Indirect reactions for astrophysics
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Indirect reactions for astrophysics @ the Tandem-Alto Pole of Orsay. Fa ïrouz Hammache (IPN-Orsay, France). LEA-workshop Catania, 13-15 October 2008. Nuclear astrophysics using indirect reactions @ Tandem-Orsay (end 2005-2008). Collaboration. Aim of the experiments. Indirect Method.

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LEA-workshop Catania, 13-15 October 2008

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Lea workshop catania 13 15 october 2008

Indirect reactions for astrophysics

@

the Tandem-Alto Pole of Orsay

Faïrouz Hammache

(IPN-Orsay, France)

LEA-workshop

Catania, 13-15 October 2008


Nuclear astrophysics using indirect reactions @ tandem orsay end 2005 2008

Nuclear astrophysics using indirect reactions @ Tandem-Orsay(end 2005-2008)

Collaboration

Aim of the experiments

Indirect Method

IPN-CSNSM-ULB-GANIL-GSI

13C(a,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(a,g)16O

He-burning in massive stars

12C(7Li,t)16O-transfer reaction

Analysis in progress

IPN-CSNSM-LNS-GANIL-SUBATECH

25Al(p,g)26Si

26Al synthesis in Novae

24Mg(3He,n)26Si*

Analysis in progress


Lea workshop catania 13 15 october 2008

Study of 13C(a,n)16Oreaction via 13C(7Li,t)17O transfer reaction

IPNO-CSNSM-ULB-GANIL-GSI

s-process nucleosynthesis (n,) half of the heavy elements in Univers

 90<A<209 low-mass

AGB stars 1-3 M (Temperatures108K)

He shell

Hydrogen shell

CO

core

12C(p,)13N(+)13C

Convective

envelope

13C pocket

13C(,n)16O

He intershell

Neutron source 13C(,n)16O

dYn/dt=Y13C.Y4He..NA<>13C(,n)-YX.Yn..NA<>X(n,)


Lea workshop catania 13 15 october 2008

Status of 13C(a,n)16Oreaction

Gamow peak ~190 keV100 pb

S-factor S(E)=E(E)exp(2)

S(E)=E(E)exp(2)

Drotleff et al.

(Sa=0.7)A (Sa=0.0)B

Ecm

7.166

6.862

? S?



6.359

6.356½+

13C+

5.939½-

n

Ecm (keV)

4.5543/2-

4.143

3.8415/2-

16O+n

S=0.3-0.7 (theoretical values)

Enough neutrons s-process nucleosynthesis

17O

 Kubono et al. 13C(6Li,d)17O(DWBA) S(exp)0.011!!!

 Keeley et al. reanalysis of Kubono data S(exp)=0.4

factor 40 ?!?!?!


Lea workshop catania 13 15 october 2008

Study of 17O states by 13C(7Li,t)17O -transfer reaction

SPLIT-POLE spectrometer (Orsay-Tandem)

E

tritons

13C(7Li,t)17O

t

13C target 80 g/cm2

pos

7Li @ 34,28MeV

Position gas chamber (B)

Faraday Cup

E proportional counter

E-E

monitor

 E7Li = 28 MeV

 Transfer measurements on 13C and 12C targets[0°-32°]

13C(7Li,7Li)13C measurements

 E7Li = 34 MeV

  • Transfer measurements on 13C and 12C targets [0°-32°]

  • 13C(7Li,7Li)13C data @ 34 MeV from Schumacher et al. NPA 212 (1973) 573


Lea workshop catania 13 15 october 2008

Comparison between our data and FRESCO calculations  S

assume :Sa=1for 7Li

For 3.055 MeV

Sa=0.260.06

Furutani et al. (S=0.25)

no need to add

compound nucleus

component

Clark et al.

