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117 results on '"Stoyer, M A"'

5. Review of even element super-heavy nuclei and search for element 120

Author

Hofmann, S., Heinz, S., Mann, R., Maurer, J., Münzenberg, G., Antalic, S., Barth, W., Burkhard, H. G., Dahl, L., Eberhardt, K., Grzywacz, R., Hamilton, J. H., Henderson, R. A., Kenneally, J. M., Kindler, B., Kojouharov, I., Lang, R., Lommel, B., Miernik, K., Miller, D., Moody, K. J., Morita, K., Nishio, K., Popeko, A. G., Roberto, J. B., Runke, J., Rykaczewski, K. P., Saro, S., Scheidenberger, C., Schött, H. J., Shaughnessy, D. A., Stoyer, M. A., Thörle-Pospiech, P., Tinschert, K., Trautmann, N., Uusitalo, J., and Yeremin, A. V.

Published
2016
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6. Remarks on the fission barriers of super-heavy nuclei

Author

Hofmann, S., Heinz, S., Mann, R., Maurer, J., Münzenberg, G., Antalic, S., Barth, W., Dahl, L., Eberhardt, K., Grzywacz, R., Hamilton, J. H., Henderson, R. A., Kenneally, J. M., Kindler, B., Kojouharov, I., Lang, R., Lommel, B., Miernik, K., Miller, D., Moody, K. J., Morita, K., Nishio, K., Popeko, A. G., Roberto, J. B., Runke, J., Rykaczewski, K. P., Scheidenberger, C., Shaughnessy, D. A., Stoyer, M. A., Thörle-Pospiech, P., Tinschert, K., Trautmann, N., Uusitalo, J., and Yeremin, A. V.

Published
2016
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7. Fission Product Yield Measurements from Neutron-Induced Fission of 235,238 U and 239Pu

Author

Stoyer M. A., Tonchev A. P., Silano J. A., Gooden M. E., Wilhelmy J. B., Tornow W., Howell C. R., Krishichayan F., and Finch S.

Subjects
Physics, QC1-999
Abstract

Fission product yields (FPY) are one of the most fundamental quantities that can be measured for a fissioning nucleus and are important for basic and applied nuclear physics. Recent measurements using mono-energetic and pulsed neutron beams generated using Triangle Universities Nuclear Laboratory’s tandem accelerator and employing a dual fission chamber setup have produced self-consistent, high-precision data critical for testing fission models for the neutron-induced fission of 235,238U and 239Pu between neutron energies of 0.5 to 15.0 MeV. These data have elucidated a low-energy dependence of FPY for several fission products using irradiations of varying lengths and neutron energies. This paper will discuss new measurements just beginning utilizing a RApid Belt-driven Irradiated Target Transfer System (RABITTS) to measure shorterlived fission products and the time dependence of fission yields, expanding the measurements from cumulative towards independent fission yields. The uniqueness of these FPY data and the impact on the development of fission theory will be discussed.

Published
2020
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8. The reaction 48Ca + 248Cm → 296116* studied at the GSI-SHIP

Author

Hofmann, S., Heinz, S., Mann, R., Maurer, J., Khuyagbaatar, J., Ackermann, D., Antalic, S., Barth, W., Block, M., Burkhard, H. G., Comas, V. F., Dahl, L., Eberhardt, K., Gostic, J., Henderson, R. A., Heredia, J. A., Heßberger, F. P., Kenneally, J. M., Kindler, B., Kojouharov, I., Kratz, J. V., Lang, R., Leino, M., Lommel, B., Moody, K. J., Münzenberg, G., Nelson, S. L., Nishio, K., Popeko, A. G., Runke, J., Saro, S., Shaughnessy, D. A., Stoyer, M. A., Thörle-Pospiech, P., Tinschert, K., Trautmann, N., Uusitalo, J., Wilk, P. A., and Yeremin, A. V.

Published
2012
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10. Bimodal fission in binary and ternary spontaneous fission of 252Cf

Author

Fong, D., Hamilton, J. H., Ramayya, A. V., Hwang, J. K., Goodin, C., Li, K., Kormicki, J., Rasmussen, J. O., Luo, Y. X., Wu, S. C., Lee, I. Y., Daniel, A. V., Ter-Akopian, G. M., Popeko, G. S., Fomichev, A. S., Rodin, A. M., Oganessian, Yu. Ts., Jandel, M., Kliman, J., Krupa, L., Cole, J. D., Stoyer, M. A., Donangelo, R., and Ma, W. C.

