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Study of the b -decay of 20 Mg. 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. rp -process. ( p, g ). ( a , g ). - PowerPoint PPT Presentation
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AARHUSUNIVERSITY
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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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AARHUSUNIVERSITY
(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+
AARHUSUNIVERSITY
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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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AARHUSUNIVERSITY
RIKEN 1992
GANIL1995
PREVIOUS MEASUREMENTS
• Berkeley 1981• RIKEN, MSU
1992• GANIL
1995
AARHUSUNIVERSITY
RIKEN 1992
Berkeley1981MSU 1992
a
a
-a
subtracted
DE-E
telescop
e
GANIL1995
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AARHUSUNIVERSITY
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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AARHUSUNIVERSITY
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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AARHUSUNIVERSITY
TWO MEASUREMENTS:
1. Gas-Si telescope
2. Large efficiency setup
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AARHUSUNIVERSITY
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AARHUSUNIVERSITY
ISOLDE production of 20Mg?
Production of Mg from SiC with RILIS (ions/mC):
2×104
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AARHUSUNIVERSITY
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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AARHUSUNIVERSITY
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