DOE/NA-0070

Office of Research, Development, Test, and Evaluation

Stockpile Stewardship Q uarterly
VOLUME 8

M|

NUMBER 1|

MARCH 2018

essage from the Assistant Deputy Administrator for Research,
Development, Test, and Evaluation, Dr. Kathleen AlexanderThis issue of the Stockpile Stewardship
Quarterly focuses on the intersection
between computer modeling andthe design and conduct of scientificexperiments that provide thephenomenological basis for computermodels. We kick off this issue with anarticle that discusses the relationshipbetween verifying and validating themodern nuclear weapons codes andthe hierarchy of experiments that mustbe performed to provide the necessary
data. With the cessation of nuclear
testing, computer modeling has become
key to assessing the safety, security,and performance of weapon systems
whose designs have evolved from tested
configurations. This requires higher
fidelity codes that incorporate multiple,
interacting physics phenomena. The levelof experimentation required to provide
data to verify these codes ranges fromsmall-scale experiments designed toassess a single physics problem to fully
integrated experiments that evaluate theinteraction of the physics involved in afull weapon system.
Subcritical experiments are performed
to gather data of complex, interacting
weapons physics. The Enhanced
Capabilities for Subcritical Experiments
project portfolio is working to achieve
the design and creation of a nextgeneration suite of diagnostics thatwill allow for data to be gathered on
the relevant physics involved in thelate-stage implosion of plutonium inweapons-relevant geometries. Thisdata will feed the complex computer
simulations to inform design options

explosives in weapon geometries anddata on the performance differences
between surrogate metals and plutonium
in experiments.

The research on display during the Poster
Session of this year’s Stewardship Science
Academic Programs Annual Review
Symposium, held in Bethesda, Maryland
on February 21-22, 2018, generated much
excitement. Above right and inset, Sarah
Hickam, University of Notre Dame, discusses
her research with Dr. Alexander. Read about the
symposium and winning posters on page 10.

for upcoming life extension programs,
as well as future assessments andcertifications.

This issue also features an article on thelatest subcritical experimental series,
Gemini, Leda, and Lyra. These series
were designed to provide data on thephysics response of using insensitivehigh explosives versus conventional

Another article discusses a complementary
approach that uses laser or pulsed-power
facilities to achieve a high energy density(HED) state of matter. The majority of
weapon processes occur in the HED
state, and so understanding the physics
that occurs in this state is essential tomodeling weapon systems. These HED
experiments are sized in the centimeterto-micrometer range yet still are able toexamine integrated weapons phenomena.
We close this issue with a nod to the nextgeneration scientists and engineers. We
share a review of and honor the awardees
from the 2018 Stewardship Science
Academic Programs Annual Review
Symposium that drew a record number ofattendees, and we highlight an academic
opportunity at the University of Michigan
in the HED field.
Incredible work is happening in the
nuclear security enterprise, and this work
is vital to the security of our Nation.

Inside2 Integrated High Energy Density Experiments Yield Critical Data for the ASC Program
4 Continuous Evolution of the Stockpile Stewardship Program: Enhanced Capabilities for				 Subcritical Experiments
6 Vega & the Lyra Series
8 Integrated Experiments in the Stockpile Stewardship Program
9 Highlight: 2018 High Energy Density Summer School
10 2018 SSAP Annual Review Symposium and Poster Winners

Comments

The Stockpile Stewardship Quarterly is produced by the National Nuclear Security Administration (NNSA) Office of Research, Development, Test, and Evaluation. Questions andcomments regarding this publication should be directed to Terri Stone at terri.stone@nnsa.doe.gov.
Technical Editor: Dr. Joseph Kindel | Publication Editor: Millicent Mischo

2Integrated High Energy Density Experiments Yield Critical Data for the Advanced Simulation andComputing Program by Bradley Beck (Los Alamos National Laboratory), David Etim (National Nuclear Security

Administration), Curt Nilsen (Sandia National Laboratories), Joe Sefcik (Lawrence LIvermore National Laboratory), andArthur Brown (Sandia National Laboratories)

During the era of nuclear testing,legacy computational codes were used
to design the United States nuclear
weapons stockpile. Throughout
development of each and every
weapon, nuclear weapon tests playeda critical role in calibrating the models
and in assessing actual performance.
Since the cessation of nuclear testingin 1992, improved codes with higher
fidelity physics models were required
to provide confidence in the ability toassess safety, security, and performanceof the current and future stockpile.

