Regular Flux Jumps in the Mixed State of Niobium

Abstract
Unusually regular flux jumps are reported in the mixed state of niobium. The most prominent experimental effects produced by these flux jumps are thermal spikes. The effect of the flux jumps on the ultrasonic attenuation coefficient is also reported. The regularity of of the interval between the flux jumps is believed to be caused by a surface barrier. The thermal spikes are interpreted as being due to avalanching of the flux lines at the surface barrier.