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SUMMARY:Experiments with tangles of quantized vortex lines in superfluid 4
 He in the T=0 limit - Golov\, A (University of Manchester)
DTSTART:20121206T160500Z
DTEND:20121206T162500Z
UID:TALK41883@talks.cam.ac.uk
CONTACT:Mustapha Amrani
DESCRIPTION:In our experiments\, we can create dense ensembles of quantize
 d vortex lines of various degrees of polarization and entanglement\, and m
 onitor either their free decay or steady state whilst forcing continuously
 . The superfluid is forced either by macroscopic bodies that generate larg
 e-scale vortex bundles or by microscopic particles (injected ions) that ge
 nerate uncorrelated vortices. Steady net polarization can be introduced by
  conducting the experiment in a rotating container. The characterization o
 f vortex tangles is done via measurements of the transport of injected ion
 s through them. The following types of tangles will be reviewed: homogeneo
 us random tangles (no large-scale polarization)\, homogeneous quasi-classi
 cal turbulence (tangles in which the dominant energy is concentrated in la
 rge-scale bundles-eddies)\, steadily polarized anisotropic tangles of eith
 er high or low polarization\, beams of parallel vortex rings. There is no 
 viscous dissipation in the T=0 limit\; the dyn amics of individual vortex 
 lines is conservative except for the Kelvin waves of extremely small wavel
 engths. The scenario and rate of the evolution of different vortex ensembl
 es largely depend on the mutual polarization of vortioces that affects the
  frequency of their reconnections. Further plans to investigate the micros
 copic processes of the quantum cascade (Kelvin wave cascade) and visualiza
 tion of individual vortex cores will be outlined.\n
LOCATION:Seminar Room 1\, Newton Institute
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