To accomplish the science-based
Stockpile Stewardship Program (SSP)
mission requires that the Advanced
Simulation and Computing (ASC) program
develop simulation codes that accurately
predict and assess the full physics
and engineering environments theseweapons encounter or may encounter.
These modern computational codes must
simulate the complexities of nuclear
physics, weapons component responses,
the weapons systems as a whole, anddetermine the impact of design changes
and aging on the nuclear weapons
stockpile. Additionally, these modern
codes serve as a means to evaluate
the full range of a nuclear weapon’s
operation. For these purposes, themodern nuclear weapon computational
codes must couple numerous physics
models together accurately. Integrationof numerous physics models makes thesetools fundamentally different from otherscientific computation codes that normally
focus only on single physics models or on
integration of a few physics models.
Development of these codes anddetermining the accuracy of theircapabilities is further complicated dueto the realization that the full physics
encountered by a nuclear weapon
are unlike normal operating physics
regimes on Earth. Critically importantis an examination that these codes areaccurately representing the necessary andcorrect physical models.

Figure 1. Hierarchical approach to V&V spansthe full problem physics.

In the development of the ASC nuclear
weapon simulation codes, the appropriate
physics must be assessed throughdetermination of the proper equations.
These equations are approximated into
numerical models and then incorporated
into the codes. After implementation, thelaboratories verify that the numericalmodels are accurately reproducing theintended equations (Code Verification)and confirm that the codes are solving thecorrect equations (Code Validation).1

The ASC Verification & Validation (V&V)
program employs a hierarchical approach(see Figure 1) in order to span theentire required physics regimes. Singlephysics experiments (e.g., modeling ofHigh Explosive detonation) provide theprogram with required information used
to validate individual physics models.
Due to the numerous individual physics
models required, this necessitatesnumerous experimental campaigns. Multiphysics tests (e.g., radiation hydrodynamic
experiments) enable a small numberof physics models be combined for anassessment. Subcomponent physics
tests increase the number of interacting
physics models assessed, and increase thecomplexity of the required experiments(e.g., pRad experiments, inertial
confinement fusion experiments).

At the most complete and complex
end of the hierarchical approach is theintegrated system tests. Examples include
experiments conducted at the following
locations (see Figure 2): U1a Complex at
the Nevada National Security Site (NNSS);
the Dual-Axis Radiographic Hydrodynamic
Test Facility (DARHT) at Los Alamos
National Laboratory; the Contained Firing
Facility (CFF) at Lawrence Livermore
National Laboratory; and the Thunder
Range Facility at Sandia National
Laboratories. Experiments conductedat these facilities enable an integrated
system assessment and more completely
test the multi-physics computational
codes in these challenging environments.
As the NNSA weapons laboratories
continue to work towards delivering
fully validated codes, the historical
nuclear testing archive and historicalintegrated experiments are assessed andincorporated into the analysis; these tests
are critical to validation efforts as they are
the experimental means that explore thefull nuclear weapon detonation physics.

Integrated Hydrotest Experiments

Integrated hydrotests experiments
provide critical data for the SSP. Theseexperiments enable scientists to detonate
a “mock-up” of the primary stage of a
nuclear weapon, but with surrogatematerials. Instead of using plutonium,
scientists use a non-fissile surrogatematerial to simulate the desired
characteristics.

Both the CFF and DARHT field diagnostics
record arrival time of an explosively
driven surface through use of pin domes
and photon Doppler velocimetry (PDV)
probes (see Figure 3). The pin dome
records when a surface interacts with thepin while the PDV probe records a time
velocity record of the surface using laser
velocimetry. High-energy radiographsof the experiment are also captured
with high-speed cameras to allow forincreased exploration of the implosion
dynamics. This combination of diagnostics

1Code verification is “the process of determining that the numerical algorithms are correctly implemented in the computer code and or identifying errors inthe software.” Code validation is “the process of determining the degree to which a model is an accurate representation of the real world from the perspectiveof the intended uses of the model.” ASME 2006, “Performance Test Code Committee 60: Verification and Validation in Computational Solid Mechanics,” Guide
for Verification and Validation in Computational Solid Mechanics, American Society for Mechanical Engineers, New York, Standard No. ASME V&V 10-2006.

Volume 8 | Number 1 | March 2018

Stockpile Stewardship Quarterly

3experiments, but in a configuration with
Plutonium and in a situation where theexperiment is prevented from goingcritical. These experiments provide
critical data that is then used by the
ASC codes to determine an accurate
assessment of their capabilities.

Whereas critical data is provided by
the current subcritical experiments, theEnhanced Capabilities for Subcritical
Experiments project (ECSE) is planningfor improved capabilities and diagnostics
that will increase the experimental
data available for the SSP and for futureassessments.

Engineering Challenges

Figure 2. Key integrated experimental facilities, suchas DARHT (top left), U1a (top right), CFF (bottom left),and Thunder Range (bottom right) enable integrated
experiments that provide the SSP with critical data used
to validate the multi-physics computational codes.

