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HANS FYNBO ON BEHALF OF

M.J.G. BORGE, J. CEDERKÄLL, L.M. FRAILE, T. GILES, K.L JENSEN, J.S. JOHANSEN, B. JONSON, G. T. KOLDSTE, E. NACHER, T. NILSSON, A. PEREA, K. RIISAGER, T. STORRA, O. TENGBLAD

Study of the b-decay of 20Mg

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(p,g)(a,g)

b

rp-process

(p,a)hCNO cycleAnn.Rev.Nucl.Part.Sci. 2010. 60:381-404

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Nucl.Phys. A616 (1997) 107c.

• Direct19Ne(p,g)20Na

measurement at Louvain-la-

Neuve (1995-2004)

Upper limit wg<15meV

• Complete spectroscopy at

Argonne with

GammaSphere (2004)

No solution as to 1+ or 3+

• Measurements of b-decay

of 20Mg (1981-1995)

Population of 2643keV not

observed

Limit too weak to exclude 1+

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bpba

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• Only 1+ states populated in

allowed GT decays

• Search for b-delayed

proton line at 450keV, or

b-delayed g-emission

• Approach challenging

due to b-delayed a-

emission from daughter

decay of 20Na

20Mg b-decay

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RIKEN 1992

GANIL1995

PREVIOUS MEASUREMENTS

• Berkeley 1981• RIKEN, MSU

1992• GANIL

1995

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RIKEN 1992

Berkeley1981MSU 1992

a

a

-a

subtracted

DE-E

telescop

e

GANIL1995

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OVERVIEW OF PREVIOUS WORK# 20Mg Yield B.R

2645keVT1/2

Berkeley ? ? No information

95+80-50ms

RIKEN ? 10-20/s <1% 114(17)ms

MSU 10400 0.7/s <0.2% 82(4)ms

GANIL 4.5 106 30-150/s <0.1% 95(3)ms

3.740(6)

3.65(6)

20O

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NEW MEASUREMENT AT ISOLDE

•Measure b-delayed proton and g spectrum with high statistics and under much improved conditions

•Measure bp, bg and gp coincidences to correctly assign p-peaks.

• Physics : Mirror symmetry GT-distribution assignment of 2645keV level

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TWO MEASUREMENTS:

1. Gas-Si telescope

2. Large efficiency setup

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ISOLDE production of 20Mg?

Production of Mg from SiC with RILIS (ions/mC):

2×104

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IMPACT OF NEW MEASUREMENT# 20Mg Yield B.R

2645keVT1/2

ISOLDE 108 1-2 103/s ~10-5

RIKEN ? 10-20/s <1% 114(17)ms

MSU 10400 0.7/s <0.2% 82(4)ms

GANIL 4.5 106 30-150/s <0.1% 95(3)ms

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SUMMARY AND BEAM REQUEST

We ask for 18 shifts of radioactive beams

• 6 shifts for Gas-Si telescope (3shifts tuning)

• 12 shifts for High Efficiency setup (3 shifts tuning)

• If scheduled at LA1 and LA2 back-to-back save 3 shifts