Published
2006
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11. Collective bands in 104,106,108Mo

Author

Jones, E. F., Gore, P. M., Zhu, S. J., Hamilton, J. H., Ramayya, A. V., Hwang, J. K., Xu, R. Q., Yang, L. M., Li, K., Jiang, Z., Zhang, Z., Xiao, S. D., Zhang, X. Q., Ma, W. C., Cole, J. D., Drigert, M. W., Lee, I. Y., Rasmussen, J. O., Luo, Y. X., and Stoyer, M. A.

Published
2006
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12. Soft chiral vibrations in 106Mo

Author

Zhu, S. J., Hamilton, J. H., Ramayya, A. V., Gore, P. M., Rasmussen, J. O., Dimitrov, V., Frauendorf, S., Xu, R. Q., Hwang, J. K., Fong, D., Yang, L. M., Li, K., Chen, Y. J., Zhang, X. Q., Jones, E. F., Luo, Y. X., Lee, I. Y., Ma, W. C., Cole, J. D., Drigert, M. W., Stoyer, M., Ter-Akopian, G. M., and Daniel, A. V.

Published
2005
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14. New elements from Dubna

Author

Oganessian, Yu. Ts., Utyonkov, V. K., Lobanov, Yu. V., Abdullin, F. Sh., Polyakov, A. N., Shirokovsky, I. V., Tsyganov, Yu. S., Gulbekian, G. G., Bogomolov, S. L., Gikal, B. N., Mezentsev, A. N., Iliev, S., Subbotin, V. G., Sukhov, A. M., Voinov, A. A., Buklanov, G. V., Subotic, K., Zagrebaev, V. I., Itkis, M. G., Patin, J. B., Moody, K. J., Wild, J. F., Stoyer, M. A., Stoyer, N. J., Shaughnessy, D. A., Kenneally, J. M., Wilk, P. A., and Lougheed, R. W.

Published
2005
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15. Angular momenta of fission fragments in the α-accompanied fission of 252Cf

Author

Jandel, M., Kliman, J., Krupa, L., Morháč, M., Hamilton, J. H., Kormicki, J., Ramayya, A. V., Hwang, J. K., Luo, Y. X., Fong, D., Gore, P., Ter-Akopian, G. M., Oganessian, Yu. Ts., Rodin, A. M., Fomichev, A. S., Popeko, G. S., Daniel, A. V., Rasmussen, J. O., Macchiavelli, A. O., Stoyer, M. A., Donangelo, R., and Cole, J. D.

Published
2005
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16. New data on the ternary fission of 252Cf from the Gammasphere facility

Author

Ter-Akopian, G. M., Daniel, A. V., Fomichev, A. S., Popeko, G. S., Rodin, A. M., Oganessian, Yu. Ts., Hamilton, J. H., Ramayya, A. V., Kormicki, J., Hwang, J. K., Fong, D., Gore, P., Cole, J. D., Jandel, M., Kliman, J., Krupa, L., Rasmussen, J. O., Lee, I. Y., Macchiavelli, A. O., Fallon, P., Stoyer, M. A., Donangelo, R., Wu, S. -C., and Greiner, W.

Published
2004
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17. Identification of gamma transitions from He and Be ternary fission fragments

Author

Hwang, J. K., Fong, D., Ramayya, A. V., Hamilton, J. H., Jandel, M., Beyer, C. J., Kormicki, J., Luo, Y. X., Gore, P., Kliman, J., Krupa, L., Morhac, M., Ter-Akopian, G. M., Oganessian, Yu. Ts., Rodin, A. M., Fomichev, A. S., Popeko, G. S., Daniel, A. V., Rasmussen, J. O., Macchiavelli, A. O., Lee, I. Y., Stoyer, M. A., Donangelo, R., and Cole, J. D.

