Experimental investigation of stellar 12C+12C fusion toward

extremely low energies by direct and indirect methods

Xiao FangUniversity of Notre Dame

The 11th International Conference on Nucleus-nucleus Collisions (NN2012)San Antonio, Texas, May 31, 2012

Indirect method:24Mg(a,a’) inelastic

Search th

e

possible

Resonances which

can’t be dire

ctly

measured

12C+12C

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

12C+13C13C+13C12C+13C13C+13C12C+13C13C+13C

Set upper limit

for possibly existed resonances of

12C+ 12C

SN 1987, Type II supernova

SN 1994D, a type Ia supernova

SN 1604

Carbon fusion project at Notre Dame

Direct Measurement:1. Efficient thick

target2. Solenoid spectrometer

Verify old resonancesand find new resonances

Upper limit for 12C+12C fusion reaction

Zickefoose (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)

13C+13C

12C+13C

12C+12C

Notre Dame

Becker

Esbensen

E

EEEES 46.021.87exp

Efficient Thick target method

12C

p

E’reaction = Ebeam – ΔEbeam

12C(12C, p)23Na

EreactionQ, Eproton, θ

Q=2.24 MeV - Eexcited (23Na)

cos122321

13121

1312

protonreactionprotonreaction EEEEQ

E pro

ton (

MeV

)Angle (deg)

P0: protons with 23Na at ground stateP1: protons with 23Na at first excited state

P0P1

Only measure proton channel Two YY1 silicon detectors at backward angle, covered with Aluminum foil to

stop scattered 12C and produced alpha particles Use thick target of thickness 1mm Detector resolution for 5.486 MeV alpha particles is 40 keV(FWHM).

0.5 pmA 12C beamfrom FN tandem

target

YY1 detector

YY1 detector

The backward angleθLab: 113.5° - 163.5°θcm: 122.5° - 166.3°

Solid angle calibrated by mixed alpha source

2.59%

Focus on: 12C(12C, p)23Na

Efficient Thick target measurement

Scan resonances in a wide range of 3 MeV<Ecm<5.3 MeV

p0

p1S* fa

ctor

(MeV

)

Ecm (MeV)

New thick target quick-scan method

−Thick target−Thin target

Ecm (MeV)

S*

fact

or (M

eV b

)

60 nb

40 nb

0.4 mb

0.4 mb

Covers 4 orders of magnitude !

p0

p1

Combined S* factor from a series of thick target measurements(primary results)

Bac

kgro

und

ND-IU-ANL-CIAE collaboration:Particle-Gamma coincidence

GEORGINA array at ND

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)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

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 HELIOSAlan WuosmaaWestern Michigan University, USA

Z(m)

E(M

eV)

Ecm=6.0 MeV, No degrader, B=3.96 T

p2p3

P4,p5p6

p7P8, p9

p10

α0

α1

p11

α2

α3

12C(12C,p)23Na (Q=2.24 MeV)12C(12C,)20Ne (Q=4.62 MeV)

60 keV apart

Excitation energy in 23Na

Resolution : 65 keV (FWHM)

Resolution of HELIOS spectrometer: ~80 keV(FWHM)

Energy resolution

p2p3

P4,p5p6

p7P8, p9

p10

Z(m)

E(M

eV)

p0p1

Ecm=5.0 MeV, Al-foil 5.8um, B=3.96 T

α0

α1

xsec(p0): 1 mb Beam: ~80 pnADuration: 6 hr

12C(12C,p)23Na12C(12C,)20Ne

After energy loss correction

Z(m)

E(M

eV)

Z(m)E(

MeV

)

Ecm=5.0 MeV

p2p3

P4,p5p6

p7P8, p9

p10

Z(m)

E(M

eV)

p0p1

Ecm=4.0 MeV, Al-foil 5.8um, B=3.96 T

α0α1

Xsec(p0): 0.01 mbBeam: ~30 pnADuration: 8 hr

12C(12C,p)23Na12C(12C,)20Ne

Simulation: Ecm=2.0 MeV, Al-foil 5.8um

Z(m)

E(M

eV)

α0α1

p2p3

P4,p5

p6

p0p1 Xsec(p0): 1 pb

Estimation of event rateTable 1 Comparisons among different experiments studying the 12C+12C fusionExperiment Beam

intensity (pmA)

Detector efficiency Event Rate (evt/day)

Ecm=2.1 MeV

Naples (world record)1 10 1.5% 0.5 (proton only)ND SAND 40 45% 120=120*2*0.5ND SAND + Gamma2 40 45%(SAND)*8%

(Gamma)

10=10*2*0.5

ND SAND + Gamma3 40 45%(SAND)*32%

(Gamma)

38=38*2*0.5

ND SSNAP 40 30% 80=80*2*0.51.J. Zickefoose, U. Conn. Thesis (2010).

