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X. Tang( 唐暁東 ), G. P. Berg , T. Kawabata ,

E381: Search of potential resonances in the 12 C+ 12 C fusion reaction using charged- particle decays from the 24 Mg( a , a ’) 24 Mg* reaction. X. Tang( 唐暁東 ), G. P. Berg , T. Kawabata ,

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X. Tang( 唐暁東 ), G. P. Berg , T. Kawabata ,

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  1. E381: Search of potential resonances in the 12C+12C fusion reaction using charged-particle decays from the 24Mg(a,a’)24Mg* reaction X. Tang(唐暁東), G. P. Berg, T. Kawabata, B. Bucher, F. Xiao, D. Patel, R. Talwar, A. Long, N. Yokota, U. Garg, M. Wiescher, Y.-W. Lui, K. Hatanaka, A. Tamii, Y. Fujita, E. Ganioglu, G. Susoy, B. Bilgier, H.C. Kozer, M. Freer University of Notre Dame, USA University of Kyoto, Japan Texas A&M University, USA Osaka University, Japan Istanbul University, Turkey University of Birmingham, UK

  2. Outline • Why do we need resonance information from indirect measurement? • Is it possible to get resonance information from 24Mg(a,a’)? • How to select the 24Mg states relevant to the 12C+12C fusion reaction? • Rate estimation.

  3. Ex(24Mg)~Ecm(12C+12C)+14 MeV • Detect Fusion Residues • Detect light charged particles • Detect gamma rays

  4. Carbon burning in the universe NSAC Long Range Plan 2007 The extrapolation to low energy is uncertain … and more experimental and theoretical studies are urgently needed. Fowler, Nobel Lecture (1983)

  5. ? ? Challenge for Laboratory nuclear-Astrophysics in Underground and Surface 2009: CLAUS2009 Large uncertainties in 12C+12C Hindrance? R. Cooper et al., APJ (2009) 702, 660 Gasques et al. PRC 72 (2005) 025806 Jiang et al. PRC 75 (2007) 015803

  6. The proposed resonances at Ecm=1.5 MeV (Ex=15.5 MeV) T. Spillane et al., Strong resonance at 2.14 MeV with width <12keV; PRL98 (2007) 122501;dismissed by a recent experiment at Naples. R. Cooper et al., APJ (2009) 702, 660

  7. 12C+13C 13C+13C 12C+13C 13C+13C 12C+13C 13C+13C Provide potential to model the smooth behavior Provide potential to model the smooth behavior 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 24Mg(a,a’) inelastic 12C(12C,8Be)16O 12C+12C

  8. A 5 MV Pelletron with ECR source in terminal. Will be installed at the end of 2011. Clover array at ANL Georgina at ND Notre Dame-ANL-IU carbon fusion experiment

  9. Naples : 10 puA beam;1.5% eff.;proton channel only ;0.5 evt/days; ND-ANL-IU: >40 puA beam;45% eff.;both proton and alpha;4*30*2 evt/days; If add particle + gamma coincidence: 240*8% evt/days

  10. Carbon core burning Explosive Carbon burning Carbon shell burning Super-burst Impact of the potential resonances to astrophysical reaction rate

  11. 16O a a 12C 12C 12C+ 12C cluster components in 24Mg (g.s.) AMD+GCM calculation by Y. Kanada-Enyo Therefore, the 12C+12C resonant states could be strongly populated by the 24Mg(a,a’)!

  12. (a) Identified 0+ ?? 2+ 0+ 2+ 2+ 4+/2+ 4+ 2+ 0+ 2+ Arbitrary unit 2+ 4+/2+ 4+ 2+ states coincide with 12C+12C Ex (MeV) Preliminary Spectrum at 0 deg from E308 counts Ex (MeV) RCNP:+0.18 MeV; KVI:+0.10 MeV (b) KVI 2+ 3- 4+

  13. 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

  14. The predicted nuclear structure for the candidate states (14MeV<Ex<17 MeV) • JP should be 0+/2+. • Decay mainly by p,a or 8Be • 12C decay branching ratio (BR): BR<1E-5 (Ecm<3 MeV) BR~10% (Ecm=6 MeV)

  15. Decay spectroscopy: • p, a and 8Be • Probe nuclear structure • Enhance spin selection • Goal: Try to find the signature for the 12C+12C states at Ecm> 3MeV(Ex>17 MeV) and then apply it to the states with Ecm<3 MeV (Ex<17MeV). The p/a decay spectroscopy has been studied at 0 deg by E308. We will perform the decay measurement at the angle where the 2+ reach its maximum. Preliminary Data from E308

  16. The 12C(12C,8Be)16O channel

  17. 8Be decay dominates? 24Mg(a,a’+8Be): new way to investigate the clustering state

  18. Decay detector setup Decay eff: 3.6% (p and a) 0.9% (8Be)

  19. 5mb/sr; 20% background; 10 enA 388 MeV a beam; 2 mg/cm^2 Rate: 3.8x104 cnt/hr GR dispersion matching set up to get resolution < 50 keV (x 3 days) Energy calibration ( 400 MeV x 1% = 40 MeV, 3 magnetic field setting)  determine resonance energy with uncertianty < 20 keV (3 hr) Angular calibration (8 hr) Angular distribution (0, 2.5, 3.7, 5, 6, 7.4, 8.8, 10.2, and 11.6 (9 angles) (24 hours) Decay measurement (4 days) Thin target: 0.2 mg/cm2 Decay eff: 3.6% (p and a) 0.9% (8Be) p/a: ~3000 cnt/day (12000 cnt/4 days) 8Be:~3000 cnt/4 days 12C/16O contamination: 1 day Total: 3 days+12 hours+1day+4 days+1 day~9 days + 12 hours

  20. Budget

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