Rozprawy doktorskie: „Proton radiation”

1

Roberts, Amy. "Investigating proton pairing in 76Se with two-proton transfer onto 74Ge". Thesis, University of Notre Dame, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3585264.

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The current experimental effort to detect neutrinoless double beta decay (0νββ) has encouraged significant interest in understanding the nuclei that are candidates for the observation of this process. The goal of this thesis is to contribute to the current body of work on the germanium isotopes near ⁷⁶Ge, a candidate nucleus currently being used by several large-scale searches for 0νββ. Single-nucleon transfer experiments have been very successful in determining the occupancies of the valence shells in the parent and daughter nuclei ⁷⁶Ge and ⁷⁶Se. However, understanding the ground-state pairing of neutrons in ⁷⁶Ge and protons in ⁷⁶Se is also crucial because 0νββ converts correlated neutron pairs to correlated proton pairs. Neutron pairing in ⁷⁶Ge has been found to be concentrated almost exclusively in the ground state, but studies on the tellurium isotopes have indicated that a fully neutron-paired ground state does not constrain the distribution of proton-pairing strength. This work uses the (³He,n) transfer reaction with a ⁷⁴Ge target to investigate the proton-pairing strength distribution in ⁷⁶Se. It is found that proton pairs transfer predominantly to the ground state of ⁷⁶Se. Proton-pair transfer to excited 0⁺ states in ⁷⁶Se is determined to be less than 4–8% of the ground-state pair-transfer strength.

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Johanson, Jan. "Two-pion production in proton-proton collisions near threshold". Doctoral thesis, Uppsala University, Department of Nuclear and Particle Physics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-507.

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Two-pion production reactions in proton-proton collisions have been studied using the PROMICE/WASA detector and an internal cluster gas-jet target at the CELSIUS storage ring in Uppsala. Three out of the four isospin-independent reaction channels have been measured at several energies in the intermediate and near threshold energy region. Important parts of the analysis include the identification of neutral pions from the invariant mass of the decay gammas, the identification of positive pions with the delayed pulse technique and the use of Monte Carlo simulations to understand the detector response. The total cross sections for the pp®ppπ⁺π^-, the pp®ppπ⁰π⁰ and the pp®pnπ⁺π⁰ reactions are presented at beam energies ranging from 650 to 775 MeV.

The production mechanism for two-pion production near threshold seems to be dominated by resonance production. The contribution from the non-resonant terms alone can not reproduce the total cross sections. In most models, two-pion production is governed by the δ and the N^* resonances in either one or both of the participating nucleons.

The N^*(1440)®N(πp)^T=0_S−wave transition has been suggested as the dominating production mechanism for two-pion production in proton-proton collisions. However, the total cross sections presented in this thesis show that other production mechanisms also must give large contributions.

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Beaumier, Michael John. "Probing the Spin Structure of the Proton Using Polarized Proton-Proton Collisions and the Production of W Bosons". Thesis, University of California, Riverside, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10181454.

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This thesis discusses the process of extracting the longitudinal asymmetry, $A_L

{W\pm}$, describing $W\rightarrow\mu$ production in forward kinematic regimes. This asymmetry is used to constrain our understanding of the polarized parton distribution functions characterizing $\bar{u}$ and $\bar{d}$ sea quarks in the proton. This asymmetry will be used to constrain the overall contribution of the sea-quarks to the total proton spin. The asymmetry is evaluated over the pseudorapidity range of the PHENIX Muon Arms, $2.1 < |\eta|2.6$, for longitudinally polarized proton-proton collisions at 510 GeV $\sqrt{s}$. In particular, I will discuss the statistical methods used to characterize real muonic $W$ decays and the various background processes is presented, including a discussion of likelihood event selection and the Extended Unbinned Maximum Likelihood fit. These statistical methods serve estimate the yields of $W$ muonic decays, which are used to calculate the longitudinal asymmetry.

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4

Salhani, Maat Bilhal. "Backprojection-then-filtering reconstruction along the most likely path in proton computed tomography". Thesis, KTH, Skolan för teknik och hälsa (STH), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189495.

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The backprojection-then-filtering algorithm was applied to proton CT data to reconstruct a map of proton stopping power relative to water (RSP) in air, water and bone. Backprojections were performed along three commonly used path estimates for the proton: straight line path, cubic spline path, and most likely path. The proton CT data was obtained through simulations using the GEANT4 simulation toolkit. Two elliptical phantoms were inspected, and an accuracy of 0.2% and 0.8% was obtained for the RSP in water and bone respectively in the region of interest, while the RSP of air was significantly underestimated.

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5

Whitehill, Craig. "Characteristics of VPE GaAs radiation detectors after proton irradiation". Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401998.

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6

Schneider, Tim. "Advancing the generation of proton minibeams for radiation therapy". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP069.

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Malgré d’importants progrès, la tolérance des tissus sains aux rayonnements demeure un facteur central en radiothérapie, limitant par exemple l’efficacité du traitement des gliomes de haute grade. La proton thérapie avec mini-faisceaux (proton minibeam radiation therapy, pMBRT) est une nouvelle stratégie thérapeutique qui a pour objectif d’améliorer la préservation des tissus sains en combinant les avantages balistiques des protons et le fractionnement spatial de la dose obtenu avec des faisceaux submillimétriques. Dans ce contexte, la pMBRT a déjà démontré sa capacité à augmenter l’index thérapeutique dans le traitement des tumeurs cérébrales de rats. Un défi important est la génération des mini-faisceaux dans un cadre clinique : contrairement à la radiothérapie conventionnelle qui utilise des faisceaux larges (diamètre d’environ 5 mm à plusieurs centimètres), les mini-faisceaux se caractérisent par un diamètre de moins d’un millimètre. Actuellement, la génération des mini-faisceaux de protons est réalisée à l’aide de collimateurs mécaniques (blocs en métal avec plusieurs fentes ou trous) ce qui comporte plusieurs inconvénients (notamment une très faible flexibilité, une réduction importante du débit de dose ainsi que la génération de particules secondaires indésirables). Une solution optimale pourrait être la génération des mini-faisceaux par focalisation magnétique. Il en découle la question principale traitée dans cette thèse : Comment la génération des mini-faisceaux de protons par focalisation magnétique peut-elle être réalisée dans un cadre clinique ? En utilisant le modèle numérique d’un pencil beam scanning nozzle (le "nozzle" est la dernière partie d’une ligne de faisceau clinique), il a été démontré que les nozzles actuels ne sont pas adéquats pour focaliser les faisceaux de protons à la taille requise, les principales raisons étant une distance focale trop grande et une présence d’air excessive. En partant de ces conclusions, un nouveau design de nozzle optimisé a été développé. Ce nouveau modèle est capable de générer des mini-faisceaux de protons par focalisation magnétique dans des conditions réalisables avec les technologies existantes. Une étude Monte Carlo a également été menée afin de comparer et de quantifier les différences entre la génération de mini-faisceaux par collimation mécanique et par focalisation magnétique. Dans un second temps, cette thèse présente une évaluation des ions d’hélium comme alternative aux protons pour la radiothérapie avec mini-faisceaux. Il a pu être démontré que les ions d’hélium peuvent être un bon compromis en offrant certains des avantages dosimétriques observés avec les ions lourds sans les risques de toxicité associés
Despite major advances over the last decades, the dose tolerance of normal tissue continues to be a central problem in radiation therapy, limiting for example the effective treatment of hypoxic tumours and high-grade gliomas. Proton minibeam radiation therapy (pMBRT) is a novel therapeutic strategy, combining the improved ballistics of protons with the enhanced tissue sparing potential of submillimetric, spatially fractionated beams (minibeams), that has already demonstrated its ability to significantly improve the therapeutic index for brain cancers in rats. In contrast to conventional proton therapy which uses comparatively large beam diameters of five millimetres to several centimetres, minibeams require beam sizes of less than 1 mm which are challenging to create in a clinical context. So far, every implementation of pMBRT at clinically relevant beam energies could only be achieved with the help of mechanical collimators (metal blocks with thin slits or holes). However, this method is inefficient, inflexible and creates high levels of unwanted secondary particles. The optimal approach may therefore be the generation of minibeams through magnetic focussing.This thesis investigates how magnetically focussed proton minibeams can be realised in a clinical context. Starting from the computer model of a modern pencil beam scanning nozzle (the term "nozzle" describes the final elements of a clinical beamline), it could be shown that current nozzles will not be suitable for this task, since their large dimensions and the presence of too much air in the beam path make it impossible to focus the beam down to the required sizes. Instead, an optimised nozzle design has been developed and evaluated with clinical beam models. It could be demonstrated that this design allows the generation of proton minibeams through magnetic focussing and that the new nozzle can be used with already existing technology. Moreover, a Monte Carlo study was performed to compare and quantify the differences between magnetically focussed minibeams and mechanically collimated minibeams.Finally, as the second aspect of this thesis, helium ions were evaluated as a potential alternative to protons for minibeam radiation therapy. It could be shown that helium ions could present a good compromise exhibiting many of the dosimetric advantages of heavier ions without the risks related to normal tissue toxicities

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7

Handley, Stephen Michael. "Monte Carlo simulations using MCNPX of proton and anti-proton beam profiles for radiation therapy". Oklahoma City : [s.n.], 2010.

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8

Mandelli, Elena. "Ionizing radiation detectors and their innovative application in proton therapy". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/21880/.

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Through this thesis we wanted to present a branch of radiotherapy that uses proton beams to destroy tumors, namely proton therapy. This technique, although relatively new (1946), is rapidly spreading thanks to the advantage of being able to precisely locate the release of the therapeutic dose of radiation. After a brief presentation of the discovery of ionizing radiations’ history and their possible applications, we focused on the study of the protons’ behavior when they interact with matter, going to show why they are so advantageous, by studying different quantities such as stopping power, flow rate, flow rate variation, multiple coulomb scattering and proton RBE. In fact, proton therapy represents a new and important therapeutic approach that allows a large part of healthy tissue to absorb less dose than in conventional therapies that use photons or electrons. The most interesting aspect of this thesis, and still with a broad future perspective, concerns the different types of detectors used in this therapy, which play a fundamental role in the progress of nuclear medicine, leading to ever better methods of prevention, diagnosis and treatment of illnesses. The future goal of this therapy is to develop new detectors, that are more equivalent to human tissues, both in behavior and detections, in order to obtain always better performances.

