Absolute resonance strength measurements of the

22Na(p,) reaction

Chris WredeCenter for Experimental Nuclear Physics and Astrophysics

University of Washington

CAWONAPSTRIUMF, Vancouver, BC, Canada

December 10th, 2010

Outline

• Nucleosynthesis in ONe novae• 22Na as a potentially detectable cosmic -

ray emitter• 22Na(p,)23Mg background information• 22Na(p,)23Mg experiment• 22Na(p,)23Mg results• 22Na production in novae• Conclusions

Classical novae• Binary system: white-dwarf

(WD) star accreting H from main-sequence star

• Slow accretion rate leads to electron-degenerate layer of H mixed with WD surface

• Temperature increases at constant pressure as hydrogen accreted

• At T ~ several MK, CNO hydrogen burning ignites thermonuclear runaway at surface

• Degeneracy lifted expansion & ejection of envelope

Classical novae• Rise time < 1 to 2 days• E ~ 1045 ergs• L ~ 104 to 105 solar

luminosities• 10-5 to 10-4 solar masses

ejected in 100-1000 s• Peak temperatures up to

0.4 GK for ONe novae• Can be recurrent (t ~10

to 100 ky)• Galactic nova rate ~ 30

yr-1 (~5 yr-1 observed)

Nucleosynthesis in ONe novae

Figure from J. Jose

Galactic 22Na

• 22Na (t1/2 = 2.6 y) never observed

from novae

• Observational upper limit of 2.7 x 10-8 Msolar of 22Na from any ONe nova (COMPTEL, 1995)

• Hydrodynamic nova-model predictions of Jose and Hernanz (Barcelona, 1999) and Bishop et al. (TRIUMF, 2003) roughly one order of magnitude lower

• Currently searched for with INTEGRAL-SPI

Iyudin et al., Astron. Astrophys. 300, 422 (2006) Jose and Hernanz, Astrophys. J., 520, 347 (1999)Bishop et al., Phys. Rev. Lett. 90, 162501 (2003)

Thermonuclear reaction rates for narrow, isolated (p,) resonances

i

kTrEiA

ieCTN /2/3

p

p

r

JJ

J

)12)(12(

)12(

target

p

pxr QEE

22Na destruction via 22Na(p,)23Mg

Figure adapted from Jose and Hernanz, Ap.J. 520, 347 (1999)

22Na(p,)23Mg history

• Goerres et al. searched for resonances (Caltech, 1989)

• Seuthe et al. measured energies and strengths of resonances down to 288 keV (Bochum, 1990)

• Stegmueller et al. measured energy and strength of new resonance at 214 keV (Bochum, 1996)

Goerres et al., Phys. Rev. C 39, 8 (1989)Seuthe et al., Nucl. Phys. A514, 471 (1990)Stegmueller et al., Nucl. Phys. A601, 168 (1996)

New resonance?

• Jenkins et al. measured 12C(12C,n)23Mg (ANL, 2004)

• Discovered new 23Mg level at Ex = 7769 keV (Er = 198 keV)

• Strength of up to 4 meV • Claim it could dominate

22Na(p,)23Mg rate• Need to measure

22Na(p,)23Mg directly at 198 keV!

Jenkins et al., Phys. Rev. Lett. 92, 031101 (2004)

22Na(p,)23Mgexperiment

proposal

• Caggiano et al. (TRIUMF, 2005)• Search for 198-keV resonance• Re-measure known

22Na(p,)23Mg resonances• Ion-implanted 22Na targets from

TRIUMF• Test with 23Na targets• Measure 22Na(p,)23Mg

somewhere with intense low-energy proton beam:

• CENPA @ U. Washington• Ph.D. thesis work of Anne

Sallaska (University of Washington)

Caggiano et al., TRIUMF Research Proposal (2005)

22Na targets

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)Brown et al., NIM B 267, 3302 (2009)

22Na targets• Based on 22,23Na tests• OFHC Cu substrate• 30-keV 22Na+ beam• 10-nA 22Na+ beam• 22Na beam rastered

over 5-mm diameter collimator

• Two 300-Ci targets • Evaporated Cr layer

Brown et al., NIM B 267, 3302 (2009)Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

