ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Stable ion beams for nuclear astrophysics: Where do we stand ? S. V. Harissopulos Tandem Accelerator Laboratory, Institute of Nuclear Physics, NCSR “Demokritos”, Athens, GR

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Nuclear Astrophysics … studies aiming at understanding HOW nuclear processes influence astrophysical phenomena.

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Astrophysical environmentsNuclear processes Novae, supernovae, X-ray bursts AGB stars, supernovae II, Neutrons stars Red giant stars, stars of the Asymptotic branch Big Bang (primordial nucleosynthesis) Hydrogen burning proton-proton chain, CNO cycle, Ne-Na cycle, Mg-Al cycle Explosive burning Hot CNO cycle Rapid proton capture (rp process) Nucleosynthesis beyond iron Slow neutron captures (s-process) Rapid neutron captures (r-process) photodisintegrations and proton captures (p-process) Helium burning 3a-process, 12 C(a,γ) 16 O Other (a,γ) and (a,n) reactions Reactions between the lightest elements p, d, He, Be, Li Advance burning stages Reactions of C, O, N, Ne, Si… Super giant stars, Wolf-Rayet stars and Pre-supernovae Main sequence (e.g. Sun) Courtesy: C. Angulo (Habilitation thesis, 2006)

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Major “stellar beams”: Major “stellar beams”: p, n, α, d, 3 He, C, O.. also γ ! Targets : Energies : Sections : Typical beam times : Targets : any nucleus (stable or unstable) Energies : depending on the temperature of the relevant stellar environment ! (from ≈10 6 K up to ≈5x10 9 K !!!) => cm-energies vary from 5 keV to 15 MeV Cross between 0.1 μb and 100 mb, BUT Sections :sometimes very very low … (≈ 1 fb !!!) Typical between 1 week and 1 month, beam however there are reactions requiring times : even years to be studied !!! OFTEN:DEMAND FOR VERY ACCURATE DATA (below 5% error !!!)

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Gamow peaks and windows : the astrophysically relevant energies charged-particle induced reactions neutron-induced reactions reaction barrier (MeV) E 0 (keV) T (K) p + p (sun) ×10 7  + 12 C (red giants) × C + 12 C (massive stars) ≈ 1×10 9 p + 74 Se (p process) ≈ 3×10 9 E o ≈ kT ∆E n = 20 ÷ 500 keV photon-induced reactions (γ,n) (γ,α)

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 S factors and reaction rates: the most wanted data …  nr (E) = exp(-2  ) S(E) S factornon-nuclear term (s-waves only) =S(E) exp dE reaction rate : reactions/sec/cm 3 E0E0

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Some typical uncertainties due to extrapolations E0E0 200 % Large uncertainties exist for many other key reactions, where the low energy limit was determined so far by beam-induced background. CNO cycle reactions (T=2 × 10 7 K) C. Angulo (Hab. thesis, 2006) A. Aprahamian et al., Prog. Part. Nucl. Phys. 54, 535 (2005) Uncertainties due to: Cosmic background Beam-induced bgd. Obsolete “tools” Underground labs Properly equipped high-current stable-beam labs Inverse kinematics Bochum data, T. Spillane et al, PRL 98, (2007)

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 LUNA : descending deep down to Gamow regions ! Courtesy: C. Angulo (Habilitation thesis, 2006) Sun’s center T=1.5 × 10 7 K Big Bang T=0.5 × 10 9 K

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Nucleosynthesis along the table of isotopes 39 Y 28 Ni 20 Ca 8O8O Fe pp chain CNO cycle NeNa cycle Si burning s process r process powered by neutrons (n,  ) /  - rp process powered by protons (p,  ) /  +   100 yr   10 8 n/cm 3 T =( )×10 9 K   1 sec   n/cm 3 T =( )×10 9 K s process: M<M ๏ ( AGB stars, red giants...) explosive nucleosynthesis MgAl cycle Novae, X-ray bursters… up to  Sn  >10 4 g/cm 3 T  (1-3)×10 9 K r process: ? (supernovae, neutron stars)

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Pathways for heavy-element nucleosynthesis - +

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 p-process reaction network “seed “ abundances s process p-nuclei abundances p process reaction network more than ( ,n), ( ,p), ( ,  ), n-, p-,  -captures,  -decays, e-captures HAUSER-FESHBACH THEORY Optical Model Potentials - Nuclear Level Densities γ-ray strength functions (32≤Z≤83, 36≤N≤131) NEED FOR GLOBAL MODELS OF OMP, NLD, …

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 r:= max. / min. M. Arnould and S. Goriely, Phys. Rep. 384, 1 (2003) Impact of nuclear physics uncertainties on p-nuclei abundances n captures p captures α captures A≈100 A≈180 obtained with 14 different sets of nuclear ingredients (OMP, NLD, …) in HF calculations. P. Demetriou et. al, Nucl. Phys. A 707, 253 (2002)

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 S factors and reaction rates: the most wanted data … We also need to study β decay properties (GT strengths, half-lives) fission (of key importance, especially for the r process) GDR and pygmy resonances Nuclear masses and binding energies Screening potentials ……….. Not only reaction rates are vital for nuclear astrophysics !

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Some views … RIB facilities can certainly provide the tools for interesting nuclear astrophysics studies (main topic : r process). For many astrophysical questions, RIBs have to comparable to stable ones, at least in terms of intensity. The necessary beam-times are in most of the cases time consuming. As such, nuclear astrophysics experiments have less chances of success in PACs. Reaction studies in inverse kinematics can certainly provide a solution to the problem of the beam-induced background. This, however, requires certain exp. conditions, like intense beams, state-of-the art separators and target optimization and development. Some “old-fashioned” direct measurements like capture reactions, cannot completely be replaced by inverse kinematics studies due to beam current limitations !!!

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Some views … Resonance physics put certain conditions to beam characteristics. A very good energy resolution is a must. Excitation function measurements require systems capable of undergoing energy changes within reasonable times. Therefore, cyclotrons and LINACs can sucessfully be used for certain applications only. VdG accelerators and especially TANDEMS are still the best tools for “standard-type” nuclear astrophysics. LUNA has decisively contributed to our understanding of stellar evolution. Underground labs have still a bright future.

ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007 Some views … Indirect methods often model-dependent BUT very useful and challenging Coulomb dissociation Trojan-Horse method Asymptotic Normalization Coefficients need also stable beams !!!

Accelerators for nuclear astrophysics ESF Workshop on The future of stable beams in Nuclear Astrophysics, Athens, Dec , 2007