Measurement of the 26Al(d,p)27Al reaction to constrain the 26Al(p,g)27Si reaction rate

1
Measurement of the 26Al(d,p)27Al reaction to
constrain the 26Al(p,g)27Si reaction rate
Steven D. Pain Oak Ridge National Laboratory

• Astrophysical significance of 26Al
• Previous measurements
• 26Al(d,p) measurement

NS12, Argonne, 2012
2
26Al - Background

• 26Al nucleus was the first radioisotope detected
  in the interstellar medium
• Half life of 7.2x105 years
• Observation of g rays associated with its decay
  provides evidence of nucleosynthesis
• Temperatures 0.03 GK, the 26gAl(p,g)27Si
  reaction is expected to contribute to the
  destruction of 26Al

N. Prantzos, R. Diehl. Physics Reports 267 1-69
(1996)
5 gs, 0 isomeric state at 228 keV
3
26Al - Background

• Core-collapse supernovae
• Novae
• Massive stars (WR, AGB)

massive star collapses Tc 3 GK long favored
source
accretion onto a white dwarf estimated lt 0.4 MO
26Al ejected depends on uncertain reactions T lt
0.4 GK
gt30 MO stars develop strong stellar winds
blowing material into space T lt 0.1 GK
N. Prantzos, R. Diehl. Physics Reports 267 1-69
(1996)
5 gs, 0 isomeric state at 228 keV
constrain 26Al(p,g) rates for massive stars
4
26Al Early inference
First inference of ongoing 26Al synthesis
February 8, 1969 Several tons of material
deposited Material dated to predate formation of
the Earth
Excess of 26Mg found in calcium and aluminium
inclusions of the Allende meteorite
Allende
5
26Al Early observation
First astronomical observation of 26Al
HEAO (High Energy Astronomy Observatory)
Largest germanium spectrometer placed in orbit at
that time
High Resolution Gamma Ray Spectrometer
(HRGRS) 50 keV - 10 MeV 3 keV resolution FOV 30
1979-1981
Four p-type Ge detectors CsI anti-coincidence
6
26Al Astronomical mapping
Compton Gamma Ray Observatory - COMPTEL
Energy resolution 5 - 8 (FWHM) Angular
resolution 1.7 - 4.4 degrees (FWHM) Launched
1991
NE 213A
NaI
Weight 1460 kg Dimensions 2.61 m x 1.76 m
diameter Power 206 W
young giant stars
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INTEGRAL
Energy resolution (FWHM) 2.2 keV at 1.33 MeV for
each detector (3 keV for the entire
spectrometer) Angular resolution 2.5 for point
sources
19 Ge detectors
Field of View fully coded 14 flat to flat, 16
corner to corner
Launched October 2002
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Galactic presence of 26Al
Line width dominated by instrumental resolution
SPI (INTEGRAL)
Doppler shifts suggest 26Al is co-rotating with
the Galaxy
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Astrophysically Important States
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Astrophysically Important States proton
transfer study
Vogelaar et al, PRC 53 1945 (1996)
127 keV
26Al(3He,d)27Si
Isotopically enriched target (6.3 26Al/27Al)
Upper limit on 127 keV resonance (Slt0.02)
189 keV
276 keV
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Identification of mirror states in 27Al
27Si 27Si 27Si 27Al
Eres (keV) Eex Jp Eex
       
6 7468 5/2  
68 7532 5/2 7578
94 7557   7858
127 7592 9/2 7806
189 7652 11/2 7948
231 7690 5/2  
241 7702 7/2  
276 7740 9/2  
332 7792 7/2  
368 7831 9/2-  
G. Lotay et al, PRL 102 162502 (2009)

• Fusion-evaporation reaction to populate states
  and study ? decays with Gammasphere
• 6 pnA, 26 MeV beam of 16O ions on 150 µg/cm² 12C
  target
• Location of low-lying resonances constrained
  stellar rate, assuming
• 0.001 lt S lt 0.02 (Vogelaar upper limit) for 127
  keV
• 0.01 lt S lt 0.3 for 68 keV resonance
• S for these states necessary for further
  constraint on the reaction rate

lowest direct (p,g) measurement C. Ruiz et al.,
PRL 96 252501 (2006)
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Identification of mirror states in 27Al
27Si 27Si 27Si 27Al
Eres (keV) Eex Jp Eex
       
