Nuclear Physics and Heavy Element Research at LLNL

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• Nuclear Physics and Heavy Element Research at
  LLNL

Mark A. Stoyer Symposium honoring the 175th
birthday of Mendeleev The Periodic Table of D.I.
Mendeleev and New Superheavy Elements Dubna,
Russia Jan. 20-21, 2009
Lawrence Livermore National Laboratory, P. O. Box
808, Livermore, CA 94551
This work performed under the auspices of the
U.S. Department of Energy by Lawrence Livermore
National Laboratory under Contract
DE-AC52-07NA27344
LLNL-PRES-409918
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Mendeleevs 1869 periodic table enabled a quantum
leap in chemical understanding
Mendeleyev used this new tool to predict the
existence of chemical elements that hadn't been
discovered yet they were found several years
later
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Now there are a variety of ways to visualize
chemical periodicity
g-orbitals are predicted to start filling at
Z120!
4
As an undergraduate student at Purdue, I
developed a healthy admiration and respect for
Mendeleev

• In 1983 I researched an extensive biographical
  report on Mendeleev for one of my history of
  science classes

A fundamental understanding of the chemical
periodicity of the elements is a powerful tool
for chemists, and to contribute to the elements
organized and contained in the periodic table is
a penultimate goal of chemists
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I have continued to read about Mendeleev and the
chemical elements

• Several more popular books Id recommend

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The experimental nuclear physics effort at LLNL
is centered on investigating nuclei at the
extremes

• Extremes of
• Spin (Gammasphere/CHICO)
• IsospinN/Z (TRIUMF/TIGRESS)
• Neutron-richness (RIB)
• Excitation energy (NIF, accel.)
• Decay and detectability (neutrinoless double
  beta-decayCUORE)
• Mass (SHE)
• Stability (SHE, RIB, Astrophysics)

Many areas clearly inter-related
Complimentary to the nuclear chemistry effort to
study the chemical properties at the extremes
heaviest elements and fast chemistry (SHE)
Roger Henderson to discuss later
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The experimental nuclear physics effort in my
group directly supports the US nuclear physics
efforts
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A rigid rotor-like mode of motion was discovered
in 236Np high spin studies using neutron-transfer
reactions
Proposed partial level scheme
236Np produced in the 237Np(116Sn,117Sn)
12 New transitions!

• Nearly equal spacing ( 37 keV) of ?-ray
  transitions discovered in 236Np
• Signature of rigid rotor-like mode of motion
  ?i13/2 ? ?j15/2 configuration suggested
• Gammasphere/CHICO collaboration ANL, LLNL,
  Rochester, Liverpool, Maryland

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A combination of gamma-ray detection and particle
detection identified 1n- and 2n-transfer
Gammasphere CHICO
The measured kinematic moment of inertia 107.4
h2?2/MeV
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The Coulomb excitation of 242mAm produced
evidence for K-mixing and depopulation of the
isomer
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The sd-pf shell gap near the Island of
Inversion was investigated by studying 29Na
Motivation

• Test predictive capability of modern nuclear
  theory
• 29Na is the transitional region for breakdown
  of traditional shell model
• Magic number N 20 vanishes for exotic
  nuclei (extreme N/Z ratio)

Goal

• Quantify the configuration mixing between the sd
  and pf major shells
• Measure B(E2) value to first excited state
  sensitive to strength of shell gap

Methodology

• Sub-barrier Coulomb excitation (Coulex)
• Post accelerated radioactive beam of
  neutron-rich 29Na _at_ TRIUMF/ISAC-II

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Experimental setup 110Pd(29Na,29Na) _at_ 70 MeV
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ISAC-II was used to study the Coulomb excitation
of 29Na

• 500 MeV, 70 ?A proton beam natTa production
  target
• Produce 29Na atoms
• natRe surface-ion source
• Produce 29Na ions
• Stripper foil
• Produce 29Na5 ions
• ISAC-II A/q 5.8

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This was the first experiment with TIGRESS and
BAMBINO
g-ray detection
particle detection
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The B(E2) of 29Na was measured and indicates a
narrowing of the sd-pf shell gap
A. Hurst, et al. submitted to PLB (2008)
The reduced matrix element in 29Na was deduced to
be 0.237(21) eb Monte Carlo shell model
calculations indicate the sd-pf shell gap narrows
from 6 MeV in stable nuclei to 3 MeV in 29Na
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A site was just chosen for the FRIB a next
generation radioactive ion beam facility in the US
MSU NSCL site of FRIB
FRIB will explore terra incognita near the proton
and neutron drip lines and to the heaviest
extremes of the chart of nuclides
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The National Ignition Facility is the worlds
largest and most powerful laser fusion facility
192 beams
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NIF gets you thinking about SCALE

