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Experimente für den astrophysikalischen p-ProzessJ. Hasper, IKP, niversität zu Köln, AG ZilgesL. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Experimental facilities for reaction studies in Nuclear Astrophysics in Cologne
L. Netterdon, M. Elvers, J. Endres, A. Hennig*, A. Sauerwein*, F. Schlüter, and A. Zilges
Institut für Kernphysik, Universität zu Köln
496th WE-Heraeus Seminar on
„Astrophysics with modern small-scale accelerators“
Bad Honnef, February 08th, 2012Supported by the DFG under contract DFG (ZI 510/5-1, INST 216/544-1)*Member of the Bonn-Cologne Graduate School of Physics and Astronomy
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Outline
MotivationCounting setup for activation measurements– Example: 168Yb(a,n)
In-beam spectroscopy @ HORUS– Example: 92Mo(p,g), 92Mo(a,g)
CologneAMSSummary
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Motivation
measurement of ion-induced reactions experimental difficulties due to:measurement at energies below the Coulomb barrier for heavy nucleie.g. for 168Yb(a,g): EGamow ≈ 7 – 11 MeV << Ecoul ≈ 24 MeV
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Motivation
σ ≈ 0.1 – 100 μb
very sensitive determination of small cross sections needed
measurement of ion-induced reactions experimental difficulties due to:measurement at energies below the Coulomb barrier for heavy nucleie.g. for 168Yb(a,g): EGamow ≈ 7 – 11 MeV << Ecoul ≈ 24 MeV
activation / in-beam / AMS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Motivation
σ ≈ 0.1 – 100 μb
very sensitive determination of small cross sections needed
measurement of ion-induced reactions experimental difficulties due to:measurement at energies below the Coulomb barrier for heavy nucleie.g. for 168Yb(a,g): EGamow ≈ 7 – 11 MeV << Ecoul ≈ 24 MeV
activation / in-beam / AMS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Counting Setup
2 HPGe clover detectorspassive background suppression by Cu and Pblow natural backgroundcovers large solid angle
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Counting Setup
2 HPGe clover detectorspassive background suppression by Cu and Pblow natural backgroundcovers large solid angle
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Counting Setup
2 HPGe clover detectorspassive background suppression by Cu and Pblow natural backgroundcovers large solid angle
different target geometries possibleaccurate target positioning to 0.1 mm
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Clover detectors
4 independent crystalsrel. efficiency of 120 %
G. D
uchêne et al., N
IM A 432 (1999) 90-110
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Clover detectors
4 independent crystalsrel. efficiency of 120 %
advantages:– higher count rates– reduced summing effects– Compton polarimetry– add-back algorithms– claim gg coincidences between crystals
and detectors
G. D
uchêne et al., N
IM A 432 (1999) 90-110
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Counting Setup
absolute photopeak efficiency @ 1332 keV ≈ 5 %distance to end cap: 13 mm
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
4 inputsADCTrigger / Filter FPGA
DSP
System FPGA
4 BGO Veto inputs
Data acquisition
XIA LLC, User‘s Manual Digital Gamma Finder DGF-4CRevision F, Version 4.03
digital data acquisition
XIA DGF-4C modules
14-bit pipeline ADC
sampling of preamplifier
output at 80 MHz
listmode data
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Data acquisition
2 m
1.8 m
digital data acquisition
XIA DGF-4C modules
14-bit pipeline ADC
sampling of preamplifier
output at 80 MHz
listmode data
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Data acquisition
digital data acquisition
XIA DGF-4C modules
14-bit pipeline ADC
sampling of preamplifier
output at 80 MHz
listmode data
cost / space saving
very good energy
resolution
higher count rates
20 cm
6 cm
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Digitizer – basic design
Detector
ADC Pipeline ADC
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Digitizer – basic design
Detector
ADC Pipeline ADC
What to do?
?
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Digitizer – basic design
Detector
ADC Pipeline ADC
What to do?