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9

Taylor, Paul Alan. "Proton radiation effects on space solar cell structures and materials". Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242506.

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Blaikley, Helen. "Measurement of the proton structure from 1996 and 1997 radiative ep scattering data using the ZEUS detector". Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301844.

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11

Flejmer, Anna M. "Radiation burden from modern radiation therapy techniques including proton therapy for breast cancer treatment - clinical implications". Doctoral thesis, Linköpings universitet, Avdelningen för kliniska vetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-127370.

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The purpose of this thesis was to study the clinical implications of modern radiotherapy techniques for breast cancer treatment. This was investigated in several individual studies. Study I investigated the implications of using the analytical anisotropic algorithm (AAA) from the perspective of clinical recommendations for breast cancer radiotherapy. Pencil beam convolution plans of 40 breast cancer patients were recalculated with AAA. The latter plans had a significantly worse coverage of the planning target volume (PTV) with the 93% isodose, higher maximum dose in hotspots, higher volumes of the ipsilateral lung receiving doses below 25 Gy and smaller volumes with doses above 25 Gy. AAA also predicted lower doses to the heart. Study II investigated the implications of using the irregular surface compensator (ISC), an electronic compensation algorithm, in comparison to three‐dimensional conformal radiotherapy (3D‐CRT) for breast cancer treatment. Ten breast cancer patients were planned with both techniques. The ISC technique led to better coverage of the clinical target volume of the tumour bed (CTV‐T) and PTV in almost all patients with significant improvement in homogeneity. Study III investigated the feasibility of using scanning pencil beam proton therapy for regional and loco‐regional breast cancer with comparison of ISC photon planning. Ten patients were included in the study, all with dose heterogeneity in the target and/or hotspots in the normal tissues outside the PTV. The proton plans showed comparable or better CTV‐T and PTV coverage, with large reductions in the mean doses to the heart and the ipsilateral lung. Study IV investigated the added value of enhanced inspiration gating (EIG) for proton therapy. Twenty patients were planned on CT datasets acquired during EIG and freebreathing (FB) using photon 3D‐CRT and scanning proton therapy. Proton spot scanning has a high potential to reduce the irradiation of organs‐at‐risk for most patients, beyond what could be achieved with EIG and photon therapy, especially in terms of mean doses to the heart and the left anterior descending artery. Study V investigated the impact of physiological breathing motion during proton radiotherapy for breast cancer. Twelve thoracic patients were planned on CT datasets during breath‐hold at inhalation phase and breath‐hold at exhalation phase. Between inhalation and exhalation phase there were very small differences in dose delivered to the target and cardiovascular structures, with very small clinical implication. The results of these studies showed the potential of various radiotherapy techniques to improve the quality of life for breast cancer patients by limiting the dose burden for normal tissues.

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Kraishan, Amani. "MEASUREMENT OF LONGITUDINAL SINGLE-SPIN ASYMMETRY FOR W± BOSON PRODUCTION IN POLARIZED PROTON-PROTON COLLISIONS AT STAR AT FORWARD RAPIDITY". Diss., Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/521379.

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Physics
Ph.D.
Spin plays a key role in the determination of the properties of fundamental particles and their interactions. The spin structure of the proton is one of the most challenging open puzzles in Quantum Chromodynamics (QCD). It was believed that the proton spin was carried by the spin of its three valence quarks. However, The results of the EMC (European Muon Collaboration) experiments in 1987 suggested that the quark intrinsic spin contributes, ∆Σ = 0.12 ± 0.09 ± 0.14 of the proton spin setting off the proton spin crisis. ”Where is the rest of the proton spin is coming from?” remains a major challenge to our understanding of the structure of the proton. The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) delivers the highest energy polarized proton-proton collisions at a center of mass energy up to 510 GeV and provides a unique opportunity to study quark and gluon spin structure of the proton and the QCD dynamics at high energy scale. The production of W −(+) bosons in polarized proton-proton collisions provides an ideal tool to study the spin-flavor structure of the proton sea quark distributions profiting from the parity-violating nature of the weak interactions. W −(+) bosons are produced in u ̄ + d (d ̄ + u) annihilation and can be detected through their leptonic decay mode. The STAR experiment can detect charged leptons e−(+) at mid and forward rapidity regions. In this analysis, the measurement of the longitudinal single-spin asymmetries at forward rapidity for W boson production will be presented based on the data sample collected in 2013 (RUN-13) corresponding to an integrated luminosity 220 pb−1 with an average beam polarization ∼ 56%.
Temple University--Theses

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13

Koch, Inken. "Measurements of 2π0 and 3π0 Production in Proton-Proton Collisions at a Center of Mass Energy of 2.465 GeV". Doctoral thesis, Uppsala universitet, Institutionen för kärn- och partikelfysik, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4350.

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Neutral two- and three-pion productions in proton-proton collisions at a center of mass energy of 2.465 GeV have been studied using the WASA detector and an internal pellet target at the CELSIUS storage ring in Uppsala. An important part of the detector for the measurments was a central electromagnetic calorimeter composed of 1012 CsI crystals, which measured the photons originating from neutral pion decays. Test measurements and calibration procedures for this detector part were carried out. An important part of the analysis was the identification of the neutral pions from the invariant mass of the decay gammas and the use of Monte Carlo simulations to understand the detector responds. Total cross sections for the pp→ppπ0π0 and pp→ppπ0π0π0 reactions are presented as well as distributions of relevant kinematical variables for the pp→ppπ0π0 reaction. The distributions show significant deviations from phase space predictions. These deviations are typical for resonance production. The excitation of two simultaneous Δ resonances seems to be the main reaction mechanism.

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Sarfehnia, Arman. "Water calorimetry-based radiation dosimetry in iridium-192 brachytherapy and proton therapy". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92297.

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Palmer, Charlotte Alexandra Jocelyn. "Approaching the radiation pressure regime of proton acceleration with high intensity lasers". Thesis, Imperial College London, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556643.

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This thesis presents experimental measurements, supported by particle-in-cell simulations, of ion beams accelerated by high intensity laser plasma interactions, spanning both the sheath acceleration and radiation pressure dominated regimes. For interactions of laser intensities rv 1020 W I cm? with micron thick gold targets rear surface sheath acceleration w~ seen to dominate. Proton beam spatial profiles revealed multiple concentric rings for target thicknesses ~ 20 tun. The number of rings increased with decreasing target thickness with no rings for thicknesses > 50 uu: It is postulated that these concentric rings stem from a larger number of recirculations of laser accelerated electrons through thinner targets. In following investigations structured proton beam profiles were observed from the interaction of nanometer scale targets at intensities of rv 1021 W Icm2. The most striking bubble-like structure, observed for the thinnest (5 nm) targets, closely resembles a Rayleigh- Taylor-like instability, a clear indication of radiation pressure driven acceleration. Both the experimental results and simulations also exhibit narrow energy spread features in the carbon ion spectra. Finally, a rv 5 ps, CO2 laser (A = 10.6 p,m) with intensity rv 1015 W Icm2 was focused onto an overdense hydrogen gas target. Transverse probing revealed a hole boring shock front associated with the first phase of radiation pressure acceleration. The accelerated proton beams contained up to 3 X 1012 protons/MeV [et, with energy spreads as low as r-;» 4 %. The ion energies scaled linearly with increasing integrated laser energy as expected from acceleration by hole boring.

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Cavan, Alicia Emily. "Digital Holographic Interferometry for Radiation Dosimetry". Thesis, University of Canterbury. Physics and Astronomy, 2015. http://hdl.handle.net/10092/10465.

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A novel optical calorimetry approach is proposed for the dosimetry of therapeutic radiation, based on the optical technique of Digital Holographic Interferometry (DHI). This detector determines the radiation absorbed dose to water by measurement of the refractive index variations arising from radiation induced temperature increases. The output consists of a time series of high resolution, two dimensional images of the spatial distribution of the projected dose map across the water sample. This absorbed dose to water is measured directly, independently of radiation type, dose rate and energy, and without perturbation of the beam. These are key features which make DHI a promising technique for radiation dosimetry. A prototype DHI detector was developed, with the aim of providing proof-of-principle of the approach. The detector consists of an optical laser interferometer based on a lensless Fourier transform digital holography (LFTDH) system, and the associated mathematical reconstruction of the absorbed dose. The conceptual basis was introduced, and a full framework was established for the measurement and analysis of the results. Methods were developed for mathematical correction of the distortions introduced by heat di usion within the system. Pilot studies of the dosimetry of a high dose rate Ir-192 brachytherapy source and a small eld proton beam were conducted in order to investigate the dosimetric potential of the technique. Results were validated against independent models of the expected radiation dose distributions. Initial measurements of absorbed dose demonstrated the ability of the DHI detector to resolve the minuscule temperature changes produced by radiation in water to within experimental uncertainty. Spatial resolution of approximately 0.03 mm/pixel was achieved, and the dose distribution around the brachytherapy source was accurately measured for short irradiation times, to within the experimental uncertainty. The experimental noise for the prototype detector was relatively large and combined with the occurrence of heat di usion, means that the method is predominantly suitable for high dose rate applications. The initial proof-of-principle results con rm that DHI dosimetry is a promising technique, with a range of potential bene ts. Further development of the technique is warranted, to improve on the limitations of the current prototype. A comprehensive analysis of the system was conducted to determine key requirements for future development of the DHI detector to be a useful contribution to the dosimetric toolbox of a range of current and emerging applications. The sources of measurement uncertainty are considered, and methods suggested to mitigate these. Improvement of the signal-to-noise ratio, and further development of the heat transport corrections for high dose gradient regions are key areas of focus highlighted for future development.

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Shin, Naomi. "Modeling secondary cancer risk following paediatric radiotherapy: a comparison of intensity modulated proton therapy and photon therapy". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106431.

