Center for Radiative Shock Hydrodynamics Fall 2010 Review Introductory overview R. Paul Drake

Page 2 What lies ahead This first presentation –Motivation and introduction to the physical system –Overview of the past year: progress, challenges, decisions Following presentations today –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 Other highlighted contributions tomorrow morning (little time! ) –Kuranz, Sokolov, Morel Posters today –See the details and meet the people 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 3 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 4 We find our motivation in astrophysical connections Radiative shocks have strong radiative energy transport that determines the shock structure Exist throughout astrophysics Ensman & Burrows ApJ92 Reighard PoP07 SN 1987A Cataclysmic binary star (see Krauland poster)

Page 5 A brief primer on shock wave structure Behind the shock, the faster sound waves connect the entire plasma Denser, Hotter Initial plasma Shock velocity, u s Mach number M > 1 unshocked shocked Mach number M = u s / c sound

Page 6 Shock waves become radiative when … radiative energy flux would exceed incoming material energy flux where post-shock temperature is proportional to u s 2. Setting these fluxes equal gives a threshold velocity of 60 km/s for our system: Material xenon gas Density 6.5 mg/cc Initial shock velocity200 km/s shocked unshocked preheated  T s 4  o u s 3 /2 Initial ion temperature 2 keV Typ. radiation temp. 50 eV

Page 7 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 Some ideas about how to approach “UQ” in general and specifically the Assessment of Predictive Capability Space weather simulation

Page 8 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 Schematic of radiograph Grid (see Doss poster)

Page 9 What we predict What the radiograph fundamentally shows us is where dense Xe exists Grid 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 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 10 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 flux- limited electron heat conduction Ongoing –Laser package –Multigroup preconditioner –I/O performance upgrade –Use of other EOS 3D Nozzle to 13 ns Material & AMR Log Density Log Electron Temperature Log Ion Temperature

Page 11 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 12 We have accomplished a lot during the past year UQ and predictive studies –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 –X-ray-driven modeling –Pure hydro nozzle study –Application to other experiments –Detailed examination of axial structures –Hydro instability studies 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 13 We have also encountered some challenges

Page 14 Initializing CRASH with Hyades proved problematic 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 But using Hyades has proven impractical –Rezoner had fidelity issues –Code revisions were slow –UQ was problematic –Results differ vs CRASH –H2D is manpower intensive The rezoner works fine for typical design studies but not for predictive science Comparison using 6 vs 3 zones in auto-rezoner: Decision: do a laser package in CRASH

Page 15 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 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 Spring 2010 Fall 2010

Page 16 Politics precluded integration of CRASH and PDT 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” 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 17 Predictive simulation roadmap

Page 18 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 19 Supplemental material follows

Page 20 People p. 1

Page 21 People p. 2

Page 22 Our experimental sequence will improve and test our assessment of predictive capability A conceptually simple experiment –Launch a Be plasma down a shock tube at ~ 200 km/s Year 5 experiment –Predict outcome and accuracy before doing year 5 experiment Goals –Improve predictive accuracy during project –Demonstrate a predictive uncertainty comparable to the observed experimental variability –A big challenge and achievement

Page 23 Conservation of energy forces the shock wave to develop complex structure Shocked xenon layer Compressed 40x Traps thermal photons Preheated region Thermal photons escape upstream Other fun complications: Instabilities Wall shocks

Page 24 Our experiments are at the Omega laser Omega 60 beams 30 kJ in 1 ns 0.35 µm wavelength One of our shots at the Omega laser Related experiments LULI & PALS & RAL, LIL (soon?) NIF & LMJ maybe someday

Page 25 How to produce radiative shocks Gas filled tubes Laser beams launch Be piston into Xe or Ar gas at > 100 km/s Piston drives shock Diagnostics measure plasma properties Gold grids provide spatial reference Parameters W/cm µm light 1 ns pulse 600 µm tube dia. Targets: Korbie Killebrew, Mike Grosskopf, Trisha Donajkowski, Donna Marion Experiments: Amy Reighard, Tony Visco, Forrest Doss

Page 26 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: Typical pressures of tens of Mbars From Drake, High-Energy-Density Physics, Springer (2006) p ~ 8.6 I 14 2/3 / µm 2/3 Mbars Radiative shocks need thinner targets than the one shown here

Page 27 For radiative shocks, target acceleration produces the high required velocities Profiles at 1.3 ns shown Laser produced pressure accelerates Be plasma Expanding Be drives shock into Xe gas Acceleration pushes velocity into radiative shock regime

Page 28 Researchers are studying these shocks with a range of diagnostics and simulations Radiographs Emission Xray Thomson scattering Interferometry Data credits: L. Boireau S. Bouquet, F. Doss M. Koenig, C. Michaut, A. Reighard, T. Visco, T. Vinci

Page 29 Radiography is our workhorse; we also use other diagnostic methods Radiographs (1 or 2 views) Data by grad students Amy Reighard (Cooper), Tony Visco, Forrest Doss, Channing Huntington Christine Krauland Transverse Streaked Optical Pyrometer (SOP) Transverse VISAR UV Thomson Scattering X-ray Thomson Scattering

Page 30 Lateral structure within the shocked layer is expected from a Vishniac-like mechanism. See E. Vishinac, ApJ 1983

Page 31 U VsVs Perturbed system Unperturbed system Be Z = H Z = 0 Vorticity features Shocked Xe Unshocked Xe Theoretical analysis shows structure internal to shocked layer for the experimental case Wavelength and growth rate of instability in reasonable agreement with observations Stereoscopic experiments will seek further evidence Forrest Doss, et al. in preparation -V s.

Page 32 Simulating these shocks is challenging but not impossible 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 20