Positron Cross Sections And Transport In Water

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Positron Cross Sections And Transport In Water

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Author : Wade Tattersall
language : en
Publisher:
Release Date : 2017

Positron Cross Sections And Transport In Water written by Wade Tattersall and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.

A detailed understanding of the behaviour of positrons and electrons as they pass through liquids is critical for a number of applications, from positron emission tomography and ion therapy to cosmic ray detectors and materials characterisation. In particular, transport in liquid water is vital for medical applications because of its similarity to human tissue, and is an area of continued research. This thesis presents newly measured experimental cross sections for positrons in water as well as several Monte Carlo simulation techniques aimed at improving our models of positron and electron transport. In particular, special efforts have been made to model the effects of elastic coherent scattering, which arise due to the position and velocity correlations between molecules in liquids and other dense media. The experimental scattering results include the first measurements of integral and differential elastic positron cross sections for water vapour, as well as detailed grand total and positronium formation cross sections for the same. Performed on the positron beamline apparatus at the Australian National University, this transmission experiment passed a high-resolution beam of positrons through a scattering cell containing water vapour. The parallel component of the energy of the positrons after scattering was analysed to determine the ratio between the scattered and unscattered portions of the beam, from which absolute total cross sections were calculated. The experiment further utilised a differentiated magnetic field to separate elastic scattering from the other scattering processes, and to distinguish between scattering angles in order to measure angle-differential cross sections. An original Monte Carlo track-structure simulation code has been written which aims to precisely model the transport behaviour of electrons and positrons in dilute gases, dense gases and liquids. This simulation incorporates several new features to improve its ability to model systems with high particle loss rates, varying electric fields and fully-differential ionisation interactions. Each feature has been rigorously tested against benchmark systems from the literature and, where necessary, against Boltzmann equation solutions of new benchmark systems. The simulation has also been applied to model elements of the positron trapping apparatus which is a critical component of the positron scattering experiment. The simulation's validity has been extended beyond dilute gases by including a treatment of the coherent elastic scattering that is caused by the structure of dense media. Following the theories of Van Hove, Cohen and Lekner, either a static or dynamic structure factor can be combined with gas-phase cross sections to form a modified scattering cross section that partially accounts for the temporal and spatial correlations of nearby molecules. The benchmarked Monte Carlo simulation techniques are then used to calculate transport profiles for positrons in liquid water, using the measured water cross sections. These profiles are estimates of the spatial distributions of positronium formation and energy deposition, from the positrons' emission until their first positronium formation event. Comparisons between simulations employing different cross section sets demonstrate the importance of a complete and accurate set of scattering cross sections for positrons in water.

Radiation Damage In Biomolecular Systems

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Author : Gustavo García Gómez-Tejedor
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-01-04

Radiation Damage In Biomolecular Systems written by Gustavo García Gómez-Tejedor and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-01-04 with Science categories.

Since the discovery of X-rays and radioactivity, ionizing radiations have been widely applied in medicine both for diagnostic and therapeutic purposes. The risks associated with radiation exposure and handling led to the parallel development of the field of radiation protection. Pioneering experiments done by Sanche and co-workers in 2000 showed that low-energy secondary electrons, which are abundantly generated along radiation tracks, are primarily responsible for radiation damage through successive interactions with the molecular constituents of the medium. Apart from ionizing processes, which are usually related to radiation damage, below the ionization level low-energy electrons can induce molecular fragmentation via dissociative processes such as internal excitation and electron attachment. This prompted collaborative projects between different research groups from European countries together with other specialists from Canada, the USA and Australia. This book summarizes the advances achieved by these research groups after more than ten years of studies on radiation damage in biomolecular systems. An extensive Part I deals with recent experimental and theoretical findings on radiation induced damage at the molecular level. It includes many contributions on electron and positron collisions with biologically relevant molecules. X-ray and ion interactions are also covered. Part II addresses different approaches to radiation damage modelling. In Part III biomedical aspects of radiation effects are treated on different scales. After the physics-oriented focus of the previous parts, there is a gradual transition to biology and medicine with the increasing size of the object studied. Finally, Part IV is dedicated to current trends and novel techniques in radiation reserach and the applications hence arising. It includes new developments in radiotherapy and related cancer therapies, as well as technical optimizations of accelerators and totally new equipment designs, giving a glimpse of the near future of radiation-based medical treatments.

Comparison Of Electron Proton And Positron Proton Elastic Scattering Cross Sections

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Author : George Lawrence Cassiday
language : en
Publisher:
Release Date : 1968

Comparison Of Electron Proton And Positron Proton Elastic Scattering Cross Sections written by George Lawrence Cassiday and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1968 with Scattering (Physics) categories.

Calculation Of Total Cross Sections For Electron And Positron Scattering On Sodium And Potassium

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Author : Ian Ellery McCarthy
language : en
Publisher:
Release Date : 1993

Calculation Of Total Cross Sections For Electron And Positron Scattering On Sodium And Potassium written by Ian Ellery McCarthy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Cross sections (Nuclear physics) categories.

Nuclear Science Abstracts

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Author :
language : en
Publisher:
Release Date : 1976-06

Nuclear Science Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1976-06 with Nuclear energy categories.

Comparison Of Inelastic Electron And Positron Scattering Cross Sections On 01c And 16al

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Author : S. Hartwig
language : en
Publisher:
Release Date : 1977

Comparison Of Inelastic Electron And Positron Scattering Cross Sections On 01c And 16al written by S. Hartwig and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with categories.

Electron And Positron Scattering

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Author : Shannon A. Murphy
language : en
Publisher:
Release Date : 1997

Electron And Positron Scattering written by Shannon A. Murphy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with categories.

Comparison Of Inelastic Electron And Positron Scattering Cross Sections On 12 C And 27 Al

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Author :
language : en
Publisher:
Release Date : 1977

Comparison Of Inelastic Electron And Positron Scattering Cross Sections On 12 C And 27 Al written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1977 with categories.

Energy Research Abstracts

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Author :
language : en
Publisher:
Release Date : 1993

Energy Research Abstracts written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with Power resources categories.

Inelastic Cross Sections For Electron Interactions In Liquid Water

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Author :
language : en
Publisher:
Release Date : 1982

Inelastic Cross Sections For Electron Interactions In Liquid Water written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982 with categories.

The task was to develop a set of cross sections for electron inelastic processes in liquid water suitable for use in a Monte Carlo transport calculation. Results are plotted as inverse mean free paths vs electron energy. (DLC).