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1
ANDRADE, MARCOS L. G. „Radiografia com elétrons induzida por nêutrons: Neutron induced eletron radiography“. reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11610.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
2
Raymond, Stéphane. „Excitations de basse énergie dans les fermions lourds par diffusion inélastique des neutrons“. Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10103.
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La technique de diffusion inelastique des neutrons a ete utilisee pour caracteriser le spectre des excitations magnetiques de basse energie dans les composes a electrons fortement correles cenisn, ce#1#-#xla#xru#2si#2 et ceru#2ge#2. Cenisn est un compose kondo semimetallique dont le spectre des excitations magnetiques est compose de deux modes d'energie 2 et 4 mev et respectivement piques au centre et bord de zone de brillouin. L'application d'un champ magnetique met en evidence la nature differente de ces modes : le premier se deplace vers les plus hautes energies et la reponse du second s'elargit. Les modeles de gap d'hybridation particularises pour ce compose permettent de relier le mode a 4 mev aux proprietes macroscopiques observees. La dynamique des moments magnetiques pres d'une instabilite magnetique a ete etudiee dans le compose ce#1##xla#xru#2si#2 avec x = 0. 075. De facon surprenante, un ordre magnetique non conventionnel a ete mis en evidence (m = 0. 02 #b et t#n = 1. 8 k). La dynamique de spin par rapport au compose pur a ete reliee, grace a la theorie des fluctuations de spin de moriya, aux mesures macroscopiques. L'application d'un champ magnetique sur le compose ceru#2si#2 met en evidence le changement de la reponse dynamique du systeme de part et d'autre de la transition pseudometamagnetique. La reponse quasielastique et a courte portee a bas champ est remplacee par un ordre statique a longue distance en champ fort (h = 12 t). Dans ce contexte, la phase antiferromagnetique du compose ferromagnetique ceru#2ge#2 a ete caracterisee. Il existe alors une analogie entre ce compose sous sa temperature de curie et ceru#2si#2 au dessus du champ metamagnetique.
3
Dale, Gregory E. „Electron accelerator-driven photoneutron source for clinical environments /“. free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3091914.
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Balédent, Victor. „Paramètre d'ordre magnétique dans la phase de pseudogap des oxydes de cuivre supraconducteurs à haute température critique“. Phd thesis, Université Paris Sud - Paris XI, 2010. http://tel.archives-ouvertes.fr/tel-00683440.
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Ce travail de thèse présente un nouvel ordre magnétique dans l'énigmatique phase de pseudo-gap des cuprates supraconducteurs à haute température critique. L'étude des composés YBa2Cu3O6+δ, HgBa2CuO4+δ et La1.92Sr0.08CuO4 par diffusion élastique de neutrons polarisés a permis de mettre en évidence un paramètre d'ordre magnétique en dessous d'une température comparable à celle de l'ouverture du pseudo-gap de ces systèmes. Nous avons également montré pour la première fois l'existence dans la famille HgBa2CuO4+δ de deux modes collectifs magnétiques associés à la phase de pseudo-gap. Tous ces résultats indiquent qu'à l'ouverture du pseudo-gap est associée une vraie transition de phase, avec un paramètre d'ordre magnétique et une symétrie brisée: la symétrie par renversement du temps. Il est toutefois important de noter que la symétrie de translation du réseau est préservée: on parle alors d'ordre à Q=0. Dans le système YBa2Cu3O6+δ, nous avons établi que lorsque l'on s'approche du composé parent, ou lorsque l'on introduit des impuretés telles que du Zn, les fluctuations de spin incommensurables autour du vecteur d'onde antiferromagnétique (QAF) se développent au détriment du nouvel ordre à Q=0. De manière similaire, nous avons pu mettre en évidence une interaction entre l'instabilité magnétique autour de QAF et le nouvel ordre à Q=0 dans La1.92Sr0.08CuO4. L'ensemble de ces résultats apporte une pièce maitresse au puzzle que représente toujours la supraconductivité à haute température critique, malgré 25 ans de recherche.
