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*