Thesis submitted in partial fulfilment of the requirements for the degree Doctor of Technology: Electrical, Electronic and Computer Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology / This research investigates the effects of sub-10 MeV protons on coatings obtained from the pulsed laser ablation of W2B5/B4C. This is in an attempt to extend the bullet proof applications of W2B5/B4C to space radiation shielding applications, offering low cost and low mass protection against radiation including X-rays, neutrons, gamma rays and protons in low Earth orbit. The focus in this research, however, is on low energy protons. The associated problems addressed in this work are solar cell degradation and Single Event Upsets in high density semiconductor devices caused by low energy protons. The relevant constraints considered are the necessity for low cost, low mass and high efficiency solutions. The work starts with a literature review of the space environment, the interaction of radiation with matter, and on pulsed laser deposition as a technique of choice for the coating synthesis. This paves the way for the pulsed laser ablation of W2B5/B4C. The resulting coating is a solid solution of the form WC1-xBx which contains crystalline and amorphous forms. Two proton irradiation experiments are carried out on this coating, and the resulting effects are analysed. The effects of 900 keV proton irradiation were the melting and subsequent growing of nanorods on the surface of the coating, the lateral transfer of the proton energy across the coating surface, and the lateral displacement of matter along the coating surface. These effects show that the coating is a promising cost effective and low mass radiation shield against low energy protons. The effects of 1 MeV protons on this coating are the three-stage melting of rods formed on the coating surface, and further evidence of lateral transfer of energy across the coating surface. Optical measurements of this coating show that it is about 73% transparent in the Ultraviolet, Visible and near Infrared range. This allows it to be used as radiation shielding for solar cells, in addition to high density semiconductor devices, against low energy protons in low Earth orbit. Simulations show that based on coulombic interactions alone, the same level of protection coverglass offers to solar cells can be achieved with about half the thickness of WC1-xBx or less.

Quando um átomo colide com outras partículas durante um processo de emissão ou absorção de fótons, seu espectro é afetado por essa interação. Esse efeito é conhecido por alargamento colisional ou alargamento por pressão e é um dos diversos mecanismos de alargamento que pode afetar uma linha espectral. A diferença entre esse mecanismo e os demais é a possibilidade de formação de um estado ligado transiente entre partícula radiadora e perturbadores durante a colisão. Esse estado é chamado quase-molécula e tem um espectro de energia distinto daquele das partículas isoladas. Assim sendo, além do alargamento, há a possibilidade de formação de linhas em comprimentos de onda que não podem ser explicados se considerado o espectro das partículas isoladas. Essas linhas são chamadas satélites, e sua presença também induz assimetrias no perfil e mudança na opacidade do gás, o que, no caso de atmosferas estelares, altera a cor das estrelas. Satélites já foram detectadas no espectro ultravioleta de estrelas anãs brancas com temperaturas próximas a 15000K. Apesar dessas identificações preliminares, ocorridas nos anos 1980, modelos de atmosfera que incluam consistentemente os efeitos quasemoleculares ainda não existem. Com o advento de grandes projetos de mapeamento do céu, como o Sloan Digital Sky Survey (SDSS), o número de anãs brancas conhecidas está crescendo significativamente. No data release 7 do SDSS, encontramos 19712 (Kleinman et al. , 2013), duplicando o número de anãs brancas conhecidas. Com os data releases 9 e 10, descobrimos outras 8800 (Kepler et al. , 2014). A boa determinação da temperatura e da massa dessas estrelas, que é importante para o entendimento do histórico de formação estelar na nossa Galáxia, depende do conhecimento da forma das linhas de Balmer, que são as mais fortes em cerca de 80% das anãs brancas. Como elas são afetadas pelas colisões com os prótons livres da atmosfera parcialmente ionizada das anãs brancas, é importante que esse efeito seja considerado. Por isso, desenvolvemos um código que permite o cálculo das contribuições quasemoleculares do H+2 ao espectro do átomo de hidrogênio. O método escolhido foi a teoria unificada em seu desenvolvimento quântico, conforme proposto por Allard et al. (1999), pois ela permite determinar a forma completa da linha. Utilizamos os dados disponibilizados por Santos & Kepler (2012) para calcular as contribuições do H+2 à série de Lyman até Lyman-δ e à série de Balmer até Balmer-10. Em seu trabalho, eles também obtiveram os perfis para todas essas linhas na aproximação quase-estática, mas tal método, devido à suposição de velocidade nula, não é válido para o centro da linha. Obtivemos os perfis em densidades de