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Proton radiotherapy is known to reduce the radiation dose delivered to normal healthy tissue compared to photon techniques. The increase in normal tissue sparing could result in fewer acute and late effects from radiation therapy. In this work proton therapy plans were created for patients previously treated using photon therapy. Intensity modulated proton therapy (IMPT) plans were planned using inverse planning in Varian's Eclipse treatment planning system with a scanning proton beam model to the same relative biological effectiveness (RBE)-weighted prescription dose as the photon plan. Proton and photon plans were compared for target dose conformity and homogeneity, body volumes receiving 2 Gy and 5 Gy, integral dose, dose to normal tissues and second cancer risk. Secondary cancer risk was determined using two methods. The relative risk of secondary cancer was found using the method described by Nguyen et al. by applying a linear relationship between integral dose and relative risk of secondary cancer. The second approach used Schneider et al.'s organ equivalent dose concept to describe the dose in the body and then calculate the excess absolute risk and cumulative risk for solid cancers in the body.IMPT and photon plans had similar target conformity and homogeneity. However IMPT plans had reduced integral dose and volumes of the body receiving low dose. Overall the risk of radiation induced secondary cancer was lower for IMPT plans compared to the corresponding photon plans with a reduction of ~36% using the integral dose model and ~50% using the organ equivalent dose model.
Un avantage connu de la radiothérapie par protons est la réduction de la dose reçue par les tissus normaux et sains par rapport aux traitements en photons. Cette réduction de dose peut résulter en une diminution des effets aigus et tardifs de la radiothérapie. Dans cet ouvrage, les plans de protonthérapie ont été créés pour des patients ayant été traités par radiothérapie en photons. Les plans de protonthérapie conformationnelle avec modulation d'intensité (PCMI) ont été conçus par planification inverse dans le système de planification de traitement Eclipse de Varian de façon à ce que le faisceau de protons en balayage produise la même dose de prescription que plan en photons, tout en tenant compte des efficacités biologiques relatives des deux types de radiation. Les plans en photons et en protons ont ensuite été comparés en termes de conformité de la dose, d'homogénéité de la dose, de volumes recevant 2 et 5 Gy, de dose intégrale, de dose aux tissus normaux et de risque de cancer secondaire. Le risque relatif de cancer secondaire a été determiné par la méthode décrite par Nguyen et al. en applicant une relation linéaire entre la dose intégrale et le risque relatif de cancer secondaire. Une deuxième approche employée dans cet ouvrage utilise le concept de dose équivalente à un organe de Schneider et al. pour décrire la dose dans le corps et par la suite calculer l'excès de risque absolu et le risque cumulatif de cancers solides dans le corps. Les traitements comparés, soit en photons et en protons, ont démontré une conformité et une homogénéité de la dose similaires dans le volume cible. Toutefois, les plans de PCMI réduisent la dose intégrale et diminuent les volumes du corps recevant une faible dose. Globalement, le risque d'induction d'un cancer secondaire est plus faible pour les plans de PCMI que pour les plans équivalents en photons avec une réduction de ~36% en utilisant le modèle de dose intégrale et ~50% en utilisant le modèle de dose équivalente à un organe.

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Bulawa, Lillith. "The Effects of Total Body Proton Irradiation on Mouse Myometrium". Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/548.

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The boundaries of human space exploration continue to expand with new technology and discoveries making it even more important to investigate the effects of space on biological systems. Although humans have explored space in small increments, reproductive studies must be conducted to determine if stable short- or long-term residences for humans can exist in space. This study explored the effects of whole-body proton radiation on uterine smooth muscle known as the myometrium. Two types of mice utilized in this study were C57BL/6 and B6.129S6Cybbtm1Din/J NOX2 knockout mice. C57BL/6 mice are standard laboratory mice that were used to represent the wildtype treatment group (N=18). The B6.129S6Cybbtm1Din/J NOX2 knockout mice have the NADPH Oxidase 2 gene shut off and represented the NOX2 Knockout treatment group (N=18). A third treatment group was made up of half of the C57BL/6 mice and were fed apocynin (N=18). Apocynin has been shown to inhibit NAPDH oxidase production in mice. NADPH Oxidase 2 is involved in the production of deleterious Reactive Oxygen Species (ROS); thus, apocynin should reduce the production of ROS in mice exposed to radiation. Different doses of radiation (0Gy, 0.5Gy, and 2.0Gy) were applied to the myometrium creating three different treatment subgroups within each mouse strain. The mice received 250 MeV protons at an approximate dose rate of 70cGy/ minute. Myometrium tissue was obtained one week following the radiation treatment. The uteri were removed, embedded, sectioned, and stained in hematoxylin and eosin solution. Thickness was determined by taking five measurements each of the outer longitudinal layer length, the inner circular layer length and the total length of both layers of the myometrium for three individual pieces of tissue for each animal. A one-way analysis of variance (ANOVA) was used to determine statistical differences between the groups and subgroups. Wildtype control mice exposed to 2.0Gy (N=5) of radiation had the thickest outer longitudinal layers compared to wildtype mice exposed to 0Gy (N=5) and 0.5Gy (N=6) (p=0.005, p=0). In the apocynin fed and Knockout treatment groups, the subgroups exposed to 0Gy had the thickest layers compared to their respective subgroups exposed to 0.5Gy and 2.0Gy. The apocynin fed mice exposed to 0Gy (N=6) outer longitudinal layer was statistically significantly thicker than the apocynin-fed mice exposed to 0.5Gy (p=0.004; N=6). The inner circular layer of the apocynin-fed mice exposed to 0.5Gy was statistically significantly thicker than the apocynin-fed mice exposed to 2.0Gy (p=0.001; N=6). Amongst the treatment groups, the wildtype control versus the apocynin fed mice exposed to 0Gy showed the apocynin-fed group to have the thicker outer longitudinal layer (p=0.003) and combined layers (p=0.001). Overall, the knockout group showed no statistical difference when compared to the wildtype control group. Further studies are necessary to reduce the possible confounding effect of the estrous cycle in the mice. The different phases of the mice estrus cycle may inadvertently affect the mouse uterine thickness due to the fluctuations in hormones. This study will add to the limited research regarding the female reproductive system in hopes of expanding the knowledge needed to actualize space colonization.

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Allums, Kimberly K. "Proton radiation and thermal stabilty [sic] of gallium nitride and gallium nitride devices". [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013123.

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Koch, Inken. "Measurements of 2π⁰ and 3π⁰ Production in Proton-Proton Collisions at a Center of Mass Energy of 2.465 GeV". Doctoral thesis, Uppsala University, Department of Nuclear and Particle Physics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4350.

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Neutral two- and three-pion productions in proton-proton collisions at a center of mass energy of 2.465 GeV have been studied using the WASA detector and an internal pellet target at the CELSIUS storage ring in Uppsala. An important part of the detector for the measurments was a central electromagnetic calorimeter composed of 1012 CsI crystals, which measured the photons originating from neutral pion decays. Test measurements and calibration procedures for this detector part were carried out. An important part of the analysis was the identification of the neutral pions from the invariant mass of the decay gammas and the use of Monte Carlo simulations to understand the detector responds.

Total cross sections for the pp→ppπ⁰π⁰ and pp→ppπ⁰π⁰π⁰ reactions are presented as well as distributions of relevant kinematical variables for the pp→ppπ⁰π⁰ reaction.

The distributions show significant deviations from phase space predictions. These deviations are typical for resonance production. The excitation of two simultaneous Δ resonances seems to be the main reaction mechanism.

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Quiñones, Catherine Thérèse. "Proton computed tomography". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI094/document.

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L'utilisation de protons dans le traitement du cancer est largement reconnue grâce au parcours fini des protons dans la matière. Pour la planification du traitement par protons, l'incertitude dans la détermination de la longueur du parcours des protons provient principalement de l'inexactitude dans la conversion des unités Hounsfield (obtenues à partir de tomographie rayons X) en pouvoir d'arrêt des protons. La tomographie proton (pCT) est une solution attrayante car cette modalité reconstruit directement la carte du pouvoir d'arrêt relatif à l'eau (RSP) de l'objet. La technique pCT classique est basée sur la mesure de la perte d'énergie des protons pour reconstruire la carte du RSP de l'objet. En plus de la perte d'énergie, les protons subissent également des diffusions coulombiennes multiples et des interactions nucléaires qui pourraient révéler d'autres propriétés intéressantes des matériaux non visibles avec les cartes de RSP. Ce travail de thèse a consisté à étudier les interactions de protons au travers de simulations Monte Carlo par le logiciel GATE et d'utiliser ces informations pour reconstruire une carte de l'objet par rétroprojection filtrée le long des chemins les plus vraisemblables des protons. Mise à part la méthode pCT conventionnelle par perte d'énergie, deux modalités de pCT ont été étudiées et mises en œuvre. La première est la pCT par atténuation qui est réalisée en utilisant l'atténuation des protons pour reconstruire le coefficient d'atténuation linéique des interactions nucléaires de l'objet. La deuxième modalité pCT est appelée pCT par diffusion qui est effectuée en mesurant la variation angulaire due à la diffusion coulombienne pour reconstruire la carte de pouvoir de diffusion, liée à la longueur de radiation du matériau. L'exactitude, la précision et la résolution spatiale des images reconstruites à partir des deux modalités de pCT ont été évaluées qualitativement et quantitativement et comparées à la pCT conventionnelle par perte d'énergie. Alors que la pCT par perte d'énergie fournit déjà les informations nécessaires pour calculer la longueur du parcours des protons pour la planification du traitement, la pCT par atténuation et par diffusion donnent des informations complémentaires sur l'objet. D'une part, les images pCT par diffusion et par atténuation fournissent une information supplémentaire intrinsèque aux matériaux de l'objet. D'autre part, dans certains des cas étudiés, les images pCT par atténuation démontrent une meilleure résolution spatiale dont l'information fournie compléterait celle de la pCT par perte d'énergie
The use of protons in cancer treatment has been widely recognized thanks to the precise stopping range of protons in matter. In proton therapy treatment planning, the uncertainty in determining the range mainly stems from the inaccuracy in the conversion of the Hounsfield units obtained from x-ray computed tomography to proton stopping power. Proton CT (pCT) has been an attractive solution as this modality directly reconstructs the relative stopping power (RSP) map of the object. The conventional pCT technique is based on measurements of the energy loss of protons to reconstruct the RSP map of the object. In addition to energy loss, protons also undergo multiple Coulomb scattering and nuclear interactions which could reveal other interesting properties of the materials not visible with the RSP maps. This PhD work is to investigate proton interactions through Monte Carlo simulations in GATE and to use this information to reconstruct a map of the object through filtered back-projection along the most likely proton paths. Aside from the conventional energy-loss pCT, two pCT modalities have been investigated and implemented. The first one is called attenuation pCT which is carried out by using the attenuation of protons to reconstruct the linear inelastic nuclear cross-section map of the object. The second pCT modality is called scattering pCT which is performed by utilizing proton scattering by measuring the angular variance to reconstruct the relative scattering power map which is related to the radiation length of the material. The accuracy, precision and spatial resolution of the images reconstructed from the two pCT modalities were evaluated qualitatively and quantitatively and compared with the conventional energy-loss pCT. While energy-loss pCT already provides the information needed to calculate the proton range for treatment planning, attenuation pCT and scattering pCT give complementary information about the object. For one, scattering pCT and attenuation pCT images provide an additional information intrinsic to the materials in the object. Another is that, in some studied cases, attenuation pCT images demonstrate a better spatial resolution and showed features that would supplement energy-loss pCT reconstructions

