Capsule Shimming Developments for National Ignition Facility (NIF) Hohlraum Asymmetry Experiments
Capsule drive in National Ignition Facility (NIF) indirect drive implosions is generated by x-ray illumination from cylindrical hohlraums. The cylindrical hohlraum geometry is axially symmetric but not spherically symmetric causing capsule-fuel drive asymmetries. We hypothesize that fabricating capsules asymmetric in wall thickness (shimmed) may compensate for drive asymmetries and improve implosion symmetry. Simulations suggest that for high compression implosions Legendre mode P 4 hohlraum flux asymmetries are the most detrimental to implosion performance. General Atomics has developed a diamond turning method to form a GDP capsule outer surface to a Legendre mode P 4 profile. The P 4 shape requires full capsule surface coverage. Thus, in order to avoid tool-lathe interference flipping the capsule part way through the machining process is required. This flipping process risks misalignment of the capsule causing a vertical step feature on the capsule surface. Recent trials have proven this step feature height can be minimized to ~0.25 µm.
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- General Atomics, San Diego, CA (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Publication Date:
- Grant/Contract Number:
- NA0001808; AC52-07NA27344
- Type:
- Accepted Manuscript
- Journal Name:
- Fusion Science and Technology
- Additional Journal Information:
- Journal Volume: 73; Journal Issue: 2; Journal ID: ISSN 1536-1055
- Publisher:
- American Nuclear Society
- Research Org:
- General Atomics, San Diego, CA (United States)
- Sponsoring Org:
- USDOE
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Hohlraum; National Ignition Facility; capsule shimming
- OSTI Identifier:
- 1402460