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Title: Capsule Shimming Developments for National Ignition Facility (NIF) Hohlraum Asymmetry Experiments

Journal Article · · Fusion Science and Technology
 [1];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [3];  [3];  [3]
  1. General Atomics, San Diego, CA (United States); General Atomics
  2. General Atomics, San Diego, CA (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
+ Show Author Affiliations

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 P4 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 P4 profile. The P4 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.

Research Organization:
General Atomics, San Diego, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
NA0001808; AC52-07NA27344
OSTI ID:
1402460
Alternate ID(s):
OSTI ID: 1458701
Journal Information:
Fusion Science and Technology, Journal Name: Fusion Science and Technology Journal Issue: 2 Vol. 73; ISSN 1536-1055
Publisher:
American Nuclear SocietyCopyright Statement
Country of Publication:
United States
Language:
English

References (11)

Surface oxygen micropatterns on glow discharge polymer targets by photo irradiation journal February 2016
Hydrodynamic instability growth and mix experiments at the National Ignition Facility journal May 2014
Fabrication of capsules with angle-dependent gold shims for hohlraum drive symmetry correction
  • Nikroo, A.; Pontelandolfo, J.; Greenwood, A. L.
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 544, Issue 1-2 https://doi.org/10.1016/j.nima.2005.01.193
journal May 2005
Polishing and local planarization of plastic spherical capsules using tumble finishing journal November 2012
3D Surface Reconstruction of ICF Shells after Full Surface Spheremapping journal May 2006
Machining of Two-Dimensional Sinusoidal Defects on Ignition-Type Capsules to Study Hydrodynamic Instability at the National Ignition Facility journal September 2016
Effects of fuel-capsule shimming and drive asymmetry on inertial-confinement-fusion symmetry and yield journal March 2016
Mitigating the impact of hohlraum asymmetries in National Ignition Facility implosions using capsule shims journal July 2016
CH Capsule Fabrication for Ignition Tuning Campaign journal January 2011
Complete Surface Mapping of ICF Shells journal March 2004
Utilizing Conventional Machining Tools with Customized Machining Techniques to Manufacture Multifaceted Targets journal April 2013

Cited By (1)

Instability growth seeded by DT density perturbations in ICF capsules journal September 2018

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Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
Hohlraum
National Ignition Facility
capsule shimming