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Grasset, Fabien. „Propriétés structurales, magnétiques et catalytiques de nouveaux oxydes à base de ruthénium ou de platine à empilements mixtes dérivés de la structure perovskite“. Phd thesis, Université Sciences et Technologies - Bordeaux I, 1998. http://tel.archives-ouvertes.fr/tel-00007279.
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Lors de l'étude de la série A3A'RuO6 (membre n = infini de la famille A3n+3A'nBn+3O9+6n) (A = Ca, Sr ; A'=Li, Na), quatre nouvelles phases ont été isolées. La structure, constituée de chaînes [RuA'O6] parallèles à l'axe c, est isotype de Sr4PtO6. Une étude comparative des propriétés magnétiques et des expériences de diffraction neutronique montre que ces phases ne semblent pas supporter de description en terme de système magnétique monodimensionnel. L'investigation du système Ba-Pt-O a permis de mettre en évidence la solution solide Ba12[BaxPt3-x]Pt6O27 (O £ x £ 3) où x représente la proportion de Pt2+ occupant les sites prismatiques. La structure de base correspond au membre n = 3 de la famille A3n+3A'NBn+3O9+6n. Il a été montré par diffraction des rayons X et des électrons que la structure de ces phases est modulée incommensurable pour x £ 1 et modulé commensurable pour x > 1. L'activité catalytique de ces composés pour l'oxydation totale du CO en CO2 a été étudiée. Dans le système Ba-Ru-O, les phases Ba5Ru2O9(O2) et Ba5Ru2O10 ont été caractérisées sur le plan structurale et magnétique. L'originalité dans la phase Ba5Ru2O9(O2) est l'existence d'ions peroxydes (O2)2- dans les couches [Ba2(O2)]. Une filiation structurale avec la structure perovskite est proposée. Ba5Ru2O9(O2) et Ba5Ru2O10 correspondant au membre n = 3 de la série [A2O2](AnBn-1O3n).
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Yuan, Junhua Filippone Bradley. „Progress towards a high precision measurement of the neutron spin--electron angular correlation in polarized neutron beta decay with ultra-cold neutrons /“. Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-01302006-153024.
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Bianchini, Matteo. „In situ diffraction studies of electrode materials for Li-ion and Na-ion batteries“. Thesis, Amiens, 2015. http://www.theses.fr/2015AMIE0022/document.
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Ce travail vise à étudier les matériaux d'électrodes pour batteries Li-ion et Na-ion lors qu’ils fonctionnent à l'intérieur des batteries. Afin de comprendre l'évolution structurelle des matériaux alors que les ions Li+ ou Na+ sont insérés/extraits de leur cadre, on utilise principalement la diffraction, exploitant neutrons, rayons X et le rayonnement synchrotron (SR). Nous avons adopté une approche combinée des mesures ex situ, in situ et operando. Au début, nous avons conçu une cellule électrochimique pour mesures in situ de diffraction de neutrons sur poudre (NPD), avec un alliage en (Ti,Zr) "transparent aux neutrons"; cette cellule s'est ajoutée à l’ensemble de nos outils pour effectuer des études de type operando. Nous avons démontré leur faisabilité en utilisant LiFePO4, montrant de bonnes performances électrochimiques et des données NPD de haute qualité pour affinements structurales Rietveld. Ensuite, nous avons réalisé des études des spinelles Li1+xMn2-xO4 (x=0,0.05,0.10) et LiNi0.4Mn1.6O4: pendant le cyclage, nous avons rapporté des évolutions structurelles, des diagrammes de phases et paramètres subtils tels que le comportement du Li, ou les facteurs de température. L’utilisation complémentaire du SR a clarifié la nature de la phase ordonnée Li0.5Mn2O4. Nos études combinées ont concernées d’autres matériaux d'électrodes prometteurs: LiVPO4O et Na3V2(PO4)2F3. Les 2 révèle des comportements complexes pendant la (de)intercalation du Li+/Na+. Les données de haute qualité ont permis des analyses quantitatives, dévoilant la structure d'un grand nombre des phases ordonnées et menant à la compréhension du comportement des cations dans ces matériauxThis work aims at studying electrode materials for Li-ion and Na-ion batteries as they function inside batteries. Diffraction is the mainly used technique, exploiting neutrons, X-Rays and synchrotron radiation (SR), to obtain insights on the structural evolution of such materials as Li+ or Na+ are inserted/extracted from their framework. We adopted a combined approach of ex situ, in situ and operando measurements to extract a maximum of information from our studies. At first, we designed an electrochemical cell for in situ neutron powder diffraction (NPD) measurements, featuring a “neutron-transparent” (Ti,Zr) alloy; this cell, joined to others previously developed in our group, gave us a complete set of tools to perform our studies. We demonstrated the feasibility of operando NPD using LiFePO4, showing good electrochemical performances and high-quality NPD patterns for Rietveld structural refinements. Then we carried out detailed studies of spinels Li1+xMn2-xO4 (x = 0, 0.05, 0.10) and LiNi0.4Mn1.6O4: we reported phase diagrams, structural evolutions and subtle parameters as lithium's behavior inside the spinel framework, or thermal displacement parameters, directly upon cycling. Complementary use of SR shed light on other features, as the nature of the ordered phase Li0.5Mn2O4. Our combined studies concerned other promising electrode materials: LiVPO4O and Na3V2(PO¬4)2F3. Both revealed complex behaviors upon Li+/Na+
