-capture measurements with theRecoil-Separator ERNA

Frank Strieder

Institut für Physik mit Ionenstrahlen Ruhr-Universität Bochum

HRIBF Workshop – Nuclear Measurements

for Astrophysics

October 23-24, 2006, Oak Ridge,

Tennessee

12C(,)16O

the Holy Grail 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

Experimental approach: ERNA

Gas target Gas pressure profile: 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

Angular acceptancealong the gas target

ERNA - Experimental approach Setup

4He gas 12C beamseparator

central position

upstream positionbeam

diameter

upstream position(energy acceptance)

full angular acceptance 100 % transmission (better 3) over the total gas target length

and full beam diameter

Angular acceptancealong the gas target

ERNA - Experimental approach Setup

-

+

Simulation ofrecoil cone

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]

12C(,)16O

the Holy Grail of

Nuclear Astrophysics

e

e

3He(,)7Be

pp chain

Explanation of Stars

1960‘s Davis, Fowler & BahcallHomestake Experiment

solar spy=

solar neutrinos

Neutrino spectroscopy ?

Sun = calibrated source

HHydrogen Burning4p 4He + 2 + 2e-

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

two types of rays are used to measure 3He(,)7Be cross section

7Be

7Li

3He+4He

2

1Ecm(MeV)

1.586MeV

4.634.57

1/2-

7/2-

3/2-

1/2-

3/2-

7/2-

0

478

1

42

9

Capture -rays:0,1,429

Delayed - rays::7Be decay: 478

10.52%

89.48%

T½ =53.3d

Q=

0,3

0,4

0,5

0,6

0,7

0,8

Par

ker&

Kav

anag

h(19

63)

Nag

atan

i,Dw

arak

anth

,Ash

ery(

1969

)

Kra

win

kel(

1982

)

Osb

orne

(198

2,19

84)

Ale

xand

er(1

984)

Hilg

emei

er(1

988)

Osb

orne

(198

2,19

84)

Rob

erts

on(1

983)

Vol

k(19

83)

Nar

a Si

ngh(

2004

)

S 34(

0) (

keV

b)

DC measurementsDelayed measurements

0.5073keVb 0.5503+-0.0143keVb

Summary for the S34(0) values

ERNA Acceptance 3He(,)7Be

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

Ecm=1.8 MeV

Inverse kinematics

0 500 1000 1500 2000 25000,2

0,3

0,4

0,5

0,6

0,7

Hilgemeier 1988 Alexander 1984 Robertson 1983 Osborn 1982 Nagatani 1969 Parker 1963 Kräwinkel 1982 Weizmann 2004 LUNA 2006 ERNA 2006

S34

fac

tor [k

eV-b

]

Ecm

[keV]

0 500 1000 1500 2000 25000,2

0,3

0,4

0,5

0,6

0,7

Hilgemeier 1988 Osborn 1982 Parker 1963 Kräwinkel 1982 Weizmann 2004 LUNA 2006 ERNA 2006

S34

fac

tor [k

eV-b

]

Ecm

[keV]

0 500 1000 1500 2000 25000,2

0,3

0,4

0,5

0,6

0,7

Hilgemeier 1988 Osborn 1982 Parker 1963 Weizmann 2004 LUNA 2006 ERNA 2006

S34

fac

tor [k

eV-b

]

Ecm

[keV]

ERNA astrophysical S Factor RESULTS

Pre

limin

ary

resu

lt

0 500 1000 1500 2000 25000,2

0,3

0,4

0,5

0,6

0,7

Hilgemeier 1988 Kräwinkel 1982 Weizmann 2004 LUNA 2006 ERNA 2006

S34

fac

tor [k

eV-b

]

Ecm

[keV]

3He(a,)7Be - measurement (free & coincidences)

12C(,)16O - measurement (jet gas target)

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)