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Title: Polar-direct-drive experiments on the National Ignition Facility

To support direct-drive inertial confinement fusion experiments at the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Opt. Eng. 43, 2841 (2004)] in its indirect-drive beam configuration, the polar-direct-drive (PDD) concept [S. Skupsky et al., Phys. Plasmas 11, 2763 (2004)] has been proposed. Ignition in PDD geometry requires direct-drive–specific beam smoothing, phase plates, and repointing the NIF beams toward the equator to ensure symmetric target irradiation. First experiments to study the energetics and preheat in PDD implosions at the NIF have been performed. These experiments utilize the NIF in its current configuration, including beam geometry, phase plates, and beam smoothing. Room-temperature, 2.2-mm-diam plastic shells filled with D₂ gas were imploded with total drive energies ranging from ~500 to 750 kJ with peak powers of 120 to 180 TW and peak on-target irradiances at the initial target radius from 8 10¹⁴ to 1.2 10¹⁵W/cm². Results from these initial experiments are presented, including measurements of shell trajectory, implosion symmetry, and the level of hot-electron preheat in plastic and Si ablators. Experiments are simulated with the 2-D hydrodynamics code DRACO including a full 3-D ray-trace to model oblique beams, and models for nonlocal electron transport and cross-beammore » energy transport (CBET). These simulations indicate that CBET affects the shell symmetry and leads to a loss of energy imparted onto the shell, consistent with the experimental data.« less
Authors:
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  1. Lab. for Laser Energetics, University of Rochester, Rochester, NY (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. U. S. Naval Research Lab., Washington, DC (United States)
  4. General Atomics, San Diego, CA (United States)
  5. MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States)
  6. U. S. Naval Research Lab., Washington, DC 20375, (United States)
Publication Date:
OSTI Identifier:
1182632
Grant/Contract Number:
NA0001857; NA0001944
Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 22; Journal Issue: 5; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Institute of Technology, Cambridge, MA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY