Fusion Science and Technology / Volume 59 / Number 1 / January 2011 / Pages 8-13
Technical Paper / Nineteenth Target Fabrication Meeting
The National Ignition Tuning Campaign involves a dozen capsule designs. These capsule designs vary in diameters, layer thicknesses, and germanium doping levels, examining implosion velocity, entropy, hot-spot shape, mix, and uncertainty. Overall yield of these tuning capsules involves meeting all individual specifications, including layer thicknesses, doping levels, outer surface smoothness, and inner diameter. The yield of scaled tuning capsules with acceptable inner diameters is greatly affected by the available mandrel diameter and its size distribution.
Surface low mode and isolated defect specifications have been tightened. The new specification allows smaller and fewer isolated defects. The surface specification is quantified in terms of low mode factors, peak velocity root-mean-square (PVRMS), mix mass, and ignition threshold function (ITF). The total mix mass from all isolated defects should be <40 ng, and the PVRMS value should be <10 m. While most current capsules meet the PVRMS requirement, only some tuning capsules have a mix mass <40 ng. The majority of capsules have a mix mass >40 ng, caused by a few larger domes. The ITF is related to isolated defects and capsule power spectra. Some capsules exceed the ITF specification value of 1.3.