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Nelson, Anthony Joseph. "Effects of Proton Irradiation on the Mechanical and Physical Properties of Carbon Nanotube Based Composites". Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25153.

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In this study, the effects of proton irradiation on carbon nanotube (CNT)-epoxy composites are investigated for potential applications in radiation shielding for spacecraft. CNT-epoxy composites were prepared using multiwall and single wall CNTs and exposed to proton beams of energies ranging from 6 MeV to 12 MeV. The nanocomposites shielding capabilities against the different energetic proton beams were measured by tracking the beam's energy before and after penetrating the samples. The microstructures of the samples were characterized using scanning electron microscopy (FESEM). The effect of proton irradiation on the electrical resistivity was measured using a high resolution multimeter. Finally the influence of the irradiation on the mechanical properties, such as the elastic modulus and hardness, was probed using instrumented nanoindentation tests. The proton stopping power of the epoxy was shown to be unchanged by the addition of CNTs, which is a promising result since the hardness of the samples was shown to be increased by addition of CNTs. Unfortunately, however, the surface of the samples proved to be too rough for nanoindentation to yield more detailed results. This was due to the use of a diamond saw in cutting the samples to size. The addition of CNTs was shown to reduce the volume electrical resistivity of the neat epoxy by almost five orders of magnitude and the irradiation further reduced it by a factor of 2-16.
Master of Science

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Olvitt, Daniel L. "Measurement of the Longitudinal Double Spin Asymmetry for Dijet Production in Polarized Proton+Proton Collisions at sqrt(s) = 510 GeV at STAR". Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/480255.

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Physics
Ph.D.
Understanding what contributes to the intrinsic angular momentum (spin) of the proton has been a major goal of the nuclear physics community. In the 1980s, it was discovered that quarks contribute 30% to the spin of the proton. This information led to a search to find other contributions to the spin of the proton. At STAR, the double spin asymmetry (ALL) is measured as it is sensitive to the polarized gluon distribution (Dg(x)). The STAR 2009 inclusive jet ALL at sqrt(s) = 200 GeV has been incorporated into two independent global fits. These fits show for the first time a statistically significant non-zero gluon contribution to the spin of the proton in the parton momentum fraction range x > 0.05. Dijet ALL is also measured at STAR. Dijets are advantageous since the parton momentum fraction (x) of the initial partons may be reconstructed to first order from final state measurements. In 2013 STAR collected an estimated 250 pb-1 of data at sqrt(s) = 510 GeV. The higher center of mass energy will allow STAR to probe Dg(x) at x values as low as 0.02. The large statistics will allow a reduction in the uncertainties. Once the data is incorporated into future global fits, it will allow for a more precise determination of Dg(x). The 2013 dijet ALL results will be presented. The results show good agreement with both global fits and previous STAR results dijet measurements.
Temple University--Theses

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Gow, Jason Peter David. "Radiation damage analysis of the swept charge device for the C1XS instrument". Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/4311.

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This thesis is concerned with ensuring high energy resolution from the swept charge device (SCD) CCD54, essentially a non-pixellated version of the charge coupled device (CCD), for use in the Chandrayaan-1 X-ray Spectrometer (C1XS). Of particular interest is the effect on performance due to the radiation damage, caused by protons, the CCD54s used in C1XS will receive during the transfer to the Moon and during the two years in lunar orbit. Chapter 2 reviews the atomic structure, the formation and detection of X-rays, and the operation of a CCD. Chapter 3 discusses the space radiation environment and the damaging effects it has on CCDs, for example increasing dark current and charge transfer inefficiency. Chapter 4 presents the basic laboratory equipment and procedure used during the experimental work, and details the initial optimisation and characterisation, the pre-flight characterisation of devices available for use in C1XS, the measurement of the depletion depth, and quantum efficiency of the CCD54. Chapter 5 details the results of the initial proton irradiation study, intended to demonstrate the ability of the CCD54 to provide excellent scientific data over the two years at the Moon. Chapter 6 describes a second irradiation study covering a more detailed investigation of the damage effects, investigating dark current, trap energy levels, and charge transfer inefficiency. Chapter 7 describes work conducted to assist the C1XS science team in the development of an X-ray fluorescence model, to be used with X-ray spectra provided by the X-ray solar monitor and the spectra detected by C1XS, to provide elemental abundance information of the lunar surface. It also presents the initial C1XS results from the Moon, and a brief comparison of the CCD54 with other semiconductor X-ray fluorescence detectors. Chapter 8 describes the final conclusions and recommendations for further work, including a study of the radiation damage effects during the two years at the Moon and the future development of SCD detectors for use in space.

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Kimstrand, Peter. "Beam Modelling for Treatment Planning of Scanned Proton Beams". Doctoral thesis, Uppsala University, Oncology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8640.

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Scanned proton beams offer the possibility to take full advantage of the dose deposition properties of proton beams, i.e. the limited range and sharp peak at the end of the range, the Bragg peak. By actively scanning the proton beam, laterally by scanning magnets and longitudinally by shifting the energy, the position of the Bragg peak can be controlled in all three dimensions, thereby enabling high dose delivery to the target volume only. A typical scanned proton beam line consists of a pair of scanning magnets to perform the lateral beam scanning and possibly a range shifter and a multi-leaf collimator (MLC). Part of this thesis deals with the development of control, supervision and verification methods for the scanned proton beam line at the The Svedberg laboratory in Uppsala, Sweden.

Radiotherapy is preceded by treatment planning, where one of the main objectives is predicting the dose to the patient. The dose is calculated by a dose calculation engine and the accuracy of the results is of course dependent on the accuracy and sophistication of the transport and interaction models of the dose engine itself. But, for the dose distribution calculation to have any bearing on the reality, it needs to be started with relevant input in accordance with the beam that is emitted from the treatment machine. This input is provided by the beam model. As such, the beam model is the link between the reality (the treatment machine) and the treatment planning system. The beam model contains methods to characterise the treatment machine and provides the dose calculation with the reconstructed beam phase space, in some convenient representation. In order for a beam model to be applicable in a treatment planning system, its methods have to be general.

In this thesis, a beam model for a scanned proton beam is developed. The beam model contains models and descriptions of the beam modifying elements of a scanned proton beam line. Based on a well-defined set of generally applicable characterisation measurements, ten beam model parameters are extracted, describing the basic properties of the beam, i.e. the energy spectrum, the radial and the angular distributions and the nominal direction. Optional beam modifying elements such as a range shifter and an MLC are modelled by dedicated Monte Carlo calculation algorithms. The algorithm that describes the MLC contains a parameterisation of collimator scatter, in which the rather complex phase space of collimator scattered protons has been parameterised by a set of analytical functions.

Dose calculations based on the phase space reconstructed by the beam model are in good agreement with experimental data. This holds both for the dose distribution of the elementary pencil beam, reflecting the modelling of the basic properties of the scanned beam, as well as for complete calculations of collimated scanned fields.

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Warren, Daniel Rosevear. "Proton radiotherapy uncertainties arising from computed tomography". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ab59f596-e277-490a-a7c1-1cb81b47b9a9.

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Proton radiotherapy is a cancer treatment which has the potential to offer greater cure rates and/or fewer serious side effects than conventional radiotherapy. Its availability in the UK is currently limited to a single low-energy fixed beamline for the treatment of ocular tumours, but a number of facilities designed to treat deep-seated tumours are in development. This thesis focusses on the quantitative use of x-ray computed tomography (CT) images in planning proton radiotherapy treatments. It arrives at several recommendations that can be used to inform clinical protocols for the acquisition of planning scans, and their subsequent use in treatment planning systems. The primary tool developed is a software CT scanner, which simulates images of an anthropomorphic virtual phantom, informed by measurements taken on a clinical scanner. The software is used to investigate the accuracy of the stoichiometric method for calibrating CT image pixel values to proton stopping power, with particular attention paid to the impact of beam hardening and photon starvation artefacts. The strength of the method adopted is in allowing comparison between CT-estimated and exactly-calculated proton stopping powers derived from the same physical data (specified in the phantom), leading to results that are difficult to obtain otherwise. A number of variations of the stoichiometric method are examined, identifying the best-performing calibration phantom and CT tube voltage (kVp). Improvements in accuracy are observed when using a second-pass beam hardening correction algorithm. Also presented is a method for identifying the proton paths where stopping power uncertainties are likely to be greatest. Estimates of the proton range uncertainties caused by CT artefacts and calibration errors are obtained for a range of realistic clinical scenarios. The current practice of including planning margins equivalent to 3.5% of the range is found to ensure coverage in all but the very worst of cases. Results herein suggest margins could be reduced to <2% if the best-performing protocol is followed; however, an analysis specific to the CT scanner and treatment site in question should be carried out before such a change is made in the clinic.

