3.A Biased Sputtering of Target Pusher Layers

Many laser fusion target designs call for metal pusher layers which have surface roughnesses of less than 50 nm and thickness uniformities of a few percent. Applying coatings which meet these requirements to spherical glass microballoons is a unique challenge. One reason for this is the problem which arises when the coating material isdeposited on a surface at oblique angles of incidence, as it must for a spherical substrate. In this situation, small defects in the surface tend to shadow the surrounding area, and therefore grow preferentially with respect to the background.', 2The rapid growth of these defects can lead to unacceptably rough surfaces.