-capture measurements with a Recoil-Separator

Frank Strieder

Institut für Physik mit Ionenstrahlen Ruhr-Universität Bochum

Int. Workshop on Gross Properties of Nuclei

and Nuclear Excitation

15th – 21st January 2006, Hirschegg, Austria

12C(,)16O

the Holy Gral of

Nuclear Astrophysics

e

e

3He(,)7Be

pp chain

Er

DANGER OF EXTRAPOLATION !

non resonant process

interaction energy E

extrapolationor measurements ? direct measurement

0

S(E)

LINEARSCALE

S(E)-FACTOR

-Er

sub-threshold resonance

low-energy tailof broad

resonance

Danger of Extrapolation

Important forExperimentsLow energy

High energy

ERNA - Experimental approach Pro & Cons

purificationseparation

A B Cn+

detection

A

coincidence

detection

Requirements

• beam purification • 100% transmission for the selected charge state• high suppression of the incident beam• inverse kinematics (gas target)

Advantages

• low background• high detection efficiency• measure tot

• background free ray spectra• gas target

Disadvantages

• difficult to do• commissioning• charge state• beam intenity ?

A different approach: recoil mass separator

C

ERNA - Experimental approach

projectiles projectiles

+ Recoils

prec = pproj

momentumconservation

SeparationDetection &

IdentificationRecoils

projectiles

focusing

He target

-ray emission Recoil cone

-Recoil Coincidences

Minimum supression factor

with = 10nbarn, ntarget=1x1018at/cm²

Nproj / Nrecoils~ 1x1014

ERNA - Experimental approach Setup

ion source dynamitron

tandem accelerator

ion beam purification

He Gastarget

singlet

60° magnet

E -E telescope

recoil separation

doublet

analysing magnet

recoil focussing

Wien filter

Wien filter Wien filter

Wien filter

magnetic qu adrupole multiplets

triplet

side FC

characteristics:

angular acceptance 32 mrad for 16O at Elab=3.0 – 15.0

MeV

for the total length of the gas target

energy acceptance 10% for 16O at Elab=3.0 – 15.0 MeV

suppression of incident beam (10-10 - 10-12)·10-2 (IC)

=> min < 1 nb

purification of incident beam < 10-22

resolution of ion chamber 250·A keV

or combination E-silicon strip detector layout COSY Infinity (recoils fit in 4” beam tube) field settings are not calculated, but tuned

ERNA - Experimental approach Setup

Gas target Gas pressure profile: 7Li()11B, 7Li()7Li

+ energy loss of: 14N, 12C, 7Li

ERNA - Experimental approach Charge State Distributions

measured for entire energy range

but question about point of origin in the gas target → no equilibrium

4He gas 12C beam

ERNA - Experimental approach Setup

Solution: a post-target-stripper

to the separator

► First test with laser ablated carbon foil: 12C(12C,8Be)16O► Final configuration: Ar post-target stripper after the 4He target

4He Ar

3He(,)7Be no post-target-stripper – measure all charge states

ERNA Motivation Helium Burning

Main reactions: 312C and 12C()16O

Stellar Helium burning: 12C()16O

12C/16O abundance ratio

Subsequent stellar evolution and nucleosynthesis

but

E0~ 300 keV, very low cross section

Accurate measurements at higher energy and

extrapolation to E0 are needed

12C

4He

16O

4He

triple alpha

12C()16O

Red Giant

ERNA E/E Matrix

12C()16O Ecm=2.5 MeV

[channel]restE0 500 1000 1500 2000 2500

E [

chan

nel

]

500

1000

1500

2000

2500

3000

SuppressionR~8*10-12

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

10000 to

t [n

b]

Ecm

[MeV]

ERNA Cross Section Curve RESULTS

ERNA astrophysical S Factor RESULTS

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

Sto

t [k

eV-b

]

Ecm

[MeV]

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

Sto

t [k

eV-b

]

Ecm

[MeV]

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

Sto

t [k

eV-b

]

Ecm

[MeV]

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

Sto

t [k

eV-b

]

Ecm

[MeV]

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

Sto

t [k

eV-b

]

Ecm

[MeV]

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.01

10

100

1000

Sto

t [k

eV-b

]

Ecm

[MeV]

ERNA Motivation Helium Burning

solar spy=

solar neutrinos

Neutrino spectroscopy ?

Sun = calibrated source

ERNA Motivation Neutrino Spectroscopy

ERNA Motivation Neutrino Spectroscopy

-8

-4

0

4

8

12

p+p 8B 7Be+e+ 3He+p p+e-+p

perc

enta

ge v

aria

tion

[%

]

LageZ/Hp+p3He+3He3He+4He7Be+p

(L ) = 0.4 %

age ) = 0.4 %Z/H ) = 3.3 %

(L ) = 0.4 %

age ) = 0.4 %Z/H ) = 3.3 %

p-p) = 2 %3He+3He) = 6 %3He+4He) = 15 %7Be+p) = 10 %

p-p) = 2 %3He+3He) = 6 %3He+4He) = 15 %7Be+p) = 10 %

Influence of different sources of uncertainties on the neutrino flux

ERNA Motivation Neutrino Spectroscopy

radio-chemical

-8

-4

0

4

8

12

gallium clorine

perc

enta

ge v

aria

tion

[%

]

L

age

Z/H

p+p

3He + 3He

3He + 4He

7Be + p

SNO

-8

-4

0

4

8

12

16

fCC fES fNC

perc

enta

ge v

aria

tion L

age

Z/H

p+p

3He + 3He

3He + 4He

7Be + p

Influence of different sources of uncertainties on the neutrino experiment

ERNA Motivation 3He(,)7Be

Gamma: S34(0) = 0.507±0.016 keVb

Activation: S34(0) = 0.563±0.018 keVb

Ex (keV) J

4570

429

0

7/2-

1/2-

3/2-

3He+4He

7Be level scheme

Q = 1587keV DC 429

DC 0

428

Ex (keV)

7Li0

EC

1/2-

3/2-

J

3He()7Be(e,)7Li*()7Li

ERNA Acceptance 3He(,)7Be

ERNA E/E Spectra 3He(,)7Be

Ecm=1.8 MeV

Inverse kinematics

ERNA astrophysical S Factor RESULTS

0 500 1000 1500 2000 25000,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

-ray measurement activity measurement ERNA Descouvemont '04

S34

fac

tor

[keV

-b]

Ecm

[keV]

Preliminary result

14N(p,)15O

16N -delayed -decay

14N(a,)18F

d(a,)6Li

ERNA - future plans and other perspectives

ERNA – present status

12C(,)16O Ecm>1.9 MeV (1.3 MeV)

3He(a,)7Be Ecm>1.1 MeV (0.6 MeV)