One of a set of beta electroscopes developed and patented at Chalk River in the 1940s under the leadership of Hugh Carmichael for the accurate measurement of radioactivity. The principle behind them was the detection of the rate of movement of thin (~6 micron) quartz fibres as beta decay introduced negative charges into a chamber. Movement of these fibers was measured under a microscope. The units were built on a 30 cm by 15 cm base and stood 30 cm tall. The radioactivity was introduced on an accurately machined holder and slid into a highly reproducible position. It is believed that numerous units were made, of different but similar design. This model was a Type T.Q.Q.B. with serial number 242.
