Positive pion-nucleus elastic scattering at 30 and 50 MeV

We present measured angular distributions for ${\pi }^{+}$-elastic scattering at 30 and 50 MeV from selected targets with $A=12\mathrm{} \mathrm{to} 208$. These angular distributions were analyzed using a phenomenological optical potential of first-order form. The mass dependence of the potential strength parameters displays the isospin dependence expected from the free $\pi N$ interaction.