Vortices in ³He-A in Restricted Geometries

We have studied vortices in ³He-A between a stack of plates with about 20 Ɓm spacing and within an array of long cylinders of 0.5 mm diameter. Taking advantage of localised surface spin-wave modes, trapped by the\hat葧 texture near the walls, we have determined the critical velocity for vortex formation as well as the pinning velocity for vortices in the plate geometry. In 0.5-mm cylinders vortices are similar to those in the bulk liquid but a broad hysteresis in the number of vortices (1-4/tube) is observed when the cryostat is accelerated or decelerated.