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Title: Quantum turbulence measurements in 3He-B at ultralow temperatures
Author: Potts, David Andrew
Awarding Body: Lancaster University
Current Institution: Lancaster University
Date of Award: 2012
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This thesis describes experiments conducted on 3He B-phase in the μK temperature regime designed to thermally detect the decay of quantum turbulence. A vibrating wire grid and vibrating wire resonator housed inside a black body radiator (BBR) are driven to high velocities so as to produce both turbulence and thermal quasiparticles originating from pair-breaking of the Cooper pairs. Careful calibration of the experimental parameters allows a direct quantitative measurement of the power leaving the radiator. Measurements reveal that at high grid and wire velocities, an additional, slowly dissipating, mechanism is present which cannot be accounted for by the simple thermal recovery of the radiator from quasiparticle heating. This mechanism is attributed to a slowly-decaying quantum turbulent tangle in the radiator. Previous experiments concerned with the decay of quantum turbulence relied on measurements of an inferred vortex line density. The current experiment directly measures the power released as a quantum turbulent tangle decays and so offers a particularly direct test of the current decay models. The measurements obtained from the current experiment are compared directly with the standard model for the decay of classical turbulence involving a cascade of energy across an inertial range from large to small length scales wherein the energy is dissipated. The results are found to fit the model remarkably well and a Kolmogorov constant is extracted from the fits which is very similar to values attributed to classical fluids . This is despite the fact that the absence of a normal fluid component in the experimental regime ensures that the classical viscous dissipation mechanism is impossible.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available