S=0.25

S=0.35

S=0.290.11

in agreement with Kelley’s value

6.356 (1/2+)

6.356 (1/2+)


13 c n 16 o astrophysical s factor

13C(,n)16O Astrophysical S-factor

S-factor(ORSAY) @ 190 keV

1.40.5 106 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

Orsay

3/2+ (843 keV)

Drotleff 93

Brune 93

Gamow peak

M.G. Pellegriti, F. Hammache et al. PRC 70 (2008) 042801

Orsay range of allowed values for <v>is substancially reduced in comparison to Nacre compilation


Lea workshop catania 13 15 october 2008

12C(a,g)16O the Holy Grail of Nuclear Astrophysics

IPNO-LT(BEJAIA)-CSNSM-ULB-GANIL-GSI

Main reactions: 312C & 12C(a,g)16O

12C/16O abundance ratio

nucleosynthesis & subsequent

stellar evolution of massive stars

12C(a,g)16O in stellar helium burning

@ T=0.2 GK

BUT: E0=300 keV, (E0) ~ 10-8 nb

2? Sa

s(E0) is expected to be dominated by

E1 & E2 transitions.

2?Sa


Lea workshop catania 13 15 october 2008

Sa values for 6.05, 6.13, 6.92 & 7.12 MeV states of 16O

J(Ex, MeV)

6Li

48 MeV

(1998)

6Li

42 MeV

(1978)

6Li

90 MeV

(1980)

7Li

34 MeV

(1978)

0+ (6.05)

0.120.05

0.81

3.58

0.12 0.04

3- (6.13)

0.290.15

1.08

0.52

0.09 0.04

2+ (6.92)

0.37 0.11

1.35

0.82

0.18 0.05

1- (7.12)

0.160.05

1.08

0.86

0.07 0.05

  • Experimental problems ?

  • Analysis procedure ?

  • optical potential parameters ?

  • overlap of interaction mechanism, multi-step effects?


Lea workshop catania 13 15 october 2008

Study of 6.92 & 7.12 MeV 16O states by 12C(7Li,t)16O -transfer reaction @ Tandem-Orsay

12C(7Li,t)16O measured spectrum

@ 9 degree

FRDWBA calculation still in progress

Very preliminary d/dcm

Thesis of N. Oulebsir (Béjaïa University)


Lea workshop catania 13 15 october 2008

26Al nucleosynthesis in Novae

IPNO-CSNSM-LNS-GANIL-SUBATECH

COMPTEL Map of Galaxy @

1.809 MeV g-ray

Stellar sources of 26Al:

 Massive stars (SNII, Wolf Rayet)

AGB stars

Novae

25Al(p,g)26Sicompetes with

25Al(b+) 25Mg (t1/2 = 7.183 s )

25Al(p,g)26Sireaction rate

  • has large uncertainties

    26Al yield abundance is unknown

Two sequences to produce 26Al (T1/2=7.2 105 yr):

26Si

25Al

26Al

m

1.809 MeV

Spectroscopy of 26Si* via

24Mg(3He,n)26Si* reaction

g.s

24Mg

25Mg

26Mg


Lea workshop catania 13 15 october 2008

24Mg(3He,n)26Si*(g)26Si measurement

ONLINE

Set-up:

Pulsed 3He beam @ 7.9 MeV

I=60 pnA

Target: 150 g/cm2 of 24Mg

Measured g-spectrum

511 keV

4th Ex  1st Ex

972 keV

1st Ex of 26Si

@ 1795 keV

4 Ge detectors

Analysis in progress

E (keV)

ToF spectrum (n-g coin)

g prompt

region

of interest

36 EDEN detectors

ToF (au)


Lea workshop catania 13 15 october 2008

Futur projects: AGB stars @ Tandem-Orsay

  • AGB stars

  • 22Ne(a,n)25Mg: neutron source in AGB stars of intermediate mass

  •  2aof low-energy resonances, J of subthreshold resonances

  •  22Ne(7Li,t)26Mg @ Split-Pole

     14C(a,g)18O&19F(a,p)22Ne: 19F nuclesynthesis

  • 2aof low-energy resonances

     Transfer reactions using MUST2 detectors or Split-Pole


Lea workshop catania 13 15 october 2008

Study of 13C(a,n)16O & 12C(a,g)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*

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)


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