Los Alamos National Laboratory

Los Alamos National Laboratory

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Materials in Extremes

Powerful working groups combine experiment and theory to understand and predict how materials in weapons change over time.

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Understanding hydrodynamic material instabilities at extremes

The National Nuclear Security Administration science-based stockpile stewardship program funds research that will improve critical physics-based dynamic materials models.

Los Alamos National Laboratory and Lawrence Livermore National Laboratory, as nuclear weapon design laboratories, are mandated to predict the reliability and durability of the nuclear weapons stockpile. This is done using state-of-the-art supercomputers and computer codes. It is also important to have state-of-the-art physics models in these codes.

Los Alamos has theory experts in dynamic materials, thus creating powerful working groups when combined with experimental experts in Physics Division and elsewhere. Key to the science-based stockpile stewardship program is making measurements of fundamental properties of materials relevant to the nuclear weapons program. Many of these properties involve the dynamic of how key materials respond to dynamic loading and subsequent unloading, or research into hydrodynamic instabilities at extremes.

Los Alamos performs research in many areas where fundamental properties are needed. Our dynamic materials program covers a broad range of applications including the following:

  • Department of Defense conventional weapons and armor
  • Advanced nuclear reactor concepts, such as radiation-induced shock and damage
  • Dynamic materials in industry, such as for aircraft wings and stress
  • Stockpile stewardship

Dynamic materials experiments over a wide range of stresses and strain rates are essential for studying constitutive relations (e.g., plasticity), damage (e.g., spall), equations of state, phase transitions and kinetics, and other properties such as the transport of small particles ejected from shock loaded metals into gasses.

Physics Division scientists, in collaboration with others both inside and outside the Laboratory, conduct experiments on shocked materials at several facilities using high explosive and gun-flyer plate type drives, and laser drives. Observations of the material's response to these shock waves provide valuable insights into how they behave under dynamic loading.

Eve experiments in support of computational modeling

The Eve experiments, performed at the Proton Radiography Facility at LANSCE, were explosively driven two-shockwave loading of tin (Sn) to study the transport and breakup of ejecta into different gasses. Presently, physics and engineering models of the transport and breakup of ejecta in gasses are being formulated in X-Computational Physics. Physics Division is supporting that effort experimentally.

In these experiments, Sn targets are twice shocked explosively. The Sn targets have perturbations on the surface away from the explosives that are characterized by their wavelengths and amplitudes. Previous work demonstrated that ejecta form as a limiting extreme of unstable Richtmyer-Meshkov (RM) phenomena. These RM instabilities have been shown to be linked to the product of the wavenumber k = 2p/l and the perturbation amplitude h, i.e., kh. The experiments had the perturbations grow into three different gasses—elium, neon, and argon—filled to an absolute pressure of 100 psi. The working assumption is that the time for an ejecta sheet to breakup scales inversely with the density of the gas squared.

The data clearly support the conclusion that the ejecta sheets break up faster in neon than helium and faster in argon than neon, as expected. Other ejecta physics of interest to the modeling community are the rates at which the ejecta sheets unstably grow after the first and second shock.

Key facilities


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