1 / 18

Underground Measurement of the 17 O+p Reactions

Underground Measurement of the 17 O+p Reactions. Carpathian SSP12. David Scott On behalf of the LUNA collaboration . Astrophysical Motivation The 17 O(p, γ ) 18 F Reaction: - Current Status - Present Investigation Future direction: The 17 O(p, α ) 14 N Reaction.

sumana
Download Presentation

Underground Measurement of the 17 O+p Reactions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Underground Measurement of the 17O+p Reactions Carpathian SSP12 David Scott On behalf of the LUNA collaboration • Astrophysical Motivation • The 17O(p,γ)18F Reaction: • - Current Status • - Present Investigation • Future direction: The 17O(p,α)14N Reaction

  2. Astrophysical Motivation 14N 17O 13C 18F • Site: Classical Novae • Significant source of 17O, 15N and 13C • Reactions: 17O(p,γ)18F and 17O(p,α)14N • Annihilation 511 keV gamma-rays following β+ decay of 18F (t1/2=110 mins) • Potential constraints on current novae models 13N 15O 17F CNO Cycle (Cygni 1992) 12C 15N 16O 18O (p,γ) (p,α) (β+ν) I II III

  3. The 17O(p,γ)18F Reaction in Novae • Classical novae T=0.1-0.4 GK => EGamow = 100 – 260 keV • Resonant Contribution: 17O(p,γ)18F resonance at Ep = 193 keV • Also Non-resonant Contribution Ex(keV) Gamow 5789 Peak Ep= 193keV 17O+p 1080 937 18F

  4. Previous Investigations (S-factor) LUNA • 1st investigation of the 17O(p,γ)18F reaction [Rolfs et al. Nuc. Phys. A217 29-70 (1973)] • S-factor calculated , 1st meas. of 193 keV resonance [Fox et al. Phys. Rev. C 71, 055801 (2005)] • Activation measurement [Chafa et al. Phys. Rev. C 75, 033810 (2007)] • Ecm = 257 – 470 keV measurement [Newton et al. Phys. Rev. C 81, 045801 (2010)] • Inverse kinematics at DRAGON [Hager et al. Phys. Rev. C 85, 035803 (2012)]

  5. Previous Investigations (Resonance) Ex(keV) 5789 Ep= 193keV 17O+p 1080 937 ωγ193= (1.2±0.2)×10-6eV[Fox et al. Phys. Rev. C 71, 055801 (2005)] ωγ193= (2.2±0.4)×10-6eV[Chafa et al. Phys. Rev. C 75, 033810 (2007)] Clear discrepancy between measurements 18F

  6. Aims of Our Investigation To Measure: • The total S-factor for the 17O(p,γ)18F reaction in the energy range important for Classical Novae. • The strength of the Ep=193 keV resonance. Measurements made using both prompt-gamma and activation techniques.

  7. The LUNA Accelerator at Gran Sasso ~1400 m

  8. Experimental setup • 400 kV electrostatic accelerator • Up to 400 keV protons with a maximumcurrent ~400 μA • 70% Enriched 17O targets on tantalum backings (prepared via anodization process) • ~5cm of lead shielding surrounding detector

  9. Oxygen Enriched Targets Strong18O resonance used to monitor target degradation Ex(keV) 8137 Ep= 151 keV Eγ=4.2 MeV Fresh Target 10C 23C 3908 38C 18O+p 19F also studied with SIMS and RBS measurements.

  10. On and Off Resonance Spectra Off-Resonance On-Resonance On-Resonance Off-Resonance

  11. New Transitions Observed Ex(keV) 5789 Ep= 193 keV Black = Previously Observed Blue = First Observation 17O+p 3839 3791 3358 3134 2523 2101 1080 1041 937 18F

  12. Coincidence Summing 2 3 1 Intensity Including summing effects No summing effects 1 3 Energy 2 • Summing-in for 3 • summing-out for 1 Simple decay cascade => summing effects generally small

  13. Results • Total reaction cross section measured between Ecm≈ 200 – 370 keV measured leading to a five-fold reduction in reaction rate uncertainty. • Resonance Strength of Ep=193 keV resonance measured within an uncertainty of 8%. (~factor 2 higher accuracy). • Results from activation and prompt-gamma measurements in good agreement. Analysis complete. Paper in preparation for publication.

  14. The 17O(p,α)14N Reaction 14N 17O 13C 18F 13N 15O 17F 12C 15N 16O 18O (p,γ) (p,α) (β+ν) I II III 17O(p,α)14N reaction in competition with 17O(p,γ)18F

  15. The 17O(p,α)14N Reaction Previous Investigations: Ep = 193 keV resonance strength: Three independent measurements in fairly good agreement (1.6±0.2) x10-3eV[Chafa et al PRC 75 (2007) 035810-1 – 15] (1.7±0.15 x10-3eV[Moazenet al PRC 75 (2007) 065801-1 – 7] (1.66±0.17)x10-3eV [Newton et al PRC 75 (2007) 055808-1 – 4] Ep = 70 keV resonance strength: Berheide et al ZPhys A 343 (1992) 483-487 Blackmon PRL 74 (1995) 2642-2645 Sergi et al PRC 82 (2010) 032801(R)

  16. Experimental Setup Target Beam Outer Al Dome Inner Cu Dome 8 Silicon Detectors, approximately 0.6π coverage (~15% efficiency) Approximately 2 counts/hour expected for 70 keV resonance. (assuming 100 μA beam current and 95% 17O enriched targets)

  17. First Spectra Acquired ~2.8 MeV α 18O(p,α)15N 18O Resonance Scan Detector Calibration

  18. The Luna Collaboration A. Formicola, M. Junker LaboratoriNazionali del Gran Sasso, INFN, ASSERGI M. Anders, D. Bemmerer, Z. ElekesForschungszentrumDresden-Rossendorf, Germany C. Salvo INFN Genova & INFN Napoli, italy Di LevaINFN, Napoli, Italy C. Broggini, A. Caciolli, R. Depalo, R.Menegazzo, C. Rossi Alvarez INFN, Padova, Italy C. GustavinoINFN, Roma La Sapienza, Italy Zs. Fülöp, Gy. Gyurky, T. Szucs, E. SomorjaInstitute of Nuclear Research (ATOMKI), Debrecen, Hungary O. StranieroOsservatorioAstronomico di Collurania, Teramo, and INFN, Napoli Italy C. Rolfs, F. Strieder, H. P. Trautvetter Ruhr-Universität Bochum, Bochum, Germany F. TerrasiSecondaUniversità di Napoli, Caserta, and INFN, Napoli, Italy M. Aliotta, T. Davinson, D. A. Scott The University of Edinburgh, UK P. Corvisiero, P. PratiUniversitàdi Genova and INFN, Genova, Italy A. Guglielmetti,M. Campeggio, D. Trezzi, C. Bruno Universitàdi Milano and INFN, Milano, Italy G. Imbriani, V. Roca Universitàdi Napoli ''Federico II'', and INFN, Napoli, Italy G. Gervino Universitàdi Torino and INFN, Torino, Italy

More Related