Liquid helium

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Liquid helium

Liquid helium in a transparent bowl, cooled below the Lambda point, where it exhibits properties of superfluidity
Properties
He
Molar mass 4.002602 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures. Liquid helium may show superfluidity.

At standard pressure, the

kilopascals) is about 125 g/L (0.125 g/ml), or about one-eighth the density of liquid water.[1]

Liquefaction

Helium was first liquefied on July 10, 1908, by the Dutch physicist

cryogenic refrigerant (which is used in cryocoolers), and liquid helium is produced commercially for use in superconducting magnets such as those used in magnetic resonance imaging (MRI), nuclear magnetic resonance (NMR), magnetoencephalography (MEG), and experiments in physics, such as low temperature Mössbauer spectroscopy. The Large Hadron Collider contains superconducting magnets that are cooled with 120 tonnes of liquid helium.[3]

Liquified helium-3

See also: Fermionic condensate § Helium-3 superfluid

A

superfluid
. These Cooper pairs are substantially larger than the interatomic separation.

Characteristics

Phase diagram of helium-4
ground state energy can decrease by a naturally occurring increase in its average interatomic distance. However at greater distances, the effects of the interatomic forces in helium are even weaker.[4]

Because of the very weak interatomic forces in helium, the element remains a liquid at atmospheric pressure all the way from its

superfluids. (See the table below.)[4] Liquid helium can be solidified only under very low temperatures and high pressures.[5]

Liquid helium-4 and the rare helium-3 are not completely

thermodynamic enthalpy
by separating.

At extremely low temperatures, the superfluid phase, rich in helium-4, can contain up to 6% helium-3 in solution. This makes the small-scale use of the

millikelvins.[6][8]

Superfluid helium-4 has substantially different properties from ordinary liquid helium.

History

In 1908, Kamerlingh-Onnes succeeded in liquifying a small quantity of helium. In 1923, he provided advice to the Canadian physicist John Cunningham McLennan, who was the first to produce quantities of liquid helium almost on demand.[9]

In 1932 Einstein reported that the liquid helium could help in creating an atomic bomb.

Important early work on the characteristics of liquid helium was done by the Soviet physicist Lev Landau, later extended by the American physicist Richard Feynman.

In 1961, Vignos and Fairbank reported the existence of a different phase of solid helium-4, designated the gamma-phase. It exists for a narrow range of pressure between 1.45 and 1.78 K.[10]

Data

Properties of liquid helium Helium-4 Helium-3
Critical temperature[4]
 5.2 K (−267.95 °C) 3.3 K (−269.85 °C)
Boiling point at one atmosphere[4] 4.2 K (−268.95 °C) 3.2 K (−269.95 °C)
Minimum melting pressure[11] 25 bar (360 psi) 29 bar (420 psi) at 0.3 K (−272.850 °C)
Superfluid transition temperature at saturated vapor pressure
 2.17 K (−270.98 °C)[12] 1 mK in the absence of a magnetic field[13]

Gallery

  • Liquid helium (in a vacuum bottle) at 4.2 K (−268.95 °C) and 1 bar (15 psi) boiling slowly.
    Liquid helium (in a vacuum bottle) at 4.2 K (−268.95 °C) and 1 bar (15 psi) boiling slowly.
  • Lambda point transition: as the liquid is cooled down through 2.17 K (−270.98 °C), the boiling suddenly becomes violent for a moment.
    Lambda point transition: as the liquid is cooled down through 2.17 K (−270.98 °C), the boiling suddenly becomes violent for a moment.
  • Superfluid phase at temperature below 2.17 K (−270.98 °C). In this state, the thermal conductivity is extremely high. This causes heat in the body of the liquid to be transferred to its surface so quickly that vaporization takes place only at the free surface of the liquid. Thus, there are no gas bubbles in the body of the liquid.
    Superfluid phase at temperature below 2.17 K (−270.98 °C). In this state, the
    thermal conductivity
    is extremely high. This causes heat in the body of the liquid to be transferred to its surface so quickly that vaporization takes place only at the free surface of the liquid. Thus, there are no gas bubbles in the body of the liquid.
  • The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the bowl and down on the outside. A drop forms. It will fall off into the liquid helium below. This will repeat until the cup is empty—provided the liquid remains superfluid.
    The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the bowl and down on the outside. A drop forms. It will fall off into the liquid helium below. This will repeat until the cup is empty—provided the liquid remains superfluid.

See also

References

  1. ^ "The Observed Properties of Liquid Helium at the Saturated Vapor Pressure". University of Oregon. 2004.
  2. ^ Wilks (1967), p. 7.
  3. ^ "Cryogenics: Low temperatures, high performance". CERN. 28 June 2023.
  4. ^ a b c d Wilks (1967), p. 1.
  5. ISBN 9780121764807
    .
  6. ^
    doi:10.1103/PhysRevLett.15.773
    .
  7. PMID 10058756
    .
  8. ^ Wilks (1967), p. 244.
  9. ^ "THE LIFE OF SIR JOHN CUNNINGHAM McLENNAN Ph.D, F.R.S.C, F.R.S., O.B.E., K.B.E. (1867 - 1935)". University of Toronto Physics. Archived from the original on 2006-05-05.
  10. doi:10.1103/PhysRevLett.6.265
    .
  11. ^ Wilks (1967), pp. 474–478.
  12. ^ Wilks (1967), p. 289.
  13. ^ Dieter Vollhart & Peter Wölfle (1990). The Superfluid Phases of Helium 3. Taylor and Francis. p. 3.
General

External links
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