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144 results on '"Ullmann J.L."'

1. Total prompt γ-ray emission in fission

Author

Wu C.Y., Chyzh A., Kwan E., Henderson R.A., Bredeweg T.A., Haight R.C., Hayes-Sterbenz A.C., Lee H.Y., O'Donnell J.M., and Ullmann J.L.

Subjects
Physics, QC1-999
Abstract

The total prompt γ-ray energy distributions were measured for the neutron-induced fission of 235U, 239,241Pu at incident neutron energy of 0.025 eV–100 keV, and the spontaneous fission of 252Cf using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments by a parallel-plate avalanche counter. Corrections were made to the measured distribution by unfolding the two-dimension spectrum of total prompt γ-ray energy vs multiplicity using a simulated DANCE response matrix. A summary of this work is presented with the emphasis on the comparison of total prompt fission γ-ray energy between our results and previous ones. The mean values of the total prompt γ-ray energy ⟨Eγ,tot⟩, determined from the unfolded distributions, are ∼20% higher than those derived from measurements using single γ-ray detector for all the fissile nuclei studied.

Published
2017
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2. Isomeric ratio measurements for the radiative neutron capture 176Lu(n,γ) at DANCE

Author

Denis-Petit D., Roig O., Méot V., Morillon B., Romain P., Jandel M., Kawano T., Vieira D.J., Bond E.M., Bredeweg T.A., Couture A.J., Haight R.C, Keksis A.L., Rundberg R.S., and Ullmann J.L.

Subjects
Physics, QC1-999
Abstract

The isomeric ratios for the neutron capture reaction 176Lu(n,γ) to the Jπ = 5/2−, 761.7 keV, T1/2 = 32.8 ns and the Jπ = 15/2+, 1356.9 keV, T1/2 = 11.1 ns levels of 177Lu, have been measured for the first time with the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos National Laboratory. These measured isomeric ratios are compared with TALYS calculations.

Published
2017
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3. 242Pu absolute neutron-capture cross section measurement

Author

Buckner M.Q., Wu C.Y., Henderson R.A., Bucher B., Chyzh A., Bredeweg T.A., Baramsai B., Couture A., Jandel M., Mosby S., O’Donnell J.M., and Ullmann J.L.

Subjects
Physics, QC1-999
Abstract

The absolute neutron-capture cross section of 242Pu was measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. During target fabrication, a small amount of 239Pu was added to the active target so that the absolute scale of the 242Pu(n,γ) cross section could be set according to the known 239Pu(n,f) resonance at En,R = 7.83 eV. The relative scale of the 242Pu(n,γ) cross section covers four orders of magnitude for incident neutron energies from thermal to ≈ 40 keV. The cross section reported in ENDF/B-VII.1 for the 242Pu(n,γ) En,R = 2.68 eV resonance was found to be 2.4% lower than the new absolute 242Pu(n,γ) cross section.

Published
2017
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4. Total prompt γ-ray emission in fission

Author

Wu C.Y., Chyzh A., Kwan E., Henserson R.A., Bredeweg T.A., Haight R.C., Hayes-Sterbenz A.C., Lee H.Y., O’Donnell J.M., and Ullmann J.L.

Subjects
Physics, QC1-999
Abstract

The total prompt γ-ray energy distributions for the neutron-induced fission of 235U, 239,241Pu at incident neutron energy of 0.025 eV ‒ 100 keV, and the spontaneous fission of 252Cf were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments by a parallel-plate avalanche counter. DANCE is a highly segmented, highly efficient 4π γ-ray calorimeter. Corrections were made to the measured distribution by unfolding the two-dimension spectrum of total γ-ray energy vs multiplicity using a simulated DANCE response matrix. The mean values of the total prompt γ-ray energy, determined from the unfolded distributions, are ~ 20% higher than those derived from measurements using single γ-ray detector for all the fissile nuclei studied. This raises serious concern on the validity of the mean total prompt γ-ray energy obtained from the product of mean values for both prompt γ-ray energy and multiplicity.

Published
2016
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5. Isomeric ratio measurements for the radiative neutron capture 176Lu(n,γ) at DANCE

Author

Denis-Petit D., Roig O., Méot V., Jandel M., Vieira D.J., Bond E.M., Bredeweg T.A., Couture A.J., Haight R.C, Keksis A.L., Rundberg R.S., and Ullmann J.L.

