An energy-loss model for low- and intermediate-energy carbon projectiles in water.

Purpose: To model interaction cross sections and energy loss for carbon projectiles C(0)-C(6+) of 1-10(4) keV/u (u: atomic mass unit) in water.

Materials And Methods: The classical trajectory Monte Carlo method was used to calculate the ionisation and charge-transfer cross sections. The excitation cross sections were scaled from proton data using equilibrium charges determined from the charge-transfer cross sections. Energy loss was obtained from the singly differential cross sections, and ionisation potentials of the target and projectile.

Results: The calculated total ionisation cross sections are consistent with measured data, while the calculated electron-capture cross sections are larger than experimental data by a factor of 3. By scaling the latter to the measured data, the cross sections were made consistent with these data for 1-10 keV/u energies. The present stopping cross sections agree well with experimental data below 10 keV/u, and with other model calculations above 2 MeV/u. Deviation from the latter is found where electron capture is competitive with ionisation, and also arises from different energy-transfer calculations.

Conclusions: In this paper we report our efforts in the developments of full slowing-down Monte Carlo track structure calculations for carbon ions. Further development and refinement of the model are currently underway.