-capture measurements with theRecoil-Separator ERNA

Frank StriederInstitut 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(,)7Bepp 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

purification separation

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

diameterupstream 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 Matrix12C()16O Ecm=2.5 MeV

[channel]restE0 500 1000 1500 2000 2500

E [c

hann

el]

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 [nb]

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

S tot [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

S tot [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

S tot [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

S tot [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

S tot [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

S tot [k

eV-b

]

Ecm [MeV]

12C(,)16O the Holy Grail of

Nuclear Astrophysics

e

e

3He(,)7Bepp 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 %

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

[%]

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

SNO

-8

-4

0

4

8

12

16

fCC fES fNC

perc

enta

ge v

aria

tion L

ageZ/Hp+p3He + 3He3He + 4He7Be + 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

Park

er&

Kav

anag

h(19

63)

Nag

atan

i,Dw

arak

anth

,Ash

ery(

1969

)

Kra

win

kel(1

982)

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) (k

eVb)

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

S 34 fa

ctor

[keV

-b]

Ecm [keV]0 500 1000 1500 2000 2500

0,2

0,3

0,4

0,5

0,6

0,7

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

S 34 fa

ctor

[keV

-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

S 34 fa

ctor

[keV

-b]

Ecm [keV]

ERNA astrophysical S Factor RESULTSPrelim

inary result

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

S 34

fact

or [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)