Measurement of negative pion capture in organic materials

The relative atomic capture rates of negative pions by the different elements present in a material are affected by the molecular and chemical structure of that material. Hence, conventional tissue equivalent materials, which do not reproduce the elemental abundances present in tissue or its molecular structure, cannot be used in a simple manner to determine the dose deposited by pion interactions. Investigations have been made of negative pion capture in tissue, tissue equivalent materials and simple organic molecules. Experimentally, this has been done by means of measurements of pionic X-rays and measurements of coincident gamma rays emitted following the pion charge exchange reaction on bound hydrogen. The objective of this work is to develop a comprehensive model of pion capture. Such a model could either provide correction factors for use when conventional tissue equivalent materials are used to determine pion dosimetry or lead to the design of a tissue equivalent material specifically for pion dosimetry. (author). 15 refs, 3 tabs