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1951: Cobalt-60

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In October 1951, the world’s first calibrated cobalt-60 therapy unit was opened at the University of Saskatchewan.  It was designed by Harold Johns of the physics department, and built by John MacKay, owner of Acme Machine and Electric Co., Saskatoon.  Cobalt-60 therapy was used for cancer treatments; Johns and his students had also developed the “most reliable and complete set of isodose tables” then available to physicians.1

Johns’ research benefited from the prior work of colleagues.  E.L. Harrington had begun research into medical use of radiation in the late 1920s, and had in fact built the first radon plant in Western Canada at the bequest of the Saskatchewan Cancer Commission.2 As head of the department of physics, Harrington was also instrumental in hiring Harold Johns, who at that time “had no prior interests in radiation physics.”  Johns was, however, “enthusiastic,...responsive to new ideas and able to absorb quickly the pertinent details and apply them to experimental investigations.”3

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 As a result of Johns’ work, Canada became a pioneer in the field of therapeutic radiology.  Following the opening of the cobalt-60 unit in Saskatoon, a second unit was opened in London, Ontario–designed by a graduate of the University of Saskatchewan–as indeed, were all those employed in the field in Canada at that time.4

Johns’ work of course had other, more substantive benefits.  His x-ray dosage table is still in use, and it is estimated that more than seven million people worldwide have been helped by cobalt-60 therapy.5   Johns died in 1998 at the age of 83.

Related Collections

Department of Physics fonds, RG 2043.


1951a: demonstration of the cobalt-60 unit. Photograph Collection, A-3519.
1951b: explanation of the cobalt-60 unit. Photograph Collection, A-3622.


1. King, p. 99.
2. King, p. 97.
3. Currie, p. 177.
4. Faculty Biographies, H.E. Johns file.
5. Faculty Biographies, H.E. Johns file.

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