Subjects
Physics, QC1-999
Abstract

The isomeric ratio for the neutron capture reaction 176Lu(n,γ) on the Jπ= 5/2−, 761.7 keV, T1/2=32.8 ns level of 177mLu, has been determined in the neutron energy range 8.5 eV-100 keV for the first time using the DANCE array at the Los Alamos National Laboratory.

Published
2016
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6. 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
Physics, QC1-999
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.

Published
2015
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7. Scissors Mode in Gd Nuclei

Author

Wu C.Y., Wouters J.M., Wilhelmy J.B., Walker C.L., Vieira G.J., Ullmann J.L., Rundberg R.S., Parker W., O'Donnell J.M., Mitchell G.E., Krtička M., Jandel M., Haight R.C., Dashdorj D., Chyzh A., Couture A., Bredeweg T.A., Bečvář F., Becker J.A., Baramsai B., and Kroll J.

Subjects
Physics, QC1-999
Abstract

Spectra of γ rays following neutron capture at isolated resonances of 6 stable Gd isotopes were measured with highly segmented BaF2 detector DANCE at the Los Alamos LANSCE spallation neutron source. The main emphasis was put on studying the γ-cascade decay of neutron resonances to get unique information on photon strength. An analysis of the accumulated γ-ray spectra within the extreme statistical model leads to an inescapable conclusion that scissors mode resonances are built not only on the ground-state, but also on excited levels in all product nuclei studied. The results on summed B(M1)↑ strength and energy of the scissors mode are compared with systematics of scissors mode parameters for the ground-state transitions deduced from nuclear resonance fluorescence measurements. A specific feature of our experiments is the investigation of scissors mode of odd nuclei, for which the nuclear resonance fluorescence provides only limited information.

Published
2012
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8. Neutron capture reactions on Lu isotopes at DANCE

Author

Wouters J.M., Ullmann J.L., Taylor W.A., Rundberg R.S., O’Donnell J.M., Morel P., Méot V., Keksis A.L., Haight R.C, Daugas J.-M., Couture A.J., Bredeweg T.A., Bond E.M., Vieira D.J., Jandel M., and Roig O.

Subjects
Physics, QC1-999
Abstract

The DANCE (Detector for Advanced Neutron Capture Experiments) array located at the Los Alamos national laboratory has been used to obtain the neutron capture cross sections for the 175Lu and 176Lu isotopes with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process in astrophysics and for applications as in reactor physics or in nuclear medicine. Three targets were used to perform these measurements. One was natLu foil and the other two were isotope-enriched targets of 175Lu and 176Lu. The cross sections are obtained for now through a precise neutron flux determination and a normalization at the thermal neutron cross section value. A comparison with the recent experimental data and the evaluated data of ENDF/B-VII.0 will be presented. In addition, resonances parameters and spin assignments for some resonances will be featured.

Published
2010
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14. Prompt Fission Gamma-ray Studies at DANCE

Author

Jandel, M., Rusev, G., Bond, E.M., Bredeweg, T.A., Chadwick, M.B., Couture, A., Fowler, M.M., Haight, R.C., Kawano, T., Keksis, A.L., Mosby, S.M., O’Donnell, J.M., Rundberg, R.S., Stetcu, I., Talou, P., Ullmann, J.L., Vieira, D.J., Wilhelmy, J.B., Stoyer, M.A., Haslett, R.J., Henderson, R.A., Becker, J.A., and Wu, C.Y.

Published
2014
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15. Vortex Pinning and Critical Current Enhancements in High-T c Superconductors with Fission-Generated Random Columnar Defects

Author

Thompson, J. R., Ossandón, J. G., Krusin-Elbaum, L., Song, K. J., Christen, D.K., Wu, J. Z., Ullmann, J.L., Beig, R., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Lipowsky, R., editor, v. Löhneysen, H., editor, Ojima, I., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Klamut, Jan, editor, Veal, Boyd W., editor, Dabrowski, Bogdan M., editor, Klamut, Piotr W., editor, and Kazimierski, Maciej, editor

Published
2000
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21. GEANT4 simulations of the DANCE array

Author

Jandel, M., Bredeweg, T.A., Couture, A., Fowler, M.M., Bond, E.M., Chadwick, M.B., Clement, R.R.C., Esch, E.-I., O’Donnell, J.M., Reifarth, R., Rundberg, R.S., Ullmann, J.L., Vieira, D.J., Wilhelmy, J.B., Wouters, J.M., Macri, R.A., Wu, C.Y., and Becker, J.A.

