Fusion Science and Technology / Volume 63 / Number 2 / March 2013 / Pages 169-176
Technical Paper / Selected papers from 20th Target Fabrication Meeting, May 20-24, 2012, Santa Fe, NM, Guest Editor: Robert C. Cook
Because isolated contaminants on an inertial confinement fusion (ICF) ablator capsule can lead to undesirable instabilities during implosion, it is critical to remove particles from the surface of plastic capsules prior to target assembly. Current National Ignition Facility (NIF) specifications require that the capsule surface contain no particles larger than 30 m3 . We have developed a solvent-based cleaning process in which a combination of wetting and hydrodynamic forces is used to dislodge, entrain, and remove particles from the surface of plastic NIF ICF ablators. The process was conceptualized by considering the adhesive force acting between particles and a surface, the hydrodynamic force acting on particles near a surface, and the effect of solvent on these forces. We also performed experiments that showed that, in addition to utilizing the appropriate solvent and hydrodynamic force, the dwell time and surface coverage of the impinging solvent stream govern particle removal efficiency. The results from this combined approach allowed us to develop the engineering and design parameters for a prototype automated cleaning station for NIF capsules. This station can remove particles at efficiencies high enough to meet ignition cleanliness requirements.