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Fulcher, TJ. "The development of an interlock and control system for a clinical proton therapy system". Thesis, Cape Technikon, 1995. http://hdl.handle.net/20.500.11838/1483.

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Thesis (Masters Diploma (Technology))--Cape Technikon, Cape Town, 1995
The development of a 200 MeV clinical proton therapy facility at the National Accelerator Centre required an interlock and control system to supervise the delivery of radiation to a patient. The interlock and control system is responsible for ensunng that nobody enters the treatment vault during an irradiation, the extraction of the beamstop devices 'from the beam-line to allow the irradiation of the patient and the insertion of those beam-stop devices when an error condition is detected. Because of its nature, the interlock and control system should be designed so that in the event of an error condition being detected, it should fail to a safe state. This is achieved by modelling the interlock and control system with an appropriate modeling method. This thesis describes a graphical modelling method called Petri-nets, which was used to model the system, and the software developed from the model.

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Fredriksson, Albin. "Robust optimization of radiation therapy accounting for geometric uncertainty". Doctoral thesis, KTH, Optimeringslära och systemteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122262.

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Geometric errors may compromise the quality of radiation therapy treatments. Optimization methods that account for errors can reduce their effects. The first paper of this thesis introduces minimax optimization to account for systematic range and setup errors in intensity-modulated proton therapy. The minimax method optimizes the worst case outcome of the errors within a given set. It is applied to three patient cases and shown to yield improved target coverage robustness and healthy structure sparing compared to conventional methods using margins, uniform beam doses, and density override. Information about the uncertainties enables the optimization to counterbalance the effects of errors. In the second paper, random setup errors of uncertain distribution---in addition to the systematic range and setup errors---are considered in a framework that enables scaling between expected value and minimax optimization. Experiments on a phantom show that the best and mean case tradeoffs between target coverage and critical structure sparing are similar between the methods of the framework, but that the worst case tradeoff improves with conservativeness. Minimax optimization only considers the worst case errors. When the planning criteria cannot be fulfilled for all errors, this may have an adverse effect on the plan quality. The third paper introduces a method for such cases that modifies the set of considered errors to maximize the probability of satisfying the planning criteria. For two cases treated with intensity-modulated photon and proton therapy, the method increased the number of satisfied criteria substantially. Grasping for a little less sometimes yields better plans. In the fourth paper, the theory for multicriteria optimization is extended to incorporate minimax optimization. Minimax optimization is shown to better exploit spatial information than objective-wise worst case optimization, which has previously been used for robust multicriteria optimization. The fifth and sixth papers introduce methods for improving treatment plans: one for deliverable Pareto surface navigation, which improves upon the Pareto set representations of previous methods; and one that minimizes healthy structure doses while constraining the doses of all structures not to deteriorate compared to a reference plan, thereby improving upon plans that have been reached with too weak planning goals.

QC 20130516

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Xu, Da. "Reconstruction and applications of QED final state radiation photons in Z->mumu decays produced in 7 TeV proton-proton collisions at the Large Hadron Collider". Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2265/.

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This thesis presents a method for including the final state radiation (FSR) photon in the reconstruction of Z bosons decaying into pairs of muons (Z ->mumu). An algorithm for the reconstruction of FSR photons has been developed. The FSR photon candidates with ET >1.3 GeV are reconstructed within dR < 0.15 cone about the axis defined by the muon momentum direction at the interaction point, using the liquid argon calorimeter of ATLAS and a special clustering efficient at low energies. Based on an integrated luminosity of 164 pb-'1 , the cross section of the Z->mumu events with at least one FSR photon within fiducial region (ET>1.3 GeV and dR <0.15) is measured: 0.073±0.001(stat)±0.006(sys)±0.002(lum) nb. This is consistent with the expectation from a NNLO QCD calculation including QED FSR. Photons within the fiducial region are reconstructed with a 70% average efficiency which increases to 85% for ET > 4 GeV. Inclusion of these photons in the dimuon invariant mass calculation was shown to lead to improved Z-boson invariant mass resolution and scale: a Gaussian fit shows that the peak of the distribution moves from 89 GeV to 91.31±0.06 GeV with a standard deviation of 2.5±0.07 GeV. A 20% of all inclusive Z->mumu events are corrected in the tail of the invariant mass (M<80 GeV). Moreover, based on a test with simulated Higgs->ZZ()-> 4mu samples, more than 20% of the events are expected to find a reconstructed FSR photon around. The improvement of the Higgs invariant mass resolution and scale by adding the reconstructed FSR photons is presented.

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Mondlane, Gracinda. "Comparative study of Radiation Therapy of Targets in the Upper Abdomen with Photon- or Scanned Proton-beams". Licentiate thesis, Stockholms universitet, Fysikum, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-144550.

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Recently, there has been an increase in the number of proton beam therapy (PBT) centers operating worldwide. For certain cases, proton beams have been shown to provide dosimetric and radiobiological advantages when used for cancer treatment, compared to the regular photon-beam based treatments. Under ideal circumstances, the dose given to the tissues surrounding a target can be reduced with PBT. The risk for side effects following treatment is then expected to decrease. Until present, mainly stationary targets, e.g. targets in the brain, have been treated with PBT. There is currently a growing interest to treat also target volumes in other parts of the body with PBT. However, there are sources of uncertainties, which must be more carefully considered when PBT is used, especially for PBT carried out with scanned proton beams. PBT is more sensitive to anatomical changes, e.g. organ motion or a variable gas content in the intestines, which requires that special precautions are taken prior to treating new tumour sites. In photon beam radiotherapy (RT) of moving targets, the main consequence of organ motion is the loss of sharpness of the dose gradients (dose smearing). When scanned proton beams are used, dose deformation caused by the fluctuations in the proton beam range, due to varying tissue heterogeneities (e.g., the ribs moving in and out of the beam path) and the so-called interplay effect, can be expected to impact the dose distributions in addition to the dose smearing. The dosimetric uncertainties, if not accounted for, may cause the planned and accurately calculated dose distribution to be distorted, compromising the main goal of RT of achieving the maximal local disease control while accepting certain risks for normal tissue complications. Currently there is a lack of clinical follow-up data regarding the outcome of PBT for different tumour sites, in particular for extra-cranial tumour sites in moving organs. On the other hand, the use of photon beams for this kind of cancer treatment is well-stablished. A treatment planning comparison between RT carried out with photons and with protons may provide guidelines for when PBT could be more suitable. New clinical applications of particle beams in cancer therapy can also be transferred from photon-beam treatments, for which there is a vast clinical experience. The evaluation of the different uncertainties influencing RT of different tumour sites carried out with photon- and with proton-beams, will hopefully create an understanding for the feasibility of treating cancers with scanned proton beams instead of photon beams. The comparison of two distinct RT modalities is normally performed by studying the dosimetric values obtained from the dose volume histograms (DVH). However, in dosimetric evaluations, the outcome of the treatments in terms of local disease control and healthy tissue toxicity are not estimated. In this regard, radiobiological models can be an indispensable tool for the prediction of the outcome of cancer treatments performed with different types of ionising radiation. In this thesis, different factors that should be taken into consideration in PBT, for treatments influenced by organ motion and density heterogeneities, were studied and their importance quantified. This thesis consists of three published articles (Articles I, II and III). In these reports, the dosimetric and biological evaluations of photon-beam and scanned proton-beam RT were performed and the results obtained were compared. The studies were made for two tumour sites influenced by organ motion and density changes, gastric cancer (GC) and liver metastases. For the GC cases, the impact of changes in tissue density, resulting from variable gas content (which can be observed inter-fractionally), was also studied. In this thesis, both conventional fractionations (implemented in the planning for GC treatments) and hypofractionated regimens (implemented in the planning for the liver metastases cases) were considered. In this work, it was found that proton therapy provided the possibility to reduce the irradiations of the normal tissue located near the target volumes, compared to photon beam RT. However, the effects of density changes were found to be more pronounced in the plans for PBT. Furthermore, with proton beams, the reduction of the integral dose given to the OARs resulted in reduced risks of treatment-induced secondary malignancies.

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Dahlgren, David. "Monte Carlo simulations of Linear Energy Transfer distributions in radiation therapy". Thesis, Uppsala universitet, Högenergifysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446550.

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In radiotherapy, a quantity asked for by clinics when calculating a treatment plan, along withdose, is linear energy transfer. Linear energy transfer is defined as the absorbed energy intissue per particle track length and has been shown to increase with relative biologicaleffectiveness untill the overkilling effect. In this master thesis the dose averaged linear energytransfer from proton and carbon ion beams was simulated using the FLUKA multi purposeMonte Carlo code. The simulated distributions have been compared to algorithms fromRaySearch Laboratories AB in order to investigate the agreement between the computationmethods. For the proton computation algorithm improvements to the current scoring algorithmwere also implemented. A first version of the linear energy transfer validation code was alsoconstructed. Scoring of linear energy transfer in the RaySearch algorithm was done with theproton Monte Carlo dose engine and the carbon pencil beam dose engine. The results indicatedthat the dose averaged linear energy transfer from RaySearch Laboratories agreed well for lowenergies for both proton and carbon beams. For higher energies shape differences were notedwhen using both a small and large field size. The protons, the RaySearch algorithm initiallyoverestimates the linear energy transfer which could result from fluence differences in FLUKAcompared to the RaySearch algorithm. For carbon ions, the difference could stem from someloss of information in the tables used to calculate the linear energy transfer in the RaySearchalgorithm. From validation γ-tests the proton linear energy transfer passed for (3%/3mm) and(1%/1mm) with no voxels out of tolerance. γ-tests for the carbon linear energy transfer passedwith no voxels out of tolerance for (5%/5mm) and a fail rate of 2.92% for (3%/3mm).

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Yoshioka, Hiroki 1967. "Application of the smart scattering method to generate an extended first collision source for electron and proton beam source problems". Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278388.

