Experiments in superconducting vortex avalanches

We detect vortex avalanches in superconducting Nb when an external field is slowly ramped up. Through the combination of micro-Hall probe magnetometry and Magneto-optical imaging, we are able to visualize the magnetic field “landscape” where the “local” vortex avalanches take place. We measure the avalanche size statistics at several locations in the magnetic landscape, comprising a number of events orders of magnitude larger than previously reported. The distributions of avalanche sizes show a nearly power-law character, and their details are strikingly independent from the specific features of the “magnetic landscape” where they take place. Some experiments in order to find spatial-temporal correlations between avalanches are also presented.