Published
2007
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22. Progress on the europium neutron capture study using DANCE

Author

Agvaanluvsan, U., Becker, J.A., Macri, R.A., Parker, W., Wilk, P., Wu, C.Y., Bredeweg, T.A., Esch, E., Haight, R.C., O’Donnell, J.M., Reifarth, R., Rundberg, R.S., Schwantes, J.M., Ullmann, J.L., Vieira, D.J., Wilhelmy, J.B., Wouters, J.M., Mitchell, G.E., Sheets, S., Bečvář, F., and Krtička, M.

Published
2007
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25. (n, γ) measurements on radioactive isotopes with DANCE

Author

Reifarth, R., Esch, E.-I., Alpizar-Vicente, A., Bond, E.M., Bredeweg, T.A., Glover, S.E., Greife, U., Hatarik, R., Haight, R.C., Kronenberg, A., O’Donnell, J.M., Rundberg, R.S., Schwantes, J.M., Ullmann, J.L., Vieira, D.J., Wilhelmy, J.B., and Wouters, J.M.

Published
2005
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26. Cross section for the neutron radiative capture on $^{173}$Lu nuclei

Author

Ebran, A., Roig, O., Méot, V., Jandel, M., Theroine, C., Bond, E.M., Bredeweg, T.A., Couture, A., Nortier, F.M., O'Donnell, J.M., Taylor, W.A., Ullmann, J.L., Vieira, D.J., Direction des Applications Militaires (DAM), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
Nuclear Reactions, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Experiment
Abstract

International audience; We report the measurement of a neutron radiative cross section on a target with a high gamma activity, at the Los Alamos DANCE detector (Detector for Advanced Neutron Capture Experiments) for the first time. The (n,γ) reaction properties of the unstable Lu173 isotope were studied. Two experimental campaigns were needed to determine the Lu173(n,γ) cross section. They were performed at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source facility. To this end, two targets were produced from an Hf sample using successively proton irradiation and chemical separations. They were composed of Lu173,Lu174, and Lu175 isotopes. The two measurements were conducted at two-year intervals, taking advantage of the difference of the isotopic decay lifetimes in order to identify resonances from the Lu173(n,γ) and Lu174(n,γ) reactions. Just over one hundred new resonances were observed, the majority of which come from the Lu173(n,γ) reaction. Only a few of them were assigned to the Lu174(n,γ) reaction. As regards the Lu173(n,γ) reaction, the radiative neutron capture cross section was determined over the energy range from thermal neutron up to 200 eV. The parameters of resonances in the resolved resonance region were extracted with the sammy code while calculations with talys determined the capture cross section in the unresolved resonances region. At the keV region, we performed standard talys calculations as well as other microscopic investigations by substituting the standard talys photon strength function by another one from QRPA models.

Published
2019

27. Studies of flux pinning by proton-induced fission tracks in multifilamentary tapes of (Bi,Pb)2Sr2Ca2Cu3O10/Ag superconductors

Author

Budhani, R.C., Willis, J.O., Suenaga, M., Maley, M.P., Couler, J.Y., Safar, H., Ullmann, J.L., and Haldar, P.

Subjects
Flux pinning -- Research, Proton-induced X-ray emission -- Research, Superconductors -- Research, Physics
Abstract

Research was conducted to show the effects of proton-induced linear defects on the dissipationless flow of current in multifilamentary Ag-sheathed tapes of (Bi1Pb)2Sr2ca2Cu3O10 superconductors in the temperature range of 55-77 K. Substantial enhancement of critical currents of the tapes are provided by randomly oriented columnar defects of estimated areal density 5 X 10 (super 10)/cm2 produced by 800 MeV proton-induced fission fragments.

Published
1997

31. Single event effects and performance predictions for space applications of RISC processors

Author

Kimbrough, J.R., Colella, N.J., Denton, S.M., Shaeffer, D.L., Shih, D., Wilburn, J.W., Coakley, P.G., Casteneda, C., Koga, R., Clark, D.A., and Ullmann, J.L.

