QFS 2016 Book of Abstracts

Abstracts

P3.8 Visualization of a vortex tangle using a quasiparticle camera in superfluid 3 He-B S.L. Ahlstrom, D.I. Bradley, E.A. Guise, R.P. Haley, G.R. Pickett, M. Poole, V. Tsepelin, A.J. Woods Department of Physics, Lancaster University, Lancaster, LA1 4YB, UK We present our measurements on visualising a vortex tangle created by a vibrating wire in superfluid 3 He-B. Measurements were carried at low temperatures where the normal component of the superfluid comprises ballistic quasiparticles. We illuminate the tangle by a quasiparticle beam and detect its presence via the ‘shadows’ cast by the Andreev scattering of incident quasiparticles by the vortices. The ‘shadows’ are measured by a 5x5 detector made from 25 miniature quartz tuning forks. Our measurements and numerical simulations show that the profile of quasiparticle beam is independent on the emitted beam power and that produced tangle is non-isotropic with respect to the motion of the wire. P3.9 Formation of Quantum Turbulence Produced by Vibrating Wire in Superfluid 4 He H. Yano, K. Ogawa, Y. Chiba, K. Obara, and O. Ishikawa Osaka City University, Graduate School of Science, Osaka 558-8585, Japan We report the formation of turbulence produced by a vibrating wire in superfluid 4 He, by studying vortex emissions with a ring size larger than 38 μ m in diameter as a function of generation power of vortex lines. An emission rate of vortex rings from the turbulence remains low until the beginning of high-rate emissions, suggesting that a portion of vortex lines produced by the wire is provided to the formation of a vortex tangle until an equilibrium is established. The formation time and the emission rate after the formation are proportional to − 1 . 2 and 2 , respectively, where is the generation power. These dependences may emerge from quantum turbulence with constant energy flux.

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