The Penetration and Diffusion ofCo60Gamma-Rays in Water Using Spherical Geometry

Ionization and Geiger-Müller counter measurements of ${\mathrm{Co}}^{60}$ gamma-rays were made in effectively spherical geometry up to a distance of 252.8 cm (16 mean free paths of the primary radiation) corresponding to an exponential attenuation of the primary radiation by a factor of 8.8×${10}^6$. The "build-up factor" was observed to climb up to 33.8 and approached closely the theoretically predicted trend of asymptotic variation $r^{1.4}$. Preliminary information on the spectral distribution of the radiation is included.