perturbadores e temperaturas que podem descrever bem a atmosfera de estrelas anãs brancas. Todos os satélites já observados foram identificados, juntamente com outros ainda não detectados. Além disso, o código foi escrito de forma que leia quaisquer potencial e momento de dipolo dados, de modo que ele pode ser utilizado para avaliar contribuições devido a outras partículas. Esperamos que os perfis obtidos possam ser incluídos em modelos de atmosfera para estrelas anãs brancas e que este estudo possa ser estendido para incluir as contribuições importantes de outros perturbadores. / When an atom collides with particles during a process of emission or absorption of a photon, its spectrum is affected by this interaction. Such effect is known as collisional broadening or pressure broadening and it’s one of many broadening mechanisms that can affect a spectral line. The difference between such mechanism and others is the possibility of formation of a transient bound state between radiating particle and perturbers during the collision. Such state is known as quasi-molecule, and it has an energy spectra different than the one by isolated particles. So, besides the broadening, there is also the possibility of lines forming at wavelengths that can not be explained in terms of the spectra of the isolated particles. Those lines are called satellites, and its presence also induces asymmetries in the profile and changes in the gas opacity, what, in the case of stellar atmospheres, alters the color of the stars. Satellites were already detected in the ultraviolet spectra of white dwarf stars with temperatures around 15000K. In spite of those early identifications, done in the 1980s, atmosphere models that take quasi-molecular effects fully in account still do not exist. With the advent of large projects of sky mapping, such as Sloan Digital Sky Survey (SDSS), the number of known white dwarfs is significantly growing. In the data release 7 of SDSS, we found 19712 (Kleinman et al. , 2013), doubling the number of known white dwarfs. With data releases 9 and 10, we discovered another 8800 (Kepler et al. , 2014). The good determination of temperature and mass for those stars, which is important to the understanding of the history of star formation in our Galaxy, depends on the knowledge of the shape of the Balmer lines, that are the strongest ones in around 80% of white dwarfs. As they are affected by collisions with free protons of the partially ionized atmosphere of the white dwarfs, it is important that such effect be considered. Thus, we developed a code that allows the calculation of quasi-molecular H+2 contributions to the spectrum of the hydrogen atom. The chosen approach was the unified theory in its quantum-mechanical development, as proposed by Allard et al. (1999), because it allows the determination of the shape of the whole line. We used data provided by Santos & Kepler (2012) to evaluate H+2 contributions to the Lyman series up to Lyman-δ and to the Balmer series up to Balmer-10. In their work, they also obtained the profiles for all those lines in the quasistatic approach, but that method, due to its assumption of zero velocity, is not valid for the line center. We obtained the profiles at perturber densities and temperatures that can describe well the atmosphere of white dwarfs stars. All the satellites already observed are identified, together with others not yet detected. Besides that, the code was written in a way that it reads any given potential energy and dipole moment data, so it can be used to evaluate contributions due to other particles. We hope that the obtained profiles can be included in atmosphere models for white dwarf stars and that this study can be extended to include contributions due to other important perturbers.

Quando um átomo colide com outras partículas durante um processo de emissão ou absorção de fótons, seu espectro é afetado por essa interação. Esse efeito é conhecido por alargamento colisional ou alargamento por pressão e é um dos diversos mecanismos de alargamento que pode afetar uma linha espectral. A diferença entre esse mecanismo e os demais é a possibilidade de formação de um estado ligado transiente entre partícula radiadora e perturbadores durante a colisão. Esse estado é chamado quase-molécula e tem um espectro de energia distinto daquele das partículas isoladas. Assim sendo, além do alargamento, há a possibilidade de formação de linhas em comprimentos de onda que não podem ser explicados se considerado o espectro das partículas isoladas. Essas linhas são chamadas satélites, e sua presença também induz assimetrias no perfil e mudança na opacidade do gás, o que, no caso de atmosferas estelares, altera a cor das estrelas. Satélites já foram detectadas no espectro ultravioleta de estrelas anãs brancas com temperaturas próximas a 15000K. Apesar dessas identificações preliminares, ocorridas nos anos 1980, modelos de atmosfera que incluam consistentemente os efeitos quasemoleculares ainda não existem. Com o advento de grandes projetos de mapeamento do céu, como o Sloan Digital Sky Survey (SDSS), o número de anãs brancas conhecidas está