Measurement of the Measurement of the 2626Al(d,p)Al(d,p)2727Al reaction to constrain the Al reaction to constrain the 2626Al(p,Al(p,))2727Si reaction rateSi reaction rate

Steven D. Pain

Oak Ridge National Laboratory

NS12, Argonne, 2012

• Astrophysical significance of 26Al

• Previous measurements

• 26Al(d,p) measurement

2626Al - BackgroundAl - Background

• 26Al nucleus was the first radioisotope detected in the interstellar medium

• Half life of 7.2x105 years

• Observation of rays associated with its decay provides evidence of nucleosynthesis

• Temperatures ≥ 0.03 GK, the 26gAl(p,)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

2626Al - BackgroundAl - Background

• Core-collapse supernovae

• Novae

• Massive stars (WR, AGB)

>30 MO stars – develop strong stellar winds blowing material into spaceT < 0.1 GK

accretion onto a white dwarfestimated < 0.4 MO 26Al ejected – depends on uncertain reactionsT < 0.4 GK

constrain 26Al(p,) rates for massive stars

massive star collapsesTc ~ 3 GKlong favored source

N. Prantzos, R. Diehl. Physics Reports 267 1-69 (1996)

5+ gs, 0+ isomeric state at 228 keV

2626Al – Early inferenceAl – Early inference

Excess of 26Mg found in calcium and aluminium inclusions of the Allende meteorite

February 8, 1969

Several tons of material deposited

Material dated to predate formation of

the Earth

First inference of ongoing 26Al synthesis

Allende

2626Al – Early observationAl – Early observation

Largest germanium spectrometer placed in orbit at that time

HEAO (High Energy Astronomy Observatory)

1979-1981

First astronomical observation of 26Al

Four p-type Ge detectors

CsI anti-coincidence

High Resolution Gamma Ray Spectrometer (HRGRS):

50 keV - 10 MeV

3 keV resolution

FOV 30°

2626Al – Astronomical mappingAl – Astronomical mapping

NE 213A

NaI

Energy resolution5 - 8% (FWHM)

Angular resolution1.7 - 4.4 degrees (FWHM)

Launched 1991

Weight: 1460 kg Dimensions: 2.61 m x 1.76 m diameter Power: 206 W

young giant stars

Compton Gamma Ray Observatory - COMPTEL

INTEGRALINTEGRAL

Launched October 2002

Field of Viewfully coded: 14° flat to flat,16° corner to corner

Energy resolution (FWHM):2.2 keV at 1.33 MeV for each detector(3 keV for the entire spectrometer)

Angular resolution2.5° for point sources

19 Gedetectors

Galactic presence of Galactic presence of 2626AlAl

SPI (INTEGRAL)

Line width dominated by instrumental

resolution

Doppler shifts suggest 26Al is co-rotating with

the Galaxy

Astrophysically Important StatesAstrophysically Important States

6

6894

127

189231

241

276

332

368

429

508

0.1 1 T(GK)

Lotay et al., PRL 102, 162502 (2009)

Astrophysically Important States – proton transfer studyAstrophysically Important States – proton transfer study

127 keV

Isotopically enriched target (6.3% 26Al/27Al)

26Al(3He,d)27Si

189 keV

276 keV

Vogelaar et al, PRC 53 1945 (1996)

Upper limit on 127 keV resonance (S<0.02)

Identification of mirror states in Identification of mirror states in 2727AlAl

• Fusion-evaporation reaction to populate states and study γ 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 < S < 0.02 (Vogelaar upper limit) for 127 keV– 0.01 < S < 0.3 for 68 keV resonance

• S for these states necessary for further constraint on the reaction rate

27Si 27Al

Eres (keV) Eex J 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-  

lowest direct (p,) measurement

C. Ruiz et al., PRL 96 252501 (2006)

G. Lotay et al, PRL 102 162502 (2009)

Identification of mirror states in Identification of mirror states in 2727AlAl

27Si 27Al

Eres (keV) Eex J 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)

lowest direct (p,) measurement

C. Ruiz et al., PRL 96 252501 (2006)

0.1 1 T(GK)

