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Xiao Fang University of Notre Dame

Experimental investigation of stellar  12 C+ 12 C fusion toward extremely low energies by direct and indirect methods. Xiao Fang University of Notre Dame. The 11 th International Conference on Nucleus-nucleus Collisions (NN2012) San Antonio, Texas, May 31, 2012. Direct Measurement:

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Xiao Fang University of Notre Dame

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  1. Experimental investigation of stellar 12C+12C fusion toward extremely low energies by direct and indirect methods Xiao Fang University of Notre Dame The 11th International Conference on Nucleus-nucleus Collisions (NN2012) San Antonio, Texas, May 31, 2012

  2. Direct Measurement: Efficient thick target 2. Solenoid spectrometer Search the possible Resonances which can’t be directly measured Indirect method: 24Mg(a,a’) inelastic Carbon fusion project at Notre Dame 12C+13C 13C+13C 12C+13C 13C+13C 12C+13C 13C+13C Set upper limit for possibly existed resonances of 12C+12C 12C+12C SN 1994D, a type Ia supernova Verify old resonances and find new resonances SN 1987, Type II supernova Cross section within Gamow window (1 ~ 3MeV) 10-22b ~10-7b SN 1604

  3. Upper limit for 12C+12C fusion reaction 13C+13C 12C+13C Notre Dame ?? ?? 12C+12C Cooper resonance (2009) Esbensen Zickefoose (2010) Becker Spillane (2007) H. Esbensen et al., Phys. Rev. C 84, 064613 (2011) M. Notani et al., Phys. Rev. C 85, 014607 (2012)

  4. Efficient Thick target method P0: protons with 23Na at ground state P1: protons with 23Na at first excited state p 12C P0 Eproton (MeV) P1 E’reaction= Ebeam– ΔEbeam 12C(12C, p)23Na Q=2.24 MeV - Eexcited(23Na) Angle (deg) Ereaction Q, Eproton, θ

  5. Only measure proton channel Two YY1 silicon detectors at backward angle, covered with Aluminum foil to stopscattered 12C and produced alpha particles Use thick target of thickness 1mm Detector resolution for 5.486 MeV alpha particles is 40 keV(FWHM). Efficient Thick target measurement Focus on: 12C(12C, p)23Na The backward angle θLab: 113.5° - 163.5° θcm: 122.5° - 166.3° Solid angle calibrated by mixed alpha source 2.59% 0.5 pmA12C beam from FN tandem YY1 detector target YY1 detector

  6. New thick target quick-scan method Scan resonances in a wide range of 3 MeV<Ecm<5.3 MeV −Thick target −Thin target p0 S* factor (MeV) p1 Ecm (MeV)

  7. Combined S* factor from a series of thick target measurements(primary results) p0 40 nb 0.4 mb Background S* factor (MeV b) Covers 4 orders of magnitude ! p1 60 nb 0.4 mb Ecm (MeV)

  8. ND-IU-ANL-CIAE collaboration:Particle-Gamma coincidence The New 5MV Accelerator at ND Silicon Array at Notre Dame (SAND), (chamber and detector frame are being build at IU; ASIC readout from WUSL) GEORGINA array at ND Tuesday, Session 14: Measurement of fusion cross sections in 12C + 12C at Low beam energies using a particle-gamma coincidence technique C.L. Jiang, ANL

  9. Capture the channels without g-ray Solenoid Spectrometer for Nuclear Astrophysics (SSNAP) Disadvantage of Particle-gamma technique: not work for the channels without g-ray (p0 and a0) which potentially have large decay branching ratios. Recent experimental results from HELIOS Alan Wuosmaa Western Michigan University, USA

  10. Ecm=6.0 MeV, No degrader, B=3.96 T 12C(12C,p)23Na (Q=2.24 MeV) 12C(12C,)20Ne (Q=4.62 MeV) α0 α1 α2 p2 E(MeV) p3 α3 P4,p5 p6 p7 P8, p9 p10 p11 Z(m)

  11. Energy resolution 60 keV apart Resolution : 65 keV (FWHM) Excitation energy in 23Na Resolution of HELIOS spectrometer: ~80 keV(FWHM)

  12. Ecm=5.0 MeV, Al-foil 5.8um, B=3.96 T 12C(12C,p)23Na 12C(12C,)20Ne p0 p1 p2 p3 P4,p5 p6 xsec(p0): 1 mb Beam: ~80 pnA Duration: 6 hr E(MeV) p7 P8, p9 p10 α0 α1 Z(m)

  13. After energy loss correction Ecm=5.0 MeV E(MeV) E(MeV) Z(m) Z(m)

  14. Ecm=4.0 MeV, Al-foil 5.8um, B=3.96 T 12C(12C,p)23Na 12C(12C,)20Ne p0 p1 p2 Xsec(p0): 0.01 mb Beam: ~30 pnA Duration: 8 hr p3 E(MeV) P4,p5 p6 p7 P8, p9 p10 α1 α0 Z(m)

