Critical-Current Reduction in Thin Superconducting Wires Due to Current   Crowding
  We demonstrate experimentally that the critical current in superconducting NbTiN wires is dependent on their geometrical shape, due to current-crowding effects. Geometric patterns such as 90 degree corners and sudden expansions of wire width are shown to result in the reduction of critical currents. The results are relevant for single-photon detectors as well as parametric amplifiers. 
H. L. Hortensius, E. F. C. Driessen, T. M. Klapwijk, K. K. Berggren,   J. R. Clem
cond-mat.supr-con