Published
2003
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18. Synthesis of superheavy nuclei in 48Ca+244Pu interactions

Author

Oganessian, Yu. Ts., Utyonkov, V. K., Lobanov, Yu. V., Abdullin, F. Sh., Polyakov, A. N., Shirokovsky, I. V., Tsyganov, Yu. S., Gulbekian, G. G., Bogomolov, S. L., Gikal, B. N., Mezentsev, A. N., Iliev, S., Subbotin, V. G., Sukhov, A. M., Ivanov, O. V., Buklanov, G. V., Subotic, K., Itkis, M. G., Moody, K. J., Wild, J. F., Stoyer, N. J., Stoyer, M. A., and Lougheed, R. W.

Published
2000
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20. A new phenomenon—shifted identical bands and new region of stable octupole deformation

Author

Hamilton, J. H., Jones, E. F., Gore, P. M., Ramayya, A. V., Dodder, R. S., Beyer, C. J., Hwang, J. K., Zhang, X. Q., Zhu, S. J., De Lima, A. P., Kormicki, J., Cole, J. D., Aryaeinejad, R., Ma, W. C., Ter-Akopian, G. M., Oganessian, Yu. Ts., Daniel, A. V., Rasmussen, J. O., Asztalos, S. J., Lee, I. Y., Macchiavelli, A. O., Stoyer, M. A., Lougheed, R. W., Prussin, S. G., and Donangelo, R.

Published
1998
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21. Beta Radiation Hardness of GYGAG(Ce) Transparent Ceramic Scintillators.

Author

Jarrell, J. T., Cherepy, N. J., Seeley, Z. M., Murphy, J. W., Swanberg, E. L., Voss, L. F., Frye, C. D., Stoyer, M. A., Henderson, R. A., O'Neal, S. P., and Nikolic, R. J.

Subjects
RADIATION, SCINTILLATORS, LIGHT absorption, HARDNESS, TRANSPARENT ceramics, ABSORPTION spectra, BETA rays
Abstract

GYGAG(Ce) transparent ceramic garnet scintillators were irradiated with electrons from 0.5 to 2 MeV with fluences from $10^{16}\,\,\text{e}^{-}$ /cm2 to $10^{19}\,\,\text{e}^{-}$ /cm2, corresponding to doses from 0.3 to 310 Gigarad. Absorption spectra were measured before and after irradiations. Light yields from alpha, beta, and gamma excitations were measured before and after irradiation and compared to preirradiation values to gain a deeper understanding of how electron irradiations can affect light yield, as well as defects generated in both the surface and bulk. Within experimental error, no degradation in light yield was observed for the electron-irradiated samples, as measured via beta or gamma excitation, with minimal degradation observed via alpha excitation. A small increase in optical absorption near the wavelength of emission was observed following the largest dose irradiation. These results suggest that GYGAG(Ce) is radiation hard to electron irradiation up to $10^{19}\,\,\text{e}^{-}$ /cm2 and doses up to 310 Gigarad. This robustness to irradiation indicates that transparent ceramic garnets may prove useful for applications such as scintillation-based nuclear batteries by allowing for higher energy beta emitters, increased power densities, and enabling long service lifetimes. [ABSTRACT FROM AUTHOR]

Published
2022
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22. Identical and shifted identical bands

Author

Dodder, R. S., Jones, E. F., Hamilton, J. H., Ramayya, A. V., Gore, P., Beyer, C. J., de Lima, A. P., Hwang, J. K., Zhang, X. Q., Zhu, S. J., Lu, Q. H., Ginter, T., Babu, B. R. S., Wang, M. G., Kormicki, J., Deng, J. K., Sh, D., Cole, J. D., Aryaeinejad, R., Butler-Moore, K., Drigert, M. W., Ma, W. C., Ter-Akopian, G. M., Oganessian, Yu. Ts., Daniel, A. V., Rasmussen, J. O., Asztalos, S. J., Lee, I. Y., Machiavelli, A. O., Stoyer, M. A., Lougheed, R. W., Dardenne, Y. X., Prussin, S. G., and Donangelo, R.

Published
1997
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23. Cold binary and ternary fragmentations in spontaneous fission of252Cf

Author

Ramayya, A. V., Hamilton, J. H., Hwang, J. K., Peker, L. K., Kormicki, J., Babu, B. R. S., Ginter, T. N., Sandulescu, A., Florescu, A., Carstoiu, F., Greiner, W., Ter-Akopian, G. M., Oganessian, Yu. Ts., Daniel, A. V., Ma, W. C., Varmette, P. G., Rasmussen, J. O., Asztalos, S. J., Chu, S. Y., Gregorich, K. E., Macchiavelli, A. O., Macleod, R. W., Cole, J. D., Aryaeinejad, R., Butler-Moore, K., Drigert, M. W., Stoyer, M. A., Bernstein, L. A., Lougheed, R. W., Moody, K. J., Prussin, S. G., Zhu, S. J., Griffin, H. C., and Donangelo, R.

