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Absolute resonance strength measurements of the 22 Na(p, g ) reaction

Absolute resonance strength measurements of the 22 Na(p, g ) reaction. Chris Wrede Center for Experimental Nuclear Physics and Astrophysics University of Washington CAWONAPS TRIUMF, Vancouver, BC, Canada December 10 th, 2010. Outline. Nucleosynthesis in ONe novae

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Absolute resonance strength measurements of the 22 Na(p, g ) reaction

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  1. Absolute resonance strength measurements of the 22Na(p,g) reaction Chris Wrede Center for Experimental Nuclear Physics and Astrophysics University of Washington CAWONAPS TRIUMF, Vancouver, BC, Canada December 10th, 2010

  2. Outline • Nucleosynthesis in ONe novae • 22Na as a potentially detectable cosmic g-ray emitter • 22Na(p,g)23Mg background information • 22Na(p,g)23Mg experiment • 22Na(p,g)23Mg results • 22Na production in novae • Conclusions

  3. 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 Þ expansion & ejection of envelope

  4. 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)

  5. Nucleosynthesis in ONe novae Figure from J. Jose

  6. 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)

  7. Thermonuclear reaction rates for narrow, isolated (p,g) resonances

  8. 22Na destructionvia 22Na(p,g)23Mg Figure adapted from Jose and Hernanz, Ap.J. 520, 347 (1999)

  9. 22Na(p,g)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)

  10. New resonance? • Jenkins et al. measured 12C(12C,ng)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,g)23Mg rate • Need to measure 22Na(p,g)23Mg directly at 198 keV! Jenkins et al., Phys. Rev. Lett. 92, 031101 (2004)

  11. 22Na(p,g)23Mgexperiment proposal • Caggiano et al. (TRIUMF, 2005) • Search for 198-keV resonance • Re-measure known 22Na(p,g)23Mg resonances • Ion-implanted 22Na targets from TRIUMF • Test with 23Na targets • Measure 22Na(p,g)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)

  12. 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)

  13. 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-mCi 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)

  14. 22Na(p,g)23Mg Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010) Sallaska et al., Phys. Rev. C (submitted)

  15. 22Na(p,g)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)

  16. Proton-beam density, rbeam • Measured 27Al(p,g)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)

  17. 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)

  18. 22Na(p,g)23Mg efficiency • 60Co, 24Na sources + 27Al(p,g) + PENELOPE Monte Carlo Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010) Sallaska et al., Phys. Rev. C (submitted)

  19. 22Na(p,g)23Mg data Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010) Sallaska et al., Phys. Rev. C (submitted)

  20. 22Na(p,g)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)

  21. Verification: 23Na(p,g)24Mgmeasurement • Strength of 91.3 +/- 12.5 meV for 512-keV 23Na(p,g) 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)

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

  23. Production of 22Na reduced by factors of 1.5 to 2.0 in hydrodynamic models of ONe novae 22Na production in ONe novae Sallaska et al., Phys. Rev. Lett. 105, 152501 (2010) Sallaska et al., Phys. Rev. C (submitted)

  24. 22Na(p,g)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)

  25. Thank You!

  26. Papers and collaborations Ph.D thesis, University of Washington (defended December 6th, 2010) A. L. Sallaska,1 Direct measurements of 22Na(p,g) 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,g) 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 Properties of23Na 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 1CENPA, University of Washington, Seattle, Washington, USA 2TRIUMF, Vancouver, British Columbia, Canada

  27. 22Na(p,g)23Mg systematics

  28. PDFs for upper limits

  29. More excitation functions

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