Due to the diversity of engineering
challenges that a nuclear weapon may
encounter, a variety of types of integrated
engineering system tests are required.
Examples of these tests at Sandia National
Laboratories include nuclear safety tests
at the Burn Facility, centrifuge/vibrafuge2
experiments at the Large Centrifuge
Facility, and explosive testing at theThunder Range to study the effects ofhostile atmospheric blast. Thunderpipe
tests were performed recently at Thunder
Range to support the Navy and Air
Force programs (see Figure 2). The data
generated are used to validate modelingpredictions from ASC tools for the shockloading and weapon response. Together,experimental data and simulation
predictions support current and future
weapon qualification efforts.

Conclusion

Figure 3. Methods for measuring implosion dynamics; left image is a pin dome where each individual
pin records a time of impact; right image is a multiplexed photon Doppler velocimetry (MPDV) probethat measures the velocimetry of a surface by measuring the Doppler shift of optical illumination.

provides a critical capability to obtaincomprehensive data on the implosion
phases of integrated weapon experiments.
Critical to the assessment of theseexperiments, the laboratories perform a
pre-shot prediction of the experimental
results and a post-shot analysis.

Integrated Subcritical Experiments

Whereas hydrotest experiments provide
critical data for the ASC program and SSP,
the use of surrogate materials requires anassessment of how well these materials
represent the actual materials. Criticallyimportant is understanding the material
dynamics similarities and differences.
Subcritical experiments conducted in the
U1a Complex of the NNSS provide critical
data by studying plutonium in relevant
configurations.
Experiments like the Vega experiment
recently conducted provide similar
diagnostics to the current hydrotest

To accomplish the mission of sustaining
a safe, secure and effective nuclear
deterrent requires that the SSP hasmodern computational tools with verified
and validated models of an increased
physics fidelity. Critical to being able todeliver these capabilities are integrated
experiments that explore the full physics
required as completely as possible.
These integrated experiments provide
critical data to the NNSA programs andenable critical assessments of the nuclear
weapon computational simulation codes.
Facilities such as DARHT, CFF, U1a, andThunder Range enable these experiments
and increase confidence for current andfuture assessments. ●2Vibrafuge is a combined examination of vibration testing on a centrifuge.

Office of Research, Development, Test, and Evaluation

Volume 8 | Number 1 | March 2018

4

Continuous Evolution of the Stockpile Stewardship Program: Enhanced Capabilities for Subcritical
Experiments by Kirk Keilholtz (National Nuclear Security Administration)
The United States conducted 1,054
nuclear tests before entering the current
moratorium in 1992. The archived datafrom these tests is the backbone of our
Stockpile Stewardship Program (SSP)
to continue the annual assessment andcertification of the safety and reliabilityof our nuclear stockpile without fullscale nuclear testing. The SSP relies onan extensive program of surveillance,
examining the current and aging stockpile,
coupled with advanced computationalmodels which are, in turn, validated
against both new and archived smalland large-scale integrated experimental
data. As computing power, and thesophistication of the physics-based
simulation models, has increased over theyears, our understanding of fundamental
operations of weapon systems andespecially the behavior of weaponmaterials has also evolved, leading to
the identification of knowledge gaps.
NNSA addresses these gaps through thedevelopment of new theoretical andanalytic models, implemented in advanced
simulation techniques, and through thediagnostics and drivers needed to produce
the experimental data to validate thesimulations. This methodology, applied
for over 25 years of stockpile stewardship,
has allowed NNSA to develop a deep
understanding of nuclear weapon scienceand engineering—both reinforcing ourexisting hypotheses and allowing us toform new ones.
One area that NNSA is currently exploring
in detail is the aging of our nuclear
weapon systems and, specifically, changes
in the special nuclear materials. Our
weapons are composed of a variety
of materials and understanding theirinteraction during weapon operation isextremely important to assess the safety
and reliability of the stockpile. Throughmost of the first 50 years of the nuclear
weapons program, that understanding
was developed, and then demonstrated,through nuclear testing. Throughout thelife of the program, our scientists andengineers have always questioned if aweapon system will behave with the samecharacteristics after 30 years, and without
underground tests, those scientists andengineers have had to look elsewhere toanswer this critical question.

Volume 8 | Number 1 | March 2018

In addition to the aging of criticalcomponents, NNSA must regularly
replace or refurbish many other weapon
components. Many of the materials andprocesses that were used in the original
production are no longer available.
Changes to our original designs, materials,
and processes require qualification andcertification that, in turn, require newsmall-scale and large-scale integrated
experiments. Necessarily, each changethat we make moves us incrementallyaway from the designs and processes thatwere successfully tested and archived
in our nuclear testing database. Barring
a return to nuclear testing, the SSP is
responsible for ensuring our nuclear
weapons continue to work as designed.
Every year, the three directors at the
NNSA national laboratories—Los Alamos
National Laboratory (LANL), Lawrence
Livermore National Laboratory (LLNL),
and Sandia National Laboratories(Sandia)—assess for the President
whether the stockpile is safe, secure,reliable, and effective. Each year, this has
been the case.

