Studies of the interactions of ionizing radiations with communications materials

This report summarizes experimental and theoretical studies designed to yield information on the interaction of ionizing radiations with various communications materials. In studies carried out during this 2-year period, we have developed various models for calculating the energy loss per unit length, or stopping power, and the inelastic mean free path for electrons in a material. We have included both organic materials such as polyethylene and inorganic materials such as SiO2. In each case, the calculated values of stopping power and mean free path have been compared with experimental values where available and, in the case of mean paths for organic materials, with those predicted from our universal formula. In addition the various models for stopping power and mean free path have been compared with each other. Measurements have been made of electron attenuation lengths (approximately electron mean free paths) as a function of incident electron energy for electrons in amorphous carbon films, as a direct check on the values predicted by our universal formula for electron mean free pths in solid organic insulators. A theory has been developed to describe charge-particle track structure in nonmetallic solids, as the track evolves in time and space.