Center for Radiative Shock
Hydrodynamics
Fall 2010 Review
Introductory overview
R. Paul Drake
What lies ahead
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This first presentation
– Motivation and introduction to the physical system
– Overview of the past year: progress, challenges, decisions
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Following presentations today
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Drake on the integrated project
Adams on transport physics and UQ
Powell on the simulations
Holloway on assessment of predictive capability
Code and verification tomorrow morning
– Toth on architecture and practices
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Other highlighted contributions tomorrow morning (little time! )
– Kuranz, Sokolov, Morel
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Posters today
– See the details and meet the people
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You will see how our priorities have been driven by becoming able
to conduct a sequence of integrated UQ studies.
Items in this color are directly responsive to 2009 review
Page 2
We are showing a visualization of CRASH 2.1+
output on the other screen
• Simulation details
– 9600 by 960 effective resolution in 2D
– Multigroup diffusion (30 groups, 0.1 eV to 20 keV)
– 5 materials, 3 AMR levels, CRASH EOS & Opacity
• Also see scale models in the room
7.6 ns
Page 3
We find our motivation in astrophysical
connections
• Radiative shocks have strong
radiative energy transport that
determines the shock structure
Ensman & Burrows ApJ92
SN 1987A
• Exist throughout astrophysics
Reighard PoP07
Cataclysmic binary star
(see Krauland poster)
Page 4
A brief primer on shock wave structure
• Behind the shock, the faster sound waves connect the
entire plasma
shocked
Denser,
Hotter
Shock velocity, us
unshocked
Initial plasma
Mach number M > 1
Mach number
M = us / csound
Page 5
Shock waves become radiative when …
• radiative energy flux would exceed incoming material energy
flux
Ts4
ous3/2 unshocked
preheated
shocked
where post-shock temperature is proportional to us2.
• Setting these fluxes equal gives a threshold velocity of
60 km/s for our system:
Material
xenon gas
Density
6.5 mg/cc
Initial ion temperature
2 keV
Initial shock velocity
200 km/s
Typ. radiation temp.
50 eV
Page 6
The CRASH project began with several elements
• An experimental system that is
challenging to model and relevant to
NNSA, motivated by astrophysics
• A 3D adaptive, well scaled,
magnetohydrodynamic (MHD) code
with a 15 year legacy and many users
• A 3D deterministic radiative transfer
code developed for parallel platforms
• A strong V&V tradition with both codes
Space weather
simulation
• Some ideas about how to approach
“UQ” in general and specifically the
Assessment of Predictive Capability
Page 7
CRASH builds on a basic experiment
• Basic Experiment:
Radiography is the primary diagnostic.
Additional data from other diagnostics.
A. Reighard et al. Phys. Plas. 2006, 2007
F. Doss, et al. Phys. Plas. 2009, HEDP 2010
Grid
Schematic of radiograph
(see Doss poster)
Page 8
What we predict
What the radiograph
fundamentally shows us is
where dense Xe exists
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We predict scalar quantities
– By predictive modeling we mean
– computing an estimate of the
probability distribution function
(pdf) of the outputs generated by
the pdf of the inputs for a
prospective field experiment,
informed by both simulation and
prior field experiments
Grid
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We predict the area where dense
xenon exists on a radiograph and
selected moments of the
distribution of such locations
– Holloway will show much more
about this
– Grosskopf has a poster on the
integrated metrics
Page 9
CRASH 2.1+ has substantial
capability
• Dynamic adaptive AMR
• Level set interfaces
• Self-consistent EOS and
opacities for 5 materials
• Multigroup-diffusion
radiation transport
• Electron physics and fluxlimited electron heat
conduction
• Ongoing
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Laser package
Multigroup preconditioner
I/O performance upgrade
Use of other EOS
Material & AMR
Log Density
Log Electron Temperature
Log Ion Temperature
3D Nozzle to Ellipse @ 13 ns
Page 10
CRASH has proven useful
• Design simulations of
radiative reverse shock
experiments
• Simulations of ongoing
NIF experiment
• Simulations of x-ray driven
radiative-shocks
• We used CRASH to help
select some details of the
radiative reverse shock
design (Krauland poster)
x-ray driven radiative-shock
(Myra poster)
Page 11
•
We have accomplished a lot
during the past year
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UQ and predictive studies
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Predictive study involving calibration
Two papers
Radiograph interpreter for integrated
metrics
Deeper analysis of experimental and of
all sources of uncertainty
Extensive studies of output sensitivity
to code details
New tests
H2D 104 run set
Predictive study with calibration from
H2D run set
Analysis of H2D limitations
3D Hydro experiment design
CRASH 2.0 released and used
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X-ray-driven modeling
Pure hydro nozzle study
Application to other experiments
Detailed examination of axial structures
Hydro instability studies
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Code improvements
– Flux limited electron heat xport
– EOS source adaptivity
– Laser package
– Progress on multigroup preconditioner
– Hydro adjoint implementation
– Reduced alchemy
– Improved parallel I/O?
– Vastly improved PDT scaling
Physics
– Radtran & radhydro theory papers
– X-ray driven walls theory
– Further work on wall shock
– Obtaining STA opacities
– Work on non-LTE effects
– SN/FLD comparison
Experiments
– Shock breakout measurements
– Initial attempts at other early time
measurements
– Late time (26 ns) measurements for
predictive study
– Radiograph analysis (compression,
background)
– UQ-driven planning for year-3
experiments
– Metrology comparison
Items in this color are directly responsive to 2009 review
Page 12
We have also encountered some challenges
Page 13
Initializing CRASH with Hyades proved problematic
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H2D has a laser package and
(now) rezoner
– Did run set for Dec 09 expt
– Superseded by 104-run set
done in early 2010
– This has produced results
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The rezoner works fine for
typical design studies but not
for predictive science
Comparison using 6 vs 3
zones in auto-rezoner:
But using Hyades has proven
impractical
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Rezoner had fidelity issues
Code revisions were slow
UQ was problematic
Results differ vs CRASH
H2D is manpower intensive
Decision:
do a laser package in CRASH
Page 14
The simulated morphological features were not
useful for UQ
• The CRASH code has yet to reliably produce the observed
morphology in runs using Hyades initialization for laser drive
Spring 2010
Fall 2010
Decisions:
1.