We have developed important
experimental platforms such as the
National Ignition Facility (see Figure 1a),
Z Pulsed Power Facility (see Figure 1b),
Omega Laser Facility, Joint Actinide
Shock Physics Experimental Research(JASPER) facility, Advanced Photon
Source, THOR, Los Alamos Neutron
Science Center, Cygnus, and others thatprobe specific material properties underthe extreme conditions encountered in
the operation of a nuclear weapon (seeStockpile Stewardship Quarterly V7 N4,December 2017). Other facilities explore
the interaction of materials in nuclear
weapon geometries such as the Dual Axis
Hydrodynamic Test Facility (DARHT) (seeFigure 1c) at LANL and the Flash X-RayContained Firing Facility (FXR-CFF) at
LLNL. However, these facilities do nothave the capability to perform dynamic
implosion experiments with plutonium,
the special nuclear material at the heartof many weapons.

To explore the dynamic behavior of highexplosively-driven plutonium in weaponlike geometries and near weapon-like
conditions, the NNSA conducts Subcritical

(a)

(b)

(c)

Figure 1. Some of NNSA's experimental
platforms: (a) the National Ignition Facility
optics, (b) Z Pulsed Power Facility, and (c)DARHT.

Experiments (SCE) at the Nevada Nuclear
Security Site (NNSS). SCE provide
essential information for stockpile
life extension programs, significant
finding investigations, and advance theunderstanding of how the stockpile
evolves. SCE address one of the criticalknowledge gaps in the properties of
plutonium by measuring its behavior
during the final stages of a primary
implosion. To make those measurements,
Stockpile Stewardship Quarterly

5

Figure 3. Daisy Acosta-Lech performing design
verification testing on the five stage solid state
pulser.

Figure 2. Shown is an illustration of the Scorpius Infrastructure at the NNSS. The main accelerator hall(“drift”) will be just over 400 feet long.

high precision penetrating radiography(such as that used with surrogatematerials at DARHT and FXR-CFF) anda diagnostic under development known
as the Neutron Diagnosed Subcritical
Experiments (NDSE) are the essential
tools.

NNSA’s activities in support of theseessential tools is called the Enhanced
Capabilities for Subcritical Experiments(ECSE) portfolio, which includes the
project to deploy a new radiographic
system (Scorpius) under the Advanced
Sources and Detectors (ASD) componentof the portfolio; the U1a Complex
Enhancements Project Line Item that will
construct the underground laboratory;
and, the NDSE diagnostic currently underdevelopment.
Scorpius is a DARHT-class, multi-pulse,
single axis, linear induction accelerator(LIA)-based radiographic system.
The ECSE Radiography & Integration
Project is responsible for the technology
maturation, design, fabrication,
installation, and commissioning of
Scorpius at the NNSS.

The Scorpius LIA-based radiographic
system consists of four major subsystems:
injector, accelerator, downstream
transport, and detector (see Figure2). The injector subsystem generates
a high current electron beam using apulsed, high-voltage vacuum diode. The
high current of the beam means thatspace charge effects dominate the beamtransport so that externally appliedmagnetic fields are used to guide thebeam into, and through, the accelerator.
The accelerator subsystem consists of aseries of many 10s of similar accelerator
cells each of which applies a pulsed
electric field adding energy to the electron
beam. The energy added at each cell isa small fraction of the total energy andis typically limited by the engineering
requirements of the accelerator celland pulsed power system powering
the cell. After the beam has acquired
the required energy while transiting
through the accelerator cells, it enters
the downstream transport subsystemthat transports and focuses the beam
onto a Bremsstrahlung x-ray converter
where the x-rays that will penetrate theexperimental test object are created.
Beyond the experimental test object,
the detector subsystem uses advanced
scintillators to convert the x-rays to visible
light, captures and stores the images ona very high-speed digital camera, andrecords the data for subsequent analysis.
In addition to the four components of
the radiographic system, operation of
Scorpius requires detailed attention to
the “Global” engineering support systems(control, power, fluid and gas, mechanical,
tooling, and safety systems) common
to all parts of the accelerator and theinterface with the U1a Complex to support
installation, commissioning, accelerator
readiness certification, and the transition
to operations for the final Scorpius system.
The project, led by LANL, is composedof partners at LLNL, Sandia, and NNSS
(see Figures 3 and 4). The team works
under a governance structure agreed

Office of Research, Development, Test, and Evaluation

Figure 4. Two-Pulse Test Cell from LANL
undergoing multi-pulse testing on Centipede
at Sandia.

to in a Memorandum of Agreement
signed by the three laboratory directorsof their respective LLCs and supported
by industrial partners such as L-3
Technologies and several component andsubsystem development contractors, andthe Naval Research Laboratory. With thismany organizations involved, the project
team must continuously emphasize
the need for frequent and engaging
communication.

