The Track Structure of Photons, Electrons and α-Particles from the Point of View of the Formation of Ionization Clusters

Großwendt, B.

doi:10.1007/978-3-642-18211-2_39

Cited by 6 publications

(2 citation statements)

References 24 publications

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“…Therefore, the track structure of ionising particles is of particular importance in view of the biological effectiveness of ionising radiation [3,4]. Nanodosimeters are radiation detectors measuring the relative frequency distribution of the ionisation cluster size, which is characteristic for the experimentally accessible ionisation component of the particle track structure [5]- [7]. The ionisation cluster size denotes the number ν of ionisations created in a target volume by a primary particle and all its secondaries.…”

Section: Introductionmentioning

confidence: 99%

Reducing the background of secondary ions in an ion-counting nanodosimeter

Hilgers

Rabus

2019

J. Inst.

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In previous investigations using the PTB Ion Counter nanodosimeter, significant deviations for large cluster sizes were found in the comparison between measured and simulated data of ionisation cluster size distributions. These deviations could be explained quantitatively using a simple parametric model for a background of secondary ions, which are produced within the transport system of the target gas ions to the ion detector. To correct for these secondary ions, unfolding procedures were applied to the measured data to remove the effects of this background. However, the parameters of the model describing the background of secondary ions strongly depend on operational parameters of the nanodosimeter, and any change in these operational parameters requires a new characterisation of the model's parameters. In this work, the influence of the nanodosimeter's operational parameters on the background of secondary ions and the collection efficiency of the detected ions was therefore systematically investigated. At the end of this process operational conditions were found where the background of secondary ions is reduced substantially while the effect on the spatial distribution of the collection efficiency is still acceptable. For some beam geometries of particular relevance for radiation biology, cluster size distributions measured with these new operational parameters can be used directly so that the unfolding procedures, and consequently the characterisation of the secondary ion background with respect to the parameters required by the corresponding model used in the unfolding, can be omitted.

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Section: Introductionmentioning

confidence: 99%

Reducing the background of secondary ions in an ion-counting nanodosimeter

Hilgers

Rabus

2019

J. Inst.

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“…Additionally, the PTra code (Grosswendt 2001, Grosswendt and Pszona 2002, Grosswendt 2002, which offers for simulations the cross-sections for nitrogen gas, was used to validate Geant4-DNA simulations. A dedicated Geant4-DNA and PTra simulations without Mylar wall were performed to evaluate the density scaling procedure.…”

Section: Track Structure Simulationsmentioning

confidence: 99%

Geant4-DNA modeling of nanodosimetric quantities in the Jet Counter for alpha particles

et al. 2021

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The purpose of this work was to validate the calculation accuracy of nanodosimetric quantities in Geant4-DNA track structure simulation code. We implemented the Jet Counter (JC) nanodosimeter geometry in the simulation platform and quantified the impact of the Geant4-DNA physics models and JC detector performance on the ionization cluster size distributions (ICSD). ICSD parameters characterize the quality of radiation field and are supposed to be correlated to the complexity of the initial DNA damage in nanoscale and eventually the response of biological systems to radiation. We compared Monte Carlo simulations of ICSD in JC geometry performed using Geant4-DNA and PTra codes with experimental data collected for alpha particles at 3.8 MeV. We investigated the impact of simulation and experimental settings, i.e., three Geant4-DNA physics models, three sizes of a nanometer sensitive volume, gas to water density scaling procedure, JC ion extraction efficiency and the presence of passive components of the detector on the ICSD and their parameters. We found that ICSD in JC geometry obtained from Geant4-DNA simulations in water correspond well to ICSD measurements in nitrogen gas for all investigated settings, while the best agreement is for Geant4-DNA physics option 4. This work also discusses the accuracy and robustness of ICSD parameters in the context of the application of track structure simulation methods for treatment planning in particle therapy.

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The track structure of α-particles from the point of view of ionization-cluster formation in "nanometric" volumes of nitrogen

Großwendt

Pszona

2002

Radiat Environ Biophys

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Probability distributions of the size of ion clusters created in "nanometric" volumes of nitrogen by single alpha-particles of a gold-plated 241Am source, were measured and compared with those calculated by Monte Carlo methods in the same geometry. The diameter of the sensitive volumes had a mass per area of between 0.015 microgram/cm2 and 1.3 micrograms/cm2 which, for a material at unit density, corresponds to a nanometric target volume 0.15-13 nm in diameter. These nanometre sizes were simulated experimentally in a device called the Jet Counter. This consists of a pulse-operated valve which injects into an interaction chamber an expansion jet of molecular nitrogen gas, which is crossed by a narrow beam of alpha-particles. The resulting ions are counted and analyzed from the point of view of ionization cluster formation. The measured or calculated cluster size probabilities prove that the formation of ionization clusters along a "nanometre" track is governed by Poisson's law only in the case of very small target volumes, due to the contributions by secondary electrons. The present ionization cluster probabilities produced in "nanometric" volumes 0.15-13 nm in diameter, are the first ever determined experimentally and confirmed by Monte Carlo simulation.

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The Track Structure of Photons, Electrons and α-Particles from the Point of View of the Formation of Ionization Clusters

Cited by 6 publications

References 24 publications

Reducing the background of secondary ions in an ion-counting nanodosimeter

Reducing the background of secondary ions in an ion-counting nanodosimeter

Geant4-DNA modeling of nanodosimetric quantities in the Jet Counter for alpha particles

The track structure of α-particles from the point of view of ionization-cluster formation in "nanometric" volumes of nitrogen

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