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 $\sigma$ 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 $\sigma$ was greatest in ${\mathrm{O}}_2$ and least in ${\mathrm{H}}_2$. At 12 MeV, values of $\overline{i}$ and $\sigma$ 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.