With ECSE coming online in the mid
2020s, our weapon scientists andengineers will have diagnostic tools
at their disposal to answer importantquestions about the Nation’s current
nuclear weapons stockpile as well as toprovide flexibility in the form of materials
and advanced manufacturing techniquesthat are necessary for our life extension
programs. ●Volume 8 | Number 1 | March 2018

6

Vega & the Lyra Series by Garry R. Maskaly (Los Alamos National Laboratory)

The Vega Experiment
Vega, the plutonium experiment thatserved as the capstone to the Lyra series,
was executed in the U1a Complex at the
Nevada Nuclear Security Site (NNSS) on
December 13, 2017. After facing many
challenges, including the need for anenhanced authorization basis and toreauthorize work at TA-55, Vega became
the first subcritical experiment (SCE) fired
since Pollux was executed in December
2012.
In Gemini, a conventional high explosive(CHE)-driven primary implosion wasstudied in both a surrogate (Castor)and in plutonium (Pollux). The Lyra
series provided data comparing that
performance to experiments using thesame pit driven with insensitive highexplosives (IHE). In both series, scaling isused to reduce the reactivity of the device
and to keep it subcritical.

IHE is being strongly considered forpotential future designs and also for reuseof a CHE pit in an IHE implosion system.
However, before Vega, the Nation had not
performed any experiments for which
there was a direct measurement of theplutonium dynamic behavior driven by
an IHE charge. As part of a plan to certify
a new design without nuclear testing,plutonium data are required to validate
the models being used to underwritethat design. The Vega experiment is an
important step in that process.
As shown in Figure 1, the experiments
conducted under the Lyra series fit
together with those from the Gemini andLeda series in a differential experimentframework with only one change between
each experiment. Two experiments wereconducted at the Dual-Axis Radiographic
Hydrotest (DARHT) facility, and six wereconducted at the U1a Complex. In theframework, there were six surrogate
experiments that provided a means tobetter understand the high explosive
drive which then, ultimately, allowed fora better understanding of the plutonium
dynamics in the SCE. Multiple surrogate
experiments provide a means to reduceany compensating errors that might
be introduced by relying too heavily
Volume 8 | Number 1 | March 2018

H4080 (12/11)
CHE
Surrogate B

DARHT - LANL

Leda (8/14)
CHE
Surrogate A

3667 (7/15)
IHE
Surrogate A

Castor (8/12)
CHE
Surrogate B

Orpheus (9/16)
IHE
Surrogate B

Pollux (12/12)
CHE
SNM

Vega (12/17)
IHE
SNM

U1a - NNSS

SNM - U1a - NNSS

Eurydice (3/17)
IHE
Surrogate C

HE change

Metal change

Figure 1. The Gemini/Leda/Lyra series differential experiment framework. H4080 was adevelopmental experiment with limited velocimetry coverage..

on any one surrogate, which might
be computationally represented withimperfect models and could then lead toerroneous model calibration. In addition
for Lyra, the design team focused on
creating a device that used various design
features to minimize the experiment’s
sensitivity to other potential areas ofphysics uncertainty. This approachallowed for a more direct focus on
the plutonium dynamics in the final
experiment.

By building off of the Gemini series andusing the same pit configuration, theLyra series allowed for a very directcomparison of the dynamics between
a CHE- and an IHE-driven implosion.
This approach provided a useful means
to understand the impacts the drive
difference had without a large need tofocus on understanding the impacts ofthe design changes as well. This approachalso more directly tied to several pit reuse
concepts for which similar questions will
be asked of a weapons system.

In order to execute this series, a large
team across the complex was required.
Scope included such activities asparts manufacturing, vessel systems,
diagnostics development, materials
science, design physics, assembly, andtransportation. Each assembly required an
extensive team to produce high-precisionparts. This precision was required toallow for a focus on the physics rather

than trying to understand deviations thatmight be caused by part variations.

The Need for Advanced Diagnostics
Learning from the Gemini series, thedesign team has identified what typesof questions can be asked with the
new diagnostics now being fielded. In
particular, velocimetry enables a whole
new series of questions to be asked of thedata. In addition, other questions wereraised that would benefit from continued
advances in diagnostics.

In Vega, we started with 11 primary
physics hypotheses that would bedirectly tested in the series. That list has
grown as new data were taken and now
stands at around 15 hypotheses, someof which have already been addressed.
In that list, there were questions that
could perhaps be better answered withnewer diagnostics in conjunction withthe original multiplexed velocimetry. In
particular, there were times when more
dynamic range would have aided theanalysis. In Lyra, Generation 3 Multiplexed
Photon Doppler Velocimetry (MPDV)
was fielded on a dynamic experiment
for the first time; as expected, it gave alarge increase in signal-to-noise over theoriginal systems fielded on Pollux. Also
new to Lyra were 8 channels of Broadband
Laser Ranging (BLR) fielded to address
specific areas of physics. Building off ofsome questions on Pollux, the designteam pushed for the incorporation
Stockpile Stewardship Quarterly

7

Figure 2. Many of the Lyra team members at U1a.

of stereoscopic visual imaging (first
fielded on Leda with monovision). The
combination of these diagnostics andCygnus radiography allows for crosscorrelation between each diagnostic tobetter understand questions that might
appear in the data.