6 7468 5/2  
68 7532 5/2 7578
94 7557   7858
127 7592 9/2 7806
189 7652 11/2 7948
231 7690 5/2  
241 7702 7/2  
276 7740 9/2  
332 7792 7/2  
368 7831 9/2-  
G. Lotay et al, PRL 102 162502 (2009)
AGB WR stars
lowest direct (p,g) measurement C. Ruiz et al.,
PRL 96 252501 (2006)
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26Al(d,p)27Al data Setup

• 117 MeV 26Al
• 5x106 pps
• 150 mg/cm2 CD2
• MCP normalization (200 kHz)

QQQ stack
SIDAR
MCPs
ORRUBA
5
12C
d
2.5
p
135
165
150
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26Al(d,p)27Al Excitation Energy
165 deg 138 deg
75 keV (CoM)
180 keV (CoM)
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
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26Al(d,p)27Al Excitation Energy
lp 0
Astro
164 deg 138 deg
75 keV (CoM)
180 keV (CoM)
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
16
26Al(d,p)27Al carbon background
PRELIMINARY
145
164
Run on carbon foil to determine form of
background from reactions on carbon
17
26Al(d,p)27Al magnesium contamination
PRELIMINARY
145
164
Astro
Astro
Run with 26Mg beam (5) to determine background
peaks from reactions 26Mg(d,p)
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26Al(d,p)27Al Background subtracted excitation
energy
PRELIMINARY
FWHM 75 keV (CoM)
5550 keV 11/2
3004 keV (9/2)
6948 keV 11/2
4510 keV (11/2)
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
19
26Al(d,p)27Al Excitation Energy
PRELIMINARY
NNDC
FWHM 75 keV (CoM)
3/2
9/2
(3/2, 5/2, 7/2)
5/2
7804(12) keV 127 keV mirror?
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
20
26Al(d,p)27Al Excitation Energy
PRELIMINARY
FWHM 75 keV (CoM)
S 0.018(6)
7804(12) keV 127 keV mirror
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
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26Al(d,p)27Al Excitation Energy
PRELIMINARY
FWHM 75 keV (CoM)
7804(12) keV 127 keV mirror
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
22
26Al(d,p)27Al Excitation Energy
PRELIMINARY
164 deg
75 keV (CoM)
150 keV (CoM)
132.5 deg
68 keV mirror
68 keV mirror
4
2
6
8
10
1
3
5
7
9
Ex (MeV)
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Summary

• 26Al is the first radioisotope to have a
  high-resolution Galactic map
• Resonances in nova() Gamow windows measured
  directly
• Understanding the structure of low-lying
  resonances is important for constraining the
  26Al(p,g)27Si rate in massive stars
• Measured single-particle strengths of mirror
  levels via 26Al(d,p) for constraining stellar
  reaction rate
• Population of mirror to the 127 keV l 0
  resonance
• (preliminary2) S 0.018(6) - comparable to
  upper limit set by (3He,d) measurement (S lt 0.02)
• Mirror calculations (Marek Ploszajczak, GANIL)
• Further analysis required to constrain l 2
  state at angles closer to 90 deg 68 keV mirror
  is very weakly populated

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Collaborators
D.W. Bardayan, C.D. Nesaraja, M.S. Smith, D.
Shapira, F. Liang Oak Ridge National
Laboratory K.Y. Chae, K.L. Jones, S.T. Pittman,
K.T. Schmitt University of Tennessee K.A. Chipps
J.A. Cizewski, P.D. OMalley, S. Hardy Rutgers
University C. Matei, W.A. Peters Oak Ridge
Associated Universities R.L. Kozub, J.F.
Shriner Tennessee Tech. University J.C.
Blackmon, M. Matos Louisiana State
University P.D. Parker Louisiana State
University G.L. Wilson University of Surrey