Theoretical shape of cavity to locate ovoid sources

A mathematical technique is described for calculating the shape of a cavity required to position an ovoid source in its appropriate location within an applicator. This locus depends only on the assumption of a fixed angle between the source and wall that the source is touching. This technique has enabled us to avoid the problems of constructing ovoid cavities where the source sticks mid-course or does not seat properly, and has therefore resulted in a considerable saving of machine shop time and hence cost.