AGB + WR stars

2626Al(d,p)Al(d,p)2727Al data – SetupAl data – Setup

• 117 MeV 26Al

• 5x106 pps

• 150 g/cm2 CD2

• MCP normalization (200 kHz)

QQQstack

ORRUBA

SIDAR

45 907560

15

10

5

100 130

10

5

115

12Cd

p

135

5

2.5

150 165

MCPs

2626Al(d,p)Al(d,p)2727Al – Excitation EnergyAl – Excitation Energy

42 6 8 101 3 5 7 9 Ex (MeV)

165 deg

138 deg

75 keV (CoM)

180 keV (CoM)

2626Al(d,p)Al(d,p)2727Al – Excitation EnergyAl – Excitation Energy

42 6 8 101 3 5 7 9 Ex (MeV)

164 deg

138 deg

ℓp = 0

75 keV (CoM)

180 keV (CoM)

Astro

2626Al(d,p)Al(d,p)2727Al – carbon backgroundAl – carbon background

PRELIMINARY

~164° ~145°

Run on carbon foil to determine form of background from reactions on carbon

2626Al(d,p)Al(d,p)2727Al – magnesium contaminationAl – magnesium contamination

PRELIMINARY

~164° ~145°

Run with 26Mg beam (5+) to determine background peaks from reactions 26Mg(d,p)

Astro

Astro

2626Al(d,p)Al(d,p)2727Al – Background subtracted excitation energyAl – Background subtracted excitation energy

42 6 8 101 3 5 7 9 Ex (MeV)

3004 keV (9/2+)

PRELIMINARY

FWHM ~ 75 keV (CoM)

4510 keV (11/2+)

5550 keV 11/2+

6948 keV 11/2+

2626Al(d,p)Al(d,p)2727Al – Excitation EnergyAl – Excitation Energy

42 6 8 101 3 5 7 9 Ex (MeV)

PRELIMINARY

7858

7806

7798

7721

3/2+

9/2+

(3/2, 5/2, 7/2)

5/2

FWHM ~ 75 keV (CoM)

7804(12) keV

127 keV mirror?

NNDC

2626Al(d,p)Al(d,p)2727Al – Excitation EnergyAl – Excitation Energy

42 6 8 101 3 5 7 9 Ex (MeV)

FWHM ~ 75 keV (CoM)PRELIMINARY

S = 0.018(6)

7804(12) keV

127 keV mirror

2626Al(d,p)Al(d,p)2727Al – Excitation EnergyAl – Excitation Energy

42 6 8 101 3 5 7 9 Ex (MeV)

FWHM ~ 75 keV (CoM)PRELIMINARY

0.1 1 T(GK)

Lotay et al., PRL 102, 162502 (2009)

7804(12) keV

127 keV mirror

2626Al(d,p)Al(d,p)2727Al – Excitation EnergyAl – Excitation Energy

PRELIMINARY

68 keV mirror

42 6 8 101 3 5 7 9 Ex (MeV)

68 keV mirror

164 deg

132.5 deg

75 keV (CoM)

150 keV (CoM)

0.1 1 T(GK)

Lotay et al., PRL 102, 162502 (2009)

• 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,)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 < 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

SummarySummary

D.W. Bardayan, C.D. Nesaraja, M.S. Smith, D. Shapira, F. LiangOak Ridge National Laboratory

K.Y. Chae, K.L. Jones, S.T. Pittman, K.T. SchmittUniversity of Tennessee

K.A. Chipps J.A. Cizewski, P.D. O’Malley, S. HardyRutgers University

C. Matei, W.A. PetersOak Ridge Associated Universities

R.L. Kozub, J.F. ShrinerTennessee Tech. University

J.C. Blackmon, M. MatosLouisiana State University

P.D. ParkerLouisiana State University

G.L. WilsonUniversity of Surrey

CollaboratorsCollaborators