Abstract
Characteristic K-shell x rays produced when protons of 60- to 500-keV energy are stopped in thick targets of magnesium, aluminum, and copper have been studied using a proportional counter of conventional design. The thick target yields were measured. The x-ray production cross sections have been calculated for the K shells. Ionization cross sections have been estimated and were found to be smaller than the values predicted by the Born approximation in all cases.