Intensity and energy absorption studies on extended gamma-ray sources.

An experimental and theoretical examination has been made of the gamma-radiation inside and in the vicinity of extended radioactive sources. Initial ionisation experiments are described in which the "air-wall" chamber method is used to study the gamma-radiation arising from extended sources composed of radio-cobalt (Co60) in aqueous solutions* Coincidence counting measurements are described for determining the absolute radioactive content of a sample Coou source. An approximate theoretical analysis is presented for multiply-scattered gamma-rays for a point source and an extended source* Previous theoretical predictions on the relationship between the roentgen and absolute energy units have been confirmed experimentally for the gamma-rays from Co60. Experimental evidence is presented that an "air-wall" ionisation chamber is suitable for the measurement of garama-radiation, expressed in roentgens or in absolute energy units, inside an extended radioactive body. The effective self-absorption coefficient for aqueous Co60 spherical sources has been deduced both experimentally and theoretically to be given by the Klein-Nishina cross-section for true energy absorption from the primary gamma-rays. [...]