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Charged particle beam source problems are difficult to simulate because of the extremely large and anisotropic scattering cross sections, and the associated singularities in angle and space. To overcome these difficulties the Extended First Collision Source method and the SMART (Simulation of Many Accumulative Rutherford Trajectories) scattering method have been developed. In this study, the extended first collision source calculation was improved in the SN code using the SMART scattering method which produces smoother and smaller effective cross sections. To determine the uncollided flux which was necessary for the first collision source calculation, the SMART scattering cross sections were used instead of screened Rutherford scattering cross sections. After the SN code was modified, it produced results that approached those obtained using the benchmark Monte Carlo code.

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Ntentas, Georgios. "Radiation dosimetry for studying the late effects of radiotherapy". Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:7fb38ff2-9618-4f38-9953-106d832ab7db.

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Evidence that radiation-related cardiovascular disease and second primary cancers can occur in cancer survivors following radiation therapy (RT) has emerged from several independent sources. Cardiotoxicity and second cancers are of particular concern for patients with good prognosis, such as those with Hodgkin lymphoma (HL). HL patients are among the youngest to receive RT, which means that those who are cured of their cancer have decades-long natural life-expectancies during which treatment-related long-term toxicities may cause years of excess morbidity or premature mortality. A considerable amount of research has been conducted to investigate the risk of radiation-related cardiotoxicity and second cancers. However, there are still substantial gaps in knowledge. It is therefore important to improve our understanding regarding these risks and develop treatment approaches and survivorship care to minimise their impact on patients' quality of life. In this thesis, I have investigated the risk of congestive heart failure (CHF) in a cohort of 2619 HL survivors and presented, for the first time, dose-response relationships for risk of CHF versus cardiac radiation doses. I also validated the radiation dosimetry method used to estimate the cardiac doses in this study as well as for other reconstruction methods, versus a gold standard based on the patients' own computed tomography scans. Additionally, I investigated what effect the dose reconstruction errors had on the dose-response relationships. I then focused on modern RT methods and specifically on proton RT. Based on published dose-response relationships (including that developed in this thesis) I predicted cardiovascular and second cancer risks for patients treated with advanced RT. This thesis has provided new knowledge in the study of late effects in HL patients who were treated decades ago as well as for patients treated more recently with advanced RT methods. The results here can be used to facilitate progress towards personalised RT in terms of choosing the appropriate RT method by integrating individualised risk prediction in advanced RT treatment planning. The research here provides the basis for further work towards evidence-based case selection for HL patients for the first NHS proton therapy centres in the UK, opening in 2018-2021.

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Armstrong, Whitney Richard. "Measurement of the proton A1 and A2 spin asymmetries| Probing color forces". Thesis, Temple University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3702966.

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The Spin Asymmetries of the Nucleon Experiment (SANE) measured the proton spin structure function g₂ in a range of Bjorken x, 0.3 < x < 0.8, where extraction of the twist-3 matrix element d₂^p (an integral of g₂ weighted by x²) is most sensitive. The data was taken from Q² equal to 2.5 GeV² up to 6.5 GeV². In this polarized electron scattering off a polarized hydrogen target experiment, two double spin asymmetries, A∥ and A_⊥ were measured using the BETA (Big Electron Telescope Array) Detector. BETA consisted of a scintillator hodoscope, gas Čerenkov counter, lucite hodoscope and a large lead glass electromagnetic calorimeter. With a unique open geometry, a threshold gas Čerenkov detector allowed BETA to cleanly identify electrons for this inclusive experiment. A measurement of d₂^p is compared to lattice QCD calculations.

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Beresford, Lydia Audrey. "Searches for dijet resonances using √s = 13 TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider". Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:c516b04b-2763-487a-a633-6c506cec93ad.

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This thesis presents three searches for new resonances in dijet invariant mass spectra. The spectra are produced using √s = 13 TeV proton-proton collision data recorded by the ATLAS detector. New dijet resonances are searched for in the mass range 200 GeV to 6.9 TeV in mass. Heavy new resonances, with masses above 1.1 TeV, are targeted by a high mass dijet search. Light new resonances, with masses down to 200 GeV, are searched for in dijet events with an associated high momentum object (a photon or a jet) arising from initial state radiation. The associated object is used to efficiently trigger the recording of low mass dijet events. All of the analyses presented in this thesis search for an excess of events, localised in mass, above a data-derived estimate of the smoothly falling QCD background. In each search no evidence for new resonances is observed, and the data are used to set 95% C.L. limits on the production cross-section times acceptance times branching ratio for model-independent Gaussian resonance shapes, as well as benchmark signals. One particular benchmark signal which is considered in all of the searches is an axial-vector Z' dark matter mediator model whose parameter space is reduced due to the results presented in this thesis.

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Neupane, Mahesh Raj. "Optimization of a sequential alignment verification and positioning system (SAVPS) for proton radiosurgery". CSUSB ScholarWorks, 2005. https://scholarworks.lib.csusb.edu/etd-project/2784.

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Functional proton-beam stereotactic radiosurgery requires sub-millimeter alignment accuracy. A patient tracking system called Sequential Alignment and Position Verification System (SAVPS) is under development at Loma Linda University Medical Center. An optical positioning system (OPS), manufactured by Vicon Peak, has been chosen to verify the correct alignment of the target with the proton beam axis. The main objective of this thesis is to optimize an existing version of SAVPS by conducting error analysis. An image processing algorithm was developed and applied to estimate the error introduced by the Patient Positioning System (PPS) in order to derive the true error of the SAVPS.

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37

MORAES, GILBERTO de O. "Obtencao de membranas tracadoras de protons a base polietileno para uso em celulas a combustivel". reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9359.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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38

De, Smet Valérie. "Neutron measurements in a proton therapy facility and comparison with Monte Carlo shielding simulations". Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/235859.

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Proton therapy uses proton beams with energies of 70 – 230 MeV to treat cancerous tumours very effectively, while preserving surrounding healthy tissues as much as possible. During nuclear interactions of these protons with matter, secondary neutrons can be produced. These neutrons can have energies ranging up to the maximum energy of the protons and can thus be particularly difficult to attenuate. In fact, the rooms of a proton therapy facility are generally surrounded by concrete walls of at least ~2 m in thickness, in order to protect the members of the staff and the public from the stray radiation. Today, the design of the shielding walls is generally based on Monte Carlo simulations. Amongst the numerous parameters on which these simulations depend, some are difficult to control and are therefore selected in a conservative manner. Despite these conservative choices, it remains important to carry out accurate neutron dose measurements inside proton therapy facilities, in order to assess the effectiveness of the shielding and the conservativeness of the simulations. There are, however, very few studies in literature which focus on the comparison of such simulations with neutron measurements performed outside the shielding in proton therapy facilities. Moreover, the published measurements were not necessarily acquired with detectors that possess a good sensitivity to neutrons with energies above 20 MeV, while these neutrons actually give an important contribution to the total dose outside the shielding. A first part of this work was dedicated to the study of the energy response function of the WENDI-2, a rem meter that possesses a good sensitivity to neutrons of more than 20 MeV. The WENDI-2 response function was simulated using the Monte Carlo code MCNPX and validation measurements were carried out with 252Cf and AmBe sources as well as high-energy quasi-monoenergetic neutron beams. Then, WENDI-2 measurements were acquired inside and outside four rooms of the proton therapy facility of Essen (Germany). MCNPX simulations, based on the same conservative choices as the original shielding design simulations, were carried out to calculate the neutron spectra and WENDI-2 responses in the measurement positions. A relatively good agreement between the simulations and the measurements was obtained in front of the shielding, whereas overestimates by at least a factor of 2 were obtained for the simulated responses outside the shielding. This confirmed the conservativeness of the simulations with respect to the neutron fluxes transmitted through the walls. Two studies were then carried out to assess the sensitivity of the MCNPX simulations to the defined concrete composition and the selected physics models for proton and neutron interactions above 150 MeV. Both aspects were found to have a significant impact on the simulated neutron doses outside the shielding. Finally, the WENDI-2 responses measured outside the fixed-beam treatment room were also compared to measurements acquired with an extended-range Bonner Sphere Spectrometer and a tissue-equivalent proportional counter. A satisfactory agreement was obtained between the results of the three measurement techniques.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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39

Lin, Dexu [Verfasser]. "Measurement of proton electromagnetic form factors using the initial-state-radiation process e+e- ppgamma at BESIII / Dexu Lin". Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1140663593/34.

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40

Vu, An T. (An Thien). "Radiation therapy of pediatric brain tumors : comparison of long-term health effects and costs between proton therapy and IMRT". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65511.

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Thesis (S.M. in Technology and Policy)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 101-109).
Radiation therapy is an important component of pediatric brain tumor treatment. However, radiation-induced damage can lead to adverse long-term health effects. Proton therapy has the ability to reduce the dose delivered to healthy tissue when compared to photon radiation therapy, but this dose benefit comes at a significantly higher initial cost, as proton therapy is 2 to 3 times more expensive to deliver than photon therapy. This thesis provides a framework for the evaluation of health and cost effectiveness of proton therapy compared to Intensity Modulated Radiation Therapy (IMRT). Proton therapy and IMRT treatment plans of patients treated for low-grade gliomas (LGGs) were analyzed to provide risk estimates of long-term health effects based on the dose distributions. A Markov simulation model was developed to estimate the health effects and costs of proton therapy and IMRT. The model tracked a pediatric cohort treated for LGGs at age 5. In the model, the patients were at risk of acquiring IQ loss, growth hormone deficiency (GHD), hypothyroidism, hearing loss, and secondary cancer. Patients faced risks of death due to tumor recurrence, secondary cancer, and normal death. In addition, a review of literature was performed to estimate the costs and additional health risks not determined from the patient treatment plans. The simulation results show that proton therapy can be cost effective in the treatment of LGGs based on the health risks estimated from the patients treatment plans. The cost associated with IQ loss and GHD were the main contributors to the total costs from long-term health effects. Proton therapy also results in a lower level of IQ loss and a lower risk of acquiring other long-term health effects. However, the relative difference in IQ point loss between the treatment modalities is small in the limited number of patients studied. There is a need to further investigate the advantages of proton therapy in reducing the dose delivered to the relevant parts of the brain to lower the risks of adverse health effects, especially for IQ loss.
by An Thien Vu.
S.M.
S.M.in Technology and Policy

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41

Adikaram, Dasuni Kalhari. "Direct measurements of two photon exchange on lepton-proton elastic scattering using simultaneous electron-positron beams in CLAS". Thesis, Old Dominion University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3580489.

