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Abstract  

Capabilities of 14 MeV neutron activation analysis with a high output generator are evaluated and found to be comparable with conventional activation analysis regarding sensitivity and precision; additional elements are instrumentally accessible at trace levels. Nuclear reactions featuring higher selectivity are listed and their sensitivity is compared to the present state of 14 MeV activation. Quasi-promt activation (T<1 sec) expands the scope of the technique to rapid nondestructive assays of trace species in bulk samples.

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Abstract  

Nuclear Analytical Chemistry at Texas A&M University is based in large part on the facilities of the Center for Chemical Characterization and Analysis and the Nuclear Science Center. This paper describes the capabilities of these two centers for instrumental and fast neutron activation analysis, neutron depth profiling, prompt gamma activation analysis, neutron radiography and the unique features of the large volume irradiation cell and reactor pulsing operation.

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Studies in heavy ion activation analysis

VIII. Hydrogen trace determination

Journal of Radioanalytical and Nuclear Chemistry
Authors: C. Friedli, E. Schweikert, and P. Lerch

Abstract  

Both7Li and10B induced radioactivation were applied to trace determination of hydrogen via the1H(7Li,n)7Be and1H(10B, )7Be reactions. In both cases, boron and magnesium present nuclear interferences, but their extent does not exceed 0.5%. At the bombarding energies used, 21 MeV7Li++ and 27 MeV10B++ the detection limits are respectively 2 and 0.5 ppm for an iron matrix irradiated for two hours. Due to the recoil of7Be, the samples were carefully prepared to avoid superficial hydrogen contamination. A series of samples which hydrogen content ranges from 15 to 120 ppm was examined, and the results obtained with the two beams were compared.

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Studies in heavy ion activation analysis

VII. Trace determination possibilities with10B ion bombardment

Journal of Radioanalytical and Nuclear Chemistry
Authors: C. Friedli, E. Schweikert, and P. Lerch

Abstract  

10B induced radioactivation was used for the trace determination of hydrogen via the1H(10B )7Be reaction. At 27 MeV10B++, only boron and magnesium present small nuclear interferences. An activation curve has been established by bombarding stacks of thin mylar foils. The comparison of this curve with the excitation function for the forward reaction, namely10B(p, )7Be, shows that the recoil range from superficial hydrogen atoms is small. Hydrogen has been determined in titanium and lead bronze at the 100 ppm level. Studies of 21 potential interfering elements suggest that10B activation might be suitable for the trace determination of lithium [6Li(10b,n)15O and7Li(10B, 2n)15O] and oxygen [18O(10B,)24Na].

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Abstract  

9Be induced radioactivation was used to study the trace determination of 19 elements at 3 different ion beam energies (Elab=14, 32 and 63 MeV9Be2+). Nine nuclear reactions, yielding radionuclides with half-lives longer than 2.5 m, present potential analytical features. Beside the very sensitive detection of B and N, the multielemental determination of Na, Si, Ca, Sc, and Zn is possible with a9Be ion beam of appropriate incident energy. Nuclear interferences have also been investigated and quantified.

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On the determination of phosphorus via charged particle activation analysis

II. Destructive and nondestructive determination of phosphorus in different matrices

Journal of Radioanalytical and Nuclear Chemistry
Authors: S. Kormali, W. James, J. Poland, and E. Schweikert

Abstract  

The application of charged particle activation analysis to the determination of phosphorus in a variety of sample materials is discussed. The activity produced via the31P(, n)34mCl reaction is quantitated either nondestructively or using postirradiation radiochemical separations depending on the characteristics of the sample matrices. Corrections which are necessary for the determination of phosphorus in pure tantalum metal due to spectral interferences are discussed.

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Abstract  

This paper describes first the application of neutron depth profiling (NDP) for measuring the distribution of6Li in LiAlO2 ceramics. Using a surface barrier detector for detecting3H produced in6Li(n, )3H,6Li was profiled to a depth of 14 m in the ceramics. Secondly, a new methodology is presented for NDP with enhanced capabilities based on measuring the energy of recoiling nuclei from (n, p) and (n, ) reactions by time-of-flight mass spectrometry. The scope of recoil nucleus time-of-flight mass spectrometry (RN-TOF-MS) includes profiling of10B,14N,17O,33S,35Cl,40K. Probe depths may be of a few tens nanometers. RN-TOF-MS complements and refines NDP based on charged particle (p or ) spectrometry.

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Abstract  

Carbon and oxygen impurities in silicon have been determined by 7.00 MeV3He activation analysis. The detection limits obtained for interference-free conditions are 0.1 ppb (wt) for carbon and 1.0 ppb (wt) for oxygen in silicon.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: J. Poland, S. Kormali, W. James, and E. Schweikert

Abstract  

The feasibility of charged particle activation analysis for phosphorus measurements was evaluated. Several nuclear reactions were studied with respect to pertinent activation data, thick target yields for calibration, relative excitation functions, and quantitative importances of interferences. Determination of phosphorus by the reaction31P(,n)34mCl was determined to be most advantagous with sensitivity competitive with other techniques.

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Résumé  

On décrit l'application de l'analyse par activation aux particules chargées (AAPC) avec mesure après irradiation à la détection de traces d'oxygène, de bore et de lithium. On utilise l'activation aux protens, aux alpha et aux3He pour le dosage non-destructif de l'oxygene dans le silicium. Les limites de détection expérimentale sont respectivement de 0,06 ppm, 0,05 ppm et 5 ppb. L'activation aux3He, couplée à une séparation radiochimique après irradiation, a été employée pour les analyses de l'oxygène dans le germanium avec une limite de détection de 10 ppb. De nouvelles techniques ont été développées pour le dosage du bore et du lithium, basées sur la mesure du8Li (T: 850 msec) et de12B (T: 20 msec), respectivement et utilisant une technique de mesure β en coïncidence avec deux scintillateurs minces de plastique. Les possibilités de cette méthode presque “prompte” sont illustrées avec des résultats concernant le silicium, le germanium et des échantillons de verre.

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