Nuclear Physics at LLNL

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LLNL-PRES-404083

• Nuclear Physics at LLNL
• (From QCD to Nuclei to Stars)

William H. Goldstein Associate Director, Physical
Sciences Directorate
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LLNL Vision National Security in a Global Context
Pursuing global security through the application
of multidisciplinary ST to enhance national
security, meet energy and environment needs and
enhance economic competitiveness
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The Laboratory was founded in 1952 by nuclear
physicists
The Laboratory Founders and First Director Ernest
Lawrence, Edward Teller and Herb York
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LLNLs approach is integrated system solutions
that relies on mission-driven multidisciplinary
science-of-scale
Multiple scientific and technical disciplines
Analysis, ST, and operations
Threats, RD, prototypes, and products
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LLNL maintains major RD Facilities in support
of its mission
Terascale Simulation Facility
Contained Firing Facility
National Ignition Facility
High-Explosives Application Facility
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Through partnership with DOE/NNSA and IBM LLNL
maintains a strong position in supercomputing

• LLNLs BlueGene/L remains first on the Top500
  List of the worlds fastest computers (Now has a
  peak speed of 596 teraFLOPS)
• We have developed scientific software that
  effectively uses all 131,000 processors

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Advances in computer power are reinvigorating
nuclear theory, and helping address the leading
questions in nuclear physics

• What did the universe look like in the first
  microsecond?
• Is QCD the correct theory for the strong
  interaction?
• How are nuclei put together?
• How were the elements made?

Phase Diagram of Nucleonic matter
X-ray burst on a Neutron Star
Advances in computing are leading to a
renaissance in nuclear theory
Chart of the Nuclides
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Goal comprehensive, unified microscopic
description of all nuclei and their low-energy
reactions from the basic interactions between the
constituent protons and neutrons
Sea of Ignorance
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Goal comprehensive, unified microscopic
description of all nuclei and their low-energy
reactions from the basic interactions between the
constituent protons and neutrons
Sea of Ignorance

• Develop an exact quantal description of all
  nuclei
• Nucleon-nucleon interaction from first principles
• The nuclear equation-of-state from first
  principles
• Predictive theory for nuclear reactions

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The fundamental problem of nuclear physics - the
interaction is not known

• Unlike electrons in the atom, the interaction is
  not known precisely, and it is COMPLICATED
• We have scattering phase shifts and bound-state
  properties of the deuteron, triton, 3He, and 4He
• Can lattice QCD tell us what it is?
• Probably not in a way that is useful for
  many-body theorists
• But it will confirm that QCD is the correct
  theory for the strong interaction

Beane, Bedaque, Orginos, Savage PRL 97, 012001
(2006)
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From QCD to the inter-nucleon interaction using
effective field theory

• Lagrangian is an infinite series of terms
  representing the exchange of pions between
  nucleons
• Based on QCD through constraints of the chiral
  limit and symmetry breaking
• Parameters (coupling constants) fit to few-body
  scattering and binding data (n-n, n-d, etc.)
• Theory has an order-parameter
• (Q/?)n, ? momentum cut off
• Expansion formalism (Next)n-to-Leading Order
  (NnLO)

Entem et al., PRC68, 041001 (2003) Navratil et
al., PRL99, 042501 (2007)
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From QCD to the inter-nucleon interaction using
effective field theory
p-p scattering phase shifts

• Lagrangian is an infinite series of terms
  representing the exchange of pions between
  nucleons
• Based on QCD through constraints of the chiral
  limit and symmetry breaking
• Parameters (coupling constants) fit to few-body
  scattering and binding data (n-n, n-d, etc.)
• Theory has an order-parameter
• (Q/?)n, ? momentum cut off
• Expansion formalism (Next)n-to-Leading Order
  (NnLO)

EFT- two-body N3LO, ?2/? 1 Entem et al.,
PRC68, 041001 (2003) EFT - three body NNLO
Navratil et al., PRL99, 042501 (2007)
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Can effective field theory be used to unify our
understanding of nuclear matter (and QCD) across
the chart of the nuclides?
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Can effective field theory be used to unify our
understanding of nuclear matter (and QCD) across
the chart of the nuclides?
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Can effective field theory be used to unify our
understanding of nuclear matter (and QCD) across
the chart of the nuclides?
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Can effective field theory be used to unify our
understanding of nuclear matter (and QCD) across
the chart of the nuclides?
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From EFT to nuclear structure using effective
interaction theory
The computational challenge Nmax6 Nbasis
32M 700M NNN m.e. 6TB 90TF Nmax8 ? 1.5 PF
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From EFT to nuclear structure using effective
interaction theory
See Erich Ormand for details
The computational challenge Nmax6 Nbasis
32M 700M NNN m.e. 6TB 90TF Nmax8 ? 1.5 PF
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Applications to level-ordering clearly reveal the
presence of 3-body interactions
Navratil et al., PRL99, 042501 (2007)
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NN interactions fail to describe the ground
state of 10B
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NN interactions fail to describe the ground
state of 10B
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Applications to level-ordering clearly reveal the
presence of 3-body interactions

