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Most designs of inertial confinement fusion (ICF) targets require ablators in the form of hollow spherical shells with an outer diameter of∼ 1− 3 mm and a wall thickness of∼ 20− 200 microns. Vapor deposition onto rolling spherical substrates (templates) is the generally preferred method for the fabrication of ICF ablators. Amorphous boron carbide (B 4 C) is a promising material for use as an ablator due to its favorable properties. However, the challenge lies in creating ultrathick B 4 C coatings with submicron-scale density uniformity on rolling spherical substrates. Here, we show examples from our ongoing systematic study of the deposition of B 4 C onto 2-mm-diameter Si spheres by radio-frequency magnetron sputtering (RFMS). We start with a RFMS recipe developed for depositing planar amorphous B 4 C films with close-to-zero residual stress and transfer the deposition process from stationary planar substrates …