crescendo significativamente. No data release 7 do SDSS, encontramos 19712 (Kleinman et al. , 2013), duplicando o número de anãs brancas conhecidas. Com os data releases 9 e 10, descobrimos outras 8800 (Kepler et al. , 2014). A boa determinação da temperatura e da massa dessas estrelas, que é importante para o entendimento do histórico de formação estelar na nossa Galáxia, depende do conhecimento da forma das linhas de Balmer, que são as mais fortes em cerca de 80% das anãs brancas. Como elas são afetadas pelas colisões com os prótons livres da atmosfera parcialmente ionizada das anãs brancas, é importante que esse efeito seja considerado. Por isso, desenvolvemos um código que permite o cálculo das contribuições quasemoleculares do H+2 ao espectro do átomo de hidrogênio. O método escolhido foi a teoria unificada em seu desenvolvimento quântico, conforme proposto por Allard et al. (1999), pois ela permite determinar a forma completa da linha. Utilizamos os dados disponibilizados por Santos & Kepler (2012) para calcular as contribuições do H+2 à série de Lyman até Lyman-δ e à série de Balmer até Balmer-10. Em seu trabalho, eles também obtiveram os perfis para todas essas linhas na aproximação quase-estática, mas tal método, devido à suposição de velocidade nula, não é válido para o centro da linha. Obtivemos os perfis em densidades de perturbadores e temperaturas que podem descrever bem a atmosfera de estrelas anãs brancas. Todos os satélites já observados foram identificados, juntamente com outros ainda não detectados. Além disso, o código foi escrito de forma que leia quaisquer potencial e momento de dipolo dados, de modo que ele pode ser utilizado para avaliar contribuições devido a outras partículas. Esperamos que os perfis obtidos possam ser incluídos em modelos de atmosfera para estrelas anãs brancas e que este estudo possa ser estendido para incluir as contribuições importantes de outros perturbadores. / When an atom collides with particles during a process of emission or absorption of a photon, its spectrum is affected by this interaction. Such effect is known as collisional broadening or pressure broadening and it’s one of many broadening mechanisms that can affect a spectral line. The difference between such mechanism and others is the possibility of formation of a transient bound state between radiating particle and perturbers during the collision. Such state is known as quasi-molecule, and it has an energy spectra different than the one by isolated particles. So, besides the broadening, there is also the possibility of lines forming at wavelengths that can not be explained in terms of the spectra of the isolated particles. Those lines are called satellites, and its presence also induces asymmetries in the profile and changes in the gas opacity, what, in the case of stellar atmospheres, alters the color of the stars. Satellites were already detected in the ultraviolet spectra of white dwarf stars with temperatures around 15000K. In spite of those early identifications, done in the 1980s, atmosphere models that take quasi-molecular effects fully in account still do not exist. With the advent of large projects of sky mapping, such as Sloan Digital Sky Survey (SDSS), the number of known white dwarfs is significantly growing. In the data release 7 of SDSS, we found 19712 (Kleinman et al. , 2013), doubling the number of known white dwarfs. With data releases 9 and 10, we discovered another 8800 (Kepler et al. , 2014). The good determination of temperature and mass for those stars, which is important to the understanding of the history of star formation in our Galaxy, depends on the knowledge of the shape of the Balmer lines, that are the strongest ones in around 80% of white dwarfs. As they are affected by collisions with free protons of the partially ionized atmosphere of the white dwarfs, it is important that such effect be considered. Thus, we developed a code that allows the calculation of quasi-molecular H+2 contributions to the spectrum of the hydrogen atom. The chosen approach was the unified theory in its quantum-mechanical development, as proposed by Allard et al. (1999), because it allows the determination of the shape of the whole line. We used data provided by Santos & Kepler (2012) to evaluate H+2 contributions to the Lyman series up to Lyman-δ and to the Balmer series up to Balmer-10. In their work, they also obtained the profiles for all those lines in the quasistatic approach, but that method, due to its assumption of zero velocity, is not valid for the line center. We obtained the profiles at perturber densities and temperatures that can describe well the atmosphere of white dwarfs stars. All the satellites already observed are identified, together with others not yet detected. Besides that, the code was written in a way that it reads any given potential energy and dipole moment data, so it can be used to evaluate contributions due to other particles. We hope that the obtained profiles can be included in atmosphere models for white dwarf stars and that this study can be extended to include contributions due to other important perturbers.

