Range ofRa−α−BeNeutrons in Water

Radial distributions of $\mathrm{Ra}-\alpha -\mathrm{Be}$ neutrons about an approximate point source in water were determined by means of indium foil activations. Values for migration area ($M^2$) derived from the data are: For all activating neutrons, 54.7 ${\mathrm{cm}}^2$; for indium resonance neutrons, 45.4 ${\mathrm{cm}}^2$.