After the First World War, the University of Toronto’s Department of Physics became the second site on Earth to successfully liquify helium. Researchers who worked with liquid helium made discoveries fundamental to the establishment of condensed matter physics.
Local research into liquefied helium emerged from the First World War when the British Admiralty sought sources of helium for airships. John Cunningham McLennan (1867 – 1935), head of the Department of Physics, was asked to lead a survey.
The Bow Island natural gas field near Calgary was found to be a productive source. McLennan led the establishment of a purification plant that operated between September 1919 and April 1920. Arriving too late for war use, some 60,000 ft³ of helium gas was available for research. It was decided that the Department of Physics would attempt to liquify helium.
At that time, Leiden University in the Netherlands remained the only site to have managed this. McLennan convinced the lead researcher Heike Kamerlingh Onnes (1853-1926) to provide technical advice and plans for the Leiden helium liquifier, likely in exchange for a supply of Canadian helium. On January 24, 1923, the University of Toronto became the second site to liquify helium. Under McLennan’s leadership, this capacity was developed into a world-class low temperature physics laboratory.
Discovering Superfluidity
When cooled to 2.17 degrees Kelvin, the common helium 4 isotope makes a critical transition below which it exhibits the remarkable characteristics of superfluidity. For instance, the liquid will climb spontaneously up and over the walls of a container, form a fountain through a narrow opening when slightly heated, or flow through the tiniest pores in a barrier. These are dramatic examples of quantum phenomena observable at the macroscopic scale. This discovery underlies much of condensed matter physics.
Much credit for this discovery belongs to two Toronto scientists, John Frank (Jack) Allen (1908-2001) and Austin Donald Misener (1911-1996), who trained at the low temperature physics laboratory. In the 1930s, both published key observations on superfluid helium.
Though fairly mundane, this container represents one of the few artifacts surviving from the early years of the low- temperature physics laboratory.
These are nitrogen dewar flasks. Filled with liquid nitrogen, such containers were used as cold traps to freeze gaseous impurities out of high vacuum pumping systems. Any gas with a boiling point greater than that of liquid nitrogen (77K or -196.15C) will freeze within a container submerged in the liquid nitrogen contained in the dewar.
Dewar with Flash lamp (mid 20th century)
This artifact embodies the close and enduring relationship between spectroscopic research and low-temperature physics that was established during McLennan’s tenure.
This dewar was used by the celebrated spectroscopist Boris P. Stoicheff (1924-2010). Stoicheff was famous for having built Canada’s first laser at the National Research Council (NRC) in 1960 as part of his research into Raman spectroscopy. He joined the University of Toronto Department of Physics in 1964, taking with him a few artifacts from his NRC work.
This apparatus combines a dewar with a high-voltage General Electric FT-524 helical flash tube. It is uncertain what specifically this flash lamp was used for. However, in the early 1960s, Stoicheff and colleague Gary Hanes used such flash lamps at the NRC to study the optical emission of a pulsed laser using a ruby crystal immersed in liquid nitrogen.