As the final experiment in the series, theVega experiment did not disappoint. It
provided exquisite detail of the imploding
plutonium. The diagnostic suite
performed as hoped, providing a means
to better understand what is happening
within the device. Even though the data
analysis is in its early phases, several
hypotheses have already been addressed,
and several new questions have beenraised. Even within an experimentthat has defined hypotheses from thestart, there is still room for exploratory
observations that are not related to thosehypotheses, but that raise questions of
their own.
This series again points to the needfor a strong SCE program. Due to thecomplexity of plutonium dynamic
behavior, surrogates simply do notprovide all of the properties needed tounderstand the details of a plutonium
implosion. The data obtained in theseexperiments enable model validation andmodel development that will be used in
the current assessment process but that
also will become even more important as
we become further removed from direct
calibration to the nuclear test history.

The Next Steps in the Lyra Series
Analysis

The data acquired in December are now
being analyzed, and a preliminary data
package was delivered in February. Thisdata package will give the primary physics
teams involved a chance to examine thedata and see if there are any regionsthat need further examination before
the final data package is released. The
preliminary data package will be released
simultaneously to the three laboratories
that provided a preshot prediction. The
final data package is expected to be

Office of Research, Development, Test, and Evaluation

released in 2018. After this, the designteam will begin preparing the final
post-shot report, which is expected to becompleted approximately one year after
the release of the final data package.

Acknowledgement

While many people contributed to thesuccess of these experimental series, David
Holtkamp was instrumental in having avision for all-optical hydrodynamic andsubcritical experiments. He also wasinstrumental in developing the diagnostics
needed to ask these important questions.
Shortly after the Eurydice experiment,
David passed away suddenly. He is deeply
missed by those with whom he interacted,
and his large contributions of theseexperiments, to the SCE program, and to
the Nation will be felt for many years. ●Volume 8 | Number 1 | March 2018

8

Integrated Experiments in the Stockpile Stewardship Program by Njema Frazier and Sean Finnegan(National Nuclear Security Administration)
Predicting the performance of an
operating nuclear weapon requires
understanding both how matter behavesin the high energy density (HED) regime
and also the nature of key physicalphenomena such as radiation transport,
radiation driven hydrodynamics, andthermonuclear burn. The Inertial
Confinement Fusion (ICF) Program
within the National Nuclear Security
Administration (NNSA) uniquely
provides experimental access to extreme
HED environments through a set ofcomplementary, specialized facilities.
The National Ignition Facility (NIF)at the Lawrence Livermore National
Laboratory, the Z Pulse Power Facility
at Sandia National Laboratories, and theOmega Laser Facility at the University ofRochester provide data that are informing
design options for Life Extension
Programs, validating models important
for weapon design codes, and providing
hostile environments for vulnerability
and hardness testing. However, there
are limits to our current capabilities. To
more completely access HED regimes
in the laboratory, HED facilities capableof driving experiments with hundredsof megajoules of energy are required.
The demonstration of ignition is therequired technological threshold to that
future multi-megajoule capability, and it
is for this reason, as well as nearer-term
benefits, that demonstrating ignition isa major Stockpile Stewardship Program(SSP) goal of the ICF Program. Each of
the HED facilities plays a unique role indeveloping the underpinning science andtechnology towards enabling the first step
to an igniting plasma.
The experiments conducted in supportof the ICF mission fall into two broad
categories: (1) focused experimentsthat attempt to isolate and test our
understanding of a specific code
algorithm or material property such asradiative opacity; and (2) integrated
experiments of varying complexity thatserve several distinct functions. Whileeach facility provides unique capabilities,
together they enable the study of physicalphenomena using different drivers in
regimes of overlap that is essential forbuilding confidence in results obtainedin new HED regimes. Below we describe

Volume 8 | Number 1 | March 2018

three such efforts that typify how theseexperiments are used in today’s SSP.
These examples are drawn from the
NIF, but comparable experiments are
performed on the Z and Omega facilities.

