VORTEX LAYER ON THE INTERFACE BETWEEN THE A-PHASE AND B-PHASE IN SUPERFLUID HE-3

Using NMR techniques we monitor the structure and number of vortices in a cylindrical container, rotating at constant angular velocity OMEGA, before and after the passage of the A-B interface. The initial A phase contains the equilibrium number of vortices. The final B phase is found to have a deficit of vortices which depends nonmonotonically on the measured time t(AB) of the A --> B transition. We argue that a vortex layer is formed in front of the moving A-B interface. The measured vortex deficit can be understood by analyzing the stability of the layer.