Hydrodynamic scaling of the deceleration-phase Rayleigh–Taylor instability
The scaling of the deceleration phase of inertial fusion direct-drive implosions is investigated for OMEGA and National Ignition Facility (NIF)-size targets. It is shown that the deceleration-phase Rayleigh–Taylor instability (RTI) does not scale hydro-equivalently with implosion size. This is because ablative stabilization resulting from thermal conduction and radiation transport in a spherically converging geometry is different on the two scales. As a consequence, NIF-scale implosions show lower hot-spot density and mass ablation velocity, allowing for higher RTI growth. On the contrary, stabilization resulting from density-gradient enhancement, caused by reabsorption of radiation emitted from the hot spot, is higher on NIF implosions. Since the RTI mitigation related to thermal conduction and radiation transport scale oppositely with implosion size, the degradation of implosion performance caused by the deceleration RTI is similar for NIF and OMEGA targets. It is found that a minimum threshold for the no-α Lawson ignition parameter of ΧΩ ≈ 0.2 at the OMEGA scale is required to demonstrate hydro-equivalent ignition at the NIF scale for symmetric direct-drive implosions.
- Univ. of Rochester, Rochester, NY (United States). Lab. for Laser Energetics, Dept. of Physics and Fusion Science Center.
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Publication Date:
- OSTI Identifier:
- Report Number(s):
Journal ID: ISSN 1070-664X; PHPAEN; 2015-1; 2195; TIC-1230
- DOE Contract Number:
- Resource Type:
- Journal Article
- Resource Relation:
- Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 7
- American Institute of Physics (AIP)
- Research Org:
- Univ. of Rochester, Rochester, NY (United States). Lab. for Laser Energetics.
- Sponsoring Org:
- Country of Publication:
- United States
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY Raleigh Taylor instabilities; thermal radiation; thermal conduction; hydrodynamics; ice