TERMIUM Plus^®

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Liquid helium existing as a superfluid below the transition point of approximately 2. 2°K at 1 atmosphere and having extremely low viscosity and extremely high thermal conductivity.  1, fiche 1, Anglais, - helium%20II

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Superfluid Helium What Is It? As the temperature of helium gas is lowered to approximately 5. 2°K, a phase transition to ordinary liquid helium(He I) takes place. The latter is unremarkable and its behavior is identical to any other liquid. As temperature is lowered further(at moderate pressures) helium does not solidify. Rather, it undergoes a phase change to a second liquid phase He II at temperature of about 2. 17°K.... the He II phase persists all the way to absolute zero.... The He II phase is referred to as superfluid helium because of its remarkable properties, including the ability to flow through microscopic passages [holes as small as 10^-7 centimeters in diameter] with no apparent friction; the quantization of vortices; and the ability to support four wave modes : first sound which is analogous to sound in ordinary gases and liquids, second sound which carries temperature and entropy perturbations with virtually no pressure variations, third sound which are waves on thin films, and fourth sound which are acoustic-like waves in the "superfluid" component of He II.  5, fiche 1, Anglais, - helium%20II

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Superfluid Helium(He II, Superfluidity). Superfluid or Helium II technology has been developed quite successfully in the past decades in both aerospace and magnet cooling systems.... Other strange properties of superfluid include the Rollin film, mechanocaloric effect and fountain effect.  6, fiche 1, Anglais, - helium%20II

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On désigne par Hélium II, l'hélium en dessous de T_lambda. L'hélium superfluide a la propriété bien connue d'avoir une viscosité nulle (il peut traverser de très fins capillaires sans frottement; il a la capacité de pouvoir remonter le long des parois, etc.).  2, fiche 1, Français, - h%C3%A9lium%20II

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En refroidissant sous la pression atmosphérique de l'hélium ordinaire [...], on constate qu'il se liquéfie à 4,2 K. Le liquide ainsi produit (hélium I) n'a rien de particulier, sa viscosité est faible, mais il se comporte comme tous les liquides usuels. En refroidissant ce liquide au-dessous de 2,17 K, on voit apparaître une phase liquide aux propriétés exceptionnelles (hélium II) souvent désignée sous le nom d'hélium superfluide en raison de sa viscosité pratiquement nulle. L'hélium II est également caractérisé par une résistivité thermique pratiquement nulle, on dit que c'est un supraconducteur thermique.  6, fiche 1, Français, - h%C3%A9lium%20II

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Fiche 2,  Justifications,  Anglais

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The superfluid liquid helium cryostat is based on ISO technology, providing temperatures down to 1. 7 K for the payload.  1, fiche 2, Anglais, - superfluid%20liquid%20helium%20cryostat

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The FIRST [Far InfraRed and Submillimetre Telescope] payload is housed inside the cryostat, which contains 2560 l of superfluid helium at 1. 65 K, giving a predicted cryostat lifetime of 4. 5 years in the L2 orbit.  2, fiche 2, Anglais, - superfluid%20liquid%20helium%20cryostat

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Grâce à un cryostat d'hélium liquide de type ISO, FIRST/Herschel pourra embarquer des récepteurs supraconducteurs à l'hélium, bolomètres ou jonctions SIS.  2, fiche 2, Français, - cryostat%20d%27h%C3%A9lium%20liquide%20superfluide

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While the microscope is capable of operation at temperatures varying from 1. 5 to 300 K, all of the results of this article are obtained with the microscope immersed in 1. 5 K superfluid liquid helium.  1, fiche 3, Anglais, - superfluid%20liquid%20helium

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A remarkable transition occurs in the properties of liquid helium at the temperature 2. 17 K, called the "lambda point" for helium. Part of the liquid becomes a "superfluid", a zero viscosity fluid which will move rapidly through any pore in the apparatus.  2, fiche 3, Anglais, - superfluid%20liquid%20helium

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L'objectif principal est de reproduire de façon la plus fidèle possible les conditions réelles d'utilisation des capteurs dans le LHC [Large Hadron Collider] : les thermomètres sont irradiés à basse température (immergés dans l'hélium liquide superfluide à 1,8 K), avec des doses totales (10¹⁵ n.cm^-2) et des spectres en énergie (1 à 10 MeV) de neutrons proches de ceux attendus dans le collisionneur.  1, fiche 3, Français, - h%C3%A9lium%20liquide%20superfluide

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... liquid helium [is a] gas extracted from selected natural gas wells. ... [It is] used for: Studies of low temperature material properties. -Superconducting magnets. -Superconducting sensors (i.e. SQUIDS).  3, fiche 4, Anglais, - liquid%20helium

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The temperature of liquid helium is normally 4 K, that is, four degrees above absolute zero.  2, fiche 4, Anglais, - liquid%20helium

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Liquid helium exists below 4.2K and is used to cool superconductors below their transition temperatures.  4, fiche 4, Anglais, - liquid%20helium

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A remarkable transition occurs in the properties of liquid helium at the temperature 2. 17 K, called the "lambda point" for helium. Part of the liquid becomes a "superfluid", a zero viscosity fluid which will move rapidly through any pore in the apparatus.  5, fiche 4, Anglais, - liquid%20helium

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LHe: The symbol for liquid helium.  2, fiche 4, Anglais, - liquid%20helium

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L'hélium liquide (-270 °C) est reçu directement liquéfié. Ce gaz a la température d'ébullition la plus basse. Son absence de viscosité à très basse température est remarquable. Il est très peu réactif : il est utilisé pour pressuriser les ergols liquides en haut des réservoirs et pour commander certaines vannes.  2, fiche 4, Français, - h%C3%A9lium%20liquide

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Only such instruments as superconducting gravimeter, ring laser gyroscope or superfluid helium gyroscope, are capable of measuring the motion of the IRP [instantaneous rotation pole] but they are still far from the operational stage.  2, fiche 5, Anglais, - superfluid%2Dhelium%20gyroscope

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When the temperature sinks on a cold winter's day water vapour becomes water and water becomes ice. These so-called phase transitions and the changed states of matter can be roughly described and understood with classical physics. What happens when the temperature falls is that the random heat movement in gases, liquids and solid bodies ceases. But the situation becomes entirely different when the temperature sinks further and approaches absolute zero,-273. 15°C. In samples of liquid helium what is termed superfluidity occurs, a phenomenon that cannot be understood in terms of classical physics. When a liquid becomes superfluid its atoms suddenly lose all their randomness and move in a coordinated manner in each movement. This causes the liquid to lack all inner friction : It can overflow a cup, flow out through very small holes, and exhibits a whole series of other non-classical effects. Fundamental understanding of the properties of such a liquid requires an advanced form of quantum physics, and these very cold liquids are therefore termed quantum liquids...  2, fiche 6, Anglais, - quantum%20liquid

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