Made available in DSpace on 2014-10-09T12:27:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:59:13Z (GMT). No. of bitstreams: 0 / Foram desenvolvidos modelos analíticos que descrevem os elementos básicos para irradiações de alvos metálicos em ciclotrons. Parâmetros importantes como valor máximo de corrente de feixe e potência térmica depositada sobre o alvo foram obtidos e confrontados com situações práticas. De forma totalmente inédita, foram determinados analiticamente as características encontradas em situações de intensos transientes térmicos, quando altas concentrações de prótons em uma pequena região do feixe provocam intensos gradientes de temperatura em pequenas regiões do alvo. A comparação dos resultados obtidos com aqueles encontrados na literatura mostraram que os modelos desenvolvidos são satisfatórios, tendo em vista todas as limitações do modelo proposto. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientadores: Edvaldo Sabadini, Munir Salomão Skaf / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-20T16:17:25Z (GMT). No. of bitstreams: 1 Cardoso_MarcusViniciusCangussu_D.pdf: 5363072 bytes, checksum: 77f8ee9c80c8ce3514b001281dfddae6 (MD5) Previous issue date: 2012 / Resumo: Soluções aquosas de mono, di, oligo, e polissacarídeos foram estudas nos níveis macroscópico e molecular, empregando-se enfoques termodinâmicos e espectroscópicos. A influência da intensidade da ligação de hidrogênio sobre a solubilidade dos carboidratos (lineares e cíclicos) mostrou-se fortemente dependente de suas solubilidades. Quanto menos solúvel o carboidrato, maior é o efeito da substituição isotópica do solvente (H2O por D2O). Este efeito sugere que carboidratos menos solúveis (e maiores) perturbam mais fortemente a estruturação das moléculas de água. Devido ao efeito cooperativo da transição coil-helix da k-carragena, o efeito isotópico sobre a gelificação é bastante intensificado. Segundo um perspectiva mais molecular, as taxas de troca protônicas, kb, entre os prótons da água e os grupos OH dos carboidratos dependem da natureza do açúcar, sendo os maiores valores observados para a forma linear, seguida pela forma piranosidea e por último pela forma furanosidea. Já as transferências de magnetização entre as populações de prótons da água e dos grupos CH-carboidratos são moduladas pelos movimentos moleculares e intermediadas pelas trocas protônicas com os grupos OH. Propõe-se que os prótons das moléculas de água interagem preferencialmente com os prótons OH e negligenciavelmente com os prótons CH. Estudos de relaxação H mostraram-se ricos para o estudo de processos moleculares de agregação micelar dos n-alquil-glicosídeos sendo possível demonstrar experimentalmente que a agregação leva a indisponibilização das hidroxilas ao interagirem com as moléculas de água / Abstract: Aqueous solutions of mono, di, oligo, and polysaccharides were studied on the macroscopic and molecular standpoints through thermodynamic and spectroscopic approaches. The effect of hydrogen-bonding strength on the solubility of a series of (linear and cyclic) saccharides showed to be strongly dependent of the solubility of the carbohydrate. As lower is the solubility of the carbohydrate, greater will be the deuterium isotopic effect of the solvent (H2O for D2O) on the carbohydrate solubilities. These results suggest that low soluble carbohydrates (and larger ones) perturb more strongly the water structure. Owing to the cooperativity of the coil-helix transition, the deuterium isotope effect on the gelling of k-carrageenan is intensified leading to stronger gels and double-helices more stable in D2O. Looking deeper onto a molecular perspective and based on spin-spin nuclear magnetic relaxation, the proton exchange rates, kb, between water and OH-carbohydrate, are dependent of the nature of the saccharide. The kb values are higher for linear than for pyranoside form, and the slowest value is found for fructofuranoside form. The transferring of magnetization between proton pools of water and CH-carbohydrates are modulated by molecular motions and intermediated by proton exchanging process between water and OH-carbohydrate protons. H NMR relaxation experiments of exchangeable protons provide to be rich in probing the micelar aggregation of n-alkyl-glucosides. It was possible to demonstrate experimentally that the aggregation of the surfactant molecules provoke a drastic reduction on the interactions between water and OH-saccharide head groups / Doutorado / Físico-Química / Doutor em Ciências