Focused effort for several months, then moved on; later
improvements made a difference: see talk by Ken Powell
2. Adopted integrated metrics that are independent of
morphological detail: see poster by Mike Grosskopf
3. Did predictive study with calibration using 1D simulations:
see talk by James Holloway
Page 15
Politics precluded integration of CRASH and PDT
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One of the TST members indicated that at the labs the combined
code would be considered UCNI
– We sought a ruling, and what came out of DOE HQ was: “The final
authority believes that the guidance is wrong and should be changed,
but under current rules such a code would be UCNI”
– We are told this will be addressed, “slowly”
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This is despite the fact that several US universities and numerous
foreign researchers are writing and even publishing codes with
analogous capabilities.
Doing an UCNI code is for us a practical non-starter
Decision: until this situation changes, we will pursue
correlated studies to understand the impact of limited fidelity
It might prove useful for the Review Team to make a very
strong recommendation to DOE about addressing this
Page 16
Predictive simulation roadmap
Page 17
We are now ready for multi-D integrated studies
• Our code is “good enough” and is getting better
• We have carried out the UQ elements needed
• The primary limitation going forward is computational
– Details and implications to be discussed at length later
– Includes core-hours limitations but also much more
– Affects approach to UQ (following talks)
• We intend to be the first academic team
– to use statistical Assessment of Predictive Capability
– to guide improvements in simulations and field experiments
– that lead to predictions, known to have improved accuracy, of
field experiments having extrapolated parameters (not physics)
– and to demonstrate this by field measurements.
Page 18
Supplemental material follows
Page 19
People p. 1
Page 20
People p. 2
Page 21
Our experimental sequence will improve and test
our assessment of predictive capability
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A conceptually simple
experiment
– Launch a Be plasma down a
shock tube at ~ 200 km/s
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Year 5 experiment
– Predict outcome and accuracy
before doing year 5 experiment
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Goals
– Improve predictive accuracy
during project
– Demonstrate a predictive
uncertainty comparable to the
observed experimental
variability
– A big challenge and
achievement
Page 22
Conservation of energy forces the shock wave to
develop complex structure
Shocked xenon layer
Compressed 40x
Traps thermal photons
Other fun
complications:
Instabilities
Wall shocks
Preheated region
Thermal photons
escape upstream
Page 23
Our experiments are at the Omega laser
One of our shots at the Omega laser
Related experiments
LULI & PALS & RAL, LIL (soon?)
NIF & LMJ maybe someday
Omega
60 beams
30 kJ in 1 ns
0.35 µm wavelength
Page 24
How to produce radiative shocks
Laser beams launch Be piston
into Xe or Ar gas at > 100 km/s
Piston drives shock
Gas filled tubes
Diagnostics measure plasma
properties
Gold grids provide spatial
reference
Parameters
1015 W/cm2
0.35 µm light
1 ns pulse
600 µm tube dia.
Targets: Korbie Killebrew, Mike Grosskopf,
Trisha Donajkowski, Donna Marion
Page 25
Experiments: Amy Reighard, Tony Visco, Forrest Doss
The laser first creates structure
at the target surface
• The laser is absorbed at less than 1% of solid
density
Ablation pressure
from momentum
balance:
p ~ 8.6 I142/3 / µm2/3 Mbars
Typical pressures of
tens of Mbars
From Drake, High-Energy-Density Physics, Springer (2006)
Radiative shocks need
thinner targets than the
one shown here
Page 26
For radiative shocks, target acceleration
produces the high required velocities
Acceleration pushes velocity
into radiative shock regime
• Profiles at 1.3 ns shown
Laser produced
pressure accelerates
Be plasma
Expanding Be drives
shock into Xe gas
Page 27
Researchers are studying these shocks with a
range of diagnostics and simulations
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Radiographs
Emission
Interferometry
Xray Thomson scattering
Data credits: L. Boireau S. Bouquet, F. Doss M.
Koenig, C. Michaut, A. Reighard, T. Visco , T. Vinci
Page 28
Radiography is our workhorse;
we also use other diagnostic methods
X-ray Thomson Transverse Streaked
Scattering
Optical Pyrometer (SOP)
Radiographs (1 or 2 views)
UV Thomson
Scattering
Data by grad students
Amy Reighard (Cooper),
Tony Visco, Forrest Doss,
Channing Huntington
Christine Krauland
Transverse VISAR
Page 29
Lateral structure within the shocked layer is
expected from a Vishniac-like mechanism.
See E. Vishinac,
ApJ 1983
Page 30
Theoretical analysis shows structure internal to
shocked layer for the experimental case
Perturbed system
Unperturbed system
Vorticity
features
Be
U
Z=H
.
Shocked
Xe
-Vs
Z=0
Vs
Unshocked Xe
• Wavelength and growth rate of instability in
Forrest Doss, et al.
reasonable agreement with observations
in preparation
• Stereoscopic experiments will seek further evidence
Page 31
Simulating these shocks is challenging but not
impossible
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Optically thin, large upstream
Electron heating by ions
Optically thin cooling layer
Optically thick downstream
This problem has
• A large range of scales
• Non-isotropic radiation
• Complex hydro
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