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Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Upper limit on the molecular resonance
strengths in the 12C+12C fusion reaction
X. Tang
University of Notre Dame
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Outline
• Superburst puzzle
• Empirical relationships among the carbon
isotope fusion reactions: 12C+12C, 12C+13C and
13C+13C
• Upper limit on the molecular resonance
strengths in the 12C+12C fusion reaction
• Comparison with the most recent direct
measurement and impact to the superburst
puzzle.
• Future ND-ANL experiments
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Superbursts
•Rare, long duration bursts; By 2009, 15 bursts from 10 sources
Kuulkers 2004, 2005; in’t Zand 2004; Remillard 2005; Keek 2008
•Recurrence times 1-2 years, energies 1042 ergs.
•Triggered by 12C+12C fusion in the ashes left over after the rp-process
Cumming & Bildsten 2001; Strohmayer & Brown 2002; Cumming 2003; Brown 2004; Cooper &
Narayan 2005; Cumming et al. 2006; Gupta et al. 2007
Normal X-Ray burst
Flux
Flux
Superburst
time
NPA5 April 7, 2011
time
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Superburst: ignited by Carbon burning
Ashes from rp process
deposit in the outer
crust.
ashes
~ 20m
Column depth (Y)
(0.5-2)x1012 g/cm2
Crust processes
(EC, pycnonuclear fusion)
crust heating
crust conductivity
Picture by E. Brown
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Superburst Puzzle: the outer crust is too cold
to ignite the carbon burning! Maybe the
carbon burning rate underestimated?
+
4U 1608-522
atmosphere
core
April 7, 2011
Keek et NPA5
al. (2007),
Astron. & Astrophys. 479: 177.
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
S * ( E)  Ee(87.21/
E 0.46 E )
1.E+20
CF88
S* (MeV*b)
1.E+19
Becker
Patterson
1.E+18
Aguilera
1.E+17
3x1016 MeV*b
1.E+16
1.E+15
1
2
3
Astrophysical
energy range
4
Ec.m. (MeV)
NPA5 April 7, 2011
5
6
7
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
S * ( E)  Ee(87.21/
E 0.46 E )
1.E+20
CF88
S* (MeV*b)
1.E+19
Becker
Patterson
1.E+18
Fit with Eilat!
1.E+17
Aguilera
3x1016 MeV*b
1.E+16
1.E+15
1
2
Astrophysical
energy range
3
4
E c.m. (MeV)
NPA5 April 7, 2011
5
6
7
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Possible resonances in
12C+12C
1.E+20
CF88
resonance 1
Becker
Patterson
Aguilera
Spillane
S* (MeV*b)
1.E+19
1.E+18
1.E+17
1.E+16
1.E+15
1
2
3
4
5
6
7
Ec.m. (MeV)
T. Spillane et al., Phys. Rev. Lett. 98, 122501 (2007)
R. Cooper et al., APJ (2009) 702, 660
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
R. Cooper et al.,
APJ (2009) 702, 660
…. in this case, observationally inferred superburst ignition depths
would accord with model predictions for a range of plausible neutron
star parameters….
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
12C+13C
12C+12C
13C+13C
Direct
measurement
12C(12C,a)20Ne
12C(12C,p)23Na
The exact
cross section
12C(12C,n)23Mg
24Mg(a,a’)
inelastic
12C(12C,8Be)16O
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
The 12C+13C experiment
Carbon stripping (100 enA)
Gas stripping
2 emA
20 emA
13C2+
13C-
Thick graphite disk
Very compact
beta counter
Ec.m.=2.83 MeV,
1puA*28hr,379 counts
12C(13C,24Na)p
10 MV FN Tandem @ ND---- Full
(Ungated)
1.37MeV
---- Gated
2.74MeV
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
S ( E )  Ee
Caltech 1983
2
2Z1Z 2
2 
 2E / m
13C+13C
Eg. for
12C+13C
12C+12C,
87.21
(E in MeV)
2 
E
12C+12C
Not good to compare xsec
among the three systems
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Use the same conversion formula for all the three carbon systems.
S * ( E)  Ee
(87.21/ E 0.46 E )
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
1.4E+17
1.4E+17
Becker
Patterson
1.2E+17
1.2E+17
C12C13(ND)
Becker
C13C13(Tren)
C12C13(DAYRAS)
Patterson
S* (MeV*b)
S* (MeV*b)
1.0E+17
1.0E+17
8.0E+16
8.0E+16
Linear scale!
