-capture measurements with the Recoil-Separator ERNA Frank Strieder Institut für Physik mit...
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Transcript of -capture measurements with the Recoil-Separator ERNA Frank Strieder Institut für Physik mit...
-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)