Biological Effect of Fast Neutrons

Abstract

CHICK embryo fibroblasts have been irradiated in vitro by 2.4 Mev. neutrons produced by bombarding 'heavy wax' with Ëœ700 microamp. of 300 kv. deuterium ions. This nuclear reaction gives rise to not more than 1 quantum of γ-radiation per 200 neutrons^1,2, and the specimens were completely protected from stray X-radiation. They were thus exposed to a practically pure beam of fast neutrons. The dose given to a culture was estimated from the radioactivity (having the decay period of radio-silicon) induced in a tiny pellet of red phosphorus placed directly above it on the cover slip of the culture slide. In a separate experiment, this radioactivity was correlated with the ionization equivalent of the neutron energy absorbed per unit volume of air, as measured by a suitable graphite ionization chamber.