LEA-workshop Catania, 13-15 October 2008
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Transcript of LEA-workshop Catania, 13-15 October 2008
LEA-workshopCatania, 13-15 October 2008
Indirect reactions for astrophysics @
the Tandem-Alto Pole of Orsay
Faïrouz Hammache (IPN-Orsay, France)
Nuclear astrophysics using indirect reactions @ Tandem-Orsay (end 2005-2008)
Collaboration Aim of the experiments Indirect Method
IPN-CSNSM-ULB-GANIL-GSI
13C(,n)16O
Neutron source in AGB stars (1-3 M)
13C(7Li,t)17O -transfer reaction
PRC77 (2008) 042801
IPN-LT(BEJAIA)-CSNSM-ULB-GANIL-
GSI
12C(,)16O
He-burning in massive stars
12C(7Li,t)16O -transfer reaction
Analysis in progress
IPN-CSNSM-LNS-GANIL-SUBATECH
25Al(p,)26Si26Al synthesis in Novae
24Mg(3He,n)26Si*
Analysis in progress
IPNO-CSNSM-ULB-GANIL-GSI
Study of 13C(,n)16O reaction via 13C(7Li,t)17O transfer reaction
s-process nucleosynthesis (n,) half of the heavy elements in Univers
90<A<209 low-mass AGB stars 1-3 M (Temperatures108K)
CO core
He shellHydrogen shell
Convective envelope
Neutron source 13C(,n)16O
dYn/dt =Y13C.Y4He..NA<>13C(,n)-YX.Yn..NA<>X(n,)
13C pocket
12C(p,)13N(+)13C
13C(,n)16O
He intershell
Gamow peak ~190 keV100 pb
Ecm (keV)
Drotleff et al.(S=0.7)A (S=0.0)B
S(E)=E(E)exp(2)
factor 40 ?!?!?! Kubono et al. 13C(6Li,d)17O(DWBA) S(exp)0.011!!! Keeley et al. reanalysis of Kubono data S(exp)=0.4
Status of 13C(,n)16O reaction
13C+6.359 6.356 ½+
5.939 ½-
16O+n
4.554 3/2- 4.143
3.841 5/2-
17O
6.862 7.166
n
Ecm
? S?
S-factor S(E)=E(E)exp(2)
S=0.3-0.7 (theoretical values)
Enough neutrons s-process nucleosynthesis
SPLIT-POLE spectrometer (Orsay-Tandem)
7Li @ 34,28MeV
13C target 80 g/cm2
E-Emonitor
t
Position gas chamber (B)E proportional counter
tritonsE
pos
Faraday Cup
E7Li = 28 MeV Transfer measurements on 13C and 12C targets[0°-32°]
13C(7Li,7Li)13C measurements
E7Li = 34 MeVTransfer measurements on 13C and 12C targets [0°-32°]
13C(7Li,7Li)13C data @ 34 MeV from Schumacher et al. NPA 212 (1973) 573
dΩ
dσ
dΩ
dσ
13C(7Li,t)17O
Study of 17O states by 13C(7Li,t)17O -transfer reaction
Comparison between our data and FRESCO calculations SComparison between our data and FRESCO calculations S
assume :S=1 for 7Li
For 3.055 MeV
S=0.260.06
Furutani et al. (S=0.25)
no need to add
compound nucleus
component
Clark et al.
6.356 (1/2+) 6.356 (1/2+)
S=0.25 S=0.35S=0.290.11
in agreement with Kelley’s value
fm 7.5r @ keV 6.613.5)(2
22 rSr
S-factor(ORSAY) @ 190 keV
1.40.5 106 MeV-b
(S1/2+ is about 70% of the total)
The contribution of the
6.356 (1/2+) subthreshold state is dominant at
astrophysical energies
Drotleff 93 Brune 93
Orsay 3/2+ (843 keV)
Gamow peak
13C(,n)16O Astrophysical S-factor
13C(,n)16O Astrophysical S-factor
1131546.196.4
1131580.180.1
smolcm1099.6
smolcm1040.5
GK09.0@T
NACRE
ORSAY
v
v
Orsay range of allowed values for <v>
is substancially reduced in comparison
to Nacre compilation
M.G. Pellegriti, F. Hammache et al. PRC 70 (2008) 042801
IPNO-LT(BEJAIA)-CSNSM-ULB-GANIL-GSI
12C(,)16O in stellar helium burning@ T=0.2 GK
12C()16O the Holy Grail of Nuclear Astrophysics
Main reactions: 312C & 12C(,)16O
12C/16O abundance ratio
nucleosynthesis & subsequentstellar evolution of massive stars
(E0) is expected to be dominated by E1 & E2 transitions.
