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

Institute for Structure and Nuclear AstrophysicsNuclear Science Laboratory

E381: Search of potential resonances in the 12C+12C fusion reaction using charged-

particle decays from the 24Mg(,’)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, USAUniversity of Kyoto, Japan

Texas A&M University, USAOsaka University, Japan

Istanbul University, TurkeyUniversity of Birmingham, UK


Outline

• Why do we need resonance information from indirect measurement?

• Is it possible to get resonance information from 24Mg(,’)?

• How to select the 24Mg states relevant to the 12C+12C fusion reaction?

• Rate estimation.


•Detect Fusion Residues •Detect light charged particles•Detect gamma rays

Ex(24Mg)~Ecm(12C+12C)+14 MeV

Institute for Structure and Nuclear AstrophysicsNuclear Science LaboratoryCarbon burning in the

universeThe extrapolation to low energy is uncertain … and more experimental and theoretical studies are urgently needed.

Fowler, Nobel Lecture (1983)

NSAC Long Range Plan 2007


Challenge for Laboratory nuclear-Astrophysics in Underground and Surface 2009: CLAUS2009

R. Cooper et al., APJ (2009) 702, 660Gasques et al. PRC 72 (2005) 025806Jiang et al. PRC 75 (2007) 015803

? ?Hindrance?

Large uncertainties in 12C+12C


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

)

No-coupling Limit Coupling Limit

resonance 1 resonance 2

this work Becker

Patterson Aguilera

Spillane

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


24Mg(a,a’) inelasticSearch

the poss

ible

resonance

s

Direct measurement

The exact cross section

12C+13C13C+13C

Provide potential to

model the smooth

behavior

12C+13C13C+13C

Provide potential to

model the smooth

behavior

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


Notre Dame-ANL-IU carbon fusion experiment

A 5 MV Pelletron with ECR source in terminal. Will be installed at the end of 2011.

Clover array at ANLGeorgina at ND


1.0E-20

1.0E-18

1.0E-16

1.0E-14

1.0E-12

1.0E-10

1.0E-08

1.0E-06

1.0E-04

1.0E-02

1.0E+00

0.00 1.00 2.00 3.00 4.00 5.00

Ecm (MeV)

xs

ec

(b

)

Cooper(res1)

Cooper(res2)

ND_estimation

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


Impact of the potential resonances to astrophysical reaction rate

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0.00 0.50 1.00 1.50 2.00

Temperature (x1E9 K)

Re

ac

tio

n R

ate

Ra

tio Er=1.5 MeV,G=0.1MeV

Er=1.6 MeV,G=0.1 MeV

Er=1.5 MeV,G=0.05MeV

Carbon core burning

Carbon shell burning

Explosive Carbon burning

Super-burst


16O

12C12C

12C+ 12C cluster components in 24Mg (g.s.)

Therefore, the 12C+12C resonant states could be strongly populated by the 24Mg(,’)!

AMD+GCM calculation by Y. Kanada-Enyo


(a)

4+

2+2+

2+0+

4+/2+

Ex (MeV)

Arb

itra

ry u

nit

4+

2+2+

2+0+

4+/2+

Ex (MeV)

co

un

ts

(b)

Identified 0+

2+ statescoincide with 12C+12C

??

2+

3-

4+

RCNP:+0.18 MeV; KVI:+0.10 MeV

PreliminarySpectrum at 0 degfrom E308

KVI


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


1.E-16

1.E-12

1.E-08

1.E-04

1.E+00

1.E+04

1.E+08

0.00 2.00 4.00 6.00 8.00

Ecm (MeV)

reso

nan

ce s

tren

gth

(eV

)

Predition

Exp

The predicted nuclear structure for the candidate states (14MeV<Ex<17 MeV)

• J should be 0+/2+.

• Decay mainly by p, or 8Be

• 12C decay branching ratio (BR):BR<1E-5 (Ecm<3 MeV)

BR~10% (Ecm=6 MeV)


Decay spectroscopy:

•p, 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).

PreliminaryData from E308

The p/ 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.


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


8Be decay dominates?

24Mg(a,a’+8Be): new way to investigate the clustering state


Decay detector setup

Decay eff: 3.6% (p and a) 0.9% (8Be)


5mb/sr; 20% background; 10 enA 388 MeV beam;

2 mg/cm^2Rate: 3.8x104 cnt/hrGR 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 ) 0.9% (8Be) p/a: ~3000 cnt/day (12000 cnt/4 days)8Be:~3000 cnt/4 days12C/16O contamination: 1 day

Total: 3 days+12 hours+1day+4 days+1 day~9 days + 12 hours


Budget

Documents

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