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

C. CHAMPION, A. L'HOIR, P. D. FAINSTEIN, R. D. RIVAROLA AND A. CHETIOUI

RADIATION RESEARCH

RADIATION RESEARCH SOC

Año: 2005 vol. 163 p. 222 - 231

0033-7587

TILDA, a new Monte Carlo track structure code for ionsin gaseous water that is valid for both high-LET (10(4) keV/mm) and low-LET ions, is presented. It is specially designedfor a comparison of the patterns of energy deposited by alarge range of ions. Low-LET ions are described in a perturbativeframe, whereas heavy ions with a very high stoppingpower are treated using the Lindhard local density approximationand the Russek and Meli statistical method. Ionizationcross sections singly differential with energy compare wellwith the experiment. As an illustration of the non-perturbativeinteraction of high-LET ions, a comparison between theion tracks of light and heavy ions with the same specific energyis 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 a much larger track radius in the first case. Forelectrons, except for the excitation cross sections that are deducedfrom experimental fits, cross sections are derived analytically.For any orientation of the target molecule, the codecalculates multiple differential cross sections as a function ofthe ejection and scattering angles and of the energy transfer.The corresponding singly differential and total ionizationcross sections are in good agreement with experimental data.The angular distribution of secondary electrons is shown todepend strongly on the orientation of the water molecule.