TY - JOUR
T1 - Spatial profiles of positrons injected at low energies into water: influence of cross section models
AU - Tattersall, Wade
AU - Cocks, Daniel
AU - Boyle, Gregory
AU - Brunger, Michael
AU - Buckman, Stephen
AU - Garcia, Gustavo
AU - Petrovic, Zoran
AU - Sullivan, James
AU - White, Ronald
PY - 2017
Y1 - 2017
N2 - We present a collated set of interaction cross sections for positrons in water, and study how the choice of ionisation energy sharing and of anisotropy in elastic cross sections influences low-energy spatial transport. A Monte Carlo code has been developed to model the transport of a beam of positrons injected at 60 eV into water, in which we compare several ionisation energy sharing models, and also vary the anisotropic scattering behaviour for elastic collisions. While the cross sections are primarily applicable to water vapour, we have investigated the inclusion of coherent elastic scattering which is present in liquid water. We present comparative profiles of positron number density, energy deposition, positronium formation, and secondary electron generation. Anisotropic scattering can increase radial diffusion by a factor of two, and a similar effect occurs as a result of coherent elastic scattering, though only at energies below the positronium formation threshold. The results emphasise the need for detailed knowledge of scattering cross sections that are differential in both scattering angles and energy transfer.
AB - We present a collated set of interaction cross sections for positrons in water, and study how the choice of ionisation energy sharing and of anisotropy in elastic cross sections influences low-energy spatial transport. A Monte Carlo code has been developed to model the transport of a beam of positrons injected at 60 eV into water, in which we compare several ionisation energy sharing models, and also vary the anisotropic scattering behaviour for elastic collisions. While the cross sections are primarily applicable to water vapour, we have investigated the inclusion of coherent elastic scattering which is present in liquid water. We present comparative profiles of positron number density, energy deposition, positronium formation, and secondary electron generation. Anisotropic scattering can increase radial diffusion by a factor of two, and a similar effect occurs as a result of coherent elastic scattering, though only at energies below the positronium formation threshold. The results emphasise the need for detailed knowledge of scattering cross sections that are differential in both scattering angles and energy transfer.
UR - https://doi.org/10.1088/1361-6595/aa5f4c
U2 - 10.1088/1361-6595/aa5f4c
DO - 10.1088/1361-6595/aa5f4c
M3 - Article
VL - 26
SP - 045010-1-045010-17
JO - Plasma Sources Science and Technology
JF - Plasma Sources Science and Technology
SN - 0963-0252
IS - 4
M1 - 045010
ER -