?
write every trace to hard disk for offline analysis≈ 500 GB / hour / channel
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Digitizer – basic design
Detector
ADC Pipeline ADC
What to do?
?
write every trace to hard disk for offline analysis≈ 500 GB / hour / channelsignal processing in hardware using combination ofField Programmable Gate Array (FPGA)Digital Signal Processor (DSP)
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Digitizer – basic design
Detector
ADC
FPGA
DSP
Pipeline ADC
Field Programmable Gate Array→ applies filter algorithms
Digital Signal Processor→ determines energy and time
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Signal processing - requirements
Trigger: select signals of interestTiming: when did the event occur relative to others?Pile-Up: reject events, if they were too close to determine energyEnergy: calculate difference between maximum and baseline
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Signal processing - requirements
Trigger: select signals of interestTiming: when did the event occur relative to others?Pile-Up: reject events, if they were too close to determine energyEnergy: calculate difference between maximum and baseline
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Trapezoidal filter algorithm
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
t
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
t
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
V
t
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S = S2 – S1 = 0
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Fast and slow filter algorithmX
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ser‘s Manual D
igital Gam
ma Finder
DG
F-4C R
evision F, Version 4.03fast filter → time determinationslow filter → energy determination
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Energy resolution
time constant t most important for good energy resolution
adjust t parameter to get best peak shape and resolution
courtesy of N. W
arr
t
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Activation measurement of 168Yb(α,n)
168Yb 170Yb 171Yb169Yb
169Lu 170Lu 171Lu 172Lu
173Hf172Hf171Hf170Hf
motivation: improvement of reaction network at 168Yb
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Activation measurement of 168Yb(α,n)
168Yb 170Yb 171Yb169Yb
169Lu 170Lu 171Lu 172Lu
173Hf172Hf171Hf170Hf
motivation: improvement of reaction network at 168Yb problems:
– 172Hf(g,a) needs unstable target(g,a)
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Activation measurement of 168Yb(α,n)
168Yb 170Yb 171Yb169Yb
169Lu 170Lu 171Lu 172Lu
173Hf172Hf171Hf170Hf
motivation: improvement of reaction network at 168Yb problems:
– 172Hf(g,a) needs unstable target– 168Yb(a,g):
• low cross section• weak & low-energetic g transitions
(a,g)
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Activation measurement of 168Yb(α,n)
168Yb 170Yb 171Yb169Yb
169Lu 170Lu 171Lu 172Lu
173Hf172Hf171Hf170Hf(α,n)
motivation: improvement of reaction network at 168Yb problems:
– 172Hf(g,a) needs unstable target– 168Yb(a,g):
• low cross section• weak & low-energetic g transitions
measure168Yb(α,n) to improve a+168Yb OMP
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Activation measurement of 168Yb(α,n)
168Yb 170Yb 171Yb169Yb
169Lu 170Lu 171Lu 172Lu
173Hf172Hf171Hf170Hf(α,n)
motivation: improvement of reaction network at 168Yb
cross section sensitive to g and neutron width
T. Rauscher, NON-SMOKERWEB,5.8.1dw
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Experimental setup @ PTB Braunschweig
a-beam
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Experimental setup @ PTB Braunschweig
a-beam
Cooling trap
Target
Wat
er c
oolin
g
U = -300V
Ea = 12.9 MeV – 15.1 MeVactivation period ≈ 5 h – 20 hcurrent ≈ 600 nAtarget thickness ≈ 230 – 450 2cm
g
a-beam
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Activation measurement of 168Yb(α,n)
Ea = 14.55 MeVcounting period ≈ 23 h
840
keV66
7 ke
V740 keV
935 keV
835 keV
168 keV95 keV≈ 5 msg.s.