4 nb
6.0E+16
6.0E+16
4.0E+16
4.0E+16
2.0E+16
2.0E+16
0.0E+00
0.0E+00
2.52.5
3.53.5
4.5
4.5
(MeV)
EE
(MeV)
c.m.
c.m.
5.5
5.5
NPA5
April 7, 2011 but suppressed!
The 12C+12C is not
enhanced
6.5
6.5
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
1.E+20
S* (MeV*b)
1.E+19
1.E+18
Becker
Patterson
Aguilera
Fowler
KNS_CC
KNS_NOC
CW
CW_NOC
1.E+17
1.E+16
1.E+15
1
2
3
4
Ec.m. (MeV)
5
6
7
KNS and CW (Woods-Saxon type) are taken from Aguilera’s paper,
PRC 73, 064601 (2006)
CC and NOC are calculated with CCFULL by Hagino et al..
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
xsec_NOC/xsec_CC
1.0
0.9
KNS
0.8
CW
WS
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
1
2
3
4
5
6
7
Ecm (MeV)
Couple channel enhancement is not sensitive to the choices of potential.
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
1.E+17
9.E+16
Becker
Patterson
Aguilera
8.E+16
Spillane
Fowler
Fowler_NOC
S* (MeV*b)
7.E+16
Linear scale!
6.E+16
5.E+16
4.E+16
3.E+16
2.E+16
1.E+16
0.E+00
1
2
3
4
5
6
Ec.m. (MeV)
First quantitative systematic description of the molecular
resonance strengths
CC: resonance
NOC: off-resonance
NPA5 Nogami-Imanishi
April 7, 2011
The observation supports
model (1968).
7
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
1.E+20
Preliminary
Cooper (2009)
S* (MeV*b)
1.E+19
X X
1.E+18
Becker
Aguilera
Fowler
KNS_NOC
Cooper resonance
CW_NOC
Spillane (2007)
1.E+17
1.E+16
1.E+15
1
2
3
4
Ec.m. (MeV)
NPA5 April 7, 2011
Patterson
Spillane
KNS_CC
Fowler_NOC
CW
HINDRANCE:
Woods Saxon potential
always over-predicts
Upper limit:
~3xCF88
5
6
Lower limit:
~1/3*CF88
OR LESS
7
I nPreliminary
s t i t u t e f o results
r S t r u cfrom
ture and Nuclear Astrophysics
Nuclear Science Laboratory
the 12C+12C fusion experiment at Caserta
proton channel only
• Uncertainties below 2.5 MeV range from 25-100% on each curve
• Gamma ray data correspond to the 440 keV line of 23Na and charged particle data to
P0 and P1 groups (normalization necessary)
• Modifications are necessary to achieve energies below 2 MeV (higher beam currents,
larger efficiency, etc.)
Tim Spillane, U. Conn Thesis (2007)
NPA5 April 7, Jim
2011 Zickefoose, U. Conn Thesis (2011)
Institute for Structure and Nuclear Astrophysics
1.E+20
Becker
Aguilera
Fowler
KNS_NOC
Cooper resonance
CW_NOC
S* (MeV*b)
1.E+19
1.E+18
Nuclear Science Laboratory
Patterson
Spillane
KNS_CC
Fowler_NOC
CW
+
1.E+17
1.E+16
1.E+15
1
2
3
4
5
6
7
Upper
4Ulimit
1608-522
Ec.m. (MeV)
If the rate can not be as 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 the
superbust!
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Notre Dame-ANL fusion experiment
Silicon Array at
Notre Dame
(SAND)
Solenoid Spectrometer for Nuclear
AstroPhysics (SSNAP)
Simulation @ Ecm=1.5 MeV
NPA5 April 7, 2011
A 5 MV Pelletron with
ECR source in terminal.
Will be installed at the
end of 2011.
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
NPA5 April 7, 2011
Institute for Structure and Nuclear Astrophysics
Nuclear Science Laboratory
Summary
• Based on an empirical correlations among three carbon
isotope fusions, the upper limit for the carbon fusion
reaction rate is defined.
• Both the strong resonance observed at Ecm=2.14 MeV
and the hypothetical strong resonance at Ecm=1.5 MeV
are not realistic. Superburst puzzle remains unsolved!
• Direct/Indirect(THM) measurement is urgently needed!
We are developing high current accelerator and highly
efficient detector arrays to conquer the challenges.
NPA5 April 7, 2011