does the 12 c+ 12 c fusion reaction ignite superbursts?
DESCRIPTION
Does the 12 C+ 12 C fusion reaction ignite superbursts?. Disk. Companion. Crust processes (EC, pycnonuclear fusion) crust heating crust conductivity. Neutron star. Superburst: ignited by Carbon burning. ashes. Ashes from rp process (He burning) deposit in the outer crust. - PowerPoint PPT PresentationTRANSCRIPT
Does the 12C+12C fusion reaction ignite superbursts?
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
ashes
Key problem: the standard rate (CF88) is too low to explain observation!
Disk Companion
Neutron star
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
)
CF88
Becker
Patterson
Aguilera
)46.0/21.87()(* EEEeES
3x1016 MeV*b
Astrophysical energy range
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
)Fowler Cooper 1 Cooper 2
Becker Patterson Aguilera
Spillane
CF88
T. Spillane et al., Strong resonance at 2.14 MeV with width <12keV; No confirmation yet. PRL98 (2007) 122501;
R. Cooper et al., APJ (2009) 702, 660
Strong resonances at deep sub-barrier energies
24Mg(a,a’) inelasticSearc
h the p
ossib
le
reso
nances
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
NPA5 April 7, 2011
10 MV FN Tandem @ ND
20 eA 13C-
2 eA 13C2+
Thick graphite disk
Carbon stripping (100 enA)Gas stripping
The 12C+13C experiment
---- Full (Un-gated)---- Gated1.37MeV
2.74MeV
Ec.m.=2.83 MeV, 1puA*28hr,379 countsVery compact
beta counter
12C(13C,24Na)p
/2
22
)(
21
2
E
ZZ
EeES
E
21.872
Eg. for 12C+12C,
(E in MeV)
Caltech 1983
Not good for comparing xsec among the three systems
12C+13C
12C+12C
13C+13C
)46.0/21.87()(* EEEeES
Use the same conversion formula for all the three carbon systems.
Good for the comparison of xsecs among the three systems!
•Ah ha, 12C+13C matches with 13C+13C very well!
•Each data set (except our data) has additional 15%-30% systematic uncertainty arising from statistical model.
•The isotope difference (mass, radius) is negligible when Ecm>2.6 MeV.
Two carbon isotope systems: 12C+13C and 13C+13C
1 b20 nb 13C+13C(Trentalange)
•Surprise! The 12C+12C is not enhanced but suppressed!
•The 12C+12C resonant xsecs of major resonances matches the xsec of the other two systems: 12C+13C and 13C+13C!
•Why ???? (Good question for the question session!)
Three carbon isotope systems: 12C+13C, 13C+13C and 12C+12C
xsec(12C+13C) or xsec(13C+13C) : Upper limit for 12C+12C13C+13C(Trentalange)
12C+12C
12C+13C
13C+13C
Above the Coulomb barrier
Extrapolation with the 12C+12C resonant cross sections
•Fit resonant cross sections with ESW (Best upper limit)
•CC-AW calculation (always over-predict xsecs at low Es, Safe upper limit )
•The first quantitative description of the 12C+12C resonant cross sections!
13C+13C(Trentalange)
•Our theory claims: 12C+13C (or 13C+13C)> 12C+12C
•The strong resonance at 2.14 MeV:the failure of our empirical relationship ?
•No confirmation of the 2.14 MeV yet: it may be a mistake in …..?
Strong resonance At 2.14 MeV
IsotopeSystematics
Systematics vs. Spillane’s Experiment
13C+13C(Trentalange)
•The preliminary data from the recent experiment at Naples* SUPPORT our finding! •No evidence for strange strong resonance!•For the Ecm=1.5 MeV resonance:Safe upper limit: 6 x Fowler rateBest estimated upper limit: ~ Fowler rate* Dr. Zickefoose, U. Connecticut thesis, 2011
Systematics wins!
IsotopeSystematics
Strong resonance At 2.14 MeV
13C+13C(Trentalange)
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
Notre Dame-ANL-IU fusion experiment
A 5 MV Pelletron with ECR source in terminal. Will be installed at the end of 2011.
Simulation @ Ecm=1.5 MeV
Solenoid Spectrometer for Nuclear AstroPhysics (SSNAP)
Silicon Array at Notre Dame (SAND)
By comparing with the Naples experiment, our setup will increase yield by two orders of magnitude!
Summary• A strong and interesting empirical correlation found among
three system: 12C+12C,12C+13C and 13C+13C.• First empirical upper limit rules out the possibility of strong
resonances at 1.5 MeV and 2.14 MeV. Impose new constrain on superburst model.
• With new detector + new accelerator building at ND and 24Mg(,’) experiment at RCNP, better data will be available soon.
• There are still many puzzles on the 12C+12C resonances even this topic is more than 50 years old.
• Hope we may solve the carbon fusion problem before the next Rutherford conference!
24Mg