X-ray imaging of cryogenic deuterium-tritium layers in a beryllium shell

Abstract

Solid deuterium-tritium (D-T) fuel layers inside copper-doped beryllium shells are robust inertial confinement fusion fuel pellets. This paper describes the first characterization of such layers using phase-contrast x-ray imaging. Good agreement is found between calculation and experimental contrast at the layer interfaces. Uniform solid D-T layers and their response to thermal asymmetries were measured in the Be(Cu) shell. The solid D-T redistribution time constant was measured to be 28 min in the Be(Cu) shell.

Solid deuterium–tritium surface roughness in a beryllium inertial confinement fusion shell

“…The direct-detection imaging using a micro-focus Cu anode x-ray source greatly improved upon earlier results using a scintillator for the imaging. [17] These recent images demonstrate that the surface roughness of the D-T layer can be accurately characterized using the x-ray phase-contrast enhanced imaging.…”

“…A previous study with the same shell and a smaller epoxy joint had less power in the low modes. [17] The slope of the roughness power spectrum changes between modes 5 and 7 in the current data and indicates roughness dominated by the epoxy joint transitioning to the inherent surface roughness. Therefore, only modes greater than 7 will be included in the RMS sum and analysis.…”

“…The free-space propagation method has been shown by calculation and experiment to render the solid D-T surface visible. [15,17] The first experimental images lacked the resolution and signal-to-noise ratio required to perform accurate surface roughness analysis. The imaging system has since been improved by making changes in both the x-ray source and detector.…”

“…However, characterization of solid D-T layers inside the optically opaque beryllium shell has proven difficult. [12][13][14] It was recently suggested [15] and demonstrated [16,17] that solid D-T could be characterized using phase-contrast enhanced x-ray imaging. However, those early experiments could not resolve the fine scale roughness necessary to meet NIF characterization requirements.…”

Cryogenic Hydrogen Fuel for Controlled Inertial Confinement Fusion (Review of World Results)

“…Согласно измерениям [111] характерная константа времени выравнивания DT-слоя по толщине (в области, близкой к тройной точке) составляет 28 мин. Однако поскольку процесс выравнивания слоя происходит с экспоненциальным затуханием, то полное время получения слоя с разнотолщинностью менее 1% составляет около суток.…”