Positive Pion-Nucleus Elastic-Scattering At 30 And 50 Mev

We present measured angular distributions for ${\ensuremath{\pi}}^{+}$-elastic scattering at 30 and 50 MeV from selected targets with $A=12 \mathrm{to} 208$. 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 $\ensuremath{\pi}N$ interaction.NUCLEAR REACTIONS Elastic scattering of 30 and 50 MeV ${\ensuremath{\pi}}^{+}$ from $^{12}\mathrm{C}$, $^{16}\mathrm{O}$, $^{40}\mathrm{Ca}$, $^{90}\mathrm{Zr}$, $^{208}\mathrm{Pb}$. Angular distributions: $25\ifmmode^\circ\else\textdegree\fi{}<{\ensuremath{\theta}}_{\mathrm{LAB}}<160\ifmmode^\circ\else\textdegree\fi{}$. Optical model analysis of cross-section data.