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The electric (G_E) and magnetic ( G_M) form factors of the proton are fundamental observables which characterize its charge and magnetization distributions. There are two methods to measure the proton form factors: the Rosenbluth separation method and the polarization transfer technique. However, the ratio of the electric and magnetic form factors measured by those methods significantly disagree at momentum transfer Q² > 1 GeV². The most likely explanation of this discrepancy is the inclusion of two-photon exchange (TPE) amplitude contributions to the elastic electron-proton cross section which significantly changes the extraction of G_E from the Rosenbluth separation measurement. The Jefferson Lab CLAS TPE experiment determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections. The primary electron beam was used to create an intense bremsstrahlung photon beam. Some of the photons were then converted to a mixed e⁺/ e^- beam which then interacted with a liquid hydrogen target. The e⁺p and e^-p events were detected by the CLAS (CEBAF Large Acceptance Spectrometer). The elastic cross section ratios ((σ( e⁺p)/(σ(e^-p)) were measured over a wide range of virtual photon polarization ϵ and Q². The cross section ratios displayed a strong ϵ dependence at Q² = 1.45 GeV². There is no significant Q² dependence observed at ϵ = 0.45. The results are consistent with a recent measurement at the VEPP-3 lepton storage ring in Novosibirsk and with the hadronic calculation by Blunders, Melnitchouk and Tjon. The hadronic calculation resolves the disagreement between the Rosenbluth separation and polarization transfer extractions of G_E/G_M at Q² up to 2 – 3 GeV². Applying the GLAS TPE correction to the Rosenbluth cross section measurements significantly decreases the extracted value of G_E and brings it into good agreement with the polarization transfer measurement at Q²∼1.75 GeV². Thus, these measurements appear to resolve the proton electric form factor discrepancy for Q² < 2 GeV².

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42

Mansouri, Ebrahim. "Studies on Radiation-induced Defects in InP/InAsP Nanowire-based Quantum Disc-in wire Photodetectors". Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-36126.

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Photodetectors are used in many applications such as digital and thermal cameras or in solar panels. They can also be designed to detect the omnipresent high-energy radiation/particles, and for radiation imaging in biomedical applications. Novel nanostructures offer significant advantages compared to traditional designs for the realization of fast, sensitive, compact and cheap sensors and efficient solar cells. Examples of such nanostructures include quantum dots (QDs), quantum wells (QWs) and NW arrays. This thesis is devoted to experimental investigations of effects of high-energy (1 MeV) protons on the optical and electrical performance of InP/InAsP NW-based QDiscs-in wire photodetectors. The proton-induced degradation of the optical performance has been studied by means of Fourier Transform Infrared (FTIR) photocurrent spectroscopy. The spectrally resolved photocurrent (PC) and current-voltage (I-V) characteristics were measured at low temperature (5 K and 77K) and at room temperature (300K) before and after 1 MeV proton irradiation under vacuum conditions with fluences ranging from 1.0×1012–3.0×1013 cm-2. The particle radiation exposure has been done in the Ion Beam Accelerator at the Department of Nuclear Physics Department at Lund University. Considering both PC and I-V characteristics, it was found that the devices were sensitive to all proton irradiation at all fluences. In general, the PC intensity significantly increased after radiation for all fluences, however, a week after exposure the PC and dark current gradually recovered. At 3×1012 p/cm2 fluence level, it was figured out that photocurrent which attributed to QDiscs disappeared for a couple of days after exposure, however, over time and gradually, those started to manifest again even at low and room temperatures, causing radiation-induced changes in device parameters to be time-dependent; however, it was not recorded any signals related to QDiscs at fluence of 3×1013 p/cm2. Substantial changes in the dark I-V characteristics, as well as increases in the dark current, are observed after irradiation. The influence of proton irradiation on light and dark current characteristics also indicated that NW structures are a good potential candidate for radiation harsh-environment applications. It was also observed a significant increase in dark current after the radiation for all devices, however, by applying the voltage to the photodetectors, the PC and I-V characteristics gradually being to diminish, which may be attributed to an annealing process.

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43

Weber, Adrian Bartholomäus [Verfasser]. "First determination of the proton electric form factor at very small momentum transfer using initial state radiation / Adrian Bartholomäus Weber". Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1131905768/34.

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Marusic, Tibor. "Ray Cast/Dose Superposition algorithm for proton grid therapy". Thesis, Stockholms universitet, Medicinsk strålningsfysik (tills m KI), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-148174.

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Purpose: To develop a Ray Cast/Dose Superposition (RC/DS) algorithm for proton grid therapy. Its functionality needed to include automatic positioning of small proton pencil beams in a grid-pattern and superimposing thin beam Monte Carlo (MC) dose distribution data on a Computer Tomography (CT) density volume. The purpose was to calculate and store un-weighted volumetric dose distributions of individual proton energies for subsequent optimization. Materials & Methods: Using the programming language Python 3.6, CT and Volume Of Interest (VOI) data of various patients and phantoms were imported. The target VOI was projected to either two or four planes, corresponding to the number of used gantry positions. Rays were then traced through the CT voxels, which were converted from Hounseld Units to density using a look up table, to calculate Water Equivalent Distance and proton energy needed to reach the proximal and distal edge of the target volume. With automated grid-pattern beam positioning, thin beam MC calculated depth dose distribution files were interpolated, scaled and superimposed on the CT volume for all beamlet positions. The algorithm reliability was tested on several CT image sets, the proton range estimation compared to a commercial TPS and the depth dose interpolation analyzed using MC simulations. Results: The RC/DS algorithm computation time was on average around 6 hours and 30 minutes for each CT set. The dose distribution output visually conformed to target locations and maintained a grid pattern for all tested CT sets. It gave unwanted dose artifacts in situations when rays outside the beamlet center passed a significant length of low/high density regions compared to the center, which yielded dose distributions of unlikely shape. Interpolating MC dose distribution values showed comparability to true MC references of same energy, yielding results with 0.5% difference in relative range and dose. Conclusions: The developed algorithm provides unweighted dose distributions specific for small beam proton grid therapy and has been shown to work for various setups and CT data. Un-optimized code caused longer computation times then intended but was presumed faster than MC simulations of the same setup. Efficiency and accuracy improvements are planed for in future work.
Proton grid therapy group

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45

CARMO, LUCAS S. do. "Dosimetria termoluminescente de altas doses de raios gama, raios beta, feixe de prótons e de nêutrons epitérmicos utilizando minerais naturais de silicatos e dosímetros de LiF: Mg, Cu, P (MCP)". reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/25192.

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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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46

SILVA, DANILO M. da. "Desenvolvimento de métodos para a geração e controle da emissão em lasers aleatórios e speckle". reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26808.

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Neste trabalho serão apresentados novos métodos baseados na geração e controle de comprimento de onda em lasers aleatórios e lasers de diodo. Na primeira parte do trabalho será demonstrado um laser aleatório com realimentação localizada em filmes em biopolímeros dopado com corante. O filme é constituído por um ácido desoxirribonucleico e cloreto de cetiltrimetilamônio (DNA-CTMA) dopado com DCM. No dispositivo proposto, a realimentação óptica para o laser aleatório é dada por centros de dispersão posicionados aleatoriamente ao longo das bordas da área ativa. Os elementos de dispersão são nanopartículas de dióxido de titânio (TiO2) ou defeitos aleatórios na interface entre o polímero ativo e ar. Diferentes espectros de emissão são observados, dependendo da geometria da área excitada. Um único ressonador aleatório com dimensões de 2.6 x 0.65 mm2 foi fabricado com emissão aleatória com realimentação obtida pela excitação do dispositivo por completo. A segunda parte deste trabalho apresenta um novo método para a geração e manipulação de franjas de contorno por meio de interferometria speckle com comprimento de onda sintética, usando um único laser de diodo com cavidade externa. A cavidade externa permite sintonizar duas emissões simultaneamente, o que por sua vez muda o intervalo entre as franjas de contorno do interferômetro, além de aumentar a estabilidade do laser. Uma análise de Fourier é proposta como alternativa para medir o comprimento de onda sintético resultante das duas emissões do laser.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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47

Zebrowska, Grazyna. "Application a la radiodosimetrie physico-chimique ou biologique des relaxations spin-reseau et spin-spin en rmn du proton (doctorat : genie biologique et medical)". Rennes 1, 1999. http://www.theses.fr/1999REN1B042.

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48

Howell, Gareth David. "Measurement of the e+p charged current cross-section with the Zeus detector at HERA". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299898.

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49

Torres, Henrique Lanza Faria. "Efeitos da radiação em transistores túnel-FET de porta tripla". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-28082018-151322/.

