Stockpile Stewardshipquarterly

DOE/NA-0070 Office of Research, Development, Test, and Evaluation Stockpile Stewardship Quarterly VOLUME 8 | NUMBER 1 | MARCH 2018 essage from the Assistant Deputy Administrator for Research, M Development, Test, and Evaluation, Dr. Kathleen Alexander This issue of the Stockpile Stewardship explosives in weapon geometries and Quarterly focuses on the intersection data on the performance differences between computer modeling and between surrogate metals and plutonium in experiments. experiments that provide the phenomenologicalthe design and conduct basis of for scientific computer Another article discusses a complementary models. We kick off this issue with an approach that uses laser or pulsed-power article that discusses the relationship facilities to achieve a high energy density between verifying and validating the (HED) state of matter. The majority of modern nuclear weapons codes and weapon processes occur in the HED the hierarchy of experiments that must state, and so understanding the physics be performed to provide the necessary that occurs in this state is essential to data. With the cessation of nuclear modeling weapon systems. These HED testing, computer modeling has become The research on display during the Poster experiments are sized in the centimeter- key to assessing the safety, security, Session of this year’s Stewardship Science to-micrometer range yet still are able to and performance of weapon systems Academic Programs Annual Review examine integrated weapons phenomena. whose designs have evolved from tested Symposium, held in Bethesda, Maryland on February 21-22, 2018, generated much We close this issue with a nod to the next- excitement. Above right and inset, Sarah generation scientists and engineers. We Hickam, University of Notre Dame, discusses interactingconfigurations. physics This phenomena. requires higher The level her research with Dr. Alexander. Read about the share a review of and honor the awardees fidelity codes that incorporate multiple, symposium and winning posters on page 10. from the 2018 Stewardship Science data to verify these codes ranges from Academic Programs Annual Review Symposium that drew a record number of small-scaleof experimentation experiments required designed to provide to for upcoming life extension programs, attendees, and we highlight an academic assess a single physics problem to fully as well as future assessments and integrated experiments that evaluate the opportunity at the University of Michigan interaction of the physics involved in a full weapon system. certifications.This issue also features an article on the Incredible work is happening in the latest subcritical experimental series, in the HED field. nuclear security enterprise, and this work Subcritical experiments are performed Gemini, Leda, and Lyra. These series is vital to the security of our Nation. to gather data of complex, interacting were designed to provide data on the weapons physics. The Enhanced physics response of using insensitive Capabilities for Subcritical Experiments high explosives versus conventional project portfolio is working to achieve the design and creation of a next- Inside generation suite of diagnostics that will allow for data to be gathered on 2 Integrated High Energy Density Experiments Yield Critical Data for the ASC Program the relevant physics involved in the 4 Continuous Evolution of the Stockpile Stewardship Program: Enhanced Capabilities for late-stage implosion of plutonium in Subcritical Experiments weapons-relevant geometries. This 6 Vega & the Lyra Series data will feed the complex computer 8 Integrated Experiments in the Stockpile Stewardship Program simulations to inform design options 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 and comments regarding this publication should be directed to Terri Stone at [email protected]. Technical Editor: Dr. Joseph Kindel | Publication Editor: Millicent Mischo 2 Integrated High Energy Density Experiments Yield Critical Data for the Advanced Simulation and Computing 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), and Arthur Brown (Sandia National Laboratories) During the era of nuclear testing, At the most complete and complex legacy computational codes were used end of the hierarchical approach is the to design the United States nuclear integrated system tests. Examples include weapons stockpile. Throughout experiments conducted at the following development of each and every weapon, nuclear weapon tests played the Nevada National Security Site (NNSS); a critical role in calibrating the models thelocations Dual-Axis (see RadiographicFigure 2): U1a Hydrodynamic Complex at and in assessing actual performance. Test Facility (DARHT) at Los Alamos Since the cessation of nuclear testing National Laboratory; the Contained Firing in 1992, improved codes with higher Facility (CFF) at Lawrence Livermore National Laboratory; and the Thunder Range Facility at Sandia National assessfidelity safety, physics security, models and were performance required Laboratories. Experiments conducted ofto theprovide current confidence and future in the stockpile. ability to at these facilities enable an integrated system assessment and more completely To accomplish the science-based test the multi-physics computational Stockpile Stewardship Program (SSP) the full problem physics. codes in these challenging environments. Figure 1. Hierarchical approach to V&V spans As the NNSA weapons laboratories Simulation and Computing (ASC) program continue to work towards delivering mission requires that the Advanced develop simulation codes that accurately In the development of the ASC nuclear fully validated codes, the historical predict and assess the full physics weapon simulation codes, the appropriate nuclear testing archive and historical and engineering environments these physics must be assessed through integrated experiments are assessed and weapons encounter or may encounter. incorporated into the analysis; these tests These modern computational codes must are critical to validation efforts as they are simulate the complexities of nuclear numericaldetermination models of the and proper then incorporated equations. the experimental means that explore the physics, weapons component responses, intoThese the equations codes. After are implementation,approximated into the full nuclear weapon detonation physics. the weapons systems as a whole, and laboratories verify that the numerical determine the impact of design changes models are accurately reproducing the Integrated Hydrotest Experiments and aging on the nuclear weapons stockpile. Additionally, these modern Integrated hydrotests experiments codes serve as a means to evaluate intended equations (Code Verification)1 provide critical data for the SSP. These the full range of a nuclear weapon’s and confirm that the codes are solving the experiments enable scientists to detonate operation. For these purposes, the correct equations (Code Validation). modern nuclear weapon computational program employs a hierarchical approach nuclear weapon, but with surrogate codes must couple numerous physics (seeThe ASCFigure Verification 1) in order & toValidation span the (V&V) materials.a “mock-up” Instead of the ofprimary using plutonium, stage of a models together accurately. Integration of numerous physics models makes these physics experiments (e.g., modeling of material to simulate the desired tools fundamentally different from other Highentire Explosive required detonation)physics regimes. provide Single- the characteristics.scientists use a non-fissile surrogate focus only on single physics models or on to validate individual physics models. integrationscientific computation of a few physics codes models. that normally Dueprogram to the with numerous required individual information physics used record arrival time of an explosively drivenBoth the surface CFF and through DARHT use field of pin diagnostics domes Development of these codes and numerous experimental campaigns. Multi- determining the accuracy of their physicsmodels required,tests (e.g., this radiation necessitates hydrodynamic probes (see Figure 3). The pin dome capabilities is further complicated due experiments) enable a small number recordsand photon when Doppler a surface velocimetry interacts with(PDV) the to the realization that the full physics of physics models be combined for an encountered by a nuclear weapon assessment. Subcomponent physics velocity record of the surface using laser are unlike normal operating physics tests increase the number of interacting velocimetry.pin while the High-energy PDV probe records radiographs a time regimes on Earth. Critically important physics models assessed, and increase the of the experiment are also captured is an examination that these codes are with high-speed cameras to allow for accurately representing the necessary and (e.g., pRad experiments, inertial increased exploration of the implosion correct physical models. complexity of the required experiments dynamics. This combination of diagnostics confinement fusion experiments). 1 Code verification is “the process of determining that the numerical

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