Equilibrium Charge-State Distributions for Iodine in Gases (1-12 MeV)

Abstract

Equilibrium charge-state fractions ${F}_{i}$ have been measured for iodine beams with energies between 1 and 12 MeV traversing gas targets of ${\mathrm{H}}_{2}$, He, ${\mathrm{O}}_{2}$, Ar, and Kr. Charge states from 0 to 14 were detected. At each energy, considerable differences in the charge-state distributions were observed in the different gases; both the mean charge $\overline{i}$ and the distribution width $\ensuremath{\sigma}$ showed strong dependence on the target gas. At energies above 3 MeV the value of $\overline{i}$ was greatest in ${\mathrm{O}}_{2}$ and least in ${\mathrm{H}}_{2}$, and at all energies the value of $\ensuremath{\sigma}$ was greatest in ${\mathrm{O}}_{2}$ and least in ${\mathrm{H}}_{2}$. At 12 MeV, values of $\overline{i}$ and $\ensuremath{\sigma}$ in ${\mathrm{O}}_{2}$ were 6.15 and 2.04, respectively, whereas in ${\mathrm{H}}_{2}$ the corresponding values were 4.02 and 1.12.