Doped CHx microshells prepared by radio frequency plasma enhanced chemicalvapor deposition for inertial confinement fusion experiments

French targets prepared for inertial confinement fusion experiments, to be shot on the Laser Megajoule facility, are organic (CHx) microshells. The mi croshell, that contains the deuterium-tritium mixture (DT), is placed in a gold holraum that converts the laser light into an x-ray flow. It is an ind irect drive to reach ignition. This microshell, whose role is an ablator to initiate compression of the target, is fabricated by plasma polymerization of organic precursors. In these implosion experiments, it is necessary to control the preheat of the deuterium-tritium fusible mixture in the capsule , and the ablation front instability, by doping the ablator layer with a sm all quantity of high Z material. The germanium or bromine doping of the CHx enables the control of the microshell opacity to prevent the preheat of DT from high energetic x rays. Titanium is used to diagnostises the implosion of the target. The coating properties evolve with the amount of dopant inc orporated in the CHx matrix. Evolution of the deposition rate, the roughnes s, the thermal stability, or the optical gap (UV/visible spectroscopy) are studied in this article. Concentration and homogeneity of the dopants are a lso determined as well as the chemical bindings between the dopants and the hydrocarbon matrix. Many characterizations are done by scanning electron m icroscopy, Rutherford backscattering spectroscopy, x-ray photoelectron spec troscopy, or Fourier-transform infrared. (C) 2001 American Vacuum Society. [DOI: 10.1116/1.1322644].