Decay of turbulence generated by spin-down to rest in superfluid 4He

We report on the extension of the experiments (P.M. Walmsley et al., Phys. Rev. Lett. 99:265302, 2007) on the decay of quasiclassical turbulence generated by an impulsive spin-down from angular velocity Ω to rest of superfluid 4He in a cubic container at temperatures 0.15 K-1.6 K. The density of quantized vortex lines L is measured by scattering negative ions. Following the spin-down, the maximal density of vortices is observed after time t ∼ 10Ω -1. By observing the propagation of ions along the axis of the initial rotation, the transient dynamics of the turbulence spreading from the perimeter of the container into its central region is investigated. Nearly homogeneous turbulence develops after time t ∼ 100Ω -1 and decays as L ∝ t -3/2. The effective kinematic viscosity in T = 0 limit is v = 0.003κ, where κ = 10 -3 cm 2s -1 is the circulation quantum. © Springer Science+Business Media, LLC 2008.