NUMERICAL-CALCULATION OF ELASTIC PINNING PARAMETERS BY POINT PINS

One-dimensional numerical simulations of the pinned vortex lattice hav e been carried out using an inverted model in which widely spaced and weak point pinning centres are distorted by a rigid lattice. This allo ws us to simulate a much larger array than if we had to find the posit ion of each vortex separately. Using steepest descent and molecular dy namics methods, the Labusch parameter is found to have similar power l aw dependencies on the density of pins and elementary pinning force to the bulk pinning force. This implies that the maximum reversible disp lacement is a constant and it is found to be roughly 0.2 of a vortex s pacing. The results are in agreement with the Larkin-Ovchinnikov theor y of collective pinning. Quasi-static shifting of the pins over the ri gid vortex lattice allowed the size of avalanches in the flow state to be measured. The distribution of avalanche sizes displays power law b ehaviour over several decades.