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The 12 C+ 12 C fusion reaction at stellar energies

The 12 C+ 12 C fusion reaction at stellar energies. Xiaodong Tang (Aggie since Aug. 1997) Joint Institute for Nuclear Astrophysics, UND. That is indeed a pretty interesting paper ! Michael Wiescher Director of Joint Institute for Nuclear Astrophysics.

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The 12 C+ 12 C fusion reaction at stellar energies

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  1. The 12C+12C fusion reaction at stellar energies Xiaodong Tang (Aggie since Aug. 1997) Joint Institute for Nuclear Astrophysics, UND

  2. That is indeed a pretty interesting paper ! Michael Wiescher Director of Joint Institute for Nuclear Astrophysics

  3. Carbon burning processes in the Universe • Carbon burning in the laboratory • Experimental efforts at Notre Dame a) Upper limit for the 12C+12C fusion cross sections b) the 12C(12C,n)23Mg at stellar energies c) direct measurement towards astrophysical relevant energies • Summary

  4. 20Ne+a Light particle: p, n, a Gamma: 440 keV (p channel) 1634 keV (a channel) Fusion residue: 20Ne, 23Na … no success under barrier 23Mg: decay spectroscopy

  5. Molecular resonances in the 12C+12C fusion reaction measured by Almqvist et al., in 1960 The world's first tandem accelerator installed at Chalk River in 1959.

  6. 12C(12C,p)23Na (Q=2.24 MeV) 12C(12C,)20Ne (Q=4.62 MeV) 12C(12C,n)23Mg (Q=-2.62MeV) 10-22 b 10-7 b

  7. Carbon burning in the universe Ignition conditions in type Ia supernovae Nucleosynthesis in massive stars Candidate for Superburst ignition t~10 s 10 hr E(erg)~1039 1041

  8. Crust processes(EC, pycnonuclear fusion) • crust heating • crust conductivity Superburst: ignited by Carbon burning Ashes from rp process (He burning) deposit in the outer crust. Key problem: With the standard rate (CF88), the crust temperature is too low to ignite the carbon fuel!  Add artificial resonance ashes Picture by E. Brown (MSU)

  9. 12C+13C 13C+13C Provide potential to model the gross structure 12C(12C,a)20Ne 12C(12C,a)20Ne 12C(12C,p)23Na Direct measurement The exact cross section 12C(12C,n)23Mg Search the possible Resonances at RCNP 24Mg(a,a’) inelastic 12C(12C,8Be)16O 12C+12C Cross section within Gamow window (1 ~ 3MeV) 10-22b ~10-7b

  10. ---- Full (Un-gated) ---- Gated The 12C+13C experiment at ND: model the gross structure of 12C+12C Gas stripping 2 emA 13C2+ 1.37MeV 20 emA 13C- 2.74MeV Thick graphite disk 12C(13C,24Na)p Ec.m.=2.83 MeV, 1puA*28hr,379 counts Very compact beta counter 10 MV FN Tandem @ ND NPA5 April 7, 2011

  11. 1mb 20nb • The new 12C+13C data follows the trend of the old data. • The smallest cross section has been pushed down by a factor of 50.

  12. 13C+13C agrees with 12C+13C! (systematic error: ~30% not included in the graph) • The isotope effect (difference in radius, mass) is negligiblewithin the observed energy range! • Where will the 12C+12C data show up?

  13. For most energies, the 12C+12C cross sections are suppressed! • Only at resonant energies, the 12C+12C cross sections matches with those of 12C+13C and 13C+13C!

  14. A simple pattern for complicated resonances • For most energies, the 12C+12C cross sections are suppressed! • Only at resonant energies, the 12C+12C cross sections matches with those of 12C+13C and 13C+13C! Below the barrier Above the barrier 12C+12C has lowest level density in the entrance channel! Why?

