  A percolation transition in the vortex state of a superconducting 2H-NbSe2
crystal is observed in the regime where vortices form a heterogeneous phase
consisting of ordered and disordered domains. The transition is signaled by a
sharp increase in critical current that occurs when the volume fraction of
disordered domains, obtained from pulsed measurements of the current-voltage
characteristics, reaches the value Pc= 0.26. Measurements on different vortex
states show that while the temperature of the transition depends on history and
measurement speed, the value of Pc and the critical exponent characterizing the
approach to it, r =1.97 $\pm$ 0.66, are universal.
