A Monte Carlo code for the simulation of heavy-ion tracks in water

C. CHAMPION, A. L´HOIR, M. F. POLITIS, P. D. FAINSTEIN, R. D. RIVAROLA Y A. CHETIOUI

RADIATION RESEARCH

Radiation Research Society

Año: 2005 vol. 163 p. 222 - 231

0033-7587

TILDA, a new Monte Carlo track structure code for ions in gaseous water that is valid for both high LET (of the order of 10 MeV/micrometro) and low-LET ions, is presented. It is spacially designed for a comparison of the patterns of energy deposited by a large range of ions. Low-LET ions are described in a perturbative frame, whereas heavy ions with a very high stopping power are treated using the Linhard local density approximation and the Russek and Meli statistical method. Ionization cross sections singly differential with energy compare well with the experiment. As an illustration for the non-perturbative interaction of high-LET ions, a comparison between the ion tracks of light and heavy ions with the same specific energy is presented (1.4 MeV/nucleon helium and uranium ions). The mean energy for ejected electrons was found to be approximately four times larger for uranium than for helium, leading to much more larger track radius in the first case. For electrons, except for the excitation cross sections that are deduced from experimental fits, cross sections are derived analitically. For any aorientation of the target molecule, the code calculates multiple differential cross sections as a function of the ejection and scattering angles and of the energy trasnfer. The corresponding singly differential and total ionization cross sections are in good agreement with experimental data. The angular distribution of secondary electrons is shown to depend strongly on the orientation of the water molecule.