  15. Predict 12C+12C cross sections with a constrained potential Coupled channels calculation with IWBC (Esbensen) 13C+13C 12C+13C ? ? Cooper resonance (2009) 12C+12C Spillane (2007) Predicted cross section CF88

  16. Useful Upper limit for lower energies Coupled channels calculation with IWBC (Esbensen) ?? ?? Cooper resonance (2009) Zickefoose [12C(12C,p), 2010] Spillane (2007) H. Esbensen et al., Phys. Rev. C 84, 064613 (2011) M. Notani et al., Phys. Rev. C 85, 014607 (2012)

  17. ashes • If the rate can not be that high, there must be some physics missing in the superburst model. • Unknown process to heat up the crust to higher temperature. • Carbon burning is not the one triggering superbursts! Private communication with E. Brown

  18. Central bore for beam tube LN2 reservoir Beam Target Polyethylene moderator 3He proportional counter Turbo Pump Measurement of 12C(12C,n)23Mg with 3He neutron detector array

  19. The impact of our measurement ND new extrapolation based on Zickefoose’s p0+p1 measurement ND measurement covers more than half of the range New resonances measured by ND T9=1.1 Dayras measurement PRELIMINARY Eth=2.6 MeV Ec.m. (MeV)

  20. Comparisons of CCN rates Carbon core burning Preliminary Carbon shell burning Explosive carbon burning T9

  21. Expect 40 pmA 12C beam Measurement of 12C(12C,p)23Na and 12C(12C,a)20Ne towards low energy Installation of the tank for the new single end 5 MV Vdg accelerator, Aug. 2011

  22. Carbon Fusion Project Approach with particle-gamma coincidence 2.1 MeV Resonance 0.3pmA*30hr Thick target yield (evt/incident 12C) 40pmA*30hr Eexcited(MeV) 0.3 pmA*30 hr 1 evt for a1-g 0 evt for p1-g Thick target yield for 12C(12C,a) Eγ(keV) Ec.m. (MeV) Using ASIC readout system provided by UW

  23. Nuclear Astrophysics at Chinese JingPin Laboratory (CJPL) 12C(a,g)16O 12C+12C 14N(p,g) 17,18O(p,g) 22Ne(p,g) 22,23Na(p,g) 26Al(p,g) 33S(p,g) …. 14C(a,g) 14,15N(a,g) 18O(a,g) 22Ne(a,g) 40Ca(a,g) …. 22Ne(a,n) 13C(a,n) 12C(12C,n) …… 12C+16O 16O+16O Low energy reactions provide the key for disseminating the chemical evolution of the universe from Big Bang to us! Good luck, Joe! Good luck, cyclotron!

  24. Summary • “The extrapolation to low energy is VERY uncertain … and more experimental and theoretical studies are urgently needed.” W. Fowler, Nobel lecture (1983) • Using Isotope fusion, the upper limit is defined. • 12C(12C,n) measured at stellar energies • Direct measurement: particle-gamma array coupling with the forthcoming new accelerator at ND • Indirect approach: 24Mg(a,a’)24Mg

  25. Collaborators ND-IU-ANL-CIAE carbon fusion project (SAND,SSNAP) University of Notre Dame: X. Fang, B. Bucher, A. Howard, J. Kolata, A. Roberts, W.P. Tan, X.D. Tang China Institute of Atomic Energy: Y.J. Li Argonne National Laboratory: H. Esbensen, C.L. Jiang, K.E. Rehm Indiana University Bloomington: R.de Souza, S. Hudan The 12C(12C,n)23Mg project B. Bucher, X. Fang, J. Browne, A. Alongi, C. Cahillane, E. Dahlstrom, A. Moncion, W. Tan, M. Notani, X.D. Tang, S. Almaraz-Calderon, A. Ayangeakaa, A. Best, M. Couder, J. DeBoer, W. Lu, D. Patel, N. Paul, A. Roberts, R. Talwar, A. Kontos, M. Smith, S. Lyons, Q. Li, K. Smith, A. Long, M. Wiescher, M. Beard, M. Pignatari

  26. 24Mg 24Mg(α, α’) measurement at RCNP University of Notre Dame: X. Fang, B. Bucher, G.Berg, R. DeBoer, U. Garg, J. Goerres, A. Long, R. Talwar, X.D. Tang, M. Wiescher Kyoto University:  T. Kawabata, N. Yokota, K. Tomosuke, Y. Matsuda, T. Kadoya Osaka University: A. Tamii, H. Fujita, Y. Fujita, K. Hatanaka, B. Liu, K. Miki Niigata University: T. Itoh Texas A&M University: Y.-W. Lui University of Birmingham: M. Freer

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