Ion Gun Sputtering Technique for Buried Multi-Composition Layers inside Liners*

Sandia National Laboratories' Z machine uses cylindrical liners for implosion onto Z-axis, a technique called Pulse-power-driven z pinches. In the implosion process, magnetic energy is converted to radial kinetic energy to compress the DT fuel into High Energy Density (HED) conditions. The implosion process is hydrodynamically unstable, any defects will grow exponentially via the Rayleigh-Taylor instability, will cause x-ray radiation, lower the temperature and kill the yield. Therefore, a diagnostic tool to understand where the mixing is coming from is needed. In this work, we designed a technique to perform interior coatings of liners by introducing a trace layer of a mid-Z element such as cobalt (which do not naturally exist into beryllium liners) followed by microns of beryllium coatings. By measuring cobalt x-ray radiation during Z-shot as function of buried layer distance from the liner inner-surface, we can probe the effective mixing distance. Conventional magnetron sputtering to coat the interior walls leads to coating thickness nonuniformity. We developed an ion beam sputtering process to coat the interior wall of the liner uniformly by using an ion gun to sputter the rod-shaped target material. This method enables to control coating composition, and thickness uniformity along the length of the liner and its azimuthal axis.