Electron emission from amorphous solid water after proton impact: Benchmarking PTra and Geant4 track structure Monte Carlo simulations |
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| Authors: | MU Bug H Rabus AB Rosenfeld |
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| Institution: | 1. Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany;2. Centre for Medical Radiation Physics, University of Wollongong, Wollongong NSW 2522, Australia;1. Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal 04510, Mexico;2. Instituto de Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo, Edicio C-3, Ciudad Universitaria, C.P. 58040, Morelia, Michoacán, Mexico;3. Departamento de Ciencias Básicas, Universidad del Bío-Bío, Casilla 447, Chillán, Chile;1. National Centre for Nuclear Research, Department of Fundamental Research, Ho?a 69, 00-681 Warsaw, Poland;2. Institute of Physics, Jan Kochanowski University, ?wi?tokrzyska 15, 25-406 Kielce, Poland;1. Departamento de Ciencias Básicas, Fundación Universitaria Los Libertadores, A. A. 75087, Bogotá, Colombia;2. Departamento de Física, Universidad Nacional de Colombia, A. A. 5997, Bogotá, Colombia;1. Institute of Applied Physics, Russian Academy of Sciences, Ulyanov Street 46, Nizhny Novgorod 603950, Russia;2. University College London, Department of Physics and Astronomy, Gower Street, London WC1E 6BT, UK;3. Lobachevsky State University of Nizhny Novgorod, 23 Prospekt Gagarina, 603950 Nizhny Novgorod, Russia;1. School of Physics & Electronics Science, Fuyang Normal College, Fuyang, 236037, People’s Republic of China;2. School of Physics & Material Science, Anhui University, Hefei, 230039, People’s Republic of China |
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| Abstract: | Track structure Monte Carlo simulations of ionising radiation in water are often used to estimate radiation damage to DNA. For this purpose, an accurate simulation of the transport of densely ionising low-energy secondary electrons is particularly important, but is impaired by a high uncertainty of the required physical interaction cross section data of liquid water.A possible tool for the verification of the secondary electron transport in a track structure simulation has been suggested by Toburen et al. (2010), who have measured the angle-dependent energy spectra of electrons, emitted from a thin layer of amorphous solid water (ASW) upon a passage of 6 MeV protons.In this work, simulations were performed for the setup of their experiment, using the PTB Track structure code (PTra) and Geant4-DNA. To enable electron transport below the ionisation threshold, additional excitation and dissociative attachment anion states were included in PTra and activated in Geant4. Additionally, a surface potential was considered in both simulations, such that the escape probability for an electron is dependent on its energy and impact angle at the ASW/vacuum interface.For vanishing surface potential, the simulated spectra are in good agreement with the measured spectra for energies above 50 eV. Below, the simulations overestimate the yield of electrons by a factor up to 4 (PTra) or 7 (Geant4-DNA), which is still a better agreement than obtained in previous simulations of this experimental situation. The agreement of the simulations with experimental data was significantly improved by using a step-like increase of the potential energy at the ASW surface. |
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