• Temperatures and pressures achieved are like the
  core of the sun (15 million degrees K and 3
  billion atmospheres) or an exploding nuclear
  weapon
• Capsule is 2 mm diameter containing 150 mg D and
  T (2 Ci 200 mg) which is imploded inside a 10 m
  diameter target chamber inside a building the
  size of the Superdome in New Orleans
• Laser pulse is 1.8 MJ in 3-4 ns with ignition
  giving 20 MJ energy in return in ps

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Several fusion reactions are possible, but DT is
by far the easiest to ignite
10 keV 8.0 106 ºC 400 keV 3.2 108 ºC
J. Lindl, Inertial Confinement Fusion The Quest
for Ignition and Energy Gain Using Indirect
Drive Springer-Verlag, New York 1998.
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A NIF point design capsule consists of a Be/Cu
ablator and cryogenically frozen DT fuel
Fusion fuel implosion efficiency is 5-15 and the
temperature is about 10 keV
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A NIF double shell design provides an alternative
non-cryogenic ignition design
Double Shell
Point design
300K
19K
Amendt
Be/Cu
1601 mm
DT gas
DT ice
The double shell capsule ignites by volume
ignition versus hot spot ignition for the point
design
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NIF compression over a short burn time creates an
enormous neutron flux
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Reactions on excited states could provide insight
into reactions on neutron-rich nuclei far from
stability
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Production of excited states in-situ at NIF does
alter the expected radiochemistry product ratios
Lee Bernstein, et al.
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The NIF capsule HEDP populates low-lying nuclear
states via NRF and NEEC
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Early NIF shots offer the opportunity to study
stellar (n,g) in a stellar HEDP environment
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To diagnose the performance of the capsule, we
position a dopant in the inner part of the
ablator, and monitor nuclear reactions on that
dopant
We also need to trace the capsule with various
isotopes to determine our collection fraction
Examples of tracers are 22Ne, 38Ar, 82Kr, 130Xe
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The search for neutrinoless double beta decay
investigates the fundamental properties of the
neutrino
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This extremely low background counting experiment
is located at the Gran Sasso Laboratory
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The use of bolometers provides the most sensitive
detectors to search for this rare process
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We have been collaborating with Dubna on SHE
research since 1989
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The 48Ca 249Bk reaction can be used to produce
element 117 for the first time, but target
material is difficult to obtain
Compound nucleus
3n evap. channel 4n evap. channel 5n evap. channel
In the 5n-channel, alpha decay would produce
previously studied nuclides
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Roger Henderson will discuss the LLNL automated
chemistry efforts later today
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Conclusions

• The experimental nuclear physics program at LLNL
  is aimed at investigating nuclei under extreme
  conditions we continue to pursue experiments at
  many facilities
• The study of SHE is a valuable part of this
  program
• Future SHE work includes
• experiments to make element 117
• experiments to synthesize new isotopes and
  elements with beams other than 48Ca
• experiments to study the chemical properties of
  elements with isotopes of suitable half-lives

LLNL looks forward to continued highly successful
collaboration with JINR
Happy 175th Birthday Dmitri Ivanovich Mendeleev!
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I am of course discussing the work of many

• LLNL (Heavy Elements Group) Ken Moody, John
  Wild, Ron Lougheed, Mark Stoyer, Nancy Stoyer,
  Caroln Laue, Dawn Shaughnessy, Jerry Landrum,
  Joshua Patin, Philip Wilk, Roger Henderson, Sarah
  Nelson
• LLNL (ENP Group) Larry Ahle, Lee Bernstein,
  Jason Burke, Ross Marrs, Eric Norman, Mark
  Stoyer, Ching-Yen Wu, Nick Scielzo, John Becker,
  Darren Bleuel, Shelly Lesher, Aaron Hurst, Steven
  Sheets, Mathis Weideking, Marisa Pedretti, Dashka
  Dashdorj
• JINR Yu. Ts. Oganessian, V.K. Utyonkov, Yu. V.
  Lobanov, F.Sh. Abdullin, A.N. Polykov, I.V.
  Shirokovsky, Yu.S. Tsyganov, G.G. Gulbekian, S.L.
  Bogomolov, B.N. Gikal, A.N. Mezentsev, S. Iliev,
  V.G. Subbotin, A.M. Sukhov, G.V. Buklanov, K.
  Subotic, M.G. Itkis, R.N. Sagaidak, S. Shishkin,
  A.A. Voinov, V.I. Zagrebaev, and S.N. Dmitriev