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Astier, Pierre. „Recherche d'oscillations de neutrinos dans le canal neutrino-muon vers neutrino-electron aupres de l'accelerateur de brookhaven“. Paris 7, 1987. http://www.theses.fr/1987PA077268.
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Heron, Heidi. „Techniques to measure the NC background in the SNO experiment“. Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244578.
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10
Fischer, Vincent. „Beta-decay emitted electronic antineutrinos as a tool for unsolved problems in neutrino oscillation physics“. Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066237/document.
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Le cadre global des oscillations de neutrinos est maintenant bien compris et nous quittons une ère d'exploration pour une ère de précision. L'expérience Double Chooz a pour but de mesurer l'angle de mélange theta13 par l'étude des oscillations des antineutrinos électroniques produits par les réacteurs de la centrale nucléaire de Chooz. Dans cette thèse, une sélection préliminaire des neutrinos détectés dans le détecteur proche est présentée. Les résultats les plus récents de Double Chooz, desquels sont extraits la mesure de theta13 la plus précise que l'expérience peut fournir à ce jour, seront également discutés. La géométrie de l'expérience, relativement simple, représente un avantage considérable afin d'effecteur des études de directionalité des neutrinos dont les résultats, obtenus en analysant les jeux de données les plus récents avec captures sur Gd et H, sont présentés. Ce concept de directionalité peut être appliqué à l'astronomie/astrophysique en offrant la possibilité de localiser des supernovas après détection de leurs neutrinos. Les résultats de simulations de directionalité effectuées avec différentes combinaisons de détecteurs seront présentées. Enfin, plusieurs anomalies pourraient s'expliquer par l'existence de nouveaux états, stériles, de neutrinos. Le but de l¿expérience CeSOX est de confirmer ou réfuter cette hypothèse en déployant une source radioactive à coté d'un grand détecteur comme KamLAND ou Borexino. Dans cette thèse seront présentés les résultats des simulations de signaux et de bruits de fond effectuées afin de valider le principe de l'expérience et de s'assurer de sa sensibilité à l'observation d'une oscillation vers un neutrino stérileThe framework of neutrino oscillations is quite well-understood and now requires precision rather than exploration. The Double Chooz experiment aims at measuring the theta13 mixing angle through the oscillations of electronic antineutrinos produced by the reactors of the Chooz nuclear power plant. The comparison of the interaction rates and spectral shapes in the two Double Chooz's detectors allows the observation of a disappearance and a spectral distortion, both driven by theta13. In this thesis, a preliminary neutrino selection with the near detector, whose data taking started in December 2014, has been performed. The most recent results of Double Chooz, providing the most precise measurement of the experiment, are presented as well.The simple layout of Double Chooz is a strong advantage to conduct directionality studies. Results of these studies using the most recent neutrino candidates with neutron captures on Gd and H are showed. Neutrino directionality can be applied to astronomy, with the localization of core-collapse supernovae. To this purpose, results of directionality measurements performed with combinations of large neutrino detectors over the globe are presented.Finally, recent anomalies observed in short baseline experiments provided hints of the hypothetical existence of additional sterile neutrino states. The goal of the CeLAND/CeSOX experiment is to test this hypothesis by deploying a radioactive source next to a large liquid scintillator detector such as KamLAND or Borexino. In this thesis, are presented results of signal and background simulations performed to validate the design and assess the sensitivity of such an experiment
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Tchoualack, Tchamako Armel. „Détecteur SiC de particules et électronique de conditionnement“. Electronic Thesis or Diss., Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0176.
