectrometry,but their ease of application is of great advantage to the fast handling of very large batches of samples from stable nuclide tracer experiments. 相似文献