In 1938, University of Toronto physicists Albert F. Prebus (1913-1997) and James Hillier (1915-2007), led a small team that built North America’s first practical electron microscope.
By the 1930s, developments in particle physics and electromagnetic lensing had opened the way to using electrons to image microscopic artifacts. The first electron microscope was built in 1931 at the University of Berlin.This instrument’s magnifying power soon exceeded the resolving power of existing optical microscopes, making it possible to image tiny objects such as viruses that had previously been invisible.
The Ontario-born physicist Eli F. Burton (1879-1948) was among those keen to explore this new technology. Burton had become head of the University of Toronto Physics Department in 1932. He had learned about electron microscopy while attending a conference in Germany in 1935. In 1937, he directed two physics graduate students, Albert F. Prebus and James Hillier, to begin work on an instrument.
There were major technical hurdles: The power supply had to provide high current at a very steady rate; imaging using electrons had to be performed in a vacuum; the sample had to be prepared, and the photo system designed, to withstand the powerful electron beam. The project took place during the Great Depression; Prebus and Hillier were both obliged to rely on repurposed parts and tools.
Begun shortly after Christmas of 1937, it took only four months to produce the 1938 model University of Toronto electron microscope. This rapid development owed much to the department’s skilled machinists. The six-foot-tall instrument , though improvised, temperamental, and difficult to use, could initially produce images at around x 5000 to x 10,000 magnification. It generated great interest at the 1938 meeting of the American Physical Society, held in Toronto.
Graduating in 1941, Hillier found work with RCA and was instrumental in assisting the development of their first commercial electron microscope. Prebus took a faculty position at Ohio State University in 1940. While there, he built an improvement over the 1938 U of T model—the first functioning electron microscope in the United States.
Little material evidence from the 1938 electron microscope survives at the University of Toronto. It was on display in the main floor hallway of the McLennan building for many years. An artifact of national significance, the microscope was given to the Canada Science and Technology Museum (CSTM) around 2010. It can be seen in their main exhibit area. The Department of Physics does have ten glass slides with high quality photographs of the microscope. These were scanned for this exhibit. Above is one example that shows the microscope with associated vacuum equipment and power supply.