Personal “pocket” dosimeters, manufactured by Stephen Ltd. in Surrey, England were used extensively at the Nuclear Power Demonstration (NPD) reactor to allow rapid checking of received radiation dosage. They were used to measure gamma and x-ray radiation. These ~12 cm long dosimeters had a range of 0-500 mR and were based on a miniature ionization chamber. In usage an anode is charged up to a positive potential as is a quartz fiber. The anode and quartz fiber then are repelled from each other and the fiber is deflected. Ionization due to received radiation reduces the charge on the anode and decreases the deflection of the quartz fiber. The amount of the deflection, which can be seen by looking down the length of the chamber, is proportional to the radiation dose received. These new units were donated complete with original boxes and instruction sheets.
