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LEA-workshop Catania, 13-15 October 2008

Indirect reactions for astrophysics @ the Tandem-Alto Pole of Orsay. Fa ïrouz Hammache (IPN-Orsay, France). LEA-workshop Catania, 13-15 October 2008. Nuclear astrophysics using indirect reactions @ Tandem-Orsay (end 2005-2008). Collaboration. Aim of the experiments. Indirect Method.

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LEA-workshop Catania, 13-15 October 2008

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  1. Indirect reactions for astrophysics @ the Tandem-Alto Pole of Orsay Faïrouz Hammache (IPN-Orsay, France) LEA-workshop Catania, 13-15 October 2008

  2. Nuclear astrophysics using indirect reactions @ Tandem-Orsay(end 2005-2008) Collaboration Aim of the experiments Indirect Method IPN-CSNSM-ULB-GANIL-GSI 13C(a,n)16O Neutron source in AGB stars (1-3 M) 13C(7Li,t)17O-transfer reaction PRC77 (2008) 042801 IPN-LT(BEJAIA)-CSNSM-ULB-GANIL-GSI 12C(a,g)16O He-burning in massive stars 12C(7Li,t)16O-transfer reaction Analysis in progress IPN-CSNSM-LNS-GANIL-SUBATECH 25Al(p,g)26Si 26Al synthesis in Novae 24Mg(3He,n)26Si* Analysis in progress

  3. Study of 13C(a,n)16Oreaction via 13C(7Li,t)17O transfer reaction IPNO-CSNSM-ULB-GANIL-GSI s-process nucleosynthesis (n,) half of the heavy elements in Univers  90<A<209 low-mass AGB stars 1-3 M (Temperatures108K) He shell Hydrogen shell CO core 12C(p,)13N(+)13C Convective envelope 13C pocket 13C(,n)16O He intershell Neutron source 13C(,n)16O dYn/dt=Y13C.Y4He..NA<>13C(,n)-YX.Yn..NA<>X(n,)

  4. Status of 13C(a,n)16Oreaction Gamow peak ~190 keV100 pb S-factor S(E)=E(E)exp(2) S(E)=E(E)exp(2) Drotleff et al. (Sa=0.7)A (Sa=0.0)B Ecm 7.166 6.862 ? S?  6.359 6.356½+ 13C+ 5.939½- n Ecm (keV) 4.5543/2- 4.143 3.8415/2- 16O+n S=0.3-0.7 (theoretical values) Enough neutrons s-process nucleosynthesis 17O  Kubono et al. 13C(6Li,d)17O(DWBA) S(exp)0.011!!!  Keeley et al. reanalysis of Kubono data S(exp)=0.4 factor 40 ?!?!?!

  5. Study of 17O states by 13C(7Li,t)17O -transfer reaction SPLIT-POLE spectrometer (Orsay-Tandem) E tritons 13C(7Li,t)17O t 13C target 80 g/cm2 pos 7Li @ 34,28MeV Position gas chamber (B) Faraday Cup E proportional counter E-E monitor  E7Li = 28 MeV  Transfer measurements on 13C and 12C targets[0°-32°] 13C(7Li,7Li)13C measurements  E7Li = 34 MeV • Transfer measurements on 13C and 12C targets [0°-32°] • 13C(7Li,7Li)13C data @ 34 MeV from Schumacher et al. NPA 212 (1973) 573

  6. Comparison between our data and FRESCO calculations  S assume :Sa=1for 7Li For 3.055 MeV Sa=0.260.06 Furutani et al. (S=0.25) no need to add compound nucleus component Clark et al. S=0.25 S=0.35 S=0.290.11 in agreement with Kelley’s value 6.356 (1/2+) 6.356 (1/2+)

  7. 13C(,n)16O Astrophysical S-factor S-factor(ORSAY) @ 190 keV  1.40.5 106 MeV-b (S1/2+ is about 70% of the total)  The contribution of the 6.356 (1/2+) subthreshold state is dominant at astrophysical energies Orsay 3/2+ (843 keV) Drotleff 93 Brune 93 Gamow peak M.G. Pellegriti, F. Hammache et al. PRC 70 (2008) 042801 Orsay range of allowed values for <v>is substancially reduced in comparison to Nacre compilation