Ignition and Uncertainty
Quantification

Ignition research and development
involves some of the most complex
integrated experiments performed at
the HED facilities. In these experiments,
solid cryogenic layers of deuteriumtritium (DT) fuel are imploded nearly
symmetrically inside millimeter radius
capsules to pressures required in an
attempt to ignite DT fuel (see Figure 1).
These experiments are heavily diagnosed
with x-ray and nuclear instruments andare designed to test hypotheses aimed
at understanding and improving target
performance. At present, implosions on
the NIF are approaching the burning
plasma regime in which the alpha particle
energy deposited in the fuel is almost
equal to the mechanical energy provided
by the imploding capsule. This extra
heating from the fusion alpha particles
results in a yield amplification required
for the experiment. Analysis suggeststhat shell distortions resulting fromdrive asymmetries and hydrodynamic
instability cause the assembled fuelto disassemble before the fusion self
heating from alpha particles has time torun away. Resolving these issues is thecurrent focus of research. Similar efforts
are underway exploring the physics ofalternate compression schemes at the Z
and Omega facilities.

An exciting emerging application ofthese ignition experiments is to test andadvance our uncertainty quantification(UQ) methodology. A multi-disciplinary
team of weapons scientists, ICF scientists,
engineers, and computational scientists
is developing new tools for application
across the stockpile stewardshipenterprise, using deep learning methods
to combine simulation results andexperimental observation. Ignition
experiments at NIF are providing a
stressing test of these new methods,
particularly where little to no data yetexist.

Material Strength of Solids at High
Pressure

Understanding the strength of materials
at high pressure is important to the SSP.
Strength is a quantitative measure of amaterial’s resistance to deformation andaffects compressibility and the material’s
evolution under deformation. It is afunction of temperature, pressure andstrain rate. Microscopically, strength is
the resistance to dislocation generationand transport. Direct observation of
dislocations requires transmission
electron microscopy (TEM)-level spatial
resolution and is not available in current

Figure 1. Schematic of a NIF hohlraum surrounding a capsule containing a cryogenic solid layer ofDT fuel. The fuel is injected through a ultra-fine fill tube less than 5 µm in diameter (a human hairis 100 µm in diameter). NIF’s 192 laser beams enter the hohlraum from the top and bottom in 4
cones of beams positioned so that the x-rays generated inside the hohlraum symmetrically illuminate
the capsule and implode it symmetrically. Actual NIF hohlraum (right) is a highly complex multicomponent assembly that must be assembled to tolerances of a few 10s of µm and that must survive
the cryogenic environment.
Stockpile Stewardship Quarterly

9
(a)

(b)

InitialundriventargetFigure 3. (a) Schematic of the capsule used in the two-shock experiment. Initial configuration (left).
After implosion (right), the D and T reactants have mixed producing DT neutrons. The signal increases
as the mixing increases. (b) Three-dimensional direct numerical simulation of interface mixing during
deceleration stage using the high-order code Miranda, showing diffusive mixing in the interior of thecapsule near the hot-spot, and turbulent mixing further out in the cooler regions of the shell.

Materialwithstrength

Material
without
strength(RT) instability (see Figure 2). Detailed
measurements of the seeded instability
growth are compared with hydrodynamic
simulations to assess the veracity ofvarious strength models.

Two-Shock Campaign
Figure 2. Simulations of material samples (red)accelerated to the right viewed in a frame
moving with the sample. The degree to which
pre-imposed perturbations become amplified
depends on the strength of the material.
Measuring this amplification allows us to test
strength models under conditions relevant for
the SSP.

dynamic experiments. Instead, integrated
experiments on the NIF assess material
strength by measuring its effect insuppressing the growth of hydrodynamic
instabilities such as the Rayleigh-Taylor

The recent NIF two-shock campaign [S.F.
Khan et al., Phys. Plasmas 23, 042708(2016)], so called because it uses a twoshock x-ray pulse to implode a capsule,was designed to test the effectiveness ofvarious implosion phase mix modelingtechniques important for the SSP. In thisplatform, a plastic capsule is filled withtritium gas while a deuterated plastic
tracer layer is situated at the inner surfaceof the capsule (see Figure 3). As thecapsule decelerates during stagnation, thetritium makes a “hot spot” and copious
TT neutrons are produced. At the sametime, RT instability causes the deuterated
capsule material to “mix” into the outerlayers of the T gas, cooling the mixed
layer of gas and reducing the TT neutron
yield. The further the capsule material
penetrates, the lower the TT yield. Someof the capsule material that penetrates thegas mixes with the tritium at an atomic
level. If this material contains deuterium
from the tracer layer, the magnitude of
the resulting DT neutron signal diagnoses
how much of the tracer material has
penetrated the gas and mixed atomically.
The DD neutron signal over and above thatconsistent with the DT signal is a separate
measure how much tracer material
penetrated the tritium hot spot but did
not mix atomically. Together, these signals
provide a tight constraint on models. ●Highlight
2018 High Energy Density Summer
SchoolTo promote the spread of broad,fundamental knowledge and to train
new entrants into the field of highenergy density physics, the Universityof Michigan, Ann Arbor is offering a
High Energy Density Summer Schoolfrom June 11-22, 2018. The in-depth
introduction to the field will include
approximately 40 hours of lectures
over 11 days. The lectures will be based
primarily on the book High-EnergyDensity Physics, 2nd ed., by Prof. R. Paul
Drake. Topics to be covered include (1)fundamental equations and equationsof state, (2) shocks, rarefactions, andtheir interacations, (3) hydrodynamic
instabilities, (4) radiative transfer, (5)radiation hydrodynamics, (6) creatinghigh energy density conditions,(7) inertial fusion, (8) experimental
astrophysics, (9) relativistic systems, and(10) magnetohydrodynamic.

