Ulrike Hager18.05.2011 ISAC Science Forum
16O(α,γ)20Ne at DRAGON
Ulrike Hager
Motivation
18.05.2011 ISAC Science Forum
He burning
T = 1 – 3 · 108 K
main end products 12C & 16O, ratio determined by 16O(α,γ)20Ne
determines abundances of products of later carbon burningmainly 20Ne, 23Na, 23,24Mg and 28Si
test case for nuclear model calculations
2 doubly magic nuclei in the entrance channel
Ulrike Hager
20Ne levels
18.05.2011 ISAC Science Forum
no excited state in 20Ne at relevant ener-gies
2− cannot be populated (entrancechannel both Jπ = 0+)
higher resonances too narrow
sub-threshold resonance too low,high centrifugal barrier
reaction via non-resonant direct capture
Ulrike Hager
Current situation
18.05.2011 ISAC Science Forum
Ecm Langanke Hahn Baye Knee0.3–0.45 MeV 2.34 MeVb 0.7 ± 0.3 MeVb 1.7 MeVb 3.37 MeVb1.7 MeV 3.665 MeVb 3.37 MeVb2.3 MeV 4.295 MeVb 2.8 MeVb 3.37 MeVb
Ulrike Hager
DRAGON
18.05.2011 ISAC Science Forum
p/q
E/q
Inverse kinematics
precoil = pbeam
Erecoil = EbeamMbeam
Mrecoil
beam suppression108 – 1013
angular acceptance≈ ±20 mrad
Ulrike Hager
DRAGON gas target
18.05.2011 ISAC Science Forum
Windowless gas target
typical pressures 4 – 8 torr
Monitor detectorsfor beam normalisation
Ulrike Hager
DRAGON gas target
18.05.2011 ISAC Science Forum
30 BGOs
geometric efficiency 89-92%
possibility to locate resonance position
Ulrike Hager
DRAGON end detectors
18.05.2011 ISAC Science Forum
Ion chamber
particle id, energy
Ulrike Hager
DRAGON end detectors
18.05.2011 ISAC Science Forum
Ion chamber
particle id, energy
MCPs
timing
Ulrike Hager
Energies
18.05.2011 ISAC Science Forum
September
beam intensity ≈ 9 × 1011 1/s≈ 10 shifts
April
beam intensity ≈ 1.8 × 1012 1/s≈ 18 shifts
Ulrike Hager
20Ne charge state distribution
18.05.2011 ISAC Science Forum
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
3 3.5 4 4.5 5 5.5 6 6.5 7
frac
tion
charge state
487 AkeV326 AkeV279 AkeV
dashed: calculated (Liu et al., NIM A 496, 2003)
Ulrike Hager
Ecm = 2263 keV (Sep. 2010)
18.05.2011 ISAC Science Forum
71(4)% S2
Ulrike Hager
Ecm = 2263 keV (Sep. 2010)
18.05.2011 ISAC Science Forum
Hahn (1987)
Costantini (2010)
S = 1.43 ± 0.22 MeVb
S0 = 0.42 ± 0.09 MeVb
S2 = 1.02 ± 0.17 MeVb
Ulrike Hager
Recoil Separation
18.05.2011 ISAC Science Forum
IC0 (channel)200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400
IC1
(cha
nnel
)
0
200
400
600
800
1000
1200
1400
1600
1800
IC_0 vs. IC_1
IC energy (channel)0 1000 2000 3000 4000 5000
MC
P T
AC
(ch
anne
l)
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
IC Sum vs. Mcp TAC
Ulrike Hager
Resonance
18.05.2011 ISAC Science Forum
max gamma energy / keV0 1000 2000 3000 4000 5000 6000 7000 80000
20
40
60
80
100
120
140
SeptemberApril
Ulrike Hager
Resonance
18.05.2011 ISAC Science Forum
Knee ’94: 10.8 ± 1.5 meV
DRAGON preliminary:
September 7 ± 3 meV
April 8 ± 2 meV
requires detailed GEANT simulations to determine branching ratios andefficiencies
Ulrike Hager
Ecm = 2263 keV DC
18.05.2011 ISAC Science Forum
Entries 447
max gamma energy / keV0 1000 2000 3000 4000 5000 6000 70000
2
4
6
8
10
12
14
16
18
20
22Entries 447
Ulrike Hager
Outlook
18.05.2011 ISAC Science Forum
resonance branching ratios
determine ratio of S0 and S2 for DC
request more beam time to measure at lower energies?
Thank you