Half-value thickness measurements of ordinary concrete for neutrons from cyclotron targets

Half-value thicknesses of a wall of ordinary concrete bricks were determined for fast neutrons emitted from a variety of cyclotron beam-target combinations. The neutrons used in the study were produced at the Oak Ridge Isochronous Cyclotron by bombarding thick targets of carbon, aluminum, copper and tantalum with beams of protons, deuterons, alpha particles and carbon ions. Attenuated and unattenuated dose rate measurements of these neutrons were made at a 80 cm thick concrete block wall which served as one side of the target room where the irradiations occurred. The ratios provided by these shielded and unshielded dose rate measurements were translated into half-value thicknesses.