The Calculation of Self Attenuation Factors for Simple Bodies in the Far Field Approximation

Microsoft Excel spreadsheet functions have been developed for the calculation of the self attenuation of gamma-rays in simple bodies viewed from afar. The cases are a uniform rod viewed along its axis, a sphere viewed along a diameter and a cylinder (or disk) viewed along a mid-plane diameter. The results for the former two cases can be expressed in closed form while the algorithm used for the third is described. We also develop useful expressions for small and large lump cases. The self attenuation functions have been used along with other numerical methods to generate and validate test data for exercising a proposed new lump correction algorithm based on exploiting the differential attenuation of different energy ?-rays emitted by an item.