• 12C to 16O use 6000 CPU hours with 3-body at
  NNLO!
• To be consistent we need to go to N3LO and add
  NNNN

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LQCD and the 3-body interaction

• Three-body interaction between pions (mesons)
  has recently been calculated from LQCD
  calculations
• 3-body interaction parameter ?3 is consistent
  with repulsive interaction
• Results give proof of concept that 3-body
  interactions can be calculated from LQCD
• Formalism for three-body baryon (e.g. NNN)
  interactions on a lattice has been established
• LQCD calculations are more involved due to
  weaker signal-to-noise ratio and Pauli-exclusion
  principle
• Preliminary numerical lattice investigations are
  planned in the upcoming years at LLNL

Definitive repulsive 3-body interaction for all
pion masses considered thus far
S.Beane, W. Detmold, T. Luu et al., PRL
100082004 (2008)
Note Expression above assumed spin-triplet and
spin-singlet scattering lengths are the same
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Extending the picture to nuclear reactions
light-ion fusion for stellar astrophysics

• First-order theory for light-ion reactions
• Use the NCSM to compute structure information
• Radiative capture is governed by the E1 matrix
  element between 7Bep and the 8B ground state
• Compute the cluster overlap ?7Bp8B?
• Interior component is ok, but it has incorrect
  asymptotic behavior due to oscillator wave
  function
• Correct with a potential model constrained by the
  experimental separation energy

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Towards an Ab initio description of nuclear
reactions
n,p ? phase shifts expt vs. 2-body theory

• A fully ab initio treatment
• Use the NCSM to compute structure information
• Use the resonating group method to map the
  many-body problem on to various channels of
  nucleon clusters and their relative motion

Next step add 3-body interactions
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Beyond light nuclei the limits of CI

• Effective interaction needs to be derived!
• No one really knows how to do this consistently
  today
• Large dimensions
• Grows dramatically with number of particles
• Consider half-filled fp-gsd (for, say, Zr90)

Current computational capability is of the order
1010 states
Even 1015 states would require a computer 106
times more powerful than any computer available
today
1020 IS NOT AN OPTION!
Density Functional Theory has well-known
limitations
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Path integral monte carlo is a handy approach to
the problem of sampling an astronomically
expanding CI space

• We have to evaluate quantities like
• The unwieldy 2-body Hamiltonian is converted to a
  1-body effective operator at the expense of
  introducing an integral over the auxiliary
  field, ?
• Expectation values become multidimensional path
  integrals over configurations of the auxiliary
  fields, which can be sampled using monte carlo
  methods

Exponential filter
Thermal trace, T1/?
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Path integral monte carlo is a handy approach to
the problem of sampling an astronomically
expanding CI space

• We have to evaluate quantities like
• The unwieldy 2-body Hamiltonian is converted to a
  1-body effective operator at the expense of
  introducing an integral over the auxiliary
  field, s
• Expectation values become multidimensional path
  integrals over configurations of the auxiliary
  fields, which can be sampled using monte carlo
  methods

Exponential filter
Thermal trace, T1/?

• Have we made progress?
• Weve transformed a calculation of O(1022) states
  to a multi-dimensional integral over O(105)
  fields
• But to use monte carlo sampling, the weight
  function W(?) must be positive definite
• But, in general, its not (the fermion sign
  problem strikes again)

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A solution has been found to the sign problem of
auxiliary field monte carlo

• Introduce a shift in the Hamiltonian
  corresponding to the maximum of W(?)

First successful application of AFMC with a
realistic interaction
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Results in 27Na and 56Fe are very promising
18. A. Schiller et al., Phys. Rev. C 68, 054326
(2003). 19. A. V. Voinov et al., Phys. Rev. C 74,
014314 (2006).
We are hopeful that we can now solve the general
CI problem exactly
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The microscopic theory of nuclear fission (W.
Younes D. Gogny)

• Statics
• Hartree-Fock-Bogoliubov (HFB) with Gogny force ?
  microscopic description of nucleus
• Effective force between nucleons is the only
  phenomenological input determined a-priori and
  independently from a few observables
• Dynamics
• Construct wave packet from HFB solutions
• Evolve wave packet to scission by laws of QM

This is a fully quantum-mechanical, dynamical
description of fission ? powerful approach that
incorporates the rich complexity of fission
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Statics 240Pu energy versus elongation (Q2)
mass asymmetry (Q3)
Densities along most likely path to scission
(bottom of valley in Q2-Q3)
240Pu
EHFB (MeV)
Q3 (b3/2)
Q2 (b)
Calculations show complex structures in the
nuclear density along the path to scission ?
fission fragments and their properties at scission
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Beyond the chart of the nuclides modeling the
EOS of nuclear matter

• LLNL participates in the Phoenix collaboration at
  RHIC, and ALICE at LHC
• New program applies LQCD to data analysis

