Calculating the fraction of nuclei in fast ion beams of light elements

The fractions $\Phi_Z$ of the nuclei in beams of fast ions with atomic numbers $Z=3\div36$ and energies $2\div200$ MeV/nucleon that have passed through a solid carbon and a gaseous nitrogen target have been determined. It is found that, at ion energies in excess of $0.15 Z^{1.8}$ MeV/nucleon, the equilibrium thicknesses $t_Z$ of the nitrogen and carbon targets are practically the same.