Subjects
Microprocessors -- Research, Electronic equipment and supplies, Effect of radiation on -- Research, Business, Electronics, Electronics and electrical industries
Abstract

Proton and ion Single Event Phenomena (SEP) tests were performed on 32-b processors including R3000A's from all commercial manufacturers along with the Performance PR3400 family, Integrated Device Technology Inc. 79R3081, LSI Logic Corporation LR33000HC, and Intel i80960MX parts. The microprocessors had acceptable upset rates for operation in a low earth orbit or a lunar mission such as CLEMENTINE with a wide range in proton total dose failure. Even though R3000A devices are 60% smaller in physical area than R3000 devices, there was a 340% increase in device Single Event Upset (SEU) cross section. Software tests of varying complexity demonstrate that registers and other functional blocks using register architecture dominate the cross section. The current approach of giving a single upset cross section can lead to erroneous upset rates depending on the application software.

Published
1994

35. The Prompt Fission Neutron Spectrum of 235 U( n , f ) below 2.5 MeV for Incident Neutrons from 0.7 to 20 MeV

Author

Devlin, M., primary, Gomez, J.A., additional, Kelly, K.J., additional, Haight, R.C., additional, O'Donnell, J.M., additional, Taddeucci, T.N., additional, Lee, H.Y., additional, Mosby, S.M., additional, Perdue, B.A., additional, Fotiades, N., additional, Ullmann, J.L., additional, Wu, C.Y., additional, Bucher, B., additional, Buckner, M.Q., additional, Henderson, R.A., additional, Neudecker, D., additional, White, M.C., additional, Talou, P., additional, Rising, M.E., additional, and Solomon, C.J., additional

Published
2018
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36. Isomeric ratio measurements for the radiative neutron capture $^{176}$Lu($n,\gamma$) at the LANL DANCE facility

Author

Denis-Petit, D., Roig, O., Méot, V., Morillon, B., Romain, P., Jandel, M., Kawano, T., Vieira, D.J., Bond, E.M., Bredeweg, T.A., Couture, A.J., Haight, R.C., Keksis, A.L., Rundberg, R.S., Ullmann, J.L., Direction des Applications Militaires (DAM), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)

Subjects
[PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex]
Abstract

International audience; The isomeric ratios for the neutron capture reaction $^{176}$Lu($n,\gamma$) to the $J^{\pi}=5/2^-$ 761.7 keV, $T_{1/2}$ =32.8 ns and the $J^{\pi}=15/2^+$, 1356.9 keV, $T_{1/2}$=11.1 ns levels of $^{177}$Lu have been measured for the first time. The experiment was carried out with the Detector for Advanced Neutron Capture Experiments (DANCE) at the Los Alamos National Laboratory. Measured isomeric ratios are compared with talys calculations using different models for photon strength functions, level densities, and optical potentials. In order to reproduce the experimental γ-ray spectra, a low-energy resonance must be added in the photon strength function used in our Hauser-Feshbach calculations.

Published
2016

46. Total promptγ-ray emission in fission

Author

Wu, C.Y., primary, Chyzh, A., additional, Kwan, E., additional, Henserson, R.A., additional, Bredeweg, T.A., additional, Haight, R.C., additional, Hayes-Sterbenz, A.C., additional, Lee, H.Y., additional, O’Donnell, J.M., additional, and Ullmann, J.L., additional

Published
2016
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49. Scissors Mode of162Dy Studied from Resonance Neutron Capture

Author

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

Published
2015
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50. Development of an Array of Liquid Scintillators to Measure the Prompt Fission Neutron Spectrum at LANSCE

Author

Perdue, B.A., primary, Taddeucci, T.N., additional, Haight, R.C., additional, Bredeweg, T., additional, Devlin, M., additional, Fotiades, N., additional, Jandel, M., additional, Laptev, A., additional, Lee, H.Y., additional, Nelson, R.O., additional, O'Donnell, J.M., additional, Ullmann, J.L., additional, Wender, S.A., additional, Wu, C.Y., additional, Kwan, E., additional, Chyzh, A., additional, Henderson, R.A., additional, and Gostic, J.M., additional

Published
2014
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