We describe measurements of the decay of pure superfluid turbulence in superfluid 3 He-B, in the low temperature regime where the normal fluid density is negligible. We follow the decay of the turbulence generated by a vibrating grid as detected by vibrating wire resonators. Despite the absence of any classical normal fluid dissipation processes, the decay is consistent with turbulence having the classical Kolmogorov energy spectrum and is remarkably similar to that measured in superfluid 4 He at relatively high temperatures. Further, our results strongly suggest that the decay is governed by the superfluid circulation quantum rather than kinematic viscosity.PACS numbers: 67.57. Fg, 67.57.De, 67.57.Hi In this paper we present the first quantitative measurements of the decay of turbulence in a pure superfluid system. This is a subject of considerable interest since no conventional dissipation mechanisms are available.In a classical fluid, turbulence at high Reynolds numbers is characterized by a range of eddy sizes obeying the well-known Kolmogorov spectrum. On large length scales the motion is dissipationless, whereas on small scales viscosity comes into play. Decay of the turbulence proceeds as energy is transferred by non-linear interactions from the largest non-dissipative length scales d (typically the size of the turbulent region) to smaller length scales where the motion is dissipated by viscous forces. The dissipation per unit volume is given by ρνω 2 where ρ is the fluid density, ν the kinematic viscosity and ω 2 the mean square vorticity [1]. An interesting question, which has received much theoretical speculation [1], is what happens in a pure superfluid with no viscous interactions?Conceptually, turbulence in a superfluid is greatly simplified. Superfluids such as He-II and 3 He-B are described by macroscopic wavefunctions with a well defined phase φ. The superfluid velocity is determined by gradients of the phase, v S = ( /m)∇φ where m is the mass of the entities constituting the superfluid (the mass of a 4 He atom for He-II or twice the mass of a 3 He atom, 2m 3 , for the Cooper pairs in 3 He-B). Consequently, in contrast to classical fluids, superfluid motion is inherently irrotational and vorticity may only be created in the superfluid by the injection of vortex lines. A superfluid vortex is a line defect around which the phase changes by 2π (ignoring here more complex structures such as in 3 He-A). The superfluid order parameter is distorted within the relatively narrow core of the vortex where all the circulation is concentrated. The superfluid flows around the core with a velocity, at distance r, given by v S = /mr corresponding to a quantized circulation κ = h/m. Vortex lines are topological defects. They cannot terminate in free space, and therefore must either form loops or * Electronic Address: s.fisher@lancaster.ac.uk terminate on container walls. Turbulence in a superfluid takes the form of a tangle of vortex lines.Superfluid hydrodynamics is further simplified by the superfluid compon...

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We report a transition in the vorticity generated by a grid moving in the B phase of superfluid 3He at T<

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