1 3 C Nanocrystalline Diamond Capsules: Fabrication, Characterization, and Opportunities for High‐Energy‐Density Experiments

Nanocrystalline diamond (NCD) targets have recently enabled inertial confinement fusion (ICF) ignition at the National Ignition Facility (NIF), with gains exceeding the input laser energy. Achieving ignition requires NCD targets with carefully tuned density profiles and high material uniformity to minimize fuel‐ablator mix. Here, we report on the fabrication of high‐isotopic‐purity 13 C‐NCD capsules with a 13 C/ 12 C ratio greater than 100 and a density of 3.64 g cm −3 , 8% higher than comparable 12 C‐NCD coatings. The higher density shortens shock transit times, offering symmetry control advantages and enabling density gradient tuning across NCD/W‐NCD interfaces for improved implosion stability. 13 C‐NCD also opens a new diagnostic platform for studying fuel‐ablator mix and yield in NIF ICF experiments through 13 N production via the 13 C(p,n) 13 N reaction. Leveraging high isotopic purity of 13 C‐NCD coatings, we perform quantitative characterization of non‐diamond carbon phases using solid‐state direct‐polarization nuclear magnetic resonance (NMR) spectroscopy. This reveals the presence of hydrogenated carbon (2.9 at.%), graphitic carbon (0.5 at.%), and tetrahedral amorphous carbon (0.4 at.%), yielding previously unavailable insight into NCD ablator composition and structure. This work clarifies the nature of NCD ablator shells and lays the foundation for new target designs that exploit 13 C‐NCD's higher density and enable diagnostics for ICF experiments.