171Yb
168Yb(a,n)
171Luε
T1/2 = 8.24 d
171Hf
667
740
840
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Results: 168Yb(a,n)171Hf
no calculation reproduces energy dependence correctlyoverprediction of cross sections up to one order of magnitude
T. Rauscher, N
ON
-SM
OK
ER
WE
B,5.8.1dwA
.J. Koning, S
. Hilaire and M
.C. D
uijvestijn,TALY
S-1.2
PRELIMINARY
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Limitations of activation technique
Activation technique not applicablein many cases because of• stable reaction products• inconvenient half-lives• weak g intensities
Only 20% of stable nuclei accessible
In-beam / AMS technique to overcome limitations
(a,g) not accessible
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Tandem accelerator in Cologne
10 MV Tandem ion acceleratorbeam intensities up to 1 µA (p) / ≈ few 100 nA (a-particles)restart in spring 2012 after complete refurbishmenthigh efficiency HPGe detector array HORUS for in-beam g spectroscopy
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
In-beam measurements @ HORUS
array of 14 HPGe detectorsup to 6 equipped with BGO shieldsabsolute photopeak efficiency @ 1332 keV: ≈ 2 %determination of angular distributionscoincidence techniques for background suppressiondigital data acquisition in preparation
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
In-beam measurements @ HORUS
Test experiment for 92Mo(p,g)
92Mo 94Mo 95Mo93Mo
93Tc 94Tc 95Tc 96Tc
97Ru96Ru95Ru94Ru
(p,g) e, b+
activation measurement can be performed simultaneouslycomparison with existing data from an activation experiment possible (T. Sauter et al., PRC 55 (1997) 3127)
Ep = 2.8 – 3.3 MeVGamow window: 1.6 – 3.6 MeV current ≈ 200 pnA
T1/2(93Tcg) =2.75 h
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
partial cross sections
92Mo(p,g)93Tc93Tc
Ep= 3300 keVQ = 4087 keV
de-excitation of compound state
19F(p,a)16O
27Al(p,g)28Si
27Al(p,g)28Si
27Al(p,p‘)
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Partial cross sectionstotal cross section
92Mo(p,g)93Tc93Tc
Ep= 3300 keVQ = 4087 keV
de-excitation of compound statetransitions to ground state
19F(p,a)16O
27Al(p,g)28Si
27Al(p,g)28Si
27Al(p,p‘)
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Partial cross sectionsTotal cross sectionproduction of 1st excited state
92Mo(p,g)93Tc93Tc
Ep= 3300 keVQ = 4087 keV
de-excitation of compound statetransitions to ground statetransitions to 1st excited state
19F(p,a)16O
27Al(p,g)28Si
27Al(p,g)28Si
27Al(p,p‘)
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Results: 92Mo(p,g)
PRELIMINARY
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Results: 92Mo(p,g)
PRELIMINARY
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Results: 92Mo(p,g)
PRELIMINARY
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Results: 92Mo(p,g)
PRELIMINARY
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
92Mo 94Mo 95Mo93Mo
93Tc 94Tc 95Tc 96Tc
97Ru96Ru95Ru94Ru
(a,g)
In-beam measurements @ HORUS
Test experiment for 92Mo(a,g)
comparison with in-beam measurement using 4p NaI detector (to be published)a energies ~ 9.3 - 10 MeVGamow window: 5.5 – 8.6 MeVcurrent ~ 30 pnA
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
92Mo(a,g)96Ru
Ea= 9300 keVQ = 1692 keV
Many background reactions:Target chamber• 27Al(a,n)30P• 27Al(a,p)30Si• 27Al(a,a‘)27Al
Tantalum coatingof chamber
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
92Mo(a,g)96Ru
Ea= 9300 keVQ = 1692 keV
Many background reactions:Target chamber• 27Al(a,n)30P• 27Al(a,p)30Si• 27Al(a,a‘)27Al
Target contaminants • 13C(a,n)16O• 17O(a,n)20Ne• 18O(a,n)21Ne
Tantalum coatingof chamber
High vacuum or „Cooling Finger“
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
92Mo(a,g)96Ru
Ea= 9300 keVQ = 1692 keV
Many background reactions:Target chamber• 27Al(a,n)30P• 27Al(a,p)30Si• 27Al(a,a‘)27Al
