Effect of thermal fluctuations in the fill tube on deuterium-tritium ice layering in an inertial confinement fusion target

•The effects of thick fill tubes on the processes of seed crystal nucleation, crystal growth, β-layering and pre-ignition temperature drop.•The thermal fluctuations and material exchange brought to the capsule by the fill tube are important for understanding of the layering process and crystallization mechanism of d-T ice.•Taken steps to mitigate the negative impacts of too-thick fill tubes, and are able to obtain d-T ice that essentially satisfies the requirements. Laser nuclear fusion is extremely demanding on the quality of deuterium-tritium (D-T) ice in the capsule, and obtaining high quality d-T ice requires a combination of crystal growth and β-layering. The fill tube of the capsule not only serves as the injection function, but also plugs the fill tube after d-T fuel rapid-freezing to isolate the inside and outside of the capsule, and the shape of the fill tube is also helpful for seed crystal nucleation. In this paper, the effect of the fill tube on the processes of seed crystal nucleation, crystal growth, β-layering and rapid temperature drop before ignition is investigated. The thermal fluctuations and material exchange that can be brought about by a fill tube that is too thick to be completely plugged by d-T ice, but this has an important role in our understanding of the layering process and crystallization mechanism of d-T ice inside the capsule. We also found remedial methods to overcome the adverse effects of the fill tube and were able to obtain a d-T ice layer that basically met the requirements, which laid a good foundation for subsequent research on the d-T ice layering process.