Stopping Power of Some Metallic Elements for 19.8-Mev Protons

The proton beam of the UCLA cyclotron, adjusted to 19.8 Mev, was used to measure the stopping power per electron relative to aluminum for 23 elements from Be to Th. An approximate straight-line relationship was found as a function of $logZ$ with deviations noted from Ta to Th, and from Ca to Fe. The latter deviation seems to be associated with the number of electrons in the $3d$ shell.