Trapping Flux Avalanches in Nb Films by Circular Stop-Holes of Different Size

Dendritic flux avalanches triggered by thermomagnetic instabilities in Nb superconducting films have been limited by inclusion of circular holes of different diameters produced by optical lithography. We have observed a compromise between dendrite and hole sizes, for which avalanches are effectively arrested. For holes much smaller than the dendrites, only individual branches are stopped. Large holes are not a good solution, since they change the film geometry. A noteworthy trapping is observed at the holes with diameter between the width of an individual branch and the size of a whole dendrite. The present work shows the trend to optimize stop-holes for limiting thermomagnetic avalanches in superconducting films.