Width of Heavy-Ion Tracks in Emulsion

Profiles of the solid core of long, flat, ending tracks of heavy primary cosmic rays in Ilford G-5 emulsion have been measured by manually tracing their enlarged (3500×) photographic image. These measurements agree well in the ending 3000 μ of residual range ($\beta <0.3\mathrm{}$) with a reformulated theory of track width based on computation of the spatial distribution of ionization energy. The measured core width in G-5 emulsion is the sum of the sensitized cylinder diameter, at which 6000 erg/${\mathrm{cm}}^3$ of ionization energy is deposited by $\delta$ rays, and the diameter of a developed grain.