Specific energy spectra at alpha-contaminated bone surfaces

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Abstract
Summary Spectra of specific energyf(z) in spherical and disc-shaped targets are determined for plane sources ofα-particles. The radioactive plane is assumed to be coincident with bone surfaces or ‘buried’ within bone. Parameters determining energy straggling and the spectrum ofδ-rays generated outside the target were determined from published parallel beam experiments with wall-less counters. An analytical procedure for calculating single and multiple event spectra for the sphere is demonstrated. For discs spectra are derived from Monte-Carlo calculations. In discs of 6.5 µm radius and 1 µm thickness adjacent to bone surfaces the mean specific energy per event is 2967 erg/g, while that in a sphere of equal volume is 5247 erg/g. The relative variation of specific energy in the disc is about twice as large as in the sphere.