Die Anwendung von Hochintensitätslasern zur Beschleunigung von Teilchen bietet eine Alternative zu klassischen Teilchenbeschleunigern und den von diesen erzeugten Strahlenqualitäten. Nach großen Fortschritten auf dem Gebiet der Laser-Teilchenbeschleunigung wurde die Anwendung der neuen Technologie in der klinischen Ionentherapie vorgeschlagen und diskutiert. Bevor es dazu kommen kann, muss aber neben der Verbesserung der Strahleigenschaften, wie z. B. der Erhöhung der Energie, und der Stabilität der Teilchenbeschleunigung auch eine geeignete physikalische und dosimetrische Charakterisierung entwickelt und die biologische Wirksamkeit dieser neuartigen, ultrakurz gepulsten Strahlenqualität mit extrem hoher Pulsdosisleistung untersucht werden. Dies erfordert eine ganze Reihe von umfangreichen Experimenten der notwendigen Translationskette, angefangen von in vitro Zellbestrahlungen über in vivo Studien bis hin zu präklinischen Untersuchungen und ersten klinischen Studien. Hierzu wurden das Verbundprojekt onCOOPtics gegründet und in einem ersten Schritt in vitro Zellbestrahlungen zur Untersuchung der biologischen Wirksamkeit laserbeschleunigter Teilchen durchgeführt. Dazu wurden Dosis-Effekt-Kurven für humane Tumor- und Normalgewebs-Zelllinien jeweils für mehrere biologische Endpunkte bestimmt. Begonnen wurde dabei mit der umfangreichen Untersuchung laserbeschleunigter Elektronen am JeTi-Lasersystem in Jena, auf welche zum Zeitpunkt der Verfügbarkeit des DRACO-Lasersystems in Dresden die dosimetrische und strahlenbiologische Charakterisierung laserbeschleunigter Protonen an diesem Lasersystem folgte. Dabei stellte die Entwicklung einer präzisen Dosimetrie zur Bestimmung der applizierten Dosis aufgrund der Strahleigenschaften laserbeschleunigter Teilchen eine große Herausforderung dar. Sie ist aber sowohl im Hinblick auf eine spätere klinische Anwendung als auch für die Durchführung quantitativer strahlenbiologischer Experimente obligatorisch. Diese Arbeit, die im Rahmen des Verbundprojektes entstanden ist, leistet dazu in vielfacher Hinsicht einen wesentlichen Beitrag: Erstens wurden geeignete Detektoren zur präzisen dosimetrischen Charakterisierung laserbeschleunigter Elektronen und Protonen entwickelt, optimiert und charakterisiert sowie präzise kalibriert. So wurden umfangreiche Studien zu verschiedenen Eigenschaften der auch in der klinischen Dosimetrie angewandten radiochromischen Filme durchgeführt und die Filme entsprechend kalibriert. Dabei wurden neue Erkenntnisse u. a. über deren Energieabhängigkeit gewonnen, die für zahlreiche Anwendungen der Filme von Bedeutung sind. Weiterhin wurden verschiedene Ionisationskammern zur Echtzeit-Strahlmonitorierung von laserbeschleunigten Elektronen und Protonen ausgewählt und dosimetrisch charakterisiert. Zudem wurde der Einsatz von CR-39 Festkörperspurdetektoren zur spektroskopischen Untersuchung laserbeschleunigter Protonen etabliert, indem die Nachverarbeitung und Auslesung der Detektoren charakterisiert und optimiert wurden und außerdem eine retrospektive Filterprozedur der detektierten Krater entwickelt und angewendet wurde. Ferner wurde ein Faraday Cup, der auf die speziellen Eigenschaften derzeitiger laserbeschleunigter Protonen-Strahlenqualitäten abgestimmt ist, entwickelt, charakterisiert und mit drei voneinander unabhängigen Methoden kalibriert. Die radiochromischen Filme und der Faraday Cup konnten daraufhin als Referenzdosimeter sowohl an den konventionellen als auch an den neuartigen Laser-Teilchenbeschleunigern erfolgreich eingesetzt werden. Zweitens bildete die durchgeführte Echtzeit- und Referenzdosimetrie laserbeschleunigter Elektronen die Grundlage für die weltweit ersten systematischen Zellbestrahlungsexperimente dieser Strahlenqualität. Dabei konnten trotz großer Pulsdosisschwankungen alle Anforderungen bezüglich Dosishomogenität, Strahlstabilität, präziser Deposition einer vorgegebenen Dosis und Unsicherheit der bestimmten applizierten Dosis, die für eine quantitative Auswertung der radiobiologischen Daten notwendig sind, erfüllt werden. Exemplarisch sei die bestimmte Gesamt-Dosisunsicherheit von unter 10% genannt. Drittens wurden auch laserbeschleunigte Protonen so präzise dosimetrisch monitoriert und charakterisiert, dass auch mit dieser Strahlenqualität quantitative strahlenbiologische Untersuchungen durchgeführt werden konnten. Herausgefordert durch die kurze Reichweite der Protonen im Submillimeterbereich und das breite Energiespektrum dieser Strahlenqualität, gelang dies neben der Charakterisierung und Kalibrierung der einzelnen Detektoren durch die Konzeption und Realisierung eines integrierten Dosimetrie- und Zellbestrahlungssystems (IDOCIS).Weltweit erstmalig wurde eine Echtzeit-Strahlmonitorierung während der Zellbestrahlungen mit laserbeschleunigten Protonen durchgeführt, die sowohl zur kontrollierten Applikation einer vorgegebenen Dosis und zur Strahlüberwachung als auch zusammen mit der durchgeführten Referenzdosimetrie zur hochpräzisen Bestimmung der absolut in den Zellen deponierten Dosis diente. Außerdem trug die parallele und redundante Verwendung zweier voneinander unabhängiger Referenzdosimetrie-Systeme erheblich zur Erreichung einer hohen Zuverlässigkeit und Sicherheit bei. Die Unsicherheit in der bestimmten deponierten Dosis betrug entsprechend für den Endpunkt der residualen DNS-Doppelstrangbrüche 24h nach Bestrahlung, für den eine vollständige