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3. E1 and E2 capture cross section and astrophysical reaction rate of the key reaction 12C( α, γ) 16O

Author

Hammer, J.W., Fey, M., Kunz, R., Kiener, J., Tatischeff, V., Haas, F., Weil, J.L., Assunção, M., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Hammache, F., Harissopulos, S., Korichi, A., Krmpotić, E., Le Du, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Papka, P., Paradellis, T., Rousseau, M., Rowley, N., Staudt, G., and Szilner, S.

Published
2005
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4. New determination of the 12C( α, γ) 16O reaction rate from γ-ray angular distribution measurements

Author

Hammer, J.W., Fey, M., Kunz, R., Kiener, J., Tatischeff, V., Haas, F., Weil, J.L., Assunção, M., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Hammache, F., Harissopulos, S., Korichi, A., Krmpotić, E., Le Du, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Papka, P., Paradellis, T., Rousseau, M., Rowley, N., Staudt, G., and Szilner, S.

Published
2005
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7. E1 and E2 S factors of C-12(alpha,gamma(0))O-16 from gamma-ray angular distributions with a 4 pi-detector array

Author

Assuncao, M., Fey, M., Lefebvre-Schuhl, A., Kiener, J., Tatischeff, V., Hammer, J.W., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Haas, F., Hammache, F., Hannachi, F., Harissopulos, S., Korichi, A., Kunz, R., LeDu, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Paradellis, Th., Rousseau, M., Rowley, N., Staudt, G., Szilner, S., Thibaud, J.P., Weil, J.L., and KVI - Center for Advanced Radiation Technology

Subjects
STELLAR ENERGIES, NUCLEOSYNTHESIS, LIGHT-NUCLEI, DYNAMITRON ACCELERATOR, C-12, ESCAPE SUPPRESSED SPECTROMETER, KEY REACTION, ASTROPHYSICAL REACTION-RATE, CROSS-SECTION, MASSIVE STARS
Abstract

A new experiment to determine the thermonuclear cross section of the C-12(alpha,gamma)O-16 reaction has been performed in regular kinematics using an intense alpha-particle beam of up to 340 mu A from the Stuttgart DYNAMITRON. For the first time, a 4 pi-germanium-detector setup has been used to measure the angular distribution of the gamma rays at all angles simultaneously. It consisted of an array of nine EUROGAM high-purity Ge detectors in close geometry, actively shielded individually with bismuth germanate crystals. The C-12 targets were isotopically enriched by magnetic separation during implantation. The depth profiles of the implanted carbon in the C-12 targets were determined by Rutherford backscattering for purposes of cross-section normalization and absolute determination of the E1 and E2 S factors. Angular distributions of the gamma decay to the O-16 ground state were measured in the energy range E-c.m.=1.30-2.78 MeV and in the angular range (lab.) 30 degrees-130 degrees. From these distributions, astrophysical E1 and E2 S-factor functions vs energy were calculated, both of which are indispensable to the modeling of this reaction and the extrapolation toward lower energies. The separation of the E1 and E2 capture channels was done both by taking the phase value phi(12) as a free parameter and by fixing it using the results of elastic alpha-particle scattering on C-12 in the same energy range.

Published
2006

8. E1- and E2-S of 12 alpha,gamma 0 16 O from gamma-ray angular distributions with a 4pi detector array

Author

Assuncao, M., Fey, M., Lefebvre-Schuhl, A., Kiener, J., Tatischeff, V., Hammer, J.W., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Haas, F., Hammache, F., Hannachi, F., Harissopulos, S., Korichi, A., Kunz, R., Ledu, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Paradellis, Th., Rousseau, Marc, Rowley, N., Staudt, G., Szilner, S., Thibaud, J.P., Weil, J.L., Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Instituto de Física (IDF), Universidade de São Paulo (USP), Institut für Strahlenphysik (IFS), Universität Stuttgart, Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), Kernfysisch Versneller Instituut (KVI), University of Groningen [Groningen], SNO (SNO), Laurentian University, Institute of Nuclear Physics (INP), N.C.S.R., Gesellschaft für Schwerionenforschung (GSI), Institut de Physique Nucléaire d'Orsay (IPNO), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Physikalisches Institut [Tübingen], Eberhard Karls Universität Tübingen = Eberhard Karls University of Tuebingen, Rudjer Boskovic Institute [Zagreb], Institute of Isotopes (II), Hungarian Academy of Sciences (MTA), Department of Physics (DP), University of Kentucky, Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Eberhard Karls Universität Tübingen, Ruder Boskovi'c Institute (RBI), and Ruder Boskovi'c Institute

