-capture measurements with the recoil-separator erna
DESCRIPTION
-capture measurements with the Recoil-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. 12 C( ,) 16 O the Holy Grail of - PowerPoint PPT PresentationTRANSCRIPT
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-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
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12C(,)16O the Holy Grail of
Nuclear Astrophysics
e
e
3He(,)7Bepp chain
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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
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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
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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
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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
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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
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Experimental approach: ERNA
Gas target Gas pressure profile: 7Li()7Li
+ energy loss of: 14N, 12C, 7Li
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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
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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
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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
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Angular acceptancealong the gas target
ERNA - Experimental approach Setup
-+
Simulation ofrecoil cone
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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
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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
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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
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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]
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12C(,)16O the Holy Grail of
Nuclear Astrophysics
e
e
3He(,)7Bepp chain
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Explanation of Stars
1960‘s Davis, Fowler & BahcallHomestake Experiment
solar spy=
solar neutrinos
Neutrino spectroscopy ?
Sun = calibrated source
HHydrogen Burning4p 4He + 2 + 2e-
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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
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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
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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=
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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
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ERNA Acceptance 3He(,)7Be
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ERNA E/E Spectra 3He(,)7Be
Ecm=1.8 MeV
Inverse kinematics
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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]
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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)