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Your search keyword '"Wilhelmy, J."' showing total 15 results
Start Over Author "Wilhelmy, J." Topic isotopes
15 results on '"Wilhelmy, J."'

1. The (14)C(n, gamma) cross section between 10 keV and 1 MeV

Author

Reifarth, R., Heil, M., Forssen, C., Besserer, U., Couture, A., Dababneh, S., Dorr, L., Gorres, J., Haight, R. C., Kappeler, F., Mengoni, A., O'Brien, S., Patronis, N., Plag, R., Rundberg, R. S., Wiescher, M., and Wilhelmy, J. B.

Subjects
heavy-elements, nuclear, nucleosynthesis, standard, rates, c-15, light, neutron diffusion, isotopes, decay
Abstract

The neutron capture cross section of (14)C is of relevance for several nucleosynthesis scenarios such as inhomogeneous Big Bang models, neutron induced CNO cycles, and neutrino driven wind models for the r process. The (14)C(n,gamma) reaction is also important for the validation of the Coulomb dissociation method, where the (n,gamma) cross section can be indirectly obtained via the time-reversed process. So far, the example of (14)C is the only case with neutrons where both, direct measurement and indirect Coulomb dissociation, have been applied. Unfortunately, the interpretation is obscured by discrepancies between several experiments and theory. Therefore, we report on new direct measurements of the (14)C(n,gamma) reaction with neutron energies ranging from 20 to 800 keV. Physical Review C

Published
2008

2. NEUTRON-INDUCED FISSION MEASUREMENTS AT THE DANCE AND LSDS FACILITIES AT LANL.

Author

JANDEL, M., BREDEWEG, T. A., BOND, E. M., CHADWICK, M. B., COUTURE, A., O'DONNELL, J. M., FOWLER, M. M., HAIGHT, R. C., HAYES-STERBENZ, A. C., RUNDBERG, R. S., RUSEV, G. Y., ULLMANN, J. L., VIEIRA, D. J., WILHELMY, J. B., WU, C. Y., BECKER, J. A., ALEXANDER, C. W., and BELIER, G.

Subjects
NEUTRON capture, NUCLEAR fission, NUCLEAR physics, NUCLEAR energy, ISOTOPES
Published
2013

3. Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE.

Author

Jandel, M., Bredeweg, T. A., Stoyer, M. A., Wu, C. Y., Fowler, M. M., Becker, J. A., Bond, E. M., Couture, A., Haight, R. C., Haslett, R. J., Henderson, R. A., Keksis, A. L., O'Donnell, J. M., Rundberg, R. S., Ullmann, J. L., Vieira, D. J., Wilhelmy, J. B., and Wouters, J. M.

Subjects
NEUTRON capture, AMERICIUM, ISOTOPES, NUCLEAR fission, NUCLEAR energy, RESONANCE, PROTONS
Abstract

Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for 241Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for 243Am for neutron energies between 10 eV and 250 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on 242mAm will be presented where the fission events were actively triggered during the experiments. In these experiments, a Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,γ) events from (n,f) events. The first direct observation of neutron capture on 242mAm in the resonance region in between 2 and 9 eV of the neutron energy was obtained. [ABSTRACT FROM AUTHOR]

Published
2009
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4. Scissors Mode of 162Dy Studied from Resonance Neutron Capture.

Author

Baramsai, B., Bečvář, F., Bredeweg, T. A., Haight, R. C., Jandel, M., Kroll, J., Krtička, M., Mitchell, G. E., O'Donnell, J. M., Rundberg, R. S., Ullmann, J. L., Valenta, S., and Wilhelmy, J. B.

Subjects
CASCADES (Fluid dynamics), NEUTRON resonance, PHOTONS, ISOTOPES, NUCLEAR magnetic resonance, NUCLEAR magnetism
Abstract

Multi-step cascade γ-ray spectra from the neutron capture at isolated resonances of 161Dy nucleus were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The objectives of this experiment were to confirm and possibly extend the spin assignment of s-wave neutron resonances and get new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. The preliminary results show that the scissors mode plays a significant role in all transitions between accessible states of the studied nucleus. The photon strength functions describing well our data are compared to results from ³He-induced reactions, (n,γ) experiments on Gd isotopes, and (γ,γ') reactions. [ABSTRACT FROM AUTHOR]

Published
2015
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10. Constraining the calculation of 234,236,238U(n,γ) cross sections with measurements of the γ-ray spectra at the DANCE facility.

Author

Ullmann, J. L., Kawano, T., Baramsai, B., Bredeweg, T. A., Couture, A., Haight, R. C., Jandel, M., O'Donnell, J. M., Rundberg, R. S., Vieira, D. J., Wilhelmy, J. B., Krtička, M., Becker, J. A., Chyzh, A., Wu, C. Y., and Mitchell, G. E.

Subjects
*PHOTONS, *ISOTOPES, *X-ray spectra
Abstract

The cross section for neutron capture in the continuum region has been difficult to calculate accurately. Previous results for 238U show that including an M1 scissors-mode contribution to the photon strength function resulted in very good agreement between calculation and measurement. This paper extends that analysis to 234,236U by using γ-ray spectra measured with the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos Neutron Science Center to constrain the photon strength function used to calculate the capture cross section. Calculations using a strong scissors-mode contribution reproduced the measured γ-ray spectra and were in excellent agreement with the reported cross sections for all three isotopes. [ABSTRACT FROM AUTHOR]

Published
2017
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