Cavendish Laboratory : Components of John Ashmead's helium liquefier
Cavendish Laboratory
<p style='text-align: justify;'>In 1949 John Ashmead built a new helium liquefier using Joule-Thomson expansion rather than adiabatic cooling as in Kapitsa's machine. Both the helium liquefier and the closed-cycle hydrogen liquefier were now enclosed in a single container, which reduced the need for hydrogen purification, the time needed to start the machine and the explosion hazard. The photograph shows components of the heat exchanger of the liquefier. Photography by Walter Andrews.</p>