Published
1997
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25. Study of the properties of the superheavy nuclei Z = 117 produced in the 249Bk + 48Ca reaction

Author

Oganessian Yu. Ts., Abdullin F. Sh., Alexander C., Binder J., Boll R. A., Dmitriev S. N., Ezold J., Felker K., Gostic J. M., Grzywacz R. K., Hamilton J. H., Henderson R. A., Itkis M. G., Miernik K., Miller D., Moody K. J., Polyakov A. N., Ramayya A. V., Roberto J. B., Ryabinin M. A., Rykaczewski K. P., Sagaidak R. N., Shaughnessy D. A., Shirokovsky I. V., Shumeiko M. V., Stoyer M. A., Stoyer N. J., Subbotin V. G., Sukhov A. M., Tsyganov Yu. S., Utyonkov V. K., Voinov A. A., and Vostokin G. K.

Subjects
Physics, QC1-999
Abstract

The reaction of 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of element 117 on a larger number of events. The experiments were performed at five projectile energies and with a total beam dose of 48Ca of about 4.6×1019. Two isotopes 293,294117 were synthesized in the 249Bk+48Ca reaction, providing excitation functions and α-decay spectra of the produced isotopes that establishes these nuclei to be the products of the 4n- and 3n-evaporation channels, respectively. Decay properties of 293,294117 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time in 2010. The new 289115 events, populated by α decay of 293117, demonstrate the same decay properties as those observed for 289115 produced in the 243Am(48Ca,2n) reaction thus providing crossbombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf – a result of the in-growth of 249Cf in the 249Bk target.

Published
2014
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29. Structure of neutron-rich even-even 124, 126Cd

Author

Kautzsch, T., Wöhr, A., Walters, W. B., Kratz, K. -L., Pfeiffer, B., Hannawald, M., Shergur, J., Arndt, O., Hennrich, S., Falahat, S., Griesel, T., Keller, O., Aprahamian, A., Brown, B. A., Mantica, P. F., Stoyer, M. A., Ravn, H. L., CHICO/Gammasphere Collaborations, Rochester, and the ISOLDE IS333

Published
2005
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32. Investigations of short half-life states from SF of 252Cf

Author

Fong, D., Hwang, J. K., Ramayya, A. V., Hamilton, J. H., Beyer, C. J., Li, K., Gore, P. M., Jones, E. F., Luo, Y. X., Rasmussen, J. O., Zhu, S. J., Wu, S. C., Lee, I. Y., Fallon, P., Stoyer, M. A., Asztalos, S. J., Ginter, T. N., Cole, J. D., Ter-Akopian, G. M., Daniel, A., and Donangelo, R.

Published
2005
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36. Selenium-iodide: A low melting point eutectic semiconductor.

Author

Voss, L. F., Murphy, J. W., Shao, Q., Henderson, R. A., Frye, C. D., Stoyer, M. A., and Nikolic, R. J.

Subjects
SELENIUM compounds, LIQUID semiconductors, ELECTRIC power production, HETEROJUNCTIONS, OPTICAL measurements
Abstract

Inorganic liquid semiconductors are of interest in harsh radiological environments, flexible electronics, and for direct printing of semiconductor devices. Many elemental and compound liquid semiconductors exist, although the lowest melting point is observed for Se at 221 °C. Recently, reports of liquid Se-S systems have shown betavoltaic and alphavoltaic power generation as a liquid with a reduced melting point of 105 °C. Here, we show the ability to depress the melting point to 57 °C by using equal atomic fractions of selenium and iodine while maintaining semiconducting behavior. A heterojunction structure using ITO and n-GaN as the contacts was selected based on chemical compatibility and predicted band lineups. Electrical and optical measurements were used to deduce the electronic and transport properties of the mixture. [ABSTRACT FROM AUTHOR]

Published
2018
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38. Collection of solid and gaseous samples to diagnose inertial confinement fusion implosions.

