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

Sandia National Laboratories Z machine employs cylindrical liners for implosion along the Z-axis, a technique known as pulse-power-driven z pinches. During the implosion process, magnetic energy is converted into radial kinetic energy to compress the DT fuel to achieve High Energy Density conditions. However, the implosion process is unstable, where defects can exponentially grow due to the Rayleigh-Taylor instability. This results in x-ray radiation, lower temperatures, and reduced yield. Therefore, a diagnostic tool is crucial to understand the source of mixing.

 

In this study, we designed a method to coat the interiors of liners by introducing a trace layer of a few nanometers of a mid-Z element such as cobalt, embedded in a layer of several microns of beryllium. By measuring cobalt x-ray radiation during Z-shots as a function of the buried layer's distance from the liner's inner surface, we can assess the effective mixing distance. Conventional magnetron sputtering for coating interior walls often leads to non-uniform coatings. To address this, we developed an ion beam sputtering process to uniformly coat the interior walls of the liner. This method employs an ion gun to sputter a rod shaped target material, enabling precise control over coating composition and thickness uniformity along the liner's length and azimuthal axis.

 

Work supported by the U.S. Department of Energy under Contract 89233119CNA000063, by US DOE under the Community College Internships (CCI), and by General Atomics under IR&D funding.