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12 C( a,g ) 16 O thermonuclear reaction rate: present status and perspectives

ESF-Athens 2007/12/14. A. Lefebvre-Schuhl. 12 C( a,g ) 16 O thermonuclear reaction rate: present status and perspectives. Problematics Present status Perspectives. A. Lefebvre-Schuhl CSNSM Orsay. December 14th 2007 ESF-Athens. 9.64. 3 -. 0+. 7.65. 3  12 C. 4.44. 2 +.

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12 C( a,g ) 16 O thermonuclear reaction rate: present status and perspectives

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  1. ESF-Athens 2007/12/14 A. Lefebvre-Schuhl 12C(a,g)16O thermonuclear reaction rate: present status and perspectives Problematics Present status Perspectives A. Lefebvre-Schuhl CSNSM Orsay December 14th 2007 ESF-Athens

  2. 9.64 3- 0+ 7.65 3 12C 4.44 2+ 9.59 1- 8.87 2- 7.12 1- (7.16) 6.92 2+ 6.13 3- Influence on: 6.05 • [C]/[O] 12C+4He 16O 0+ • Further hydrostatic burning stages 0+ • Final states of stars 0 12C+4He ESF-Athens 2007/12/14 0+ A. Lefebvre-Schuhl 16O Helium burning

  3. 12C (a, g) 16O E1 : large 1- subthreshold resonance + 1- level below the reaction threshold E2 : Direct capture + 2+ level below the reaction threshold A. Lefebvre-Schuhl T ~ 0.2 x 109 K  E(Gamow peak) ~ 300 keV • (300 keV) 10-17 barn ! Reaction rates  Extrapolation : R- or K-matrix formalism Microscopic cluster models For each contribution: capture to the ground state and to excited states Need of E1, E2 for E*  ground state (g-ray angular distributions) and for E*  excited state ESF-Athens 2007/12/14

  4. ESF-Athens 2007/12/14 Indirect methods : R:79  21 keVb K: 82  26 keVb • b-delayed a-decay of 16N • 16O Coulomb breakup • Transfer reaction, ANC method • Trojan-horse method • b-delayed p-decay of 17Ne SE1(300) A. Lefebvre-Schuhl 16N → b- + 16O → a + 12C Azuma et al. Phys. Rev. C 50, (1994) 1194

  5. 12C targets: isotopically pure and resistant to a-beams : 12C implantation efficient water cooling ESF-Athens 2007/12/14 A. Lefebvre-Schuhl Direct methods in direct kinematics: a-beam, 12C target • g-ray angular distribution : in a few steps (turn table) • simultaneously (4p-array) • Intense a-beam : up to 700 pmA (Stuttgart dynamitron) pulsed a-beams (Tokyo, Karlsruhe) • sophisticated g-ray arrays: angular distribution, background suppression: shieldings or coincidences with pulsed beams

  6. g-ray angular distributions : in a few steps: turn table (as Kunz et al, Fey et al...) simultaneously: 4p-array (as Assunçao et al) ESF-Athens 2007/12/14 Ex : Assunçao et al. PRC 73 (2006) 055801 : « Eurogam » setup g-ray angular distribution at 9 different angles simultaneously with 9 HP-Ge detectors very good energy resolution Ecm eff = 1.310 MeV Compton suppression (active BGO shields) A. Lefebvre-Schuhl Total g efficiency at 10 MeV : 1.2x10-3 in experimental conditions (7 10-3 at 1.33MeV)

  7. c2 Best -> SE1(300) = 7717 keVb Hammer et al. Nucl. Phys. A758 (2005) 363 ESF-Athens 2007/12/14 A. Lefebvre-Schuhl Present SE1 results to the ground state SE1 • R-matrix fits of • a-scattering data • b-delayed a-decay of 16N • the radiative capture data taking into account 3 levels  4 interference combinations

  8. c2 SE2 Best -> SE2(300) = 81  22 keVb Hammer et al.Nucl. Phys. A758 (2005) 363 ESF-Athens 2007/12/14 A. Lefebvre-Schuhl Present SE2 results to the ground state • R-matrix fits of • a-scattering data • the radiative capture data taking into account 5 levels  16 interference combinations

  9. Cascades and Stot • SE1, SE2 to ground state • and the others : g-cascades through: 6.05, 6.92, 7.12 MeV levels High g-ray background: Up to 2006, only based on intensities of the 6.92 MeV and 7.12 MeV or both together g-ray considered as giving the cascade amount:  only an upper limit Results obtained either in direct or inverse kinematics

  10. Cascades to the 6.92 and 7.12 MeV levels x : Kettner et al. Z. Phys. A 308 (1982) 73 - : Redder et al. Nucl.Phys. A462, 385 (1987) 6.92 S6.9(300) =7+13 keVb -4 Buchmann& Barnes Nucl. Phys. A777 (2006) 254 A. Lefebvre-Schuhl FINUSTAR 2 2007/09/12 Redder et al. Nucl.Phys. A462, 385 (1987) S6.9(300) =7 keVb S7.1(300) = 1.3 keVb

  11. 12Cn+ Ecm=2.0MeV s ≈ 10 nb 16Om+ 16O ESF-Athens 2007/12/14 A. Lefebvre-Schuhl Direct methods in inverse kinematics: 12C-beam, 4He-gas target g-ray detection 16O-recoil measurement DE-E European Recoil Separator for Nuclear Astrophysics