BUT: E0=300 keV, (E0) ~ 10-8 nb
2? S
2?S
J(Ex, MeV) 6Li
48 MeV
(1998)
6Li
42 MeV
(1978)
6Li
90 MeV
(1980)
7Li
34 MeV
(1978)
0+ (6.05) 0.120.05 0.81 3.58 0.12 0.04
0.09 0.04
0.18 0.05
0.07 0.05
3- (6.13) 0.290.15 1.08 0.52
2+ (6.92) 0.37 0.11 1.35 0.82
1- (7.12) 0.160.05 1.08 0.86
S values for 6.05, 6.13, 6.92 & 7.12 MeV states of 16O
Experimental problems ? Analysis procedure ?
optical potential parameters ? overlap of interaction mechanism, multi-step effects?
FRDWBA calculation still in
progress
12C(7Li,t)16O measured spectrum @ 9 degree
Very preliminary d/dcm
Study of 6.92 & 7.12 MeV 16O states by 12C(7Li,t)16O -transfer reaction @ Tandem-Orsay
Thesis of N. Oulebsir (Béjaïa University)
Spectroscopy of 26Si* via 24Mg(3He,n)26Si* reaction
26Al nucleosynthesis in NovaeIPNO-CSNSM-LNS-GANIL-SUBATECH
24Mg 25Mg 26Mg
26Al25Al
26Si
g.sm
1.809 MeV
Two sequences to produce 26Al (T1/2=7.2 105 yr):
25Al(p26Si competes with 25Al) 25Mg (7.183 s )
25Al(p26Si reaction rate has large uncertainties
26Al yield abundance is unknown
COMPTEL Map of Galaxy @ 1.809 MeV -ray
Stellar sources of 26Al:
Massive stars (SNII, Wolf Rayet)AGB stars
Novae
24Mg(3He,n)26Si*()26Si measurement
Set-up: Pulsed 3He beam @ 7.9 MeV I=60 pnA Target: 150 g/cm2 of 24Mg
4 Ge detectors
36 EDEN
detectors
Measured -spectrum
1st Ex of 26Si@ 1795 keV
511 keV
4th Ex 1st Ex 972 keV
E (keV)
ONLINE
Analysis in progress
ToF spectrum (n- coin)
region of interest
prompt
ToF (au)
Futur projects: AGB stars @ Tandem-Orsay
AGB stars
22Ne(,n)25Mg : neutron source in AGB stars of intermediate mass
2of low-energy resonances, J of subthreshold resonances
22Ne(7Li,t)26Mg @ Split-Pole
14C(,)18O & 19F(,p)22Ne: 19F nuclesynthesis
2of low-energy resonances
Transfer reactions using MUST2 detectors or Split-Pole
sssN. De Séréville, F.Hammache, S. Giron, S. Fortier, P. Roussel, M Baptiste, D. Beaumel, M. Chabot, M. Ferraton, S. Franchoo, F. Maréchal, C. Petrache, J.A. Scarpaci,
I. Stefan, D. Verney (IPN-Orsay)
A. Coc, J. Duprat, C. Hamadache, J. Kiener, A. Lefebvre-Schuhl (CSNSM-Orsay)
J.C. Dalouzy, F. Grancy, F. De Oliveira, J.C. Thomas (GANIL)
L. Lamia, G. Pizzone, S. Romano (LNS-Catania)
M. Fallot, L. Giot (SUBATECH)
Study of 13C(,n)16O & 12C(,)16O reactions via (7Li,t) -transfer reactions
sss
F.Hammache, M. G. Pellegriti*, P. Roussel, L. Audouin, D. Beaumel, S. Fortier (IPN-Orsay) N. Oulebsir (LT-Béjaïa)
J. Kiener, A. Lefebvre-Schuhl, V. Tatischeff (CSNSM-Orsay)P. Descouvemont (ULB-Brussels)
L. Gaudefroy (GANIL-Caen)M. Stanoiu (GSI-Darmstadt)
* LNS-Catania
Spectroscopy of 26Si via 24Mg(3He,n)26Si*