The movie shows the initial penetration of a flux front into a sample with clustered pinning sites. We add vortices at a constant rate to an unpinned region at the left edge of the sample, creating a gradient in vortex density that drives the vortices into the pinned region. Circles represent vortices, and lines are drawn tracing the path each vortex follows through the sample.
The parabolic pins in this sample are placed in randomly located clusters. The density of an equal number of uniformly placed pins is np = 0.80 (Pinning site density) and the pins are all of strength fp = 3.0 (Pinning site strength) Vortices that fall into the very strong pinning sites remain pinned for the rest of the movie and repel the other vortices moving through the sample. Vortices fill the pinning sites on the outer edges of the clusters of pins and prevent other vortices from reaching the pinning sites in the center of the pinning clusters. As a result, a large number of the pinning sites are ineffective and empty. The large spaces between pinning clusters offer routes of unimpeded vortex motion, and all moving vortices follow these broad channels, guided by the repulsion from the vortices pinned at the edges of the clusters.
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Created by: Cynthia Olson and Jared Groth
Last modified: 12/18/96