  12. ERNA‘s data Schürmann et al. EpJ A 26 (2005) 301 Thanks Schürmann, Kunz, Strieder et al. ESF-Athens 2007/12/14 A. Lefebvre-Schuhl E1,E2, cascades (6.92+7.12) and total contributions R-Matrix calculation Kunz et al. Ap.J. 567 (2002) 643 E1 and E2 data Assunçao et al. PRC 73(2006)055801 and Fey et al. to be published

  13. ESF-Athens 2007/12/14 g-array: BGO A. Lefebvre-Schuhl Detectorof Recoils and Gammas of Nuclearreactions

  14. ESF-Athens 2007/12/14 Cascades to the 6.045 MeV level S6.0(300) = 25+16 keVb -15 A. Lefebvre-Schuhl Matei et al. PRL 97 (2006) 242503 DRAGON TRIUMF Detectorof Recoils and Gammas of Nuclearreactions

  15. ERNA‘s data Schürmann et al. EpJ A 26 (2005) 301 Thanks Kunz, Strieder et al. ESF-Athens 2007/12/14 A. Lefebvre-Schuhl Preliminary results : new R-matrix calculation, Kunz et al. Preliminary results : new R-matrix calculation, Kunz et al.

  16. FINUSTAR 2 2007/09/12 • Buchmann and Barnes • (2006) • All available data • + ERNA +DRAGON • 80  20 keVb • 53+13 keVb • 7+13 keVb (6.92 MeV) • 25+16 keVb (6.05 MeV) -18 -4 -15 (S=165 keVb) A. Lefebvre-Schuhl 3 R-matrix calculations S(300) • E10 • E20 • Casc. • Total • Fey et al • (2004) • 2 experiments + previous • Ecm eff: 0.89-2.8 MeV • 77  17 keVb • 81  22 keVb • 4  4 keVb • 162  39 keVb • NACRE • (1999) • 79  21 keVb • 120  60 keVb

  17. 16N → b- + 16O → a + 12C New measurements to increase the precision on the SE1 R&D R&D A. Lefebvre-Schuhl FINUSTAR 2 2007/09/12 Recoil separators : 2 in use : DRAGON (TRIUMF) and ERNA (Bochum) Detection efficiency : up to 100% of the more probable charge state at the charge equilibrium (50% of the 16O with a poststripper) • - present limitations : intensity through WF, target extension • only the total cross section Future : Dense jet gas vs 12C targets (Coincidences with) a new g-ray detector array (angular distributions, cascades)

  18. Future : Accelerator of intense 4He beam Such as a 3 to 5 MV Pelletron with ECR source With pulsed beams? + a recoil separator (for inverse kinematics studies) with dense jet gas target (R&D needed to reach low energies)

  19. + a new g-ray detector array to separate the transitions enough statistics 27Al (p,g) 28Si Ep = 992 keV Preliminary results : Cimala et al. Kraków, Debrecen, Orsay, Warsaw K 4.74 4.61 4.50 1.78 10.76 7.93 6.02 A Paris detector ? (LaBr3 + CsI) LaBr3(Ce) 2’’x2’’ energy resolution vs efficiency With Ge detectors ? or new ones ? Preliminary results : Cimala et al. Kraków, Debrecen, Orsay Warsaw

  20. Eurogam-detector collaboration M. Assunção, M. Fey, A. Lefebvre-Schuhl, J. Kiener, V. Tatischeff, J.W. Hammer, C. Beck, C. Boukari-Pelissie, A. Coc, J.J. Correia, S. Courtin, F. Fleurot, E. Galanopoulos, C. Grama, F. Haas, F. Hammache, F. Hannachi, S. Harissopulos, A. Korichi, R. Kunz, D. Ledu, A. Lopez-Martens, D. Malcherek, R. Meunier, Th. Paradellis, M. Rousseau, N. Rowley, G. Staudt, S. Szilner, J.P. Thibaud, J.L. Weil CSNSM-Orsay; IfS-Stuttgart; IPHC/IReS-Strasbourg; KVI-Groningen; INP-Athens; GSI-Darmstadt (IPN-Orsay); PI-Tübingen; DP-Lexington (II-Budapest) ERNA’s collaboration L. Gialanella, G. Imbriani, A. Ordine, V. Roca, M. Romano, R. Kunz, A. di Leva, D. Rogalla, C. Rolfs, D. Schürmann, F. Strieder, N. De Cesare, A. D'Onofrio, C. Lubritto, F. Terrasi, A. Lefebvre-Schuhl, J.P. Thibaud, C. Beck, S. Courtin, F. Haas, D. Lebhertz, M.-D. Salsac, F. Hammache, N de Séréville, F. de Oliveira; P. Papka, S. Harissopulos, A. Lagoyannis, Th. Konstantinopoulos INFN & Univ.-Naples; IE3-Bochum; CSNSM-Orsay; IPHC-Strasbourg; IPN-Orsay; GANIL-CAEN; iTLABS; INP-Demokritos PARIS collaboration 100 physicists, engineers and PhD students, 38 institutions from 16 countries and principally : IFJ PAN-Kraków, ATOMKI-Debrecen, CSNSN-Orsay and Univ.-Warsaw

  21. LaBr3(Ce) 2’’x2’’ 0. 10.7  NaI 4’’x4’’ 0. 10.7 

  22. To separate cascades through 7.12, 6.92, 6.05 ? In inverse kinematics, Doppler shift : not too constraining !

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