Subjects
gamma)16O, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], thermonuclear stellar burning, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], E1 S factor, gamma angular distributions, 4pi gamma Germainum array, nuclear astrophysics, 25.55.-e, 24.30.-v, 26.20.+f, 27.20.+n, 12C(alpha, E2 S factor, cross-section measurements
Abstract

postscript file : 43 pages to appear in PRC : 19 pages in PRC - 1st preprint CSNSM 2004-02; 2nd preprint IPHC 06-001; A new experiment to determine the thermonuclear cross section of the 12C(alpha,gamma_0)16O reaction has been performed in regular kinematics using an intense alpha-particle beam of up to 340 muA from the Stuttgart DYNAMITRON. For the first time a 4pi-Germanium-detector setup has been used to measure the angular distribution of the gamma rays at all angles simultaneously. It consisted of an array of 9 EUROGAM HPGe detectors in close geometry, actively shielded individually with BGO crystals. The 12C targets were isotopically enriched by magnetic separation during implantation. The depth profiles of the implanted carbon in the 12C targets have been determined by Rutherford backscattering for purposes of cross section normalization and absolute determination of the E1 and E2 S factors. Angular distributions of the gamma decay to the 16O ground state have been measured in the energy range E_c.m.= 1.30-2.78 MeV and in the angular range (lab.) 30-130 degre. From these distributions, astrophysical E1 and E2 S-factor functions vs. energy have been calculated, both of which are indispensable for the modeling of this reaction and the extrapolation towards lower energies. The separation of the E1 and E2 capture channels has been done both by taking the phase value phi_12 as a free parameter and by fixing it using the results of elastic alpha-particle scattering on 12C in the same energy range.

Published
2006

9. New determination of the C-12(alpha, gamma)O-16 reaction rate from gamma-ray angular distribution measurements

Author

Hammer, J.W., Fey, M., Kunz, R., Kiener, J., Tatischeff, V., Haas, F., Weil, J.L., Assuncao, M., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Hammache, F., Harissopulos, S., Korichi, A., Krmpotic, E., Le Du, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Papka, P., Paradellis, T., Rousseau, M., Rowley, N., Staudt, G., Szilner, Suzana, and KVI - Center for Advanced Radiation Technology

Subjects
C-12(alpha, gamma)O-16 cross-section, thermonuclear reaction-rates, delayed alpha-spectrum, massive stars, low energies, nucleosynthesis, N-16, NUCLEOSYNTHESIS, C-12(ALPHA,GAMMA)O-16 CROSS-SECTION, DELAYED ALPHA-SPECTRUM, THERMONUCLEAR REACTION-RATES, CONSTRAINTS, NUCLEAR, LOW ENERGIES, MASSIVE STARS
Abstract

no abstract

Published
2005

10. E1 and E2 capture cross section and astrophysical reaction rate of the key reaction C-12(alpha, gamma)O-16

Author

Hammer, J.W, Fey, M., Kunz, R., Kiener, J., Tatischeff, V., Haas, F., Weil, J.L., Assuncao, M., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Hammache, F., Harissopulos, S., Korichi, A., Krmpotic, E., Le Du, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Papka, P., Paradellis, T., Rousseau, M., Rowley, N., Staudt, G., and Szilner, Suzana

Subjects
massive stars, nucleosynthesis, nuclear
Abstract

no abstract

Published
2005

11. New determination of the $^{12}C (\alpha, \gamma)^{16}O$ reaction rate from the gamma-ray angular distribution measurements

Author

Hammer, J.W., Fey, M., Kunz, R., Kiener, J., Tatischeff, V., Haas, F., Weil, J.L., Assuncao, M., Beck, C., Boukari-Pelissie, C., Coc, A., Correia, J.J., Courtin, S., Fleurot, F., Galanopoulos, E., Grama, C., Hammache, F., Harissopulos, S., Korichi, A., Krmpotic, E., Le Du, D., Lopez-Martens, A., Malcherek, D., Meunier, R., Papka, P., Paradellis, Th., Rousseau, Marc, Rowley, N., Staudt, G., Szilner, S., Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches Subatomiques (IReS), and Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS)

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

The astrophysical reaction rate of the key reaction 12C(alpha,gamma)16O has been determined with the +/- 25% accuracy by two direct experiments at the Stuttgart DYNAMITRON in the framework of a large internatiuonal collaboration. The E1 and E2 capture amplitudes were deduced from 37 new gamma angular distributions in the energy range Ecm = 0.89-2.8 MeV. Highest sensitivity at a picobarn level was reached by using either a close 4pi array of 9 EUROGAM Phase II detectors or the GANDI array of 4 large movable Ge detectors. The S-factor values of the S_E1 and S_E2 excitation functions were calculated by a R-matrix analysis considering also elastic alpha-scattering data and the beta-delayed alpha-decay on 16N.

Published
2005

14. New determination of the 12C(α, γ)16O reaction rate from γ-ray angular distribution measurements

Author

Hammer, J.W., primary, Fey, M., additional, Kunz, R., additional, Kiener, J., additional, Tatischeff, V., additional, Haas, F., additional, Weil, J.L., additional, Assunção, M., additional, Beck, C., additional, Boukari-Pelissie, C., additional, Coc, A., additional, Correia, J.J., additional, Courtin, S., additional, Fleurot, F., additional, Galanopoulos, E., additional, Grama, C., additional, Hammache, F., additional, Harissopulos, S., additional, Korichi, A., additional, Krmpotić, E., additional, Le Du, D., additional, Lopez-Martens, A., additional, Malcherek, D., additional, Meunier, R., additional, Papka, P., additional, Paradellis, T., additional, Rousseau, M., additional, Rowley, N., additional, Staudt, G., additional, and Szilner, S., additional

Published
2005
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