  15. Simulation: Ecm=2.0 MeV, Al-foil 5.8um p0 Xsec(p0): 1 pb p1 E(MeV) p2 p3 P4,p5 p6 α0 α1 Z(m)

  16. Estimation of event rate 2.1 MeV: ~10-11 b 1.7 MeV: ~10-13 b

  17. 16O a a 12C 12C 24Mg(α, α’) measurement at RCNP • Search of the potential resonances in the 12C+12C fusion reaction using the 24Mg(a,a’) reaction • Establish correlation between the two reactions at higher energies • Provide prediction at lower energies with 24Mg(a,a’) (Nov. 2011) AMD+GCM calculation by Y. Kanada-Enyo Grand Raiden at RCNP, Osaka University Precise energy calibration (<20 keV)  confirm the correlation Excellent energy resolution (<50 keV)  Resolving states Measurement of angular distribution Check spin assignment

  18. Preliminary result Black: 12C(12C, α)20Ne Red: 12C(12C,p)23Na S* factor 2+ Red: 0+ Blue: 2+ Mint: 4+ 0+ 2+ 12C(12C,p0,1) Strength 4+ 2+ 2+ Black: 4.5 deg Blue: 0 deg Counts 24Mg(a,a’) 0 1 2 3 4 5 6 7 Ec.m. (12C+12C)

  19. Summary • Set an upper limit for potential existed resonances in 12C+12C fusion • Silicon Array at Notre Dame (SAND), efficient thick target method: • to measure cross section of 12C+12C precisely (3MeV – 6MeV) • Disadvantage: suffer from background at lower energies • Particle-Gamma coincidence method: • to obtain reliable experimental data at lower energies (1.7MeV – 3MeV) • Disadvantage: not be able to detect p0 and α0 • Solenoid spectrometer: • to obtain data of p0 and α0 channels • Indirect method: • To search potential resonances of 12C+12C fusion by studying 24Mg(α,α’)

  20. Collaborators 24Mg(α, α’) measurement at RCNP University of Notre Dame: 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 Efficient thick target method (University of Notre Dame) Brian Bucher, S. Almaraz-Calderon, A. Alongi, D. Ayangeakaa, A. Best, Craig Cahillane, E. Dahlstroma, Q. Li, S. Lyons, N. Paul, M. Smith, WanpengTan, and Xiao-Dong Tang ND-IU-ANL-CIAE carbon fusion project (SAND,SSNAP) University of Notre Dame: B. Bucher, A. Howard, J. Kolata, A. Roberts, W.P. Tan, X.D. Tang China Institute of Atomic Energy: X.X. Bai, B. Guo, Y.J. Li, W.P. Liu Argonne National Laboratory: H. Esbensen, C.L. Jiang, K.E. Rehm Indiana University Bloomington: R.de Souza, S. Hudan

  21. 24Mg

  22. 12C+12C Fusion Range investigated Ec.m.=1 – 3MeV 12C(12C,p)23Na (Q=2.24 MeV) 12C(12C,)20Ne (Q=4.62 MeV) 12C(12C,n)23Mg (Q=-2.62MeV) Light particle: , p, n Gamma: 440 keV (p channel) 1634 keV(channel) Fusion residue: 20Ne, 23Na … no success under barrier 23Mg: decay spectroscopy

  23. Estimation of energy limit A 5 MV Pelletron with ECR source in terminal is being built. It is expected to provide beam in the summer of 2012. Naples : 10 puA beam;1.5% efficiency, 0.5 evt/day (proton channel only); ND-ANL-IU: ~40 puA beam;45% efficiency, 120 evt/day(proton and alpha); If add particle + gamma coincidence: 120*8%= 9.6evt/day

  24. 12C+12C fusion at low energies Cooper resonance (2009) [Costantini et al., Rep. Prog. Phys. 72, 086301 (2009)] • Astrophysical important energy range: 1-3 MeV • Large uncertainties in extrapolation • Need better data at lower energies! s~10-11 b @ 2.1 MeV 12C(12C,p)23Na 12C(12C,)20Ne 12C(12C,n)23Mg

  25. Determination of reaction energy P0 Beam energy P0: protons with 23Na at ground state P1: protons with 23Na at first excited state Red: Q(p0)=2.24 MeV Black: Q(p1)=1.80 MeV p1 Count P0 Eproton (MeV) P1 Angle (deg) Reconstructed reaction energy: Ereaction(MeV) 12C(12C, p)23Na Q=Qvalue-Eexcited(23Na) Q, Eproton, θ Ereaction With knowing the exact reaction Q value (Q)  Good reaction energy determination (90 keV for Elab 45 keV for Ecm).

  26. S* factor from a thick target measurement S* factor extracted from Ebeam=8.2 MeV Ecm = 4.1 MeV Ecm=0.5*Ebeam P1 p0 S* factor (MeV b) Simulation with a constant S* Ecm (MeV)

  27. Angular distribution for the12C(12C, p0)and 12C(12C,p1) ds/dW*E*exp(87.21/sqrt(E)+0.46*E) Ecm (MeV) Lab Angle (deg) Lab Angle (deg) Zickfoose only measure ds/dW at 135 deg in the lab frame. Zickfoose, Ph.D. Thesis, U. Conn 2010

  28. P0 angular distribution at Ecm=5 MeV P1 angular distribution at Ecm=5 MeV P3 angular distribution at Ecm=5 MeV

  29. P0 angular distribution at Ecm=4.1 MeV P1 angular distribution at Ecm=4.1 MeV P3 angular distribution at Ecm=4.1 MeV

  30. The fractions for the gamma-decay channels 440 keV for 23Na 1634 keV for 20Ne Proton and alpha channel data taken from Mazarakis

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