Author

Stoyer, M. A., Velsko, C. A., Spears, B. K., Hicks, D. G., Hudson, G. B., Sangster, T. C., and Freeman, C. G.

Subjects
*PLASMA gases, *INERTIA (Mechanics), *NOBLE gases, *INERTIAL confinement fusion, *COPPER
Abstract

Collection of representative samples of debris following inertial confinement fusion implosions in order to diagnose implosion conditions and efficacy is a challenging endeavor because of the unique conditions within the target chamber such as unconverted laser light, intense pulse of x-rays, physical chunks of debris, and other ablative effects. We present collection of gas samples following an implosion for the first time. High collection fractions for noble gases were achieved. We also present collection of solid debris samples on flat plate collectors. Geometrical collection efficiencies for Au hohlraum material were achieved and collection of capsule debris (Be and Cu) was also observed. Asymmetric debris distributions were observed for Au and Be samples. Collection of Be capsule debris was higher for solid collectors viewing the capsule through the laser entrance hole in the hohlraum than for solid collectors viewing the capsule around the waist of the hohlraum. Collection of Au hohlraum material showed the opposite pattern: more Au debris was collected around the waist than through the laser entrance hole. The solid debris collectors were not optimized for minimal Cu backgrounds, which limited the conclusions about the symmetry of the Cu debris. The quality of the data limited conclusions on chemical fractionation effects within the burning, expanding, and then cooling plasma. [ABSTRACT FROM AUTHOR]

Published
2012
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39. ODD-PARITY BANDS OF 108,110,112Ru.

Author

LUO, Y. X., ZHU, S. J., HAMILTON, J. H., RAMAYYA, A. V., GOODIN, C., LI, K., CHE, X. L., HWANG, J. K., LEE, I. Y., JIANG, Z., TER-AKOPIAN, G. M., DANIEL, A. V., STOYER, M. A., DONANGELO, R., FRAUENDORF, S., DIMITROV, V., JING-YE ZHANG, COLE, J. D., STONE, N. J., and RASMUSSEN, J. O.

Subjects
GAMMA rays, GAMMASPHERE, PARTICLES (Nuclear physics), ELECTROMAGNETIC waves, NUCLEAR physics
Abstract

Two similar sets of odd-parity bands are observed in each of three even–even neighbors, 108,110,112Ru, from a study of prompt spontaneous-fission gamma rays at Gammasphere. A careful study of the odd-parity levels of these nuclei shows evidence for the features of chiral doubling. Comparisons are made with reported other candidates for chiral doubling. [ABSTRACT FROM AUTHOR]

Published
2009
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40. EVEN-PARITY BANDS OF 108, 110, 112Ru.

Author

ZHU, S. J., LUO, Y. X., HAMILTON, J. H., RAMAYYA, A. V., CHE, X. L., JIANG, Z., HWANG, J. K., WOOD, J. L., STOYER, M. A., DONANGELO, R., COLE, J. D., GOODIN, C., and RASMUSSEN, J. O.

Subjects
PARTICLES (Nuclear physics), NUCLEAR fission, GAMMASPHERE, NUCLEAR reactions, NUCLEAR physics
Abstract

High-spin, even-parity bands in neutron-rich 108, 110, 112Ru nuclei were reinvestigated and considerably expanded by measuring many-fold prompt γ-ray coincidence events following the spontaneous fission of 252Cf with Gammasphere. Our high statistics data allow us to detect weaker transitions and bands not previously published. Also, gamma branching ratios, which are important for theory, are carefully measured from all levels. In 110Ru, we find a doubling of levels for both ground and quasi-gamma bands above the 8+ levels. There are likely two-phonon quasi-gamma bands in 110, 112Ru, as well as a bandhead level in 108Ru. The odd–even spin energy band staggering observed in the quasi-gamma bands in 108, 110, 112Ru and the doubling of levels in 110Ru present a challenge to theory. [ABSTRACT FROM AUTHOR]

Published
2009
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41. Prompt radiochemistry at the National Ignition Facility (invited).

