Schmollack, J. U., Klaumuenzer, S. L. and Kiefer, J. Stochastic Radial Dose Distributions and Track Structure Theory.

Measured single-event distributions of the specific energy deposited in cylindrical volumes with simulated diameters down to 150 nm for ⁴He and ¹²C ions with energies of 25 MeV/nucleon and ¹⁶O ions with 21 MeV/nucleon and radial distances up to 12 μm are presented. The mean specific energy per ion ⟨z(r)⟩, the mean specific energy per target hit z₁(r), and the relative frequency of target hits ν(r) as a function of radial distance are evaluated and compared with the corresponding quantities of the track structure model of Kiefer and Straaten (Phys. Med. Biol. 31, 1201–1209, 1986). Though there are some discrepancies in the absolute values, the radial dependence of ⟨z(r)⟩, z₁(r) and v(r) for ¹²C and ¹⁶O ions is reproduced satisfactorily. The model fails to describe the data for ⁴He ions. A more detailed comparison of the radial shape of the mean specific energies calculated from the experimental data from the present work and data from the literature reveals a significant projectile charge dependence which is not included in track structure models.