Presentation on theme: "Underground Measurement of the 17 O+p Reactions David Scott On behalf of the LUNA collaboration Carpathian SSP12 Astrophysical Motivation The 17 O(p, γ."— Presentation transcript:
Underground Measurement of the 17 O+p Reactions David Scott On behalf of the LUNA collaboration Carpathian SSP12 Astrophysical Motivation The 17 O(p, γ ) 18 F Reaction: - Current Status - Present Investigation Future direction: The 17 O(p, α ) 14 N Reaction
Site: Classical Novae Significant source of 17 O, 15 N and 13 C Reactions: 17 O(p, γ ) 18 F and 17 O(p, α ) 14 N Annihilation 511 keV gamma-rays following β + decay of 18 F (t 1/2 =110 mins) Potential constraints on current novae models Astrophysical Motivation (p, γ ) (β+ν)(β+ν) (p, α ) 17 O 18 F 14 N 13 C 13 N 12 C 15 N 16 O 18 O 15 O 17 F CNO Cycle I IIIII (Cygni 1992)
Classical novae T= GK => E Gamow = 100 – 260 keV Resonant Contribution: 17 O(p, γ ) 18 F resonance at E p = 193 keV Also Non-resonant Contribution The 17 O(p, γ ) 18 F Reaction in Novae 18 F 17 O+p E p = 193keV Gamow Peak E x (keV)
Previous Investigations (S-factor) 1st investigation of the 17 O(p, γ ) 18 F reaction [Rolfs et al. Nuc. Phys. A (1973)] S-factor calculated, 1 st meas. of 193 keV resonance [Fox et al. Phys. Rev. C 71, (2005)] Activation measurement [Chafa et al. Phys. Rev. C 75, (2007)] E cm = 257 – 470 keV measurement [Newton et al. Phys. Rev. C 81, (2010)] Inverse kinematics at DRAGON [Hager et al. Phys. Rev. C 85, (2012)] LUNA
Previous Investigations (Resonance) 18 F 17 O+p E p = 193keV E x (keV) ω γ 193 = (1.2±0.2)×10 -6 eV [Fox et al. Phys. Rev. C 71, (2005)] ω γ 193 = (2.2±0.4)×10 -6 eV [Chafa et al. Phys. Rev. C 75, (2007)] Clear discrepancy between measurements
Aims of Our Investigation The total S-factor for the 17 O(p, γ ) 18 F reaction in the energy range important for Classical Novae. The strength of the E p =193 keV resonance. To Measure: Measurements made using both prompt-gamma and activation techniques.
The LUNA Accelerator at Gran Sasso ~ 1400 m
Experimental setup 400 kV electrostatic accelerator Up to 400 keV protons with a maximum current ~ 400 μA 70% Enriched 17 O targets on tantalum backings (prepared via anodization process) ~ 5cm of lead shielding surrounding detector
Oxygen Enriched Targets Strong 18 O resonance used to monitor target degradation 19 F 18 O+p E p = 151 keV E γ =4.2 MeV E x (keV) Fresh Target 10C 23C 38C also studied with SIMS and RBS measurements.
On-Resonance Off-Resonance On-Resonance Off-Resonance On and Off Resonance Spectra
New Transitions Observed 18 F 17 O+p E p = 193 keV E x (keV) Black = Previously Observed Blue = First Observation
Coincidence Summing No summing effects Including summing effects Energy Intensity Simple decay cascade => summing effects generally small
Total reaction cross section measured between E cm ≈ 200 – 370 keV measured leading to a five-fold reduction in reaction rate uncertainty. Resonance Strength of E p =193 keV resonance measured within an uncertainty of 8%. ( ~ factor 2 higher accuracy). Results from activation and prompt-gamma measurements in good agreement. Results Analysis complete. Paper in preparation for publication.
The 17 O(p, α ) 14 N Reaction (p, γ ) (β+ν)(β+ν) (p, α ) 17 O 18 F 14 N 13 C 13 N 12 C 15 N 16 O 18 O 15 O 17 F I IIIII 17 O(p, α ) 14 N reaction in competition with 17 O(p, γ ) 18 F
The 17 O(p, α ) 14 N Reaction Previous Investigations: E p = 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] E p = 70 keV resonance strength: Berheide et al ZPhys A 343 (1992) Blackmon PRL 74 (1995) Sergi et al PRC 82 (2010) (R)
Beam Target 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% 17 O enriched targets) Experimental Setup
First Spectra Acquired ~ 2.8 MeV α 18 O(p, α ) 15 N 18 O Resonance Scan Detector Calibration
The Luna Collaboration A. Formicola, M. Junker Laboratori Nazionali del Gran Sasso, INFN, ASSERGI M. Anders, D. Bemmerer, Z. Elekes Forschungszentrum Dresden-Rossendorf, Germany C. Salvo INFN Genova & INFN Napoli, italy Di Leva INFN, Napoli, Italy C. Broggini, A. Caciolli, R. Depalo, R.Menegazzo, C. Rossi Alvarez INFN, Padova, Italy C. Gustavino INFN, Roma La Sapienza, Italy Zs. Fülöp, Gy. Gyurky, T. Szucs, E. Somorja Institute of Nuclear Research (ATOMKI), Debrecen, Hungary O. Straniero Osservatorio Astronomico di Collurania, Teramo, and INFN, Napoli Italy C. Rolfs, F. Strieder, H. P. Trautvetter Ruhr-Universität Bochum, Bochum, Germany F. Terrasi Seconda Università di Napoli, Caserta, and INFN, Napoli, Italy M. Aliotta, T. Davinson, D. A. Scott The University of Edinburgh, UK P. Corvisiero, P. Prati Università di Genova and INFN, Genova, Italy A. Guglielmetti, M. Campeggio, D. Trezzi, C. Bruno Università di Milano and INFN, Milano, Italy G. Imbriani, V. Roca Università di Napoli ''Federico II'', and INFN, Napoli, Italy G. Gervino Università di Torino and INFN, Torino, Italy