A thermocapillary-driven method for liquid spreading inside cryogenic spherical cavities

Fuel solidification morphology in cryogenic spherical cavities critically determines the energy yield of inertial confinement fusion (ICF). However, liquid layer rupture can prematurely terminate solidification by disrupting the phase-change supply. To address this issue, this study proposes an actively regulated thermocapillary spreading strategy in which a vertical temperature gradient is applied to drive directional migration of liquid fuel along the inner cavity wall. Numerical simulations are performed to elucidate the flow behavior and gas-liquid interface evolution under controlled thermal driving. The results demonstrate that thermocapillary stress serves as the dominant mechanism governing liquid transport in cryogenic confined conditions, while the coupled effects of the size and temperature effectively regulate interfacial morphology. Under the baseline case, a specific imposed temperature gradient of 0.45 K maintains a sufficient liquid layer thickness. Furthermore, in-situ experiment results confirm the feasibility of this method in repairing liquid layer rupture and restoring continuous fuel coverage. These findings establish a thermal design framework for fuel solidification, highlighting the role of active thermocapillary regulation as a critical design element.