the 12 c+ 12 c fusion reaction at stellar energies

Institute for Structure and Nuclear AstrophysicsNuclear Science Laboratory

The 12C+12C fusion reaction at stellar energies

Xiaodong Tang (Aggie since Aug. 1997)Joint Institute for Nuclear Astrophysics, UND

International Workshop on Nuclear Dynamics and Thermodynamics

Texas A&M University, College Station, Texas


That is indeed a pretty interesting paper !

Michael WiescherDirector of Joint Institute forNuclear Astrophysics


• 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


20Ne+

Light particle: p, n, Gamma: 440 keV (p channel)

1634 keV ( channel)Fusion residue: 20Ne, 23Na …no success under barrier23Mg: decay spectroscopy


The world's first tandem accelerator installed at Chalk River in 1959.

Molecular resonances in the 12C+12C fusion reaction measured by Almqvist et al., in 1960


1.E+15

1.E+16

1.E+17

1.E+18

1.E+19

1.E+20

1 2 3 4 5 6 7

Ec.m. (MeV)

S*

(Me

V*b

)

Becker Patterson

Aguilera Spillane

CF(1988) Cooper 1

Cooper 2 Jiang (2007)

Barnes(1984) Yalkolev(2010)

10-22 b 10-7 b

12C(12C,p)23Na (Q=2.24 MeV)12C(12C,)20Ne (Q=4.62 MeV)12C(12C,n)23Mg (Q=-2.62MeV)

E

EEEES 46.0

21.87exp


Ignition conditions in type Ia supernovaeNucleosynthesis in massive stars

Candidate for Superburst ignition

Carbon burning in the universe

t~10 s 10 hrE(erg)~1039 1041


Superburst: ignited by Carbon burning

Ashes from rp process (He burning) deposit in the outer crust.

Crust processes(EC, pycnonuclear fusion)crust heatingcrust conductivity

Picture by E. Brown (MSU)

ashes

Key problem: With the standard rate (CF88), the crust temperature is too low to ignite the carbon fuel! Add artificial resonance


24Mg(a,a’) inelasticSearc

h the p

ossib

le

Resonance

s at R

CNP

Direct measurement

The exact cross section

Provide potential

to model the

gross structure

12C+13C13C+13C 12C+12C

12C(12C,n)23Mg

12C(12C,p)23Na

12C(12C,a)20Ne

12C(12C,8Be)16O

12C(12C,a)20Ne

Cross section within Gamow window (1 ~ 3MeV)10-22b ~10-7b

Cross section within Gamow window (1 ~ 3MeV)10-22b ~10-7b


NPA5 April 7, 2011

10 MV FN Tandem @ ND

20 eA 13C-

2 eA 13C2+

Thick graphite disk

Gas stripping

The 12C+13C experiment at ND: model the gross structure of 12C+12C

---- Full (Un-gated)---- Gated1.37MeV

2.74MeV

Ec.m.=2.83 MeV, 1puA*28hr,379 countsVery compact

beta counter

12C(13C,24Na)p


)46.0/21.87()(* EEEeES •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.

1b20nb


•13C+13C agrees with 12C+13C! (systematic error: ~30% not included in the graph)

•The isotope effect (difference in radius, mass) is negligible within the observed energy range!

•Where will the 12C+12C data show up?


•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

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!Why?

12C+12C has lowest level density in the entrance channel!


Predict 12C+12C cross sections with a constrained potential

13C+13C

12C+13C

12C+12CSpillane (2007)

CF88

Predicted cross section

??Cooper resonance (2009)

E

EEEES 46.0

21.87exp

Coupled channels calculation with IWBC (Esbensen)


Useful Upper limit for lower energies

Zickefoose [12C(12C,p), 2010]

????

Spillane (2007)

Cooper resonance (2009)

H. Esbensen et al., Phys. Rev. C 84, 064613 (2011)M. Notani et al., Phys. Rev. C 85, 014607 (2012)

E

EEEES 46.0

21.87exp

Coupled channels calculation with IWBC (Esbensen)


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!

ashes

Private communication with E. Brown


Measurement of 12C(12C,n)23Mg with 3He neutron detector array

BeamTarget

LN2 reservoir

Turbo Pump3He proportional counter

Polyethylene moderator

Central bore for beam tube


Ec.m. (MeV)

ND new extrapolation based on Zickefoose’s p0+p1 measurement

Dayras measurement

The impact of our measurement

New resonances measured by ND

ND measurement covers more than half of the range

Eth=2.6 MeV

T9=1.1

PRELIM

INAR

Y


Carbon shell burning

Carbon core burning

Explosive carbon burning

T9

Comparisons of CCN rates

Preliminary


Installation of the tank for the new single end 5 MV Vdg accelerator, Aug. 2011

Measurement of 12C(12C,p)23Na and 12C(12C,a)20Ne towards low energy

Expect 40 pA 12C beam

Institute for Structure and Nuclear AstrophysicsNuclear Science LaboratoryCarbon Fusion Project

Approach with particle-gamma coincidence

Eγ(keV)

E exc

ited

(MeV

)

0.3 pA*30 hr1 evt for 1-0 evt for p1-

Using ASIC readout system provided by UW Ec.m. (MeV)

0.3pA*30hr

40pA*30hr

Thic

k ta

rget

yie

ld (e

vt/i

ncid

ent 12

C)

Thick target yield for12C(12C,)

2.1 MeVResonance

Institute for Structure and Nuclear AstrophysicsNuclear Science LaboratoryNuclear Astrophysics at Chinese JingPin Laboratory (CJPL)

12C(,)16O12C+12C

14N(p,)17,18O(p,)22Ne(p,)

22,23Na(p,)26Al(p,)33S(p,)

….14C(a,)

14,15N(,)18O(,)

22Ne(a,)40Ca(,)

….22Ne(,n)13C(,n)

12C(12C,n)……

12C+16O16O+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!


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 NDIndirect approach: 24Mg(a,a’)24Mg


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. TangChina Institute of Atomic Energy: Y.J. LiArgonne National Laboratory: H. Esbensen, C.L. Jiang, K.E. RehmIndiana 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


24Mg

24Mg(α, α’) measurement at RCNPUniversity of Notre Dame: X. Fang, B. Bucher, G.Berg, R. DeBoer, U. Garg, J. Goerres, A. Long, R. Talwar, X.D. Tang, M. WiescherKyoto University: T. Kawabata, N. Yokota, K. Tomosuke, Y. Matsuda, T. KadoyaOsaka University: A. Tamii, H. Fujita, Y. Fujita, K. Hatanaka, B. Liu, K. MikiNiigata University: T. ItohTexas A&M University: Y.-W. LuiUniversity of Birmingham: M. Freer

the 12 c+ 12 c fusion reaction at stellar energies

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