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Nuclear Reactions at Low Energies

Nuclear Reactions at Low Energies

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Nuclear Reactions at Low Energies

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  1. Institut "Jožef Stefan" Nuclear Reactions at Low Energies Matej Lipoglavšek Jožef Stefan Institute, Ljubljana, Slovenia Russbach, March 2019

  2. BBN reaction network 7Be 1: 2: 3: 4: 3He 5: 3He 6: 3He 7: 4He 8: 4He 9: 3He4He 10: 7Li 11: 3He7Be 12: 7Be7Li 12 11 7Li 9 3He 4He 8 10 7 4 5 6 2 2d 1H 3t 3 1 1n Reactions important for the production of the lightest elements (B. D. Fields, Annual Reviews of Nuclear and Particle Science61, 2011)

  3. Reaction cross section C.M.S. Energy [MeV] A.Coc, E.VangioniInt.J.Mod.Phys. E26, 1741002 (2017)

  4. Measurements @ JSI 2 MV Tandem van de Graaf accelerator

  5. Implanted deuterium targets Deuterium implanted into graphite or titanium at 3.5 kV resulting in about 10 at. % deuterium concentration. Proton beam energy between 260 and 300 keV from the 2MV Tandetron accelerator.

  6. Cross section results Differential cross section at θ = 135˚ P r e l i m i n a r y

  7. Angular Distribution L. Marcucci et al., PRL 116, 102501 (2016)

  8. S-factor Sommerfeld parameter:

  9. Electron detection Detecting electrons with ΔE – E technique beam current Ge detector graphite target beam Si detector CsI detector

  10. Bi-207 source

  11. Electrons 2H(p,γ)3He 2H(p,e-)3He

  12. Results Beam energy at half target thickness: 243 keV Cross section: 2H(p,γ)3He, σ=1.0(2) μb 2H(p,e-)3He, σ=0.3(1) nb Our We can only say that in at least 7% of the screened reactions an electron is emitted instead of a γ ray.

  13. Catalysis of nuclear reactions by muons Instead of 2H(p,γ)3He Alvarez measured 2H(p,μ)3He

  14. Ec Potential V(r) Rn 0 Ra r Electron Screening Cross section increases at low energies when the interacting nucleiare not bare. Enhancement factor where Ue is the screeening potential. electron cloud Ue=Z1Z2e2/4pe0Ra E + Ue= Eeff nuclear radius Bohr radius H. J. Assenbaum, K. Langanke and C. Rolfs, Z. Phys. A 327 (1987) 461. 305 citations (Web of Science, March 2016).

  15. Previous Results 1 for d(d,p)t reaction from F. Raiola et al., Eur. Phys. J. A19 (2004) 283.

  16. Previous Results 2 J. Kasagi, Prog. Theo. Phys. Suppl. 154 (2004) 365. for the d(d,p)t reaction Ue=310±30 eV @ 7% H/Pd => concentration dependence

  17. Previous Results 3 for d(d,p)t reaction from K. Czerskiet al., J. Phys. G35(2008)014012. for zirconium metal Ue=319±3 eV

  18. Previous Results 4 J. Cruz et al., Phys. Lett. B 624 (2005) 181; J. Phys. G 35 (2008) 014004. PdLi1%:Ue=3.7 ± 0.3 keV Li metal: Ue=1.18 ± 0.06 keV Li2WO4: Ue=237+133eV S(E)=0.055+0.21E-0.31E2[MeV b] -77

  19. Previous Results 5 L. Lamiaet al., Astron. Astrophys. 541, A158 (2012). Trojan horse method → bare S factor S(E)=0.053+0.213E-0.336E2[MeV b] Adiabatic limit: Ue= 240 eV 7Li(p,α)4He reaction Ue= 425 ± 60 eV in Li metal

  20. Measurements @ JSI X-ray detector beam current target beam Pb absorber neutron detector Ge detector

  21. Comparison to previous results d+d F. Raiola et al., Eur. Phys. J. A19 (2004) 283. p+7Li J. Cruz et al., Phys. Lett. B 624 (2005) 181. 7Li+p J. Vesicet al., Eur. Phys. J.A50(2014) 153.

  22. Thick targets 1H(7Li,α)4He Adiabatic limit: Ue= 0.24 keV

  23. Thin targets and resonances Breit Wigner resonance cross section Infinitely thick target yield of narrow resonance Integral over the resonance C. Iliadis, Nuclear Physics of Stars, Wiley-VCH, Weinheim, (2007) p. 341.

  24. The 19F(p,αγ)16O reaction K. Spyrouet al., Z. Phys. A 357 (1997) 283; Eur. Phys. J. A 7 (2000) 79.

  25. Fluorine results A. Cvetinović, PhD Thesis, University of Ljubljana (2015).

  26. The 11B(p,αα)4He reaction H. W. Becker et al., Z. Phys., A 327, 341 (1987).

  27. Results A. Cvetinović, Phys. Rev. C 92 (2015) 065801.

  28. Crystal symmetry small screening large screening fcc (Pd) Hexagonal Graphite

  29. Hydrogen molecular ion 0 r He 2.0 axialni del Elektronska H v gostota + 2 L H 2.5 + = 1.5 D @ L H z au 1.0 0.5 0.0 r 1 - - 2 1 = D au @ z H 2 + H 2 = 0 L r = 0.2 r 2 r 0.4

  30. Hydrogen molecular ion

  31. Measurement setup In addition to 2H(p,γ)3He we looked for electrons from the 2H(p,e-)3He reaction Proton beam energy: 260 keV, intensity: 7 μA, 8 days Target: graphite implanted with deuterium at 3 keV once a day for ½ hour at 0.8 mA resulted in 8 at.% of deuterium per carbon atom down to a depth of about 270 nm CsI-Si timestamped Expectations: 4.3

  32. Conclusions • During the electron screening process the electrons come close to the nucleus. • A substantial number of fusion reactions in the Sun proceeds with electron emission. • Electron screening could help in lithium abundance problem. • Different screening potentials are due to different proportions of target nuclei on active and inactive sites. • For stellar plasma we really need to understand what happens in the laboratory experiments.