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Il s'agit à la fois d'étudier des détecteurs de particules (électrons et neutrons) en carbure de silicium à l'état de l'art, et de réaliser une interface électronique reconfigurable et intégrée adaptative à partir de technologies durcies pour le conditionnement et le traitement du signal électrique généré. Le front-end électronique (électronique de lecture) devra être capable d'extraire les signaux utiles (réponse en courant) des détecteurs ayant des caractéristiques différentes (dimensions, temps de réponse) et de fournir des données résolues (nature de la particule, spectroscopie, etc.) à l'aide de processeur embarqué. Plusieurs scénarios de co-intégration de l’ensemble " détecteur et électronique de lecture " prenant en compte l'environnement d'utilisation seront étudiés pour concevoir un détecteur de particules muni d'intelligence embarquée et plaçant ainsi l'étude à l'état de l’artIt involves both studying a state-of-the-art silicon carbide particles (electrons and neutrons) detector and producing an adaptive integrated reconfigurable electronics interface from hardened technologies for the conditioning and processing electrical signal generated. The electronics front-end will be capable to extract all useful signals (current answer) from the detector having different characteristics (dimensions, response times) and providing resolved data (nature of the particle, spectroscopy, etc.) using on-board processor. Several scenarios of co-integration of the "detector and electronic reading" assembly taking into account the environment of use will be studied to design a particle detector equipped with on-board intelligence and placing the study in the state of art
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Caravaca, Rodríguez Javier. „Measurement of the electron-neutrino component of the T2K beam and search for electron-neutrino disappearance at the T2K Near Detector“. Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/283399.
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T2K es un experimento de oscilaciones de neutrinos de largo recorrido en el que por primera vez se
ha observado la aparición de neutrinos electrónicos en un haz de neutrinos muónicos. Así pues, el único ángulo de mezcla que quedaba por conocer, q13, es medido con gran precisión. el background principal de esta medida es la contaminación de neutrinos electrónicos producida en el haz junto con la componente de neutrinos muónicos. Ésta es una componente irreducible que ha de ser medida y controlada.
La componente intrínseca de neutrinos electrónicos es medida antes de las oscilaciones en el detector cercano de T2K confirmando la predicción de la simulación con un precisión del 10%. Se establece que el background de neutrinos electrónicos está bien reproducido y que la principal medida del experimento T2K es exacta.
Por otro lado, estudiar la componente de neutrinos electrónicos es interesante para investigar el comportamiento anómalo de algunos experimentos. Estudios en reactores nucleares y resultados en la calibración de experimentos de neutrinos solares con Galio han observado un déficit de neutrinos electrónicos a cortas distancias de la fuente. Este déficit no es compatible con oscilaciones de neutrinos estándar, pero puede ser conciliado en el marco de las oscilaciones, mediante la introducción de un cuarto neutrino con una masa del orden de 1eV². Este nuevo neutrino no sentiría ninguna fuerza del Modelo Estándar y por ello es comúnmente llamado neutrino estéril. Asumiendo que se mezcla con los neutrinos de tipo electrónico, explicaría la desaparición a cortas distancias de los mismos. El detector cercano de T2K se encuentra a una distancia de la fuente óptima para el estudio de oscilaciones de neutrinos estériles ligeros. El modelo más simple de neutrinos estériles con un sólo neutrino adicional es investigado, definiendo intervalos de confianza para los parámetros de oscilación y comparándolos con la literatura.The T2K experiment is a long baseline neutrino experiment that has observed for first time the appearance of electron-neutrinos in a muon-neutrino beam. Thanks to this analysis, the last unknown neutrino mixing angle q13 is measured with a good precision. The main background to this measurement is the contamination of electron-neutrinos produced in the neutrino beam together with the dominant muon-neutrino