Nuclear Reactions and Nuclear Astrophysics

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Nuclear Reactions and Nuclear Astrophysics

• Focus on Physics

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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 12C12C fusion reaction

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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

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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)

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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
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TAMU exps _at_ 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 _at_ 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 ?!

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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 Pains talk

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75As d,p?

• 73As/74As 1/2 s74(n,2n) ?n (D.Vieira)
• Isotope ratios measured after event
• (n,2n) reactions most important
• (n,?) reactions can effect results

August 8, 2009
ANL
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Decay from excited 76As
August 8, 2009
ANL
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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!

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(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, A30 recoil detector

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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

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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
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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

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Decay Continuum spectroscopy Using MARS-HiRA

• 6Be 10C

PL B 677, 30 (2009) PRC in press (2009)
PRC 78 031602 (2008) 75 051304 (2007) in
press (2009)

1. Decay paths, branching ratios determined for all
   known levels.
2. A branch of the 6.57 MeV state has the best
   diproton correlation observed to date!
3. Did NOT confirm previous identified state at
   4.2 MeV thought to be the 0 (Curtis et al.,
   PRC77, 021301 (2008).
4. 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.)
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After that perhaps 14C
9Be(7Li,10Bea) Soic, PRC 68, 014321 (03)
? 2a6He
Gd.st
1st excited state
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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-
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(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

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Other means

• AMS as a tool for astrophysics

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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

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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

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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??!!...