A Note on the Pressure Field Within an Outward Moving Free Annulus

In both earlier and current ICF blanket designs a problem of a free annulus radial expansion emerges after microexplosion. If the annulus fractures, it could increase the total liquid surface area available for condensation by hundreds times. Whether the fragmentation can happen or not depends on the internal pressure and surface stability. In this paper a model based on incompressible cylindrically symmetric flow is used to get a theoretical solution similar to that of the Rayleigh's solution for bubble dynamics. The pressure inside the annulus is found positive at all time but the peak is lowering during the expansion. Besides, both surfaces are Taylor stable during such motion. Thus, it is concluded that an annulus in outward radial motion will not cavitate or breakup.