Spatial Distribution of Thermal Neutrons from a Polonium-Beryllium Source in Water-Zirconium Mixtures

The spatial distribution of neutrons emitted by a Po–Be source and moderated by water‐zirconium mixtures has been measured for four water‐zirconium volume ratios. From these data, migration areas of source neutrons to energies below the cadmium cutoff have been determined with an uncertainty of ±2%. The experimental values of the migration area M² are: $$\begin{array}{cc}{\mathrm{Zr/H}}_2\mathrm{O}\hspace{0.17em}\mathrm{ratio}& M^2({\mathrm{cm}}^2)\\ \text{0.00}& \text{69.6}\\ \text{0.25}& \text{81.3}\\ \text{0.50}& \text{89.7}\\ \text{1.00}& \text{112.8}\end{array}$$