component. This is an irreducible component that needs to be measured and controlled. The prediction of this component at SuperKamiokande is based on the constrain of the neutrino flux and cross sections by a muon-neutrino selection at the T2K near detector ND280. To confirm this prediction, we measure the electron-neutrino event rates at ND280 before the oscillations occur, establishing that the electron-neutrino component is correctly reproduced by the simulation at the 10% level. In addition, studying the electron-neutrino component is interesting to investigate the abnormal behaviour of some neutrino experiments. The reactor neutrino experiments as well as the results from calibration with radioactive sources in solar neutrino experiment with gallium have observed a deficit of electron-neutrino at very short distances from the neutrino source. This depletion is not compatible with standard neutrino oscillation, but it can be explained by invoking a fourth neutrino with a mass of the order of 1eV². This neutrino does not feel any force of the Standard Model and hence is called sterile neutrino. Assuming that it mixes with the electron-neutrinos, it would be responsible of the short base-line electron-neutrino disappearance due to neutrino oscillation. The T2K near detector is located at a position short enough to study the light sterile neutrino oscillations. The neutrino model with an additional sterile neutrino apart from the three active species is tested and some constraints to the oscillation parameters are set and compared with the literature.
13
Lai, Chi-hsuan. „Neutrino electron plasma instability /“. Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Helme, Lucy. „Neutron Scattering Studies of Correlated Electron Systems“. Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491531.
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This thesis presents neutron scattering studies of three correlated electron systems, each of which exhibit different competing interactions. These include charge order, magnetic order and lattice degrees of freedom. The main focus is on magnetic excitations within the systems. In all cases the experimental data have been analysed through comparison with theoretical models. Chapter 3 presents an investigation into the Jahn-Teller effect in the rare earth oxide Pr02, through inelastic neutron scattering studies of the crystal field transitions above and below a static structural distortion temperature. The data are compared with a point-charge model of the crystal field levels. \Ve conclude that the observed temperature evolution of the crystal field levels originates from the structural distortion due to the Jahn-Teller effect. Chapter 4 describes studies of magnetic excitations in the layered charge-ordered transition-metal oxide La1.5Sro.5Co04 through inelastic neutron scattering studies, and subsequent comparison with spin-wave dispersion models. It was found that the spin-wave excitations were decoupled from the charge order. Inclusion of the strong crystal anisotropy was necessary in order to successfully describe the data. Chapters 5 and 6 present studies of the magnetically ordered phase of Nax Co02 with x rv 0.75, a metallic layered transition-metal oxide. Chapter 5 describes investigations into the magnetic excitations in the compound, which were successfully modelled by linear spin-wave theory, including terms for the anisotropy. The excitations were found to be highly three dimensional despite the layered nature of the crystal structure. Chapter 6 presents a diffraction study of a spin-flop transition in an applied magnetic field, which confirmed the magnetic order. The transition field was found to be in excellent agreement with the exchange and anisotropy parameters extracted in chapter 5.
15
Paoli, M. P. „Electron-volt neutron spectroscopy of condensed matter“. Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235080.
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Klimenko, Alexei V. Kuhn Sebastian. „Electron scattering from a high momentum neutron in deuterium /“. Connect to this resource. (Authorized users only), 2004.
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17
Salagnac, Thomas. „Recherche d'un neutrino stérile avec l'expérience STEREO : développement de l'électronique et identification des neutrinos“. Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY068/document.
