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Title: Numerical Modeling of the Sensitivity of X-Ray Driven Implosions to Low-Mode Flux Asymmetries

In this study, the sensitivity of inertial confinement fusion implosions of the type performed on the National Ignition Facility (NIF) [1] to low-mode flux asymmetries has been investigated numerically. It is shown that large-amplitude, low-order mode shapes (Legendre polynomial P4), resulting from associated low order flux asymmetries, cause spatial variations in capsule and fuel momentum that prevent the DT “ice” layer from being decelerated uniformly by the hot spot pressure. This reduces the transfer of kinetic to internal energy of the central hot spot, thus reducing neutron yield. Furthermore, synthetic gated x-ray images indicate that the P4 component of hot spot self-emission shape is insensitive to P4 hot spot shapes, and a positive P4 asymmetry aliases itself as a negative or oblate P2 in these images. Correction of this apparent P2 distortion can further distort the implosion while creating a round x-ray image. Long wavelength asymmetries may be playing a significant role in the observed yield reduction of NIF DT implosions relative to detailed post-shot 2D simulations.
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2]
  1. STFC Rutherford Appleton Lab., Didcot (United Kingdom)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. STFC Rutherford Appleton Lab., Didcot (United Kingdom); Univ. of Oxford, Oxford (United Kingdom)
Publication Date:
OSTI Identifier:
1244662
Report Number(s):
LLNL-JRNL--607756
Journal ID: ISSN 0031-9007; PRLTAO
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 110; Journal Issue: 7; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 70 PLASMA PHYSICS AND FUSION