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Title: Exploration of the Transition from the Hydrodynamic-like to the Strongly Kinetic Regime in Shock-Driven Implosions

Clear evidence of the transition from hydrodynamiclike to strongly kinetic shock-driven implosions is, for the first time, revealed and quantitatively assessed. Implosions with a range of initial equimolar D 3He gas densities show that as the density is decreased, hydrodynamic simulations strongly diverge from and increasingly over-predict the observed nuclear yields, from a factor of ~2 at 3.1 mg/cm 3 to a factor of 100 at 0.14 mg/cm 3. (The corresponding Knudsen number, the ratio of ion mean-free path to minimum shell radius, varied from 0.3 to 9; similarly, the ratio of fusion burn duration to ion diffusion time, another figure of merit of kinetic effects, varied from 0.3 to 14.) This result is shown to be unrelated to the effects of hydrodynamic mix. As a first step to garner insight into this transition, a reduced ion kinetic (RIK) model that includes gradient-diffusion and loss-term approximations to several transport processes was implemented within the framework of a one-dimensional radiation-transport code. After empirical calibration, the RIK simulations reproduce the observed yield trends, largely as a result of ion diffusion and the depletion of the reacting tail ions.
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  1. MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States). Plasma Science and Fusion Center
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Univ. of Roma, Roma (Italy). Dipartimento SBAI
  5. Univ. of Rochester, NY (United States). Lab. for Laser Energetics
  6. Univ. of Rochester, NY (United States). Lab. for Laser EnergeticsUniv. of Rochester, NY (United States). Lab. for Laser Energetics
  7. General Atomics, San Diego, CA (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 112; Journal Issue: 18; Journal ID: ISSN 0031-9007
American Physical Society (APS)
Research Org:
MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States). High Energy Density Physics Division, Plasma Science and Fusion Center
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
OSTI Identifier: