Ulrike Hager06.10.2010 ISAC Science Forum

16O(α,γ)20Ne at DRAGON

Ulrike Hager

Motivation

06.10.2010 ISAC Science Forum

He burning

T = 1 – 3 · 108 K

main end products 12C & 16O, ratio determined by16O(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

06.10.2010 ISAC Science Forum

no excited state in 20Ne at relevantenergies

2− cannot be populated (en-trance channel both Jπ = 0+)

higher resonances too narrow

sub-threshold resonance toolow, high centrifugal barrier

reaction via non-resonant direct cap-ture

Ulrike Hager

Current situation

06.10.2010 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

06.10.2010 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

06.10.2010 ISAC Science Forum

Windowless gas target

typical pressures 4 – 8 torr

Monitor detectorsfor beam normalisation

Ulrike Hager

DRAGON gas target

06.10.2010 ISAC Science Forum

30 BGOs

geometric efficiency 89-92%

possibility to locate resonance position

Ulrike Hager

DRAGON end detectors

06.10.2010 ISAC Science Forum

Ion chamber

particle id, energy

Ulrike Hager

DRAGON end detectors

06.10.2010 ISAC Science Forum

Ion chamber

particle id, energy

MCPs

timing

Ulrike Hager

Energies

06.10.2010 ISAC Science Forum

proposal

beam intensity 1.3 × 1012 1/s

28 shifts approved

September run

beam intensity ≈ 9 × 1011 1/s

≈ 10 shifts

Ulrike Hager

Energies

06.10.2010 ISAC Science Forum

Ulrike Hager

Recoil Separation

06.10.2010 ISAC Science Forum

IC energy (channel)0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

MC

P T

AC

(ch

anne

l)

0

500

1000

1500

2000

2500

3000

3500

4000

ahIcSumVsTACEntries 1093Mean x 5902Mean y 2870RMS x 856.9RMS y 94.08

ahIcSumVsTACEntries 1093Mean x 5902Mean y 2870RMS x 856.9RMS y 94.08

IC Sum vs. Mcp TAC

CS: 4+

Ulrike Hager

Yields

06.10.2010 ISAC Science Forum

used calculated CSDs→ need to be measured

BGO efficiency from GEANT

on-resonance:decay scheme known

off-resonance:assumed different ratios for decay to ground state and 1st

excited state

Ulrike Hager

Yields

06.10.2010 ISAC Science Forum

2.30 2.35 2.40E_cm [MeV]

10-14

10-13

10-12

yie

ld

Reaction yield

Ulrike Hager

Resonance strength

06.10.2010 ISAC Science Forum

Knee thesis (’94) : 10.8 ± 1.5 meV

DRAGON preliminary:

singles 10.1 ± 3.5 meV

coincidences 9.4 ± 3.1 meV

S-factor

≈ 80% S2

Ulrike Hager

BGO energies

06.10.2010 ISAC Science Forum

Ulrike Hager

BGO energies

06.10.2010 ISAC Science Forum

0 100 200 300 400 500 600 700 8000

5

10

15

20

25

30

BGO E_0 (cut)

Ulrike Hager

BGO energies

06.10.2010 ISAC Science Forum

E0 (channel)0 100 200 300 400 500 600 700 800

E1

(cha

nnel

)

0

50

100

150

200

250

300

350

400

(cut)0 v BGO1BGO

Ulrike Hager

Outlook

06.10.2010 ISAC Science Forum

measure CSDs

more detailed GEANT simulations

determine ratio of S0 and S2

more beam time to measure at lower energies

Thank you