Thick GDP Microshells for LIL and LMJ Targets

Abstract

Amorphous hydrogenated carbon (a-C:H) is the nominal ablator to be used in French inertial confinement fusion (ICF) experiments. These capsules, containing the deuterium-tritium mixture, are developed for the LIL (Laser Integration Line) and the future Megajoule laser (LMJ) of the CEA. Coatings are prepared by glow discharge polymerization (GDP) with trans-2-butene and hydrogen. The films properties have been investigated. Laser fusion targets must have optimized characteristics: a diameter of about 1 mm for LIL targets and about 2.4 mm for LMJ targets, a thickness up to 175 μm, an outer and an inner roughness lower than 20 nm at high modes, a sphericity and a thickness concentricity better than 99%. This paper presents the first microshells obtained at the CEA with a GDP (Glow Discharge Polymerization) coater. Amorphous hydrogenated carbon shells of 175 μm with 1 mm or 2.4 mm diameter have been successfully prepared. The measured roughness at high modes is lower than 10 nm for a 30×30 μm characterization window.