2.Only took the photopeak efficiency (440 keV and 1630 keV)

3.Used all the gamma energy > 0.1 MeV

2.1 MeV: ~10-11 b1.7 MeV: ~10-13 b

Search of the potential resonances in the 12C+12C fusion reaction using the 24Mg(,’) reaction Establish correlation between the two reactions at higher energies Provide prediction at lower energies with 24Mg(,’)

Grand Raiden at RCNP, Osaka UniversityPrecise energy calibration (<20 keV) confirm the correlationExcellent energy resolution (<50 keV) Resolving statesMeasurement of angular distribution Check spin assignment

(Nov. 2011)

0.1

1

10

100

0 5 10 15 20cm (deg)

d

/dW

(a.u

.)

DL=0

DL=2

DL=4

24Mg(α, α’) measurement at RCNP

16O

12C 12C

AMD+GCM calculation by Y. Kanada-Enyo

0 1 2 3 4 5 6 7Ec.m. (12C+12C)

Black: 12C(12C, α)20NeRed: 12C(12C,p)23Na

Black: 4.5 degBlue: 0 deg

Preliminary result

Red: 0+Blue: 2+Mint: 4+

S* fa

ctor

Stre

ngth

Cou

nts

0+

4+

2+ 2+

2+2+

12C(12C,p0,1)

24Mg(,’)

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’)

Collaborators

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, Wanpeng Tan, 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. TangChina Institute of Atomic Energy: X.X. Bai, B. Guo, Y.J. Li, W.P. LiuArgonne National Laboratory: H. Esbensen, C.L. Jiang, K.E. RehmIndiana University Bloomington: R.de Souza, S. Hudan

24Mg(α, α’) measurement at RCNPUniversity of Notre Dame: 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

24Mg

12C+12C Fusion

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 barrier23Mg: decay spectroscopy

Rang

e in

vest

igat

ed

Ec.m.=1 – 3MeV

1.0E-201.0E-181.0E-161.0E-141.0E-121.0E-101.0E-081.0E-061.0E-041.0E-021.0E+00

0.00 1.00 2.00 3.00 4.00 5.00

Ecm (MeV)

xsec

(b)

Cooper(res1)

Cooper(res2)

ND_estimation

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%= 9.6 evt/day

A 5 MV Pelletron with ECR source in terminal is being built. It is expected to provide beam in the summer of 2012.

Estimation of energy limit

[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!

12C+12C fusion at low energies

12C(12C,p)23Na12C(12C,)20Ne 12C(12C,n)23Mg

~10-11 b @ 2.1 MeV

Cooper resonance (2009)

Beam energy

Reconstructed reaction energy: Ereaction (MeV)C

ount

Red: Q(p0)=2.24 MeVBlack: Q(p1)=1.80 MeV

With knowing the exact reaction Q value (Q) Good reaction energy determination (90 keV for Elab 45 keV for Ecm).

Determination of reaction energy

12C(12C, p)23Na

Ereaction

Q, Eproton, θ

Q=Qvalue-Eexcited (23Na)

Epr

oton

(MeV

)

Angle (deg)

P0: protons with 23Na at ground stateP1: protons with 23Na at first excited state

P0

P1

P0

p1

S* factor extracted from Ebeam=8.2 MeV

p0

P1

Simulation with a constant S*

Ecm (MeV)

S*

fact

or (M

eV b

)

Ecm=0.5*Ebeam

S* factor from a thick target measurement

Ecm = 4.1 MeV

Lab Angle (deg) Lab Angle (deg)

Ecm

(MeV

)Angular distribution for the

12C(12C, p0)and 12C(12C,p1)

d/dW*E*exp(87.21/sqrt(E)+0.46*E)

Zickfoose only measure d/dW at 135 deg in the lab frame. Zickfoose, Ph.D. Thesis, U. Conn 2010

P0 angular distribution at Ecm=5 MeV P1 angular distribution at Ecm=5 MeV

P3 angular distribution at Ecm=5 MeV

P0 angular distribution at Ecm=4.1 MeV P1 angular distribution at Ecm=4.1 MeV

P3 angular distribution at Ecm=4.1 MeV

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 2 4 6 8

S440

_obs

/S_p

Ecm (MeV)

4% Ge

1% Ge

0.1% Ge

Statisical Model 0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 2 4 6 8

S163

4_ob

s/S_

Ecm (MeV)

8% Ge

1% Ge

0.1%

Statistical Model

The fractions for the gamma-decay channels

440 keV for 23Na 1634 keV for 20Ne

Proton and alpha channel data taken from Mazarakis