Presentation on theme: "Underground Measurement of the 17O+p Reactions"— Presentation transcript:
1 Underground Measurement of the 17O+p Reactions Carpathian SSP12David ScottOn behalf of the LUNA collaborationAstrophysical MotivationThe 17O(p,γ)18F Reaction:- Current Status- Present InvestigationFuture direction: The 17O(p,α)14N Reaction
2 Astrophysical Motivation Site: Classical NovaeSignificant source of 17O, 15N and 13CReactions: 17O(p,γ)18F and 17O(p,α)14NAnnihilation 511 keV gamma-rays following β+ decay of 18F (t1/2=110 mins)Potential constraints on current novae models(Cygni 1992)(p,γ)(β+ν)(p,α)17O18F14N13C13N12C15N16O18O15O17FCNO CycleIIIIII
3 The 17O(p,γ)18F Reaction in Novae Classical novae T= GK => EGamow = 100 – 260 keVResonant Contribution: 17O(p,γ)18F resonance at Ep = 193 keVAlso Non-resonant ContributionEx(keV)Gamow5789Ep= 193keVPeak17O+p108093718F
4 Previous Investigations (S-factor) LUNA1st investigation of the 17O(p,γ)18F reaction [Rolfs et al. Nuc. Phys. A (1973)]S-factor calculated , 1st meas. of 193 keV resonance [Fox et al. Phys. Rev. C 71, (2005)]Activation measurement [Chafa et al. Phys. Rev. C 75, (2007)]Ecm = 257 – 470 keV measurement [Newton et al. Phys. Rev. C 81, (2010)]Inverse kinematics at DRAGON [Hager et al. Phys. Rev. C 85, (2012)]
5 Previous Investigations (Resonance) 18F17O+pEp= 193keV57891080937Ex(keV)ωγ193= (1.2±0.2)×10-6 eV [Fox et al. Phys. Rev. C 71, (2005)]ωγ193= (2.2±0.4)×10-6 eV [Chafa et al. Phys. Rev. C 75, (2007)]Clear discrepancy between measurements
6 Aims of Our Investigation 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.To Measure:Measurements made using both prompt-gamma and activation techniques.
8 Experimental setup 400 kV electrostatic accelerator Up to 400 keV protons with a maximum current ~400 μA70% Enriched 17O targets on tantalum backings (prepared via anodization process)~5cm of lead shielding surrounding detector
9 Oxygen Enriched Targets Strong 18O resonance used to monitor target degradation19F18O+pEp = 151 keV81373908Eγ=4.2 MeVEx(keV)Fresh Target10C23C38Calso studied with SIMS and RBS measurements.
10 On and Off Resonance Spectra On-ResonanceOn-ResonanceOff-Resonance
11 New Transitions Observed 18F17O+pEp= 193 keV578910809373839379133583134252321011041Ex(keV)Black = Previously ObservedBlue = First Observation
12 Coincidence Summing Summing-in for 3 ∝B1B2ε1ε2 IntensityIncluding summing effectsNo summing effectsEnergySumming-in for 3 ∝B1B2ε1ε2summing-out for 1 ∝B1B2ε1εT2Simple decay cascade => summing effects generally small
13 Analysis complete. Paper in preparation for publication. ResultsTotal 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 17O(p,α)14N reaction in competition with 17O(p,γ)18F The 17O(p,α)14N Reaction(p,γ)(β+ν)(p,α)17O18F14N13C13N12C15N16O18O15O17FIIIIII17O(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) x10-3 eV [Chafa et al PRC 75 (2007) – 15](1.7±0.15 x10-3 eV [Moazen et al PRC 75 (2007) – 7](1.66±0.17) x10-3 eV [Newton et al PRC 75 (2007) – 4]Ep = 70 keV resonance strength:Berheide et al ZPhys A 343 (1992)Blackmon PRL 74 (1995)Sergi et al PRC 82 (2010) (R)
16 Experimental SetupBeamTargetOuter Al DomeInner Cu Dome8 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 18O Resonance ScanDetector Calibration~2.8 MeV α18O(p,α)15N
18 The Luna Collaboration A. Formicola, M. Junker Laboratori Nazionali del Gran Sasso, INFN, ASSERGIM. Anders, D. Bemmerer, Z. Elekes Forschungszentrum Dresden-Rossendorf, GermanyC. Salvo INFN Genova & INFN Napoli, italyDi Leva INFN, Napoli, ItalyC. Broggini, A. Caciolli, R. Depalo, R.Menegazzo, C. Rossi Alvarez INFN, Padova, ItalyC. Gustavino INFN, Roma La Sapienza, ItalyZs. Fülöp, Gy. Gyurky, T. Szucs, E. Somorja Institute of Nuclear Research (ATOMKI), Debrecen, HungaryO. Straniero Osservatorio Astronomico di Collurania, Teramo, and INFN, Napoli ItalyC. Rolfs, F. Strieder, H. P. Trautvetter Ruhr-Universität Bochum, Bochum, GermanyF. Terrasi Seconda Università di Napoli, Caserta, and INFN, Napoli, ItalyM. Aliotta, T. Davinson, D. A. Scott The University of Edinburgh, UKP. Corvisiero, P. Prati Università di Genova and INFN, Genova, ItalyA. Guglielmetti, M. Campeggio, D. Trezzi, C. Bruno Università di Milano and INFN, Milano, ItalyG. Imbriani, V. Roca Università di Napoli ''Federico II'', and INFN, Napoli, ItalyG. Gervino Università di Torino and INFN, Torino, Italy