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Nuclear Reactions and Nuclear Astrophysics

Nuclear Reactions and Nuclear Astrophysics. Focus on Physics. Speakers. Phillipe Collon – Possibilities for AMS experiments at ATLAS Livius Trache – Single-nucleon transfer between p-shell nuclei around 10 MeV/u William Peters – (d,p g ) as a surrogate for (n, g )

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Nuclear Reactions and Nuclear Astrophysics

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  1. Nuclear Reactions and Nuclear Astrophysics Focus on Physics

  2. Speakers • Phillipe Collon – Possibilities for AMS experiments at ATLAS • Livius Trache – Single-nucleon transfer between p-shell nuclei around 10 MeV/u • William Peters – (d,pg) as a surrogate for (n,g) • Lee Sobotka – Decay spectroscopy – next up 14C • Catherine Deibel – Studying the (a,p) process at ATLAS • Xiaodong Tang – The 12C+12C fusion reaction

  3. Themes • Nucleon transfer reactions for structure, astrophysics, and applications • Other reactions for structure • (In)elastic scattering for optical-model potentials, structure • Other means – AMS, production/counting for astrophysics

  4. Transfer reactions for structure and astrophysics • Heavy-ion single-particle transfer for nuclear astrophysics • ANC studies linked to determination of (p,g) reaction rates • Need for accurate optical-model potentials • Need high-quality beams, intensity for production of high-quality secondary beams (energy resolution, low emittance)

  5. Details and problems angular resolution (limited!) Beam res. 0.8 – 2 deg! Energy resolution (bad!) Beam res. 1-2% 2-4 MeV Ang distr → ANC → astrophys S-factor → react rate

  6. TAMU exps @ 12 MeV/u 12N on melamine Optical Model Potentials for Nucleus-Nucleus collisions for RNBs ~ 10 MeV/u • Essential to make credible DWBA calc needed in transfer r. • Have established semi-microscopic double folding using JLM effective interaction: • Established from exps with stable loosely bound p-shell nuclei: 6,7Li, 10B, 13C, 14N … @ 10 MeV/u • Parameters: renormalization coeff. • Predicts well elastic scatt for RNBs: • 7Be, 8B, 11C, 12N, 13N, 17F • 7-10% uncertainty in DWBA calc • L. Trache ea, PRC 61 (2000) • F Carstoiu ea PRC 70 (2004) A. Banu ea, PRC 79, 025805 (2009) • OMP: need extension to sd-shell: • Work on stable projectiles at TAMU • RNB of good quality – ATLAS ?! • Energy and angular resolution • Trojan-horse with RNB ?!

  7. Transfer reactions as surrogates – Inverse (d,pg) as a tool to probe (n,g), (n,2n) • Applications: • Astrophysics • Nuclear reactors and device modeling • Stockpile stewardship and waste storage • Needs: • Reasonable intensity for RNBs – at least 105 to 106 pps • Coulomb-barrier energy beams • Gammasphere for g efficiency • Particle detector with reasonable spatial resolution • See also instrumentation & Steve Pain’s talk

  8. 75Asd,pγ • 73As/74As = 1/2 σ74(n,2n)Фn (D.Vieira) • Isotope ratios measured after event • (n,2n) reactions most important • (n,γ) reactions can effect results 8 ANL August 8, 2009

  9. Decay from excited 76As Doppler corrected 6 keV FWHM 9 ANL August 8, 2009 Partial level scheme (from ENDSF) of 76As used to identify successful (d,pγ) events. Quoted branching are from (n,γ) experiments. 511 165 Spectrum not Doppler corrected Gamma Spectrum (keV)

  10. My two cents • Nucleon transfer for “Classical” nuclear physics with RNB • Spectroscopic factors to test wave functions from (d,p), (d,3He), (d,t), (a,t) ... • In light nuclei – tests of ab-initio calculations • Single-particle states around, say, 132Sn... • Needs: More intense RNB further than 1 nucleon from stability at Coulomb-barrier + energies • Intense primary beams • High energies (20 MeV/u) for very negative Q-value reactions • Robust production targets • New separator • RF sweeper at HELIOS • CARIBU!

