Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

Pyotr Leonidovich Kapitsa Pyotr Leonidovich Kapitsa or Peter Kapitza (Russian: Пётр Леонидович Капица, Romanian: Petre Capița ( – 8 April 1984) was a leading Soviet physicist and Nobel laureate, best known for his work in low-temperature physic ...

Don Misener Don Misener (A.D. Misener) (1911-1996) was a physicist. Along with Pyotr Leonidovich Kapitsa and John F. Allen, Misener discovered the superfluid phase of matter in 1937. Misener was a graduate student at the University of Toronto in 1935. He j ...

superfluid Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two ...

phase of matter In the physical sciences, a phase is a region of space (a thermodynamic system), throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, magnetiza ...

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

Mond Laboratory Modified Newtonian dynamics (MOND) is a hypothesis that proposes a modification of Newton's law of universal gravitation to account for observed properties of galaxies. It is an alternative to the hypothesis of dark matter in terms of explaining ...

Cambridge Cambridge ( ) is a College town, university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cam ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

Winnipeg Winnipeg () is the capital and largest city of the province of Manitoba in Canada. It is centred on the confluence of the Red and Assiniboine rivers, near the longitudinal centre of North America. , Winnipeg had a city population of 749, ...

University of Manitoba The University of Manitoba (U of M, UManitoba, or UM) is a Canadian public research university in the province of Manitoba.University of Manitoba The University of Manitoba (U of M, UManitoba, or UM) is a Canadian public research university in the province of Manitoba. and undertook his PhD working with John McLennan about superconductivity. He there developed and built his first cryostat which was taken by John McLennan for a demonstration of superconductivity in a public lecture to the Royal Institution in

London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...

. He obtained his PhD degree in 1933. With a two-year US National Research Council Fellowship which he obtained in 1933, he went to work as a postdoctoral researcher at

Caltech The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...

between 1933 and 1935. In 1935, he joined the Mond Laboratory of the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

in

Cambridge Cambridge ( ) is a College town, university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cam ...

to work with

Pyotr Kapitsa Pyotr Leonidovich Kapitsa or Peter Kapitza ( Russian: Пётр Леонидович Капица, Romanian: Petre Capița ( – 8 April 1984) was a leading Soviet physicist and Nobel laureate, best known for his work in low-temperature physics ...

on low temperature experiments. However, Kapitsa could not return from a visit of his mother in the Soviet Union in 1934 and never returned to Cambridge. So John Allen worked independently of Kapitsa on properties of helium at very low temperatures and published reports on the discovery of

superfluidity Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two ...

in helium which were published side by side in Nature in January 1938. Despite the independent discovery at about the same time, the Nobel prize for

Superfluidity Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two ...

was awarded only to Kapitsa in 1978. He stayed in Cambridge until 1947, when he took up an appointment as a professor in natural philosophy at the

University of St Andrews (Aien aristeuein) , motto_lang = grc , mottoeng = Ever to ExcelorEver to be the Best , established = , type = Public research university Ancient university , endowment ...

,

Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

in 1947. In 1949, he was elected a

Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathemat ...

. During his tenure at the University of St Andrews, he was twice dean of the Faculty of Science, and oversaw the creation of a separate Faculty of Applied Science at Dundee as well as the development of the Science complex on the North Haugh in St Andrews, which opened in 1966. He was chair of the Very Low Temperature Commission of the

International Union of Pure and Applied Physics The International Union of Pure and Applied Physics (IUPAP ) is an international non-governmental organization whose mission is to assist in the worldwide development of physics, to foster international cooperation in physics, and to help in the ...

from 1966 to 1969 and member of the British National Committee for Physics of the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

. In 1978, he retired, retaining emeritus status until his death. He died in St Andrews in Fife of a stroke. Allen received an honorary doctorate from Heriot-Watt University in 1984. The building of the School of Physics and Astronomy of the University of St Andrews is named after John Allen, as is the library in the J.F. Allen building. Allen died of a stroke on 22 April 2001.

Family

Allen married his wife, Elfriede Hiebert, in 1933. The two divorced later. They had one adopted son.

Scientific work

During his work on low temperature physics, Allen developed a number of techniques that are still in use today. In 1937, he introduced the

O-ring An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more par ...

for use as a seal for vacuum systems. He further invented in 1947 indium gaskets to create leak tight seals for low temperature applications. In 1937, Allen discovered

superfluid Superfluidity is the characteristic property of a fluid with zero viscosity which therefore flows without any loss of kinetic energy. When stirred, a superfluid forms vortices that continue to rotate indefinitely. Superfluidity occurs in two ...

helium together with his student

Don Misener Don Misener (A.D. Misener) (1911-1996) was a physicist. Along with Pyotr Leonidovich Kapitsa and John F. Allen, Misener discovered the superfluid phase of matter in 1937. Misener was a graduate student at the University of Toronto in 1935. He j ...

in the Mond laboratory in Cambridge, independent of

Pyotr Kapitsa Pyotr Leonidovich Kapitsa or Peter Kapitza ( Russian: Пётр Леонидович Капица, Romanian: Petre Capița ( – 8 April 1984) was a leading Soviet physicist and Nobel laureate, best known for his work in low-temperature physics ...

in Moscow. His student, Ernest Ganz, later observed the second sound in liquid helium, and Allen and his collaborator possibly also measured the third sound that occurs in thin films, however they did not report their results. When

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

broke out and he worked on projects supporting the army. During

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

, this included the development of on-board oxygen generators for bombers, and a variable time fuse for anti-aircraft shells. Allen also used a

movie camera A movie camera (also known as a film camera and cine-camera) is a type of photographic camera that rapidly takes a sequence of photographs, either on an image sensor or onto film stock, in order to produce a moving image to project onto a movie sc ...

to film his experiments, such as the superfluid helium fountain, which he discovered in 1938 with the help of a pocket flashlight. Over a ten-year period Allen made a movie of the various two-fluid phenomena exhibited by liquid

helium-4 Helium-4 () is a stable isotope of the element helium. It is by far the more abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consis ...

. The photography of these effects was a real challenge, because liquid helium-4 is essentially transparent. This unique colour movie (the fifth edition was completed in 1982) is one of Allen's great legacies to physics. His was an early user of moving images to document experiments and inform students and the general public.

Pictorial biography

References

{{DEFAULTSORT:Allen, John F. Canadian physicists Fellows of the Royal Society Fellows of the Royal Society of Edinburgh People from Winnipeg Canadian people of Scottish descent Scottish physicists Academics of the University of St Andrews Canadian expatriate academics in the United Kingdom 1908 births 2001 deaths Superfluidity

Life

Family

Scientific work

Pictorial biography

See also

References