AIRBORNE ALPHA-EMITTERS MONITORED BY A GLASS-FIBER SCINTILLATOR BUNDLE

A trivalent cerium doped oxide glass scintillator possessing good ther mal characteristics for fibre drawing was developed and drawn into 50 mu m fibres. These fibres were close-packed to form a fibre bundle wit h pores between them. Air containing radon was allowed to flow through these pores. The strategy was to increase the mean residence time of radon atoms (Rn-222) in the sensor and to give the alphas an immediate access to scintillators by providing a large detector surface area. A prototype radon gas sensor with a pore volume of 0.865 cm(3) was buil t and tested with radon gas. The mean residence time of radon atoms at the sensor was found to be 113.2 s in contrast to the residence time of 0.12 s calculated from the bulk how rate. This increased residence time should provide a sensitivity enhancement of a factor of this magn itude per unit volume compared with a conventional scintillation detec tor.