Dosis-Effekt-Kurve ermittelt wurde, nur ca. 10%. Die Unsicherheit liegt damit schon fast in dem Bereich, der an klinisch angewandten Beschleunigern zulässig ist (3-5%). Dagegen konnte zu Beginn dieser Arbeit die Dosis laserbeschleunigter Protonen nur mit einer Ungenauigkeit von mehr als 50% abgeschätzt werden. Viertens wurden die zur Bestimmung der relativen biologischen Wirksamkeit notwendigen Vergleichsbestrahlungen mit konventionellen Elektronen- und Protonenstrahlenquellen und die zur Vergleichbarkeit der konventionellen und laserbeschleunigten Strahlenqualitäten erforderlichen Referenzbestrahlungen mit 200kVp Röntgenröhren im Rahmen dieser Arbeit ebenfalls dosimetrisch optimiert und genau charakterisiert. Die dosimetrischen Ergebnisse der vorliegenden Arbeit waren eine notwendige Voraussetzung für die im Rahmen anderer Arbeiten vollzogene strahlenbiologische Auswertung der durchgeführten Zellbestrahlungen. Dabei wurde insgesamt kein signifikanter Unterschied in der strahlenbiologischen Wirksamkeit zwischen laserbeschleunigten, ultrakurz gepulsten und konventionellen, kontinuierlichen Strahlenqualitäten weder für Elektronen noch für Protonen festgestellt. Durch die Konsistenz dieser Ergebnisse für beide Teilchenarten und unterschiedliche biologische Endpunkte ist damit die nächste Stufe auf dem translationalen Weg hin zur klinischen Anwendung laserbeschleunigter Teilchen begehbar: Die Durchführung von in vivo Untersuchungen. Dabei muss zwar von einer zweidimensionalen (Zell-Monolayer) auf eine dreidimensionale Zielvolumenbestrahlung (Tumor) übergegangen werden, wobei aber die im Rahmen der vorliegenden Arbeit entwickelten Dosimetrieverfahren und Detektoren auch bei den Tierbestrahlungen angewendet und eingesetzt werden können. / The application of high-intensity lasers for particle acceleration provides an alternative to conventional particle accelerators and also alternative beam qualities. Soon after the recent progress in the field of laser particle acceleration, its application in clinical ion therapy was proposed and discussed widely. Besides the improvement of the beam properties (increasing of beam energy and stability of particle acceleration process, e. g.) a capable physical and dosimetric characterization has to be developed before the technology can be applied in cancer therapy. The same is true for investigation of the biological effectiveness of this new, ultra-short pulsed beam quality with extremely high pulse dose rate. Hence, the whole translational chain, beginning from in vitro cell irradiation over in vivo studies to the point of preclinical investigations and first clinical trials, is necessary. For this reason, in a first step the joint research project onCOOPtics was founded and in vitro cell irradiation experiments were performed to study the biological effectiveness of laser accelerated particles. Therefore, dose-effect-curves for tumor and normal tissue cell lines were determined for different biological endpoints. Starting with extensive experiments with laser accelerated electrons at the JeTi laser system in Jena, the investigations were continued with dosimetric and radiobiological characterization of laser accelerated protons at the DRACO laser system in Dresden shortly after the DRACO laser started its operation. In this process, the development of a precise dosimetry for determination of the applied dose posed a great challenge due to the beam properties of laser accelerated particles. However, this is a crucial and compulsive requirement for both, the future clinical application and also for the realization of quantitative radiobiological experiments. Compiled in the onCOOPtics framework, this paper contributed to this task in multiple key aspects: Firstly, capable detectors for precise dosimetric characterization of laser accelerated electrons and protons were developed, optimized and characterized as well as precisely calibrated. Thus, comprehensive investigations were performed studying different properties of radiochromic films which are also applied in clinical dosimetry. In addition, these films were precisely calibrated for different beam qualities. Thereby, new findings of the energy dependence of radiochromic films were obtained which are of importance for numerous applications of these films. Moreover, different ionization chambers for real-time beam monitoring of laser accelerated electrons and protons were selected and characterized. Furthermore, the application of CR-39 solid state track detectors was established for spectroscopic investigations of laser accelerated protons by characterizing and optimizing the postirradiation processing and the readout of the detectors. Also a retrospective filter procedure of the detected tracks was developed and applied. Moreover, a Faraday Cup adjusted to the special properties of current laser accelerated proton beam qualities was developed, characterized and precisely calibrated by means of three independent calibration