Synthesis and characterization of diamond capsules for direct-drive inertial confinement fusion

• Published in: Diamond and related materials Vol. 86; pp. 15 - 19
• Main Authors: Kato, Hiroki, Yamada, Hideaki, Ohmagari, Shinya, Chayahara, Akiyoshi, Mokuno, Yoshiaki, Fukuyama, Yuji, Fujiwara, Neo, Miyanishi, Kouhei, Hironaka, Yoichiro, Shigemori, Keisuke
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2018; Elsevier BV
• Subjects: Ablative materials; Chemical vapor deposition; Diamonds; Film thickness; Fusion; Inertial confinement fusion; Irradiation; Mechanical polishing; Organic chemistry; Plasmas; Polycrystalline diamond; Smoothness; Stiffness; Studies; Symmetry; Synthesis
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2018.04.010

Aiming at improving performance of inertial confinement fusion (ICF) targets, we developed synthesis technology of diamond capsules. In direct-drive ICF for which a spherical target capsule is irradiated directly with intense laser light, laser imprinting due to irradiation non-uniformity on the capsule surface degrades symmetry of the target implosion and performance as a result. We demonstrated that material stiffness is the effective parameter for mitigation of laser imprinting [Kato, et al., Phys. Plasmas, 25, 032706 (2018)]. In this study, we fabricated polycrystalline diamond capsules as the ablator material of direct-drive ICF targets by using the hot filament chemical vapor deposition method. The capsule (diameter ~500 μm) with sphericity 99.7%, film thickness < 10 μm, and the surface smoothness <0.1 μm was obtained without mechanical polishing. Synthesis of diamond capsule is achieved by continuously rotating the Si spheres by using a vibrator during Hot filament CVD. Diamond capsule with the grain size and surface roughness of several nm to several tens nm level was obtained. Efficient way without mechanical-polishing to prepare diamond capsule for inertial confinement fusion experiments was realized. [Display omitted] •Diamond capsule with the grain size of several tens nm level was obtained by hot filament CVD.•The capsule with sphericity 99.7 % and the surface smoothness < 0.1 μm was obtained without mechanical polishing.•An efficient method to prepare diamond capsules for inertial confinement fusion experiments was found.