A damping length scale for superfluid turbulence

We show that a damping length scale l(sd) exists for superfluid turbulence at nonzero temperatures, where the supertluid component is coupled by mutua l friction to a viscous normal fluid. Superfluid vortex structures at lengt h scales smaller than l(sd) will lose energy to the normal fluid and will b e dissipated. We derive the Reynolds-number dependence of this length scale and discuss the consequences of this length scale for the possible existen ce of a Kolmogorov -5/3 power law for the superfluid energy spectrum.