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LUNA at LNGS

L aboratory U nderground N uclear A strophysics. LUNA at LNGS. Alessandra Guglielmetti Universita’ degli Studi di Milano and INFN, Milano, ITALY. Outline: -Nuclear Fusion reactions in stars -Why going underground -The Luna Experiment -Future perspective. Hydrogen burning.

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LUNA at LNGS

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  1. LaboratoryUndergroundNuclearAstrophysics LUNA at LNGS Alessandra Guglielmetti Universita’ degli Studi di Milano and INFN, Milano, ITALY • Outline: • -Nuclear Fusion reactions in stars • -Why going underground • -The Luna Experiment • -Future perspective

  2. Hydrogen burning p + p d + e+ + ne d + p 3He + g pp chain 84.7 % 13.8 % 3He +3He a + 2p 3He +4He 7Be+g 0.02 % 13.78 % 7Be+e- 7Li+g +ne 7Be +p 8B+g 7Li +p a + a 8B 2a + e++ ne Produces energy for most of the life of the stars 4p  4He + 2e+ + 2e + 26.73 MeV

  3. Nuclear reactions in stars Sun: T= 1.5 107 K kT = 1 keV<< EC (0.5-2 MeV) Reaction E0 3He(3He,2p)4He 21 keV d(p,)3He 6 keV 14N(p,)15O 27 keV 3He(4He,g)7Be 22 keV

  4. Cross section and astrophysical S factor Astrophysical factor Gamow energy region Gamow factor EG Cross section of the order of pb! S factor can be extrapolated to zero energy but if resonances are present?

  5. Mesurements Extrapol. Sub-Thr resonance Tail of a broad resonance Narrow resonance Non resonant process Danger in extrapolations!

  6. Sun Luminosity (irradiated energy per time) = 2 ·1039 MeV/s Q-value (energy for each reaction) = 26.73 MeV  Reaction rate = 1038 s-1 Laboratory Rlab= ··Ip··Nav/A e ~ 10 % IP ~ mA  ~ mg/cm2 pb < s < nb event/month < Rlab < event/day  Underground Laboratory

  7. Environmental radioactivity has to be considered underground  shielding Beam induced bck from impurities in beam & targets  high purity 3MeV < Eg < 8MeV 0.0002 Counts/s 3MeV < Eg < 8MeV: 0.5 Counts/s HpGe GOING UNDERGROUND Cross section measurement requirements Rlab> Bcosm+Benv+Bbeaminduced

  8. Laboratory forUnderground Nuclear Astrophysics LUNA 1 (1992-2001) 50 kV LUNA 2 (2000…) 400 kV LUNA site LNGS (shielding  4000 m w.e.)

  9. Laboratory for Underground Nuclear Astrophysics 400 kV Accelerator : E beam 50 – 400 keV I max  500 A protons I max  250 A alphas Energy spread 70 eV Long term stability  5eV/h

  10. LUNA "non solar phase" 2006-ongoing (p,g) reactions on : Nitrogen, Oxygen, Neon, Sodium and Magnesium isotopes belonging to: CNO, NeNa and MgAl cycles of Hydrogen burning Important for second generation stars with temperature and mass higher than those of our Sun Seeds of the reactions already present Higher Coulomb barrier: these cycles are unimportant for energy generation but essential for nucleosynthesis of elements with A>20

  11. D(4He,g)6Li 6Li detected in metal poor stars is unexpectedly large compared to BBN predictions. D(4He,g)6Li is the main reaction for 6Li production No direct measurements for Ecm<650 keV Theoretical calculations for the S-factor differ by more than one order of magnitude

  12. data taking concluded CNO cycle In progress Ne-Na cycle BBN In progress proposal approved by LNGS SC in 2007

  13. LOI to LNGS for a new accelerator for He-burning key reactions Reaction rate Estimate At LUNA 12C(,)16O The “Holy Grail” Reaction rate Estimate At LUNA 13C(,n)16O Reaction rate Estimate At LUNA 22Ne(,n)25Mg 3.5 MeV accelerator

  14. Recoil mass separator approach A+aC+g Cn+ a A detection A/C>1015  A detection separation coincidence - low induced background - high detection efficiency - measurement of stot - low background g-ray spectra

  15. European Recoil-separator for Nuclear Astrophysics ion source tandem accelerator recoil focusing ion beam purification: velocity and momentum filter beam preparation • detection setup magnetic quadrupole multiplets ion beam emittance control 4He gas target Wien filter (velocity) Wien filter (velocity) recoils separation 60° magnet (momentum) TOF/DE-E detector

  16. ERNA experimental program Hydrogen burning and neutrino flux from 8B 3He(a,g)7Be measured in Bochum 7Be(p,g)8B Helium burning and synthesis of Oxygen and Fluorine 12C(a,g)16O measured in Bochum down to ~2 MeV CM 14N(a,g)18F(b+)18O 15N(a,g)19F

  17. LUNA COLLABORATION Laboratori Nazionali del Gran Sasso, INFN, ASSERGI:A.Formicola, C.Gustavino, M.Junker Forschungszentrum Dresden-Rossendorf, GermanyD. Bemmerer, M.Marta INFN, Padova, ItalyC. Broggini, A. Caciolli, M. Erhard, R.Menegazzo, C. Rossi Alvarez Institute of Nuclear Research (ATOMKI), Debrecen, HungaryZ.Elekes, Zs.Fülöp, Gy. Gyurky, E.Somorjai Osservatorio Astronomico di Collurania, Teramo, and INFN, Napoli, ItalyO. Straniero Ruhr-Universität Bochum, Bochum, GermanyC.Rolfs, F.Strieder, H.P.Trautvetter Seconda Università di Napoli, Caserta, and INFN, Napoli, ItalyF.Terrasi Università di Genova and INFN, Genova, ItalyF. Confortola, P.Corvisiero, H. Costantini, A. Lemut, P.Prati Università di Milano and INFN, Milano, ItalyV. Capogrosso,A.Guglielmetti, C. Mazzocchi Università di Napoli ''Federico II'', and INFN, Napoli, ItalyG.Imbriani,B. Limata, V.Roca Università di Torino and INFN, Torino, ItalyG.Gervino

  18. ERNA COLLABORATION INFN, Napoli, ItalyM. De Cesare, N. De Cesare, A. Di Leva, A. D'Onofrio, L. Gialanella, G. Imbriani, B. Limata, M. Romano, D. Schuermann, F.Terrasi, S. Cristallo, L. Piersanti INFN, Napoli, ItalyM. Busso, R. Guandalini, M. Nucci, S. Palmerini. A. Salterelli Ruhr-Universität Bochum, Bochum, GermanyD. Rogalla, C.Rolfs, F.Strieder Institute of Nuclear Research (ATOMKI), Debrecen, Hungary University of Connecticut, USA CNRS Orsay, France University of Jerusalem, Israel

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