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Title: Implosion Dynamics in Direct-Drive Experiments

Increasing the ablation pressure is a path to achieving cryogenic implosion performance on the OMEGA laser that will hydrodynamically scale to ignition on the National Ignition Facility. An increased ablation pressure will allow a more-massive shell (i.e. thicker and more hydrodynamically stable) and a higher adiabat to achieve ignition-relevant velocities (>3.5 × 10⁷ cm s⁻¹), areal densities (>300 mg cm⁻²) and hot-spot pressures (>100 Gbar). Two approaches have demonstrated increased ablation pressure: (1) a target design is shown that uses a Be ablator to increase the hydrodynamic efficiency, resulting in a ~10% increase in the ablation pressure, in comparison to a CH ablator; (2) reducing the beam size is shown to recover all of the ablation pressure lost to cross-beam energy transfer (CBET), i.e. the ablation pressure calculated without CBET, but the degraded illumination uniformity reduces the integrated target performance. The hydrodynamic efficiency is measured for the current cryogenic design, multiple ablator material design and CH capsule designs with various beam focal-spot sizes. In each case, an excellent agreement is observed with 1D hydrodynamic simulations that include CBET and nonlocal heat-transport models.
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  1. Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plasma Physics and Controlled Fusion; Journal Volume: 57; Journal Issue: 1
IOP Science
Research Org:
Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Org:
Country of Publication:
United States
70 PLASMA PHYSICS AND FUSION TECHNOLOGY fusion; hydrodynamic efficiency; direct drive; cryogenic; self-emission; ablator; zooming