Born in Chengdu, West China on July 4, 1915, Harold Johns returned to Canada with his missionary parents in 1927. After taking MA and PhD degrees in physics from the University of Toronto, he was a lecturer at the University of Alberta, where he made radiographic images of aircraft castings.
In 1945 he received a joint appointment in the Department of Physics at the University of Saskatchewan as assistant professor and as physicist for the Saskatchewan Cancer Commission. There he created, almost single-handedly, a Canadian field of Medical Physics, and in 1948 was instrumental in securing Canada's first betatron. In 1951, he was the key figure in the development of the world's first Cobalt-60 unit for the treatment of cancer. Under his direction, radiation therapists and physicists at the University of Saskatchewan led the world in the development of high-technology cancer treatment.
In 1956 he was appointed head of the Physics Division of the Ontario Cancer Institute, and in 1958 professor and head of the Department of Medical Biophysics at the University of Toronto, where he continued to maintain an active research and teaching program until his mandatory retirement in 1980.
Johns published over 200 peer-reviewed papers; trained over 100 graduate and postdoctoral fellows, many of whom hold or have held key medical physics positions in Canada and around the world; and wrote the foremost textbook in medical radiation physics.
Sylvia O. Fedoruk