The Range of 18-Mev Protons in Aluminum

The circulating beam of protons in the cyclotron was multiply scattered upward by a strip of Th suspended vertically inside the dee. The energy of the scattered beam was defined by the Th strip and two slits in the magnetic field of the cyclotron. From a plot of the magnetic field along the path of the scattered protons, the mean energy was determined to be 18.00±0.02 Mev. By determining the thickness of Al that stopped half the incident beam, the mean range was found to be 447.0±0.5 mg/${\mathrm{cm}}^2$.