  11. (a,p) reactions and HELIOS • Information about ap process and X-ray bursts • Requires “intense” secondary in-flight beams, Coulomb-barrier- energies • Tool – HELIOS instrumented with cryogenic 4He target, A~30 recoil detector

  12. ap-process in X-Ray Bursts • The early rp-process a series of (p,g), (a,g) and (a,p) reactions • Stalls where (p,g) and (g,p) reactions come into equilibrium and must wait for b+ decay • (a,p) reactions can break out if they are faster than the b+ decay • May be responsible for double-peaked luminosity profiles • Sensitivity studies have shown many of these reactions have significant effects on final abundances and energy output

  13. ap-process studies with HELIOS • Original design • Solid targets • Detection of backward light recoils • Detection of heavy recoils at 0° • Additions: • Gas target: allows 3,4He targets • Full Si array allows almost 4p acceptance • PPAC and IC allows for more robust particle identification of heavier recoils, beam, and beam contaminants Si Array Beam Gas target PPAC and IC

  14. Other reactions for structure: Breakup and resonant particle spectroscopy • Study multi-particle correlations following inelastic excitation • Physics of exotic cluster states at high excitation energy • Needs high energy, “intense” (at least few X 105) pps

  15. Decay Continuum spectroscopy – Using MARS-HiRA PL B 677, 30 (2009); PRC in press (2009) PRC 78 031602 (2008); 75 051304 (2007); in press (2009) 6Be 10C • Decay paths, branching ratios determined for all known levels. • A branch of the 6.57 MeV state has the best “diproton” correlation observed to date! • Did NOT confirm previous “identified” state at 4.2 MeV thought to be the 0+ (Curtis et al., PRC77, 021301 (2008). • Found new state at 8.4 MeV Perhaps we should do 10C + p (inelastic) to really find this 0+. (But will it be excited? Just above threshold.)

  16. After that – perhaps 14C 9Be(7Li,10Be+a) Soic’, PRC 68, 014321 (03)  2a6He Gd.st 1st excited state 2+ But most channels not Observed, i.e. 12C + 2n 12C* + 2n 8Be + 6He 8Be* + 6He i.e. aa6He (and intermediates) Calls for a 3 cp + neutron correlation Experiment. HiRA + WU neutron detectors 2nd grp 2+,1-,0+,2-

  17. (In)elastic scattering • Necessary, especially for RNBS, to determine optical potentials • Needed to interpret ANC measurements • And Spectroscopic factor measurements • 15-20 MeV/u measurements of (p,p) on RNBs as a benchmark for higher energy studies, probe asymmetry dependence in dispersive optical potential • Use (p,p’) as a spectroscopic tool – search for the excited 0+ cluster state in 10C? Moments and transition matrix elements? • Needs high-energy beams, HELIOS is the tool

  18. Other means • AMS as a tool for astrophysics

  19. Present status of AMS experiments at ATLAS • A number of AMS experiments have been performed at ATLAS • Environmental science (39Ar, 81Kr, …) • Stellar nucleosynthesis (59Ni, 62Ni(n,g)63Ni, 146Sm, 182Hf,…) • WIMP dark matter detector development (39Ar) • AMS relies on a number of factors • Good isobaric separation (high energies help!) • Stability of the entire system • High overall transmission

  20. Other means • AMS as a tool for astrophysics • Production studies for p-process nuclei • Use intense ATLAS beam to do, e.g., 144Sm(a,g), 142Nd(a,g), 154Gd(a,g) followed by AMS counting – needs very intense, high-energy beams

  21. Discussions – my interpretation so blame me • (d,n) reactions as a spectroscopic tool – neutron detection capabilities? • Resolution and sensitivity are key for uncovering the physics. (No kidding, really?) • High beam energies are most welcome • High intensities useful for extending the reach of the secondary in-flight program • Where can we get a tritium target??!!...

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