492-DEGREE FROST IN HELIUM PLANT

Press, Volume CI, Issue 29830, 24 May 1962, Page 15

492-DEGREE FROST IN HELIUM PLANT

A frost of nearly 500 degrees was recorded yesterday in a new belium-lique-fying plant operating at the University of Canterbury for the first time. Its core was by far the coldest spot ever known in this country. The reading was minus 460 degrees Fahrenheit. Average room temperature is 65 degrees Fahrenheit, water freezes at 32 degrees, the coldest temperature yet recorded in the Antarctic was minus 126. air becomes liquid at minus 320 degrees, and air becomes solid at minus 350 degrees. Helium becomes liquid at minus 452 degrees, and that has been the purpose of months of work at the university in installing £17,000 worth of new plant from Boston under an Education Department grant. Mr T. J. Seed, a senior lecturer in physics in charge of the project, said that until 10 years ago liquid helium production was erratic and rare, and the liquid had to be used within a few hours. With the new plant production became routine, but the Commonwealth Scientific and Industrial Research Organisation in Sydney was the only other owner of such equipment in’this part of the world. - : >'■ Research Field An enormous field of research on the behaviour of solids now opened, said Mr Seed. Under the extremely low temperatures of liquid helium, electrical resistance of metals fell so much that they became super-conduc-tors. A current, once started, would flow without external source of power. Copper wire one-tenth of an inch in diameter would carry 500 amperes; it would fuse at 25 amperes at ordinary temperatures.

These properties, induced by liquid helium, permitted exceedingly compact circuits in computers, said Mr Seed. They also permitted the operation of masers, which reduce noise and amplify signals in radio astronomy. At the University of Canterbury liquid helium would be used first to study impurity ions in crystal lattices. The massive Canterbury University plant comprises a four-stage compressor, which supplies helium gas at 30 cubic feet a minute and at a pressure of 92001 b a square inch through heat exchangers to two expansion engines, where the gas cools very rapidly in much the same way as air escaping from the tyre. The final delivery from a special valve brings temperatures low enough to liquefy the helium Motor-car engines freeze in

a moderate frost. Lubrication is therefore (he biggest problem in engines producing liquid helium at nearly 500 degrees of frost. Since even air would become solid at these temperatures, all this equipment operates in a vacuum and in a tank of liquir nitrogen (at minus 360 degrees) to prevent radiated heat from the outside vapourising the liquid aS it is made. The engines are lubricated by the helium itself. Drawn oft . into super vacuum flasks, with jackets of liquid nitrogen, the liquid helium can be stored for long periods and it can practically all be recovered when it boils off as a gas again during experiments. The whole installation was done by the physics department's technicians (Messrs J. P. Pollard. J. C. Wornall, and D. Greig) under the direction of Mr M. H. Streeter, who represents the makers.