Radiation detector, 'Smart Ion', plastic / metal, made by Mini Instruments Inc, Burnham on Crouch, Essex, England, 2000-2005
This detector is a white plastic unit with a black handle mounted to the front. The front of the detector has a readout screen and white buttons on a blue background. The back of the unit has a round metal disk on a sliding mechanism that slides down to reveal another round metal disk that detects beta radiation.
The Smart Ion is a micro computer based instrument of advanced design for the measurement of gamma, beta and x-ray radiation. It provides functions previously not available in meters of this type, including data logging, dose rate alarm, remote calibration and security features. Operation is simple, reliable and maintenance free, and the instrument is housed in a robust plastic case of attractive appearance.
The meter employs an ion chamber for detecting gamma radiation and beta particles. A potential applied between a central electrode and the chamber wall attracts the positive and negative parts of the ionised particle. The resulting current flow generates a voltage that is detected and amplified to give an indication of radiation intensity. The meter always measures gamma radiation that penetrates the case from any angle. Beta radiation however is subject to considerable attenuation through the case. Beta radiation is measured through the thin window in the base of the meter. A shield can be slid across this window to exclude beta particles; while this cover is closed, the meter is only sensitive to gamma radiation.