Competitive reactions• 92Mo(a,p)95Tc
Target contaminants • 13C(a,n)16O• 17O(a,n)20Ne• 18O(a,n)21Ne
Decay of radioactive reaction products
Tantalum coatingof chamber
High vacuum or „Cooling Finger“
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
92Mo(a,g)96Ru
Ea= 9300 keVQ = 1692 keV
Many background reactions:Target chamber• 27Al(a,n)30P• 27Al(a,p)30Si• 27Al(a,a‘)27Al
Competitive reactions• 92Mo(a,p)95Tc
Target contaminants • 13C(a,n)16O• 17O(a,n)20Ne• 18O(a,n)21Ne
Decay of radioactive reaction products
Tantalum coatingof chamber
High vacuum or „Cooling Finger“ + use gg coincidence
techniques
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Coincidence with Eg=833 keV
Eg [keV]
No coincidence
92Mo(a,g)96Ru
600 800 1000 1200 1400 1600 1800
Eg [keV]
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Coincidence with Eg=833 keV
Eg [keV]
No coincidence
92Mo(a,g)96Ru
600 800 1000 1200 1400 1600 1800
Eg [keV]
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Coincidence with Eg=833 keV
No coincidence
92Mo(a,g)96Ru
Eg [keV]
In-beam measurements @ HORUS
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Cologne AMS
Tandetron accelerator with 6 MV terminal voltagestandard isotopes: 10Be, 14C, 26Al, 36Cl, 41Ca, 129I(geosciences, pre- and protohistory)ample beam time reserved for nuclear physics applications
Universitätzu Köln
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Cologne AMS
Status:first 14C test measurement successful in February 2011start of standard operation in fall 2011
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Cologne AMS
Isotopes Precision for acceptance
Measured precision
10Be / 9Be 3 % at 10-12 1.9 %14C / 12C 0.5 % at 10-12 0.3 %
26Al / 27Al 3 % at 10-11 1.3 %36Cl / 35Cl 3 % at 10-12 1.3 %
courtesy of S. H
einze
results from first performance test for standard cosmogenic nuclides
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Cologne AMS
Isotopes Precision for acceptance
Measured precision
10Be / 9Be 3 % at 10-12 1.9 %14C / 12C 0.5 % at 10-12 0.3 %
26Al / 27Al 3 % at 10-11 1.3 %36Cl / 35Cl 3 % at 10-12 1.3 %
courtesy of S. H
einze
results from first performance test for standard cosmogenic nuclides
prime example for Nuclear Astrophysics:144Sm(a,g)148Gd
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Summary & Outlook
several techniques to study (p,g) and (a,g) reactions of astrophysical relevance on stable nuclei
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Summary & Outlook
several techniques to study (p,g) and (a,g) reactions of astrophysical relevance on stable nucleiactivation technique– counting setup with 2 HPGe clover detectors– gg coincidences and advantages of digital data
acquisitionin-beam technique– HORUS array provides large amount of information
accelerator mass spectrometry
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Summary & Outlook
several techniques to study (p,g) and (a,g) reactions of astrophysical relevance on stable nucleiactivation technique– counting setup with 2 HPGe clover detectors– gg coincidences and advantages of digital data
acquisitionin-beam technique– HORUS array provides large amount of information
accelerator mass spectrometry
provide experimental data base for (p,g) and (a,g) reactionsderive reliable global properties, e.g., optical model potentials
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
Experimental Facilities for Reaction Studies in Nuclear Astrophysics in Cologne
V. Derya, M. Elvers, J. Endres, A. Hennig, J. Mayer, S. Pascu, S. Pickstone, A. Sauerwein, F. Schlüter, M. Spieker, K. O. Zell, and A. Zilges
U. Giesen
H.W. Becker and D. Rogalla
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L. Netterdon, IKP, Universität zu Köln, AG Zilges Experimental facilities for reaction studies in Nuclear Astrophysics
168Yb(a,g)171Hf - Sensitivity