Transcript ppt - (FLEROVLAB) JINR

Lawrence Livermore National Laboratory
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
Mendeleev’s 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
Now there are a variety of ways to visualize chemical
periodicity
g-orbitals
are
predicted to
start filling
at Z=120!
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
I have continued to read about Mendeleev and the
chemical elements
 Several more popular books I’d recommend …
The experimental nuclear physics effort at LLNL is
centered on investigating nuclei at the extremes
 Extremes of
• Spin (Gammasphere/CHICO)
Many areas clearly
• Isospin—N/Z (TRIUMF/TIGRESS)
inter-related
• Neutron-richness (RIB)
• Excitation energy (NIF, accel.)
• Decay and detectability (neutrinoless double betadecay—CUORE)
• Mass (SHE)
• Stability (SHE, RIB, Astrophysics)
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
The experimental nuclear physics effort in my group
directly supports the US nuclear physics efforts
Important issues in nuclear structure stated in 2002 NSAC Long Range Plan
• What are the limits of nuclear existence?
• How do weak binding and extreme proton-to-neutron asymmetries
affect nuclear properties?
• How do the properties of nuclei evolve with changes in proton and
neutron number, excitation energy, and angular momentum?
Important issues probable for 2007 NSAC Long Range Plan
• Development of a comprehensive and unified description of nuclei
requiring new data on exotic isotopes
• Construction of the Facility for Rare Isotope Beams
• Effective utilization of current facilities such as NSCL, HRIBF and
ATLAS
• A program of experiments to investigate neutrino properties and
fundamental symmetries
A rigid rotor-like mode of motion was discovered in
236Np high spin studies using neutron-transfer reactions
236Np
produced in the 237Np(116Sn,117Sn)
Proposed partial level scheme
12 New transitions!
1.
Nearly equal spacing (~ 37 keV) of -ray transitions discovered in 236Np
2.
Signature of rigid rotor-like mode of motion; i13/2  j15/2 configuration suggested
3.
Gammasphere/CHICO collaboration: ANL, LLNL, Rochester, Liverpool, Maryland
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
The Coulomb excitation of 242mAm produced evidence
for K-mixing and depopulation of the isomer
(ANL/Atlas/Gammasphere/Rochester/LLNL/ANL/MSU/Youngstown Collaboration)
K = 5-, 5-
T1/2, Ex
?
?
141 yr, 48.6
K = 1-, 1-
16 hr, 0.0
K = 6-, 6-
Results are Surprising!
Two strongly coupled bands
242mAm
242Am
Gammasphere Data
– 2 bands equally populated
• K-mixing and depopulation of isomer
• Spectroscopy of Am isotopes important for
robust A
• 242mAm sample, > 98 %, unique to LLNL
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 @ TRIUMF/ISAC-II
Experimental setup: 110Pd(29Na,29Na*) @ 70 MeV
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
This was the first experiment with TIGRESS and
BAMBINO
-ray
detection
particle
detection
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
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
The National Ignition Facility is the world’s largest and most
powerful laser fusion facility
192 beams
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 g D and T (2 Ci =
200 g) 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
Several fusion reactions are possible, but DT is by far
the easiest to ignite
Reaction
VC (MeV) Q (MeV)
P + P --> 2He
0.500
14.578
P + D --> 3He
0.442
5.494
D + D --> 3He + n
0.397
3.27
D + D --> T + P
0.397
4.033
D + T --> 4He + n
0.370
17.59
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.
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
A NIF double shell design provides an alternative noncryogenic ignition design
Double Shell
Point design
300°K Amendt
19°K
Be/Cu
Au/Cu
1601 m
DT gas
DT ice
1 cm
1601 m
DT
FOAM
Be/Cu
The double shell capsule ignites by volume ignition versus hot spot
ignition for the point design
NIF compression over a short burn time creates an
enormous neutron flux
Reactions on excited states could provide insight into reactions on
neutron-rich nuclei far from stability*
126
V(x)
Near Drip Line
82
Near Stability
50
x
Is shell structure “quenched” in highly excited states?
*L.G. Moretto, U.C. Berkeley
Production of excited states in-situ at NIF does alter the
expected radiochemistry product ratios
Toy Radiochemical Model
A-4
0.002
Value
0.002
A-3
A-2
A-1
A
0.5 fs Excited States
5 fs excited states
50 fs Excited States
Reactions on excited
states have a clear
radiochemical
signature
0.001
0.001
0.000
A-2/A-1
A-3/A-2
Ratio
A-4/A-3
Lee Bernstein, et al.
The NIF capsule HEDP populates low-lying nuclear
states* via NRF and NEEC**
Early NIF shots offer the opportunity to study stellar
(n,) in a stellar HEDP environment
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
Radiochemical dopant
Be
Ablator
DT
Ice
Examples of
dopants are 18O,
79Br, 127I, 126Xe,
65Cu, 48Ti, 76Ge
• The inner part of the ablator is not blown off
during the compression phase of the
implosion
• This location is ideally suited to investigate
ablator/fuel mix and is very near the high
fluence region of the capsule
DT Gas
• We have investigated spatial loadings of
dopants for one asymmetry mode (P6), but
signal is just as robust with symmetric
loadings (for those asymmetries investigated
(P6 and P4)
• Amounts of dopant are low enough to not
affect the implosion (for this location) and are
on the order of 1×1014 – 1×1015 atoms
We also need to trace the capsule with various isotopes to determine our collection fraction
Examples of tracers are 22Ne, 38Ar, 82Kr, 130Xe
The search for neutrinoless double beta decay
investigates the fundamental properties of the neutrino
This extremely low background counting experiment is
located at the Gran Sasso Laboratory
The use of bolometers provides the most sensitive
detectors to search for this rare process
We have been collaborating with Dubna on SHE
research since 1989
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 5nchannel, alpha
decay would
produce
previously
studied
nuclides
Roger Henderson will discuss the LLNL automated
chemistry efforts later today
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!
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