Abstract: An environmental radioactivity monitor comprises a filter (12) through which air is caused to flow, and a detector (13) of radiation emitted from the particles trapped on the filter. The signals from the radiation detector are analyzed into a multiplicity of energy channels, for example with a multi-channel analyzer (22), the counts in at least two energy windows (W1, W2; W3, W4) being used to determine the shapes of the low-energy tails of the peaks of the naturally occurring radio-nuclides ThC′ and RaC′, so their effects can be eliminated. The shape of the ThC′ peak is used to predict and strip out the ThC peak, and the shape of the RaC′ peak is then used to predict and strip out the RaA peak, so all background effects are eliminated. Accurate measurements of air-borne radioactivity are hence possible with short counting times.

Abstract: An environmental radioactivity monitor comprises a filter (12) through which air is caused to flow, and a detector (13) of radiation emitted from the particles trapped on the filter. The signals from the radiation detector are analyzed into a multiplicity of energy channels, for example with a multi-channel analyzer (22), the counts in at least two energy windows (W1, W2; W3, W4) being used to determine the shapes of the low-energy tails of the peaks of the naturally occurring radio-nuclides ThC′ and RaC′, so their effects can be eliminated. The shape of the ThC′ peak is used to predict and strip out the ThC peak, and the shape of the RaC′ peak is then used to predict and strip out the RaA peak, so all background effects are eliminated. Accurate measurements of air-borne radioactivity are hence possible with short counting times.

Abstract: The invention relates to light sources and, in particular, to light sources for use in navigational aids such as lighthouses and lighted buoys.In more detail, the light source of the present invention comprises a radio isotope fuel source, thermal insulation against heat loss, a biological shield against the escape of ionizing radiation, a material having a surface which attains incandescence when subject to isotope decay heat and means for transferring energy from the insulated fuel source to produce incandescence of the surface and thereby emit light.