  8. 12C(a,g)16O the Holy Grail of Nuclear Astrophysics IPNO-LT(BEJAIA)-CSNSM-ULB-GANIL-GSI Main reactions: 312C & 12C(a,g)16O 12C/16O abundance ratio nucleosynthesis & subsequent stellar evolution of massive stars 12C(a,g)16O in stellar helium burning @ T=0.2 GK BUT: E0=300 keV, (E0) ~ 10-8 nb 2? Sa s(E0) is expected to be dominated by E1 & E2 transitions. 2?Sa

  9. Sa values for 6.05, 6.13, 6.92 & 7.12 MeV states of 16O J(Ex, MeV) 6Li 48 MeV (1998) 6Li 42 MeV (1978) 6Li 90 MeV (1980) 7Li 34 MeV (1978) 0+ (6.05) 0.120.05 0.81 3.58 0.12 0.04 3- (6.13) 0.290.15 1.08 0.52 0.09 0.04 2+ (6.92) 0.37 0.11 1.35 0.82 0.18 0.05 1- (7.12) 0.160.05 1.08 0.86 0.07 0.05 • Experimental problems ? • Analysis procedure ? • optical potential parameters ? • overlap of interaction mechanism, multi-step effects?

  10. Study of 6.92 & 7.12 MeV 16O states by 12C(7Li,t)16O -transfer reaction @ Tandem-Orsay 12C(7Li,t)16O measured spectrum @ 9 degree FRDWBA calculation still in progress Very preliminary d/dcm Thesis of N. Oulebsir (Béjaïa University)

  11. 26Al nucleosynthesis in Novae IPNO-CSNSM-LNS-GANIL-SUBATECH COMPTEL Map of Galaxy @ 1.809 MeV g-ray Stellar sources of 26Al:  Massive stars (SNII, Wolf Rayet) AGB stars Novae 25Al(p,g)26Sicompetes with 25Al(b+) 25Mg (t1/2 = 7.183 s ) 25Al(p,g)26Sireaction rate • has large uncertainties  26Al yield abundance is unknown Two sequences to produce 26Al (T1/2=7.2 105 yr): 26Si 25Al 26Al m 1.809 MeV Spectroscopy of 26Si* via 24Mg(3He,n)26Si* reaction g.s 24Mg 25Mg 26Mg

  12. 24Mg(3He,n)26Si*(g)26Si measurement ONLINE Set-up: Pulsed 3He beam @ 7.9 MeV I=60 pnA Target: 150 g/cm2 of 24Mg Measured g-spectrum 511 keV 4th Ex  1st Ex 972 keV 1st Ex of 26Si @ 1795 keV 4 Ge detectors Analysis in progress E (keV) ToF spectrum (n-g coin) g prompt region of interest 36 EDEN detectors ToF (au)

  13. Futur projects: AGB stars @ Tandem-Orsay • AGB stars • 22Ne(a,n)25Mg: neutron source in AGB stars of intermediate mass •  2aof low-energy resonances, J of subthreshold resonances •  22Ne(7Li,t)26Mg @ Split-Pole  14C(a,g)18O&19F(a,p)22Ne: 19F nuclesynthesis • 2aof low-energy resonances  Transfer reactions using MUST2 detectors or Split-Pole

  14. Study of 13C(a,n)16O & 12C(a,g)16O reactions via (7Li,t) -transfer reactions sss F.Hammache, M. G. Pellegriti*, P. Roussel, L. Audouin, D. Beaumel, S. Fortier (IPN-Orsay) N. Oulebsir(LT-Béjaïa) J. Kiener, A. Lefebvre-Schuhl, V. Tatischeff (CSNSM-Orsay) P. Descouvemont (ULB-Brussels) L. Gaudefroy (GANIL-Caen) M. Stanoiu (GSI-Darmstadt) * LNS-Catania Spectroscopy of 26Si via 24Mg(3He,n)26Si* sssN. De Séréville, F.Hammache, S. Giron, S. Fortier, P. Roussel, M Baptiste, D. Beaumel, M. Chabot, M. Ferraton, S. Franchoo, F. Maréchal, C. Petrache, J.A. Scarpaci, I. Stefan, D. Verney (IPN-Orsay) A. Coc, J. Duprat, C. Hamadache, J. Kiener, A. Lefebvre-Schuhl (CSNSM-Orsay) J.C. Dalouzy, F. Grancy, F. De Oliveira, J.C. Thomas (GANIL) L. Lamia, G. Pizzone, S. Romano (LNS-Catania) M. Fallot, L. Giot (SUBATECH)

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