For more information, you may contact
Jan Beltran at (734) 936-0494 (jbeltran@umich.edu) visit http://clasp-research.
engin.umich.edu/workshops/hedss/
index.html. ●Office of Research, Development, Test, and Evaluation

SuggestionsorComments ?
Do you have a great idea for
an article or comments about
this issue of the Stockpile
Stewardship Quarterly? If so,please email Terri Stone at
terri.stone@nnsa.doe.gov.

Volume 8 | Number 1 | March 2018

102018 Stewardship Science Academic Programs Annual Review SymposiumThis year's Stewardship Science Academic
Programs Annual Review Symposium
drew a record number of attendees.
Approximately 350 individuals from the
National Nuclear Security Administration(NNSA) and other government agencies,
DOE/NNSA national laboratories, andacademia attended this year’s annual

review symposium held in Bethesda,
Maryland on February 21-22, 2018. The
symposium featured overviews of work todate from ongoing grants and cooperative
agreements from the Stewardship Science
Academic Alliances Program; the NNSAsupported grants from the Joint Programfor High Energy Density Laboratory
Plasmas; and grants awarded under the
National Laser Users’ Facility Program.

The Office of Research, Development,
Test, and Evaluation's (RDT&E's) Dr.
Kathleen B. Alexander gave the keynote
address this year. She shared with theattendees the experiences that led toher current role as the Assistant Deputy
Administrator for RDT&E. She highlighted
her work at the national labs, and thevalue of those experiences in her work at
NNSA. She also spoke to how she cameto the decision to enter management
at the Federal level, and the personalcommitment that that decision required.
When asked what she plans to do next,
Dr. Alexander replied, "I have the best job
in the Federal Government. Why would I
want to do anything else?"

Top: Haylie Lobeck, University of Notre Dame
(ND), presented her poster, Transformationof Uranyl Phosphate and Arsenate Minerals to
Soluble Nanoscale Cage Clusters, during theposter session. Bottom: Full-size photo of theinset from the cover featuring Sarah Hickam.
The title of her poster is Dissolution of Uranium
Dioxide in Uranyl Peroxide Cluster-Forming
Conditions: Influence of Alkali Metals.

The Poster Session and reception followed.
There were approximately 135 posters,
107 of which were student posters, onview during this year’s session on topics
including low energy nuclear science,
radiochemistry, properties of materials
under extreme conditions and/or hydrodynamics, and high energy density physics.
The winners of the Poster Session follow.
Kristyn Holley Brandenburg
Ohio University
Developing a Long Counterfor (alpha,n) Measurements
Relevant to the Alpha-Process
and Nuclear Reactor Diagnostics
at Ohio University
Samantha Couper
University of Utah
Deformation of a Lower
Mantle Assemblage at High
Temperature2018 Stewardship Science Academic Programs
AnnualVolume 8 | Number 1 | March 2018

Sakun Duwal
Washington State University
Transformation of
Hydrazinium Azide (N5H5) toN8 at 40 GPa

Yuankan Fang
University of California, San
DiegoHigh Pressure Effects on BiS2Based Compounds
Dan Hoff
Washington State University in
St. Louis
Producing Huge Spin
Alignment in Inelastic
Excitations of Clustered Nuclei
Rebecca Lewis
Michigan State University
Experimentally Constrained
73Zn(n,g)74Zn Cross Section
Marc-Andre Schaeuble
University of Texas, Austin
Helium at White Dwarf
Photosphere Conditions:
Experimental Line Shifts andWidthsHannah Shelton
University of Hawaii, Manoa
Cristobalite X-I: A Bridge
Between Low and High Density
Silica Polymorphs
Hong Sio, Massachusetts
Institute of Technology
Implications of Differences
Between Measured and
Rad-Hydo-Simulated Reaction
Histories in Hydro-like Implosions
on OMEGA
Jeff Woolstrum
University of Michigan
New Computational andRadiographic Capabilities at
the University of Michigan
Liangyu Yao
Oregon State University
Target Making for Nuclear
Reaction Studies
To request copies of the 2018 SSAP
Annual, contact Terri Stone at terri.
stone@nnsa.doe.gov. ●Stockpile Stewardship Quarterly