methods. Finally, the radiochromic films and the Faraday Cup could be used as reference dosimeters both for conventional accelerators and also for novel laser particle accelerators. Secondly, the performed real-time and reference dosimetry of laser accelerated electrons was the prerequisite of the first systematic cell irradiation experiments with this beam quality worldwide. Despite high pulse dose fluctuations, all requirements were satisfied concerning dose homogeneity, beam stability, precise deposition of a prescribed dose and uncertainty of the applied dose, that are all necessary for a quantitative evaluation of the radiobiological data. Exemplary, a total dose uncertainty below 10% was reached. Thirdly, laser accelerated protons were precisely monitored and characterized allowing quantitative, well-founded radiobiological investigations with this beam quality. This task was very much challenged by the short range of the protons in the sub-millimeter range and the broad energy spectrum of the beam quality. It was succeeded not only due to the comprehensive characterization and precise calibration of the different detectors but also due to the conception and realization of an integrated dosimetry and cell irradiation system (IDOCIS). For the first time, a real-time beam monitoring during cell irradiation with laser accelerated protons was performed. This real-time monitoring was not only used for controlled application of the prescribed dose and beam monitoring and also – together with the performed reference dosimetry – for precise determination of the deposited dose at cell location. In addition, high reliability and safety was considerably ensured by using two independent reference dosimetry systems in parallel. Hence, the determined uncertainty of the deposited dose was only about 10% for the biological endpoint of the residual DNA double strand breaks 24h after irradiation. For this endpoint a complete dose-effect-curve was obtained. Therefore, the achieved uncertainty is almost as small as necessary at clinically applied accelerators (3

La radioactivité deux-protons est un mode de décroissance du noyau atomique ne se produisant que pour des noyaux extrêmement riches en protons, situés au-delà de la limite de cohésion proton des noyaux (drip line). Prédit dans les années 1960, ce phénomène n’a été mis en évidence expérimentalement qu’en 2002 avec l’observation de la décroissance de 45Fe. Jusqu’à maintenant, seuls quatre noyaux se désintégrant par radioactivité deux-protons étaient connus : 45Fe, 48Ni, 54Zn et 19Mg. La recherche de nouveaux émetteurs a été menée lors d’une expérience avec le dispositif EURICA-WAS3ABi au centre RIKEN Nishina en 2015. La décroissance de 59Ge, 63Se, 67Kr et 68Kr a été observée pour la première fois. La radioactivité deux-protons de 67Kr a pu être étudiée ainsi que la décroissance bêta et l’émission retardée de protons de noyaux exotiques de la région. Une chambre à projection temporelle ou TPC (Time Projection Chamber) conçue par le CENBG (2004-2011) a permis d’étudier les corrélations entre les protons pour 45Fe et 54Zn. Une deuxième génération de TPC est développée au sein de la collaboration ACTAR TPC (ACtive TARget for TPC). Ce détecteur doit permettre une vraie reconstruction tridimensionnelle de l’énergie déposée par les particules dans le volume actif, afin d’obtenir une reconstruction des traces plus performantes que l’ancienne TPC. L’électronique générique GET (General Electronics for TPCs) gère le traitement et l’acquisition des signaux. La caractérisation de l’électronique GET ainsi que du démonstrateur de la TPC au CENBG est le deuxième aspect de ce travail de thèse. / Two-proton radioactivity is a decay mode of proton-rich nuclei located beyond the proton nuclear existence limit (drip line). Predicted in the 1960s, this process was observed for the first time in 2002 in the 45Fe decay study. Only four two-proton emitters were known so far: 45Fe, 48Ni, 54Zn and 19Mg. A search for new emitters was performed with the EURICA- WAS3ABi setup at the RIKEN Nishina center in 2015. The decay of 59Ge, 63Se, 67Kr and 68Kr was observed for the first time. Two-proton radioactivity of 67Kr together with the beta and delayed proton decay of exotic nuclei in the region were studied. A time projection chamber (TPC) developed at the CENBG (2004-2011) enabled the study of the correlations between the protons for 45Fe and 54Zn. A second generation of TPC is under construction within the ACTAR TPC (ACtive TARget for TPC) collaboration. This detector enables a reconstruction in three dimensions of the energy deposited in the active volume which allows a more efficient reconstruction of the tracks as compared to the previous TPC. The generic electronics GET (General Electronics for TPCs) manages the processing and acquisition of the signals. The characterisation of the GET electronics and the TPC demonstrator at CENBG is devoted to the second aspect of this PhD work.