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Frente à crescente necessidade de que novas tecnologias sejam capazes de operar com confiabilidade em ambientes hostis, a análise dos efeitos da radiação ionizante em dispositivos semicondutores se tornou um ramo de pesquisa em contínua ascensão, contribuindo para o desenvolvimento de tecnologias estratégicas e promovendo o aprimoramento científico e o desenvolvimento tecnológico da humanidade. Por outro lado, a atual tecnologia CMOS de fabricação de circuitos integrados apresenta sinais de limitação, em grande parte, devido às características físicas inerentes ao seu princípio de funcionamento, sendo necessário, portanto, que dispositivos com novos mecanismos de operação e geometrias sejam desenvolvidos. Dentre eles, transistores de tunelamento induzido por efeito de campo (TFET) se destacam por apresentarem menor corrente de dreno quando desligados e a possibilidade de se atingir inclinações de sublimiar abaixo do limite teórico estabelecido por dispositivos MOSFET de 60 mV/déc à temperatura ambiente, permitindo-se a redução da tensão de alimentação dos transistores para cerca de 0,5 V. Buscando contribuir com as necessidades destas duas áreas de pesquisa, neste projeto de mestrado, foi analisado o comportamento de TFETs de silício com porta tripla, fabricados sobre lâmina SOI (silício sobre isolante), submetidos a até 10 Mrad(Si) de dose acumulada total enquanto não polarizados, gerada por uma fonte de prótons de 600 keV de energia. Em uma análise inicial, após exposição de dispositivos de 1 µm de largura de aleta a uma dose de 1 Mrad(Si), foi possível observar uma redução no nível corrente de dreno de estado ligado do dispositivo (ION ? 300 pA) de até 10%, não associada à uma alteração da corrente de porta. Além disso, o efeito da radiação nesses transistores reduz de 10% para 2% quando se aumenta o comprimento do canal de 150 nm para 1 µm. As razões para ambos os fenômenos foram discutidas com base na competição entre os efeitos de divisão da corrente de dreno na primeira e segunda interfaces e do aumento da resistência de canal em dispositivos mais longos. Para uma análise em função da dose acumulada total, dispositivos SOI TFET e SOI MOSFET, ambos de porta tripla, foram caracterizados eletricamente 14 dias após cada etapa de irradiação. De maneira geral, dispositivos de ambas as tecnologias, com largura de aleta igual a 40 nm, apresentaram baixa susceptibilidade aos efeitos cumulativos da radiação ionizante. No entanto, quando considerados dispositivos com largura de aleta muito maior que a altura da aleta (WFIN = 1 µm), nos quais a influência das portas laterais sobre o acoplamento eletrostático do canal é praticamente inexistente, transistores túnel-FET se destacaram positivamente. Esses dispositivos se mostraram resistentes aos efeitos de dose ionizante total (TID) mesmo para doses de 5 Mrad(Si), enquanto os transistores SOI MOSFET apresentaram uma variação gradual de seus parâmetros a cada dose acumulada. Um exemplo disso é a variação observada na inclinação de sublimiar, de 32,5% nos transistores SOI MOSFET e 5,6% nos transistores SOI TFET. Somente após 10 Mrad(Si) de irradiação por prótons é que os TFETs de aleta larga apresentaram variações mais significativas em sua curva de transferência (ID x VG). Tanto para a configuração como tipo P quanto para a configuração como tipo N, notou-se um deslocamento de até 80 mV da curva de transferência do dispositivo para a esquerda, provocado, segundo análise via simulações, pelas cargas fixas positivas geradas pela irradiação no óxido enterrado do dispositivo. Adicionalmente, foi possível observar um aumento da corrente de tunelamento assistido por armadilhas (TAT) nesses dispositivos, provocada pelo aumento da densidade de estados de interface causada também pelos efeitos de TID. O aumento de TAT foi reconhecido como o principal responsável pela degradação de 23,3% da inclinação de sublimiar dos TFETs, com WFIN igual 1 µm, após 10 Mrad(Si). Apesar das mudanças observadas, foi possível se sugerir, através da comparação com transistores SOI MOSFET de dimensões equivalentes, que transistores de tunelamento induzido por efeito de campo podem, futuramente, se tornar referência no quesito imunidade aos efeitos de dose ionizante total.
In light of the increasing need for new technologies to be able to operate reliably in harsh environments, the analysis of the effects of ionizing radiation on semiconductor devices has become a continually rising field of research, contributing to the development of strategic technologies and promoting scientific improvement and technological development of humankind. On the other hand, the current CMOS technology for the manufacture of integrated circuits shows signs of limitation, mostly, due to the physical characteristics inherent to its operating principle, thus, it is necessary that devices with new operating mechanisms and geometries be developed. Among them, tunnel field-effect transistors (TFET) stand out because of its lower OFF state current and the possibility of reaching subthreshold swing below the theoretical limit established by MOSFET devices of 60 mV/dec at room temperature, allowing to reduce transistors supply voltage to about 0.5 V. In order to contribute with both areas, the behavior of silicon based triple gate TFETs fabricated on a SOI (silicon-on-insulator) substrate and exposed to a total cumulative dose of 10 Mrad (Si) (while not biased) generated by a 600 keV proton beam was analyzed. In an initial analysis after exposure of 1 µm width devices to 1 Mrad(Si), it was possible to observe an ON state current reduction (ION ? 300 pA) up to 10%, not associated to a gate current change. Beyond that, irradiation effects on these devices reduce from 10% to 2% with the channel length increasing from 150 nm to 1 µm. The reasons behind these phenomena were discussed based on the competition between a high channel resistance present in longer devices and the TFET drain current reduction due to the irradiation. For a total cumulative dose analysis, triple gate SOI TFET and triple gate SOI MOSFET devices were characterized 14 days after each irradiation phase. In general, devices of both technologies, with 40 nm fin width, presented low susceptibility to the cumulative effects of ionizing radiation. However, for devices with fin width larger than fin height (WFIN = 1 µm) in which the influence of side gates on the electrostatic coupling of the channel is weak, tunnel-FET transistors have stood out. These devices were resistant to the effects of total ionizing dose (TID) even for doses as high as 5 Mrad(Si), while SOI MOSFET transistors showed a gradual variation of their parameters at each accumulated dose. The variation observed for the subthreshold swing, for example, was about 32.5% for SOI MOSFET devices and 5.6% for SOI TFET devices. TFETs with wider fin have shown significant variations on its transfer characteristic (ID x VG) only after 10 Mrad(Si) of proton irradiation. For both P-type and N-type configurations, it was observed a shift of the transfer curve to the left up to 80 mV caused by, according to simulations, the positive fixed charges generated in the buried oxide by irradiation. In addition, it was possible to observe a trap assisted tunneling (TAT) current increase caused by interface states promoted by TID effects. The increase of TAT was recognized as the main responsible for the degradation of 23.3% of the subthreshold swing of the TFETs after 10 Mrad(Si). In spite of the observed changes, it was possible to suggest, through comparison with SOI MOSFET devices of equivalent dimensions, which tunnel field-effect transistors may become a reference when considering immunity against total ionizing dose effects.

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50

Bokrantz, Rasmus. "Multicriteria optimization for managing tradeoffs in radiation therapy treatment planning". Doctoral thesis, KTH, Optimeringslära och systemteori, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122663.

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Treatment planning for radiation therapy inherently involves tradeoffs, such as between tumor control and normal tissue sparing, between time-efficiency and dose quality, and between nominal plan quality and robustness. The purpose of this thesis is to develop methods that can facilitate decision making related to such tradeoffs. The main focus of the thesis is on multicriteria optimization methods where a representative set of treatment plans are first calculated and the most appropriate plan contained in this representation then selected by the treatment planner through continuous interpolation between the precalculated alternatives. These alternatives constitute a subset of the set of Pareto optimal plans, meaning plans such that no criterion can be improved without a sacrifice in another. Approximation of Pareto optimal sets is first studied with respect to fluence map optimization for intensity-modulated radiation therapy. The approximation error of a discrete representation is minimized by calculation of points one at the time at the location where the distance between an inner and outer approximation of the Pareto set currently attains its maximum. A technique for calculating this distance that is orders of magnitude more efficient than the best previous method is presented. A generalization to distributed computational environments is also proposed. Approximation of Pareto optimal sets is also considered with respect to direct machine parameter optimization. Optimization of this form is used to calculate representations where any interpolated treatment plan is directly deliverable. The fact that finite representations of Pareto optimal sets have approximation errors with respect to Pareto optimality is addressed by a technique that removes these errors by a projection onto the exact Pareto set. Projections are also studied subject to constraints that prevent the dose-volume histogram from deteriorating. Multicriteria optimization is extended to treatment planning for volumetric-modulated arc therapy and intensity-modulated proton therapy. Proton therapy plans that are robust against geometric errors are calculated by optimization of the worst case outcome. The theory for multicriteria optimization is extended to accommodate this formulation. Worst case optimization is shown to be preferable to a previous more conservative method that also protects against uncertainties which cannot be realized in practice.
En viktig aspekt av planering av strålterapibehandlingar är avvägningar mellan behandlingsmål vilka står i konflikt med varandra. Exempel på sådana avvägningar är mellan tumörkontroll och dos till omkringliggande frisk vävnad, mellan behandlingstid och doskvalitet, och mellan nominell plankvalitet och robusthet med avseende på geometriska fel. Denna avhandling syftar till att utveckla metoder som kan underlätta beslutsfattande kring motstridiga behandlingsmål. Primärt studeras en metod för flermålsoptimering där behandlingsplanen väljs genom kontinuerlig interpolation över ett representativt urval av förberäknade alternativ. De förberäknade behandlingsplanerna utgör en delmängd av de Paretooptimala planerna, det vill säga de planer sådana att en förbättring enligt ett kriterium inte kan ske annat än genom en försämring enligt ett annat. Beräkning av en approximativ representation av mängden av Paretooptimala planer studeras först med avseende på fluensoptimering för intensitetsmodulerad strålterapi. Felet för den approximativa representationen minimeras genom att innesluta mängden av Paretooptimala planer mellan inre och yttre approximationer. Dessa approximationer förfinas iterativt genom att varje ny plan genereras där avståndet mellan approximationerna för tillfället är som störst. En teknik för att beräkna det maximala avståndet mellan approximationerna föreslås vilken är flera storleksordningar snabbare än den bästa tidigare kända metoden. En generalisering till distribuerade beräkningsmiljöer föreslås även. Approximation av mängden av Paretooptimala planer studeras även för direkt maskinparameteroptimering, som används för att beräkna representationer där varje interpolerad behandlingsplan är direkt levererbar. Det faktum att en ändlig representation av mängden av Paretooptimala lösningar har ett approximationsfel till Paretooptimalitet hanteras via en metod där en interpolerad behandlingsplan projiceras på Paretomängden. Projektioner studeras även under bivillkor som förhindrar att den interpolerade planens dos-volym histogram kan försämras. Flermålsoptimering utökas till planering av rotationsterapi och intensitetsmodulerad protonterapi. Protonplaner som är robusta mot geometriska fel beräknas genom optimering med avseende på det värsta möjliga utfallet av de föreliggande osäkerheterna. Flermålsoptimering utökas även teoretiskt till att innefatta denna formulering. Nyttan av värsta fallet-optimering jämfört med tidigare mer konservativa metoder som även skyddar mot osäkerheter som inte kan realiseras i praktiken demonstreras experimentellt.

QC 20130527

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Rozprawy doktorskie na temat „Proton radiation”

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