22Na(p,)23Mg

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

22Na(p,)23Mg @ CENPA

• 22Na target on water-cooled mount

• Proton beam magnetically rastered over target

• 2 HPGe’s at ±55o

• 26 mm of Pb shielding to reduce 22Na radiation

• Annular scintillator for cosmic-ray anticoincidence

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

beamTNYdE

Proton-beam density, beam

• Measured 27Al(p,)28Si• Two thick Al targets -extended target -5-mm “coin” target• Two energies• Supplemented by

Monte Carlo

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

beamTNYdE

Number of 22Na target atoms, NT

• NT from in-situ measurement of 22Na activity

• 22Na target degradation minimal thanks to Cr coating

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

beamTNYdE

22Na(p,)23Mg efficiency

• 60Co, 24Na sources + 27Al(p,) + PENELOPE Monte Carlo

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

beamTNYdE

22Na(p,)23Mg data

keV 213rE

beamTNYdE Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

keV 610rE

keV 198rE

22Na(p,)23Mg results

• Resonance energies in good agreement with previous work• Resonance strengths 2.4 to 3.2 times higher!• Good limit for 198-keV resonance

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

Verification: 23Na(p,)24Mgmeasurement

• Strength of 91.3 +/- 12.5 meV for 512-keV 23Na(p,) resonance is a recommended standard

• Using an implanted 23Na target, we measured the strength of this resonance to be 79 +/- 17 meV

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)Iliadis et al. Ap.J.S.S. 134, 151 (2001)

22Na(p,)23Mg rate

• Re-evaluated thermonuclear 22Na(p,)23Mg reaction rate

• Energies and strengths primarily from present work

• Monte-Carlo method to determine uncertainties

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)Schmidt et al., Nucl. Phys. A521, 227 (1995)

22Na production in ONe novae

• Production of 22Na reduced by factors of 1.5 to 2.0 in hydrodynamic models of ONe novae

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

WD mass 22Na (previous) 22Na (present) factor

1.15 Msolar 1.6 x 10-4 Msolar 7.8 x10-5 Msolar 2.0

1.25 Msolar 1.9 x 10-4 Msolar 1.0 x10-4 Msolar 1.9

1.35 Msolar 5.9 x 10-4 Msolar 3.8 x10-4 Msolar 1.5

22Na(p,)23Mg conclusions

• 198-keV resonance proposed by Jenkins et al. (ANL, 2004) does not dominate

• 213-keV and 288-keV resonances still dominate and are ~3x stronger than previously thought

• 22Na production in ONe-nova models reduced by factors of 1.5 to 2.0

Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010)Sallaska et al., Phys. Rev. C (submitted)

Thank You!

Papers and collaborations

1CENPA, University of Washington, Seattle, Washington, USA2TRIUMF, Vancouver, British Columbia, Canada

Properties of 23Na implanted targets, NIM B 267, 3302 (2009)T.A.D. Brown,1 K. Deryckx,1 A. Garcia,1 A. L. Sallaska,1 K. A. Snover,1 D. W. Storm,1

C. Wrede1

Direct measurements of 22Na(p,) resonances and consequences for 22Na production in classical novae, PRL 105, 152501 (2010)

A. L. Sallaska,1 C. Wrede,1 A. Garcia,1 D. W. Storm,1 T. A. D. Brown,1 C. Ruiz,2 K. Snover,1 D. F. Ottewell,2 L. Buchmann,2 C. Vockenhuber,2 D. A. Hutcheon,2 J. A. Caggiano2

Absolute determination of the 22Na(p,) reaction rate in novae, PRC (submitted)A. L. Sallaska,1 C. Wrede,1 A. Garcia,1 D. W. Storm,1 T. A. D. Brown,1 C. Ruiz,2 K.

Snover,1 D. F. Ottewell,2 L. Buchmann,2 C. Vockenhuber,2 D. A. Hutcheon,2 J. A. Caggiano2

Ph.D thesis, University of Washington (defended December 6th, 2010) A. L. Sallaska,1

22Na(p,)23Mg systematics

PDFs for upper limits

More excitation functions