Ischemic strokes cause excessive release of glutamate, leading to overactivation of N-methyl-D-aspartate receptors (NMDARs) and excitotoxicity-induced neuronal death. For this reason, inhibition of NMDARs has been a central focus in identifying mechanisms to avert this extensive neuronal damage. N-acetyl-aspartyl-glutamate (NAAG), the most abundant neuropeptide in the brain, is neuroprotective in ischemic conditions in vivo. Despite this evidence, the exact mechanism underlying its neuroprotection, and more specifically its effect on NMDARs, is currently unknown due to conflicting results in the literature. Here, we uncover a pH-dependent and subunit specific action of NAAG on NMDARs. Using whole-cell electrophysiological recordings on acute hippocampal slices from adult mice and on HEK293 cells, we found that NAAG increases synaptic GluN2A-containing NMDAR excitatory postsynaptic currents (EPSCs), while effectively decreasing extrasynaptic GluN2B-containing NMDAR EPSCs in physiological pH. Intriguingly, the results of our study further show that in low pH, which is a physiological occurrence during ischemia, NAAG depresses GluN2A-containing NMDAR EPSCs and amplifies its inhibitory effect on GluN2B-containing NMDAR EPSCs, as well as upregulates the surface expression of the GluN2A subunit. Altogether, our data demonstrate that NAAG has differential effects on NMDAR function based on subunit composition and extracellular pH levels. These findings suggest that the role of NAAG as a neuroprotective agent during an ischemic stroke is likely mediated by its ability to reduce NMDAR excitation. The inhibitory effect of NAAG on NMDARs and its enhanced function in acidic conditions makes NAAG a prime therapeutic agent for the treatment of ischemic events.

Advances in space and nuclear technologies are limited by the capabilities of the conventional silicon (Si) electronics. Hence, there is a need to explore materials beyond Si with enhanced properties to operate in extreme environments. In this regards, silicon carbide (4H-SiC), a wide bandgap semiconductor, provides suitable solutions. In this thesis, radiation effects of 4H-SiC bipolar devices, circuits and dielectrics for SiC are investigated under various radiation types. We have demonstrated for the first time the radiation hardness of 4H-SiC logic circuits exposed to extremely high doses (332 Mrad) of gamma radiation and protons. Comparisons with previously available literature show that our 4H-SiC bipolar junction transistor (BJT) is 2 orders of magnitude more tolerant under gamma radiation to existing Si-technology. 4H-SiC devices and circuits irradiated with 3 MeV protons show about one order of magnitude higher tolerance in comparison to Si. Numerical simulations of the device showed that the ionization is most influential in the degradation process by introducing interface states and oxide charges that lower the current gain. Due to the gain reduction of the BJT, the voltage reference of the logic circuit has been affected and this, in turn, degrades the voltage transfer characteristics of the OR-NOR gates. One of the key advantages of 4H-SiC over other wide bandgap materials is the possibility to thermally grow silicon oxide (SiO2) and process device in line with advanced silicon technology. However, there are still questions about the reliability of SiC/SiO2 interface under high power, high temperature and radiation rich environments. In this regard, aluminium oxide (Al2O3), a chemically and thermally stable dielectric, has been investigated. It has been shown that the surface cleaning treatment prior to deposition of a dielectric layer together with the post dielectric annealing has a crucial effect on interface and oxide quality. We have demonstrated a new method to evaluate the interface between dielectric/4H-SiC utilizing an optical free carrier absorption technique to quantitative measure the charge carrier trapping dynamics. The radiation hardness of Al2O3/4H-SiC is demonstrated and the data suggests that Al2O3 is better choice of dielectric for devices in radiation rich applications. / <p>QC 20170119</p>

The present work reports the experimental evidence of anomalous energy loss, energy straggling, and the corresponding ion-induced electron emission yields of channeled protons in silicon.