Characterization of Thin Copper Diffusion Barrier Layer in Beryllium Capsules

The point design of beryllium capsules includes three Cu-doped layers in a 160-m-thick beryllium shell to achieve the desired X-ray absorption profile. The beryllium capsules were deposited on glow discharge polymer mandrels using a magnetron sputtering process. Cu diffusion during pyrolysis to remove the mandrels after coating has caused nonuniform distribution of Cu along the azimuthal direction due to inhomogeneous diffusion. This nonuniformity along the azimuthal direction could lead to Rayleigh-Taylor instability during capsule implosion. One of the methods to solve this issue is to incorporate a beryllium oxide diffusion barrier layer at the beryllium-Cu-doped-beryllium layer interfaces. In situ and ex situ beryllium oxide layers have proved to be effective in stopping Cu diffusion. This paper will focus on the approaches we have developed to characterize the in situ and ex situ oxide barrier layer thickness by using a combination of Auger electron spectroscopy profiles and Rutherford backscattering spectrometry measurements.