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The HotQCD collaboration has been formed to apply
LLNL computer resources to the problem of quark
matter EOS
MILC

• RBC-Bielefeld

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The HotQCD collaboration has been formed to apply
LLNL computer resources to the problem of quark
matter EOS
MILC

• RBC-Bielefeld

Physics goals N?8 Tc/EOS with continuum
corrections and chirally symmetric actions
(domain wall fermions)
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Transition Temperature - Deconfinement

• Polyakov Loop and Strange Quark Number
  Susceptibility

HotQCD Preliminary
Lines at 185,195 MeV to set range of N?8
transition
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Transition Temperature - Chiral

• Subtracted Chiral Condensate and Total Chiral
  Susceptibility

HotQCD Preliminary
Same lines at (185,195 MeV) set range for chiral
N?8 transition
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Equation of State LQCD N?8

• Definitive Equation of State from HotQCD to be
  published soon
• (HBT expected to improve at expense of proton v2)

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Lattice QCD is an archetypal supercomputing
problem

• Sustained 59.1 teraFLOPS (later increased to
  70.9) Lattice Quantum Chromodynamics (LQCD)
  calculation by a team of scientists from IBM and
  LLNL
• Perfect linear scaling to 131,072 cpu cores,
  highest performance ever achieved by LQCD codes

2006 Gordon Bell Prize
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2007 IEEE/AIP Petaflop Essay Contest Winner

• Sponsored by IEEE/AIP Computing in Science and
  Engineering, What would you do with a Petaflop?

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The LLNL heavy element group has collaborated
with scientists at the Flerov Laboratory (FLNR)
of the Joint Institute for Nuclear Research
(JINR) since 1989
Since 1998, collaborative research between FLNR
and LLNL has produced more than 30 new nuclides
and 5 new elements, including 113, 114, 115, 116,
and 118
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LLNL has developed novel nuclear chemistry
techniques for the collaboration
Clean Ta and Nb separation

• Group 5 separation based on reverse phase
  chromatography to identify the long-lived Db
  decay descendant of element 115
• Total chemistry time (target removal until
  samples on counter) was about 5 hours with yields
  about 80

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The LLNL heavy element group has been studying
fission of the heaviest elements for 30 years

• In the 1980's, the LLNL heavy element group
  discovered two fission modes that compete in the
  spontaneous fission of several heavy actinide
  nuclides
• Low energy form with broad mass distribution
• High energy form with sharply symmetric mass
  division
• This "bimodal fission" decay challenged nuclear
  theory and resulted in fundamental changes in the
  way the fission barrier is modeled

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P03410-whg-u-020
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NIF will create 1033 neutrons per cm2 per
second, equivalent to a supernova
NIF will create thermal plasmas at the conditions
of stellar interiors
NIF generates pressures found at the center of
Jupiter
NIF will produce enough x-ray flux to simulate
conditions in an accretion disk
NIF will access unprecedented energy densities
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NIF creates unique environments for nuclear
science
Stellar Energy Production Nucleosynthesis
Nuclear Physics in a Plasma environment
Reactions on excited states
HT(D) shots provide the first NIF nuclear science
opportunity s-process nucleosynthesis in a
stellar environment
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The NIF environment offers an opportunity to
study plasma effects on nuclear astrophysics
S-process branching near thulium
Plasma effects
The s-process at kT8 30 keV moves along valley
of stability with temperature dependent branch
points where ?-decay competes with neutron capture
In a plasma, internal conversion processes, like
nuclear excitation by electron capture, may
populate low-lying excited nuclear states
G. Gosselin P. Morel Phys. Rev. C 70 064603
(2004)

• If the nucleus is in an excited state, the (n,?)
  cross section is likely to be different
• The neutron capture cross section may be
  measurable under relevant plasma conditions at
  NIF

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A 171Tm(n,?) experiment at NIF
Insert 1015-16 171Tm169 Tm
Co-loading known and unknown isotopes minimizes
systematic uncertainties
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This work is being done by

• Erich Ormand
• Ron Soltz
• Pavlos Vranos
• Tom Luu
• Walid Younes
• Mark Stoyer
• Daniel Gogny
• Petr Navritil
• Sophia Quaglioni
• Gergana Stoitcheva
• James Vary (ISU)

• Lee Bernstein
• Rob Hoffman
• Darren Bleuel
• Mathias Weidekind
• Ken Moody
• Dawn Shaughessy
• John Wild
• Ron Lougheed
• Jackie Kenneally
• Nancy Stoyer
• Philip Wilk

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• LLNL is participating in a renaissance of nuclear
  structure and reaction theory, enabled by high
  performance compuing
• Great progress has been made in understanding
  inter-nucleon interactions and describing light
  nuclei from first principles
• Promising new methods are available for treating
  heavy nuclei
• Work is underway on the nuclear matter
  equation-of-state
• NIF may provide a new experimental capability for
  nuclear science

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