Author

Grim, G. P., Bradley, P. A., Bredeweg, T. A., Keksis, A. L., Fowler, M. M., Hayes, A. C., Jungman, G., Obst, A. W., Rundberg, R. S., Vieira, D. J., Wilhelmy, J. B., Bernstein, L. A., Cerjan, C. J., Fortner, R. J., Moody, K. J., Schneider, D. H., Shaughnessy, D. A., Stoeffl, W., and Stoyer, M. A.

Subjects
RADIOCHEMISTRY, PARTICLES (Nuclear physics), DEUTERIUM, TRITIUM, FUSION (Phase transformation), MATHEMATICAL models, PROTONS, HELIUM
Abstract

Understanding mix in inertial confinement fusion (ICF) experiments at the National Ignition Facility requires the diagnosis of charged-particle reactions within an imploded target. Radiochemical diagnostics of these reactions are currently under study by scientists at Los Alamos and Lawrence Livermore National Laboratories. Measurement of these reactions requires assay of activated debris and tracer gases from the target. Presented below is an overview of the prompt radiochemistry diagnostic development efforts, including a discussion of the reactions of interest as well as the progress being made to collect and count activated material. [ABSTRACT FROM AUTHOR]

Published
2008
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43. Collective bands in 104,106,108Mo.

Author

Jones, E. F., Gore, P. M., Zhu, S. J., Hamilton, J. H., Ramayya, A. V., Hwang, J. K., Xu, R. Q., Yang, L. M., Li, K., Jiang, Z., Zhang, Z., Xiao, S. D., Zhang, X. Q., Ma, W. C., Cole, J. D., Drigert, M. W., Lee, I. Y., Rasmussen, J. O., Luo, Y. X., and Stoyer, M. A.

Subjects
MOMENTS of inertia, SPONTANEOUS fission, GAMMASPHERE, ANGULAR momentum (Nuclear physics), MOLYBDENUM, TRANSPLUTONIUM elements, CHIRALITY, PHONONS
Abstract

We have used our analysis of γ-γ-γ data (5.7 × 1011 triples and higher folds) taken with Gammasphere from prompt γ rays emitted in the spontaneous fission of 252Cf to study the collective bands in 104,106,108Mo. The one-phonon and two-phonon γ-vibrational bands and known two-quasiparticle bands in neutron-rich 104,106Mo were extended to higher spins. The one-and two-phonon γ-vibrational bands have remarkably close energies for transitions from the same spin states and identical moments of inertia. Several new bands are observed and are proposed as quasiparticle bands in 104,106Mo, along with the first β-type vibrational band in 106Mo. The quasiparticle bands have essentially constant moments of inertia near the rigid-body value that indicate blocking of the pairing interaction. Candidates for chiral doublet bands in 106Mo are strong. These are the first reported chiral vibrational bands in an even-even nucleus. [ABSTRACT FROM AUTHOR]

Published
2006
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44. Angular momenta of fission fragments in the α-accompanied fission of252Cf.

Author

Jandel, M., Kliman, J., Krupa, L., Morháč, M., Hamilton, J. H., Kormicki, J., Ramayya, A. V., Hwang, J. K., Luo, Y. X., Fong, D., Gore, P., Ter-Akopian, G. M., Oganessian, Yu. Ts., Rodin, A. M., Fomichev, A. S., Popeko, G. S., Daniel, A. V., Rasmussen, J. O., Macchiavelli, A. O., and Stoyer, M. A.

Subjects
ANGULAR momentum (Nuclear physics), NUCLEAR moments, NUCLEAR fission in art, PARTICLES (Nuclear physics), NUCLEAR physics
Abstract

For the first time, average angular momenta of the ternary fission fragments100, 102Zr,106Mo,144, 146Ba and138, 140, 142Xe from the α-accompanied fission of252Cf were obtained from relative intensities of prompt γ-ray transitions with the use of the statistical model calculation. Average values of the angular momenta were compared with the corresponding values for the same fission fragments from the binary fission of252Cf. Results indicate the presence of a decreasing trend in the average values of angular momenta induced in ternary fission fragments compared to the same binary fission fragments. On the average, the total angular momentum extracted for ternary fission fragments is ∼1.4 ℏ lower than in binary fission. Consequently, results indicate that the mechanism of the ternary α-particles emission may directly effect an induction of angular momenta of fission fragments, and possible scenarios of such mechanisms are discussed. Further, the dependence of the angular momenta of106Mo and140Xe on the number of emitted neutrons from correlated pairs of primary fragments was obtained also showing a decreasing dependence of average angular momenta with increasing number of emitted neutrons. Consequences are briefly discussed. [ABSTRACT FROM AUTHOR]

Published
2005
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46. Nuclear diagnostics for petawatt experiments (invited).

