Ionization cross section data of nitrogen, methane, and propane for light ions and electrons and their suitability for use in track structure simulations

Abstract

Rabus, H. (2013). Ionization cross section data of nitrogen, methane, and propane for light ions and electrons and their suitability for use in track structure simulations. Physical Review E: Statistical, Nonlinear, and Soft Matter Physics, 88 (4), 043308-1-043308-21.Ionization cross section data of nitrogen, methane, and propane for light ions and electrons and their suitability for use in track structure simulations AbstractTrack structure Monte Carlo simulations are frequently applied in micro-and nanodosimetry to calculate the radiation transport in detail. The use of a well-validated set of cross section data in such simulation codes ensures accurate calculations of transport parameters, such as ionization yields. These cross section data are, however, scarce and often discrepant when measured by different groups. This work surveys literature data on ionization and charge-transfer cross sections of nitrogen, methane, and propane for electrons, protons, and helium particles, focusing on the energy range between 100 keV and 20 MeV. Based on the evaluated data, different models for the parametrization of the cross section data are implemented in the code PTRA, developed for simulating proton and alpha particle transport in an ion-counting nanodosimeter. The suitability of the cross section data is investigated by comparing the calculated mean ionization cluster size and energy loss with experimental results in either nitrogen or propane. For protons, generally good agreement between measured and simulated data is found when the Rudd model is used in PTRA. For alpha particles, however, a considerable influence of different parametrizations of cross sections for ionization and charge transfer is observed. The PTRA code using the charge-transfer data is, nevertheless, successfully benchmarked by the experimental data for the calculation of nanodosimetric quantities, but remaining discrepancies still have to be further investigated (up to 13% lower energy loss and 19% lower mean ionization cluster size than in the experiment). A continuation of this work should investigate data for the energy loss per interaction as well as differential cross section data of nitrogen and propane. Interpolation models for ionization and chargetransfer data are proposed. The Barkas model, frequently used for a determination of the effective charge in the ionization cross section, significantly underestimates both the energy loss (by up to 19%) and the mean ionization cluster size (up to 65%) for alpha particles. It is, therefore, not recommended for particle-track simulations. Track structure Monte Carlo simulations are frequently applied in micro-and nanodosimetry to calculate the radiation transport in detail. The use of a well-validated set of cross section data in such simulation codes ensures accurate calculations of transport parameters, such as ionization yields. These cross section data are, however, scarce and often discrepant when measured by different groups. This work surveys literature data on ionization and charge-tra...

Secondary ionisations in a wall-less ion-counting nanodosimeter: quantitative analysis and the effect on the comparison of measured and simulated track structure parameters in nanometric volumes

“…Below this energy, the simulated data deviate from the measured values by as much as 25% which is more than the experimental uncertainties. This deviation may be due to the poor knowledge of the ionisation and charge transfer cross sections used in the simulations for energies around and lower than the Bragg peak energy [21].…”

“…Measured and simulated mean ionisation cluster sizes M 1 (Q) for protons of different kinetic energy T in 1.2 mbar N 2 and 1.2 mbar C 3 H 8 have been compared by Bug et al [21]. Further comparison appears in Figures 10 and 11 of this present work for measured and simulated ionisation cluster size distributions P ν (Q) for protons and alpha particles of two different energies in 1.2 mbar N 2 and 1.2 mbar C 3 H 8 .…”

“…The code and the models, which it contains, were described in references [3,21], and in particular the cross sections implemented in the code and the extensions to the models to simulate the radiation transport in the vicinity of the Bragg peak were discussed extensively in reference [21].…”

“…Due to the limitations of the vacuum system and the vacuum measuring system, the maximum pressure which can be applied in the ionisation volume is 1.2 mbar. According to the mean free path calculated from cross sections used in PTra [20,21], equivalent cluster size distributions for protons and alpha particles in both media should be obtained for pressures of 0.34 mbar C 3 H 8 and 1.2 mbar N 2 . However, since the spatial distribution of the extraction efficiency (see Fig.…”

On the use of additivity rules to estimate electron production cross sections in proton-biomolecule collisions

“…The validity of these models has been assessed by comparison with experimental cross sections for collisions with water vapor in reference [1]. Moreover, the comparison of ion-track simulations with experimental results has been recently employed to gauge the accuracy of ionization cross sections for H + , He 2+ and He + collisions with N 2 and propane [2].…”