Nuclear Reactions and Nuclear AstrophysicsFocus on Physics

SpeakersPhillipe Collon Possibilities for AMS experiments at ATLASLivius Trache Single-nucleon transfer between p-shell nuclei around 10 MeV/uWilliam Peters (d,pg) as a surrogate for (n,g)Lee Sobotka Decay spectroscopy next up 14CCatherine Deibel Studying the (a,p) process at ATLASXiaodong Tang The 12C+12C fusion reaction

ThemesNucleon transfer reactions for structure, astrophysics, and applicationsOther reactions for structure(In)elastic scattering for optical-model potentials, structureOther means AMS, production/counting for astrophysics

Transfer reactions for structure and astrophysicsHeavy-ion single-particle transfer for nuclear astrophysicsANC studies linked to determination of (p,g) reaction ratesNeed for accurate optical-model potentialsNeed high-quality beams, intensity for production of high-quality secondary beams (energy resolution, low emittance)

Details and problemsEnergy resolution (bad!)Beam res. 1-2% 2-4 MeVangular resolution (limited!)Beam res. 0.8 2 deg! Ang distr ANC astrophys S-factor react rate

12N on melamineTAMU exps @ 12 MeV/uA. Banu ea,PRC 79, 025805 (2009)Optical Model Potentials for Nucleus-Nucleus collisionsfor RNBs ~ 10 MeV/uEssential 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/uParameters: renormalization coeff. Predicts well elastic scatt for RNBs: 7Be, 8B, 11C, 12N, 13N, 17F7-10% uncertainty in DWBA calc

L. Trache ea, PRC 61 (2000)F Carstoiu ea PRC 70 (2004)OMP: need extension to sd-shell:Work on stable projectiles at TAMURNB of good quality ATLAS ?!Energy and angular resolutionTrojan-horse with RNB ?!

Transfer reactions as surrogates Inverse (d,pg) as a tool to probe (n,g), (n,2n)Applications:AstrophysicsNuclear reactors and device modelingStockpile stewardship and waste storageNeeds:Reasonable intensity for RNBs at least 105 to 106 ppsCoulomb-barrier energy beamsGammasphere for g efficiencyParticle detector with reasonable spatial resolutionSee also instrumentation & Steve Pains talk

73As/74As = 1/2 74(n,2n) n (D.Vieira)Isotope ratios measured after event(n,2n) reactions most important(n,) reactions can effect results

August 8, 2009ANL*

August 8, 2009ANL*

My two centsNucleon transfer for Classical nuclear physics with RNBSpectroscopic factors to test wave functions from (d,p), (d,3He), (d,t), (a,t) ...In light nuclei tests of ab-initio calculationsSingle-particle states around, say, 132Sn...Needs: More intense RNB further than 1 nucleon from stability at Coulomb-barrier + energiesIntense primary beamsHigh energies (20 MeV/u) for very negative Q-value reactionsRobust production targetsNew separatorRF sweeper at HELIOSCARIBU!

(a,p) reactions and HELIOSInformation about ap process and X-ray burstsRequires intense secondary in-flight beams, Coulomb-barrier- energiesTool HELIOS instrumented with cryogenic 4He target, A~30 recoil detector

ap-process in X-Ray BurstsThe 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

ap-process studies with HELIOS Si ArrayGas targetPPAC and ICOriginal designSolid targetsDetection of backward light recoilsDetection of heavy recoils at 0

Additions:Gas target: allows 3,4He targetsFull Si array allows almost 4p acceptancePPAC and IC allows for more robust particle identification of heavier recoils, beam, and beam contaminants

Beam

Other reactions for structure: Breakup and resonant particle spectroscopyStudy multi-particle correlations following inelastic excitation Physics of exotic cluster states at high excitation energyNeeds high energy, intense (at least few X 105) pps

Decay Continuum spectroscopy Using MARS-HiRA6Be 10CPL B 677, 30 (2009); PRC in press (2009) PRC 78 031602 (2008); 75 051304 (2007); in press (2009) 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.)

9Be(7Li,10Be+a)Soic, PRC 68, 014321 (03)2+2+,1-,0+,2-But most channels not Observed, i.e.12C + 2n12C* + 2n8Be + 6He8Be* + 6He

i.e. aa6He (and intermediates)

Calls for a 3 cp + neutron correlation Experiment.

HiRA + WU neutron detectors After that perhaps 14CGd.st1st excited state2nd grp 2a6He

(In)elastic scattering Necessary, especially for RNBS, to determine optical potentialsNeeded to interpret ANC measurementsAnd Spectroscopic factor measurements15-20 MeV/u measurements of (p,p) on RNBs as a benchmark for higher energy studies, probe asymmetry dependence in dispersive optical potentialUse (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

Other meansAMS as a tool for astrophysics

Present status of AMS experiments at ATLASA number of AMS experiments have been performed at ATLASEnvironmental science (39Ar, 81Kr, )Stellar nucleosynthesis (59Ni, 62Ni(n,g)63Ni, 146Sm, 182Hf,)WIMP dark matter detector development (39Ar)AMS relies on a number of factorsGood isobaric separation (high energies help!)Stability of the entire systemHigh overall transmission

Other meansAMS as a tool for astrophysicsProduction studies for p-process nucleiUse 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

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 welcomeHigh intensities useful for extending the reach of the secondary in-flight programWhere can we get a tritium target??!!...

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