Author

Stoyer, M. A., Sangster, T. C., Henry, E. A., Cable, M. D., Cowan, T. E., Hatchett, S. P., Key, M.H., Moran, M. J., Pennington, D. M., Perry, M. D., Phillips, T. W., Singh, M. S., Snavely, R. A., Tabak, M., and Wilks, S. C.

Subjects
*LASERS in plasma diagnostics, *PLASMA diagnostics
Abstract

With the operation of successively more intense and powerful lasers, such as the NOVA petawatt laser with I∼3×10[sup 20] W/cm[sup 2], several novel (to laser physics) nuclear diagnostics were used to determine the nature of the laser/matter interaction at the target surface. A broad beam of hot electrons, whose centroid varied from shot to shot, width was remarkably constant, and intensity was about 40% of the incident laser energy was observed. New nuclear phenomenon included photonuclear reactions [e.g., (γ,xn)], photofission of [sup 238]U and intense beams of ions. Photonuclear reactions were observed and quantified in Cu, Ni, and Au samples, and produced activation products as neutron deficient as [sup 191]Au [a (γ,6n) reaction!], requiring gamma rays exceeding 50 MeV in energy. The spectral features of the gamma-ray source have been investigated by comparing activation ratios in Ni and Au samples, and angular distributions of higher energy photons have been measured with activation of spatially distributed Au samples. Extraordinarily intense beams of charged particles (primarily protons) were observed normal to the rear surface of the target and quantified using the charged particle reaction [sup 48]Ti(p,n)[sup 48]V, radiochromic film and CR39 plastic track detectors. Approximately 3×10[sup 13] protons, with energies up to 55 MeV were observed in some experiments. Collimation of this beam increases with increasing proton energy. Correlations of activation with laser performance will be discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2001
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47. Petawatt laser system and experiments.

Author

Pennington, D.M., Brown, C.G., Cowan, T.E., Hatchett, S.P., Henry, E., Herman, S., Kartz, M., Key, M., Koch, J., MacKinnon, A.J., Perry, M.D., Phillips, T.W., Roth, M., Sangster, T.C., Singh, M., Snavely, R.A., Stoyer, M., Stuart, B.C., and Wilks, S.C.

Abstract

We have developed a hybrid Ti:sapphire-Nd:glass laser system that produces more than 1.5 PW of peak power. The system has produced up to 680 J of energy on target at 1054 nm in a compressed 440±20-fs pulse by use of 94-cm diffraction gratings. A focused irradiance of up to 6×1020 W/cm2 was achieved using an on-axis parabolic mirror and adaptive optic wavefront control. Experiments with the petawatt laser system focused the beam on solid targets and produced a strongly relativistic interaction. Energy content, spectra, and angular pattern of the photon, electron, and ion radiations were diagnosed in a number of ways, including several nuclear activation techniques. Approximately 40-50% of the laser energy was converted to broadly beamed hot electrons, with an associated bremsstrahlung beam. High luminosity ion beams were observed normal to the rear surface of various targets with energies up to ≥55 MeV, representing ∼7% of the laser energy. These and other results are presented. [ABSTRACT FROM PUBLISHER]

Published
2000
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50. Random probability analysis of recent 48Ca experiments.

Author

Stoyer, M. A., Patin, J. B., Kenneally, J. M., Moody, K. J., Shaughnessy, D. A., Stoyer, N. J., Wild, J. F., Wilk, P. A., Utyonkov, V. K., and Oganessian, Yu. Ts.

Subjects
*MONTE Carlo method, *NUCLIDES, *PROBABILITY theory, *NUCLEAR physics, *PHYSICS
Abstract

A Monte Carlo random probability analysis developed at LLNL for heavy element research was performed for recent experiments aimed at the synthesis of nuclides with Z≥112 and N≥170, to estimate the probability that observed decay chains were a result of a random event. Low probabilities ( < 10-4% for most decay chains) were found. [ABSTRACT FROM AUTHOR]

Published
2005
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