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  • 1
    Electronic Resource
    Electronic Resource
    Detection of Single Quanta of Circulation in Rotating Helium II (1958)
    [s.l.] : Nature Publishing Group
    Nature 181 (1958), S. 1524-1525 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The apparatus consists essentially of a brass tube (internal diameter, 26, 5 mm.) down the centre of which is stretched a fine beryllium-copper wire (diameter, 2a, 0-001 in. ; 5 cm. long). The tube can be placed in a cryostat and filled with liquid helium, and the whole tube assembly can be rotated ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1811524a0
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal excitation of waves on quantized vortices (1985)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 28 (1985), S. 498-504 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We consider the problem of the thermal excitation of vortex waves on quantized vortex lines and rings. We discover that this problem, which has been largely neglected in the past, apparently presents a "free energy catastrophe'' above about 1.85 K; that is, if one naively proceeds to compute the thermally induced vortex waves on rings or lines, the entropy of the waves becomes so large that the free energy of vortices is driven negative, and superfluidity could not exist. Various mechanisms for eliminating this problem are considered; it appears to be necessary to consider the relevant system to be the vortex plus the bath in order to avoid double counting of states. We comment on the relevance of this calculation to the problem of thermally induced nucleation of vortices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865113
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  • 3
    Electronic Resource
    Electronic Resource
    Friction on quantized vortices in helium II. A review (1983)
    Springer
    Journal of low temperature physics 52 (1983), S. 189-247 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present an analysis of recent data on friction and drag on quantized vortices in helium II. From these data, we deduce values of the phenomenological and microscopic coefficients of friction on vortex lines and rings over a wide range of temperatures at the saturated vapor pressure. We demonstrate that the microscopic parameters are unusually sensitive to the input data. We include brief discussions of the vortex core parameter, and present the results of precision fits of a number of thermodynamic and transport properties of He II which are used in mutual friction calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682247
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  • 4
    Electronic Resource
    Electronic Resource
    Ions trapped near the free surface of superfluid helium: A review (1995)
    Springer
    The European physical journal 98 (1995), S. 299-301 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Suitable ions or other charged particles can be trapped electrostatically just below the free surface of superfluid4He. Examples of such particles are the socalled “negative ion”, which is an electron in a bubble, and the so-called “positive ion”, which is a4He+ ion surrounded by a small region (“snowball”) of solid helium. The trapping mechanism can be used to create two-dimensional pools of ions. Three types of experiment can be carried out with such pools: those that relate to the ionic structure; those in which the ions are used as probes of the properties of the superfluid helium; and those in which the pools are studied as examples of simple two-dimensional fluids or solids. Experiments that have been carried out so far are reviewed, and prospects for the future are assessed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01338393
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  • 5
    Electronic Resource
    Electronic Resource
    Turbulence in a Superfluid (2000)
    Springer
    Journal of low temperature physics 121 (2000), S. 367-376 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Turbulence in a superfluid was first observed and recognized in the 1950s, when it was established that the mutual friction accompanying a counterflow of the two fluids in helium II was due to the presence of a tangled turbulent array of quantized vortex lines in the superfluid component. This type of turbulence has no classical analogue, and it is fairly well understood. More recently other types of turbulence in helium II have been studied that do have classical analogues; these studies have included experiments, theories and computer simulations. An introductory account of this more recent work is given, with particular reference to turbulence produced by flow through a grid. There are similarities in comparison with classical turbulence for large length scales; but there must be important differences on length scales comparable with or less than the vortex line spacing. Emphasis is placed on behaviour at these small length scales (where quantum effects dominate), on a number of unsolved problems, and on the need for experiments at very low temperatures, where the influence of the normal fluid is likely to be small. The case for studying turbulence in superfluid 3 He-B is mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017593428347
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  • 6
    Electronic Resource
    Electronic Resource
    Iordanskii and Lifshitz-Pitaevskii Forces in the Two-Fluid Model (2000)
    Springer
    Journal of low temperature physics 121 (2000), S. 411-416 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It has been known since the pioneering work of Onsager and Feynman that the statistical mechanics and dynamics of vortices play an essential role in the behavior of superfluids and superconductors. However, the theory of vortices in quantum fluids remains in a most unsatisfactory state, with many conflicting results in the literature. In this paper we review the theory of Thouless, Ao and Niu, which gives an expression for the total transverse force acting on a quantized vortex that is in apparent disagreement with the word of lordanskii and of Lifshitz and Pitaevskii. In particular, no transverse force proportional to the asymptotic normal fluid velocity was found. We use two-fluid hydrodynamics to study this discrepancy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017553814235
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  • 7
    Electronic Resource
    Electronic Resource
    The ripplon-limited mobility of ions trapped below the free surface of superfluid helium (1994)
    Springer
    Journal of low temperature physics 97 (1994), S. 349-364 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New measurements are reported of the damping of two-dimensional plasma resonances in circular pools of negative ions trapped below the free surface of superfluid4He at temperatures down to about 15 mK. At the lowest temperatures the damping is determined by a ripplon-limited ionic mobility. The observed dependence of this mobility on temperature and trapping depth is shown to be similar to that found in earlier experiments on pools of positive ions. A theory of the ripplon-limited mobility is described, based on a calculation of the scattering of capillary waves by a single ion. It is shown that the theory accounts for the observed temperature and depth dependences, but that it yields absolute values that are too large by a factor of about 10 for both species of ion. Possible reasons for this discrepancy are discussed, but no satisfactory explanation has been found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00754298
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  • 8
    Electronic Resource
    Electronic Resource
    Vortex configurations in a freely rotating superfluid drop (1995)
    Springer
    Journal of low temperature physics 98 (1995), S. 47-65 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The equilibrium configurations of a single vortex in a freely rotating superfluid drop have been determined. The potential barrier to vortex nucleation has also been examined. A freely rotating drop is constrained to rotate at a fixed angular momentum, as opposed to fluid in a rotating vessel, where the vessel is usually constrained to rotate at fixed angular velocity. Vortex configurations that minimize the free energy have been found for a range of angular momenta. These configurations are not necessarily on the axis of rotation as is the case for a vessel rotating at a constant angular velocity. The nucleation of a vortex is shown to be opposed by a barrier in the free energy. This barrier narrows and decreases in height as the angular momentum of the drop is increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00754067
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  • 9
    Electronic Resource
    Electronic Resource
    The lifetime of interacting ripplons on the surface of superfluid helium (1993)
    Springer
    Journal of low temperature physics 92 (1993), S. 239-261 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ripplons, or quantised surface waves, are known to exist on the surface of superfluid4He. We follow the work of previous authors and describe these excitations by quantising the classical expressions for the energy of such surface waves. The resulting quantum mechanical Hamiltonian consists of a term describing free ripplons, together with an additional term (cubic in the ripplon variables) which induces the mutual scattering of ripplons and has the effect of causing any one ripplon to have a finite lifetime. We present here a many body calculation which investigates the lifetimes of ripplons at a temperatureT=0 and the lifetimes of acoustic ripplons at a finite temperature. In these two limits our calculation agrees with separate calculations performed by previous authors carried out at the two limits; however our calculations readily allow a sensible interpolation between these limits. We report hitherto unsuspected divergences in the calculations at finite temperature and we comment on the relevance of such calculations to the results of recent experiments which yield information on the ripplon lifetimes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682340
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