PRODUCTION AND CHARACTERIZATION OF DOPED MANDRELS FOR INERTIAL-CONFINEMENT FUSION EXPERIMENTS

A key feature of current inertial-confinement fusion (ICF) experiments is the incorporation of dopant atoms into the thin polymer microshell which, in a finished ICF capsule, forms its inner wall. These dopants provide a spectroscopic signal during the implosion that can be used to diagnose the degree of mix at the capsule-fuel interface. The high-Z dopants can also be used to directly image the fuel-pusher interface. The current status of doped mandrel development is reviewed, with a focus on the mandrel surface smoothness. With the development of unique surface mapping characterization tools which will be described, it has been discovered that mandrel surface smoothness is a function of the polymers used to form the mandrels. In this report it will be shown that Cl-doped mandrels produced from a blend of polystyrene and poly(p-chlorostyrene) are rough on a length scale of 10's of microns with amplitudes of as much as a 100 nm. The origin of this roughness will be discussed, and it will be shown that this roughness can be removed by using a copolymer rather than a blend of two polymers. Also it will be shown how Cr-doped mandrels become rough with age due to ambient light exposure.