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Depuis 2011, la réévaluation de plus d’une vingtaine de mesures de flux de neutrinos de réacteur mesurés à courtes distances suggère la présence d’un déficit de 7 % par rapport aux prédictions. Cette anomalie est statistiquement significative à environ 3 sigmas, tout comme une autre anomalie similaire correspondant à l’observation d’un déficit de neutrinos émis par des sources intenses de désintégrations beta. Ces anomalies peuvent être expliquées soit par un biais dans la prédiction des flux de neutrinos, soit par l’existence d’un nouvel état de neutrino, un neutrino stérile léger, vers lequel les trois neutrinos du modèle standard pourraient osciller. Ce nouveau neutrino, n’interagissant pas par interaction faible, serait uniquement « visible » grâce à ces oscillations. L’objectif de l’expérience STEREO est de répondre à la question de l’existence d'un neutrino stérile avec une masse de l’ordre de 1 eV, en utilisant le flux de neutrinos émis par le réacteur de recherche de l’« Institut Laue-Langevin » (ILL) à Grenoble, en France. Pour cela, le détecteur STEREO est segmenté en 6 cellules afin de mesurer l’hypothétique distorsion du spectre en énergie des neutrinos en fonction de la distance au réacteur (entre 9 et 11m de distance). Après quelques années de construction du détecteur et de préparation, l’expérience STEREO a pu commencer la prise de données en novembre 2016 avec une premier période d’acquisition qui s’est terminée en mars 2017. Cette thèse s’inscrit dans ces deux périodes distinctes de l’expérience STEREO. Une première partie a été consacrée à la caractérisation et la validation de l’électronique tout au long du processus de développement jusqu’à sa conception finale. Dans ce cadre, une méthode de mesure de la linéarité de la réponse en charge des photomultiplicateurs et de leurs embases a été développée avec une précision meilleure que 1 %, pour répondre au exigence de sensibilité à l’hypothèse d’un neutrino stérile. Cette exigence a d'ailleurs été validée par une analyse statistique de l’expérience. Une deuxième partie de la thèse a concerné l’analyse des premières données et plus particulièrement, l’identification des différents types de bruit de fond et la recherche des candidats neutrinosSince 2011, the re-evaluation of about twenty neutrino flux measurements at short distance from reactors suggests a deficit of about 7 % with respect to predictions. This anomaly has a 3 sigmas significance, as another similar anomaly which corresponds to the deficit of neutrinos emitted from intense source of beta-decay. These anomalies could be explain either by a bias in the flux prediction or by the existence of a new neutrino state, a light sterile neutrino, possibly mixing with the three neutrino states of the standard model. This new neutrino, with no ordinary weak interaction, could only be “visible” via the neutrino oscillation. The STEREO experiment goal is to answer the question of the sterile neutrino existence with mass around 1 eV, using neutrino flux emitted from the research reactor of the « Institut Laue-Langevin » (ILL) at Grenoble, France. To achieve this, the STEREO detector is segmented in 6 cells to measure a hypothetical distortion of the neutrino energy spectrum at different distances from the reactor (between 9 et 11m). Afters few years of detector construction and preparation, the STEREO experiment has started taking data in November 2016 with a first period over in Mars 2017. This thesis took place during two distinct phases of the STEREO experiment. A first part was dedicated to the characterisation and the validation of the electronics, during all its development process until its final conception. In this context, a method to measure the charge response linearity of photomultipliers and their bases, with a precision better than 1 %, has been developed, in order to fulfill the desired sensitivity to the light sterile neutrino hypothesis. This requirement on the precision has been validated by a statistical analysis of the experiment. The second part of the thesis was devoted to the analysis of the first data and more particularly to the identification of the different kinds of background and to the search of neutrino candidates
18
Rutt, Paul Martin. „The recoil momentum dependence of the deuterium(electron, electron' neutron)proton cross section“. W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539623831.
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We measured of the recoil momentum dependence of the d(e,e$\sp\prime$n)p cross section at a central $\vec q$ of 335 MeV/c. These measurements were part of experiment 85-05 at the Bates Linear Accelerator Center which also measured the electric and magnetic form factors of the neutron, G$\sbsp{\rm E}{n}$ and G$\sbsp{\rm M}{n}$. The experiment was run with a 444 MeV electron beam incident on a 5 cm target of liquid deuterium. Outgoing electrons of different momenta were selected by changing the dipole field of the electron spectrometer OHIPS which was at a fixed angle of 47$\sp\circ$. Neutrons were measured using an 1 x 4 array of mineral oil scintillators at an angle of $-$57$\sp\circ$. The recoil momentum transfer covered a range of $-$43 to 165 MeV/C in six overlapping points. The kinematics were such that extensive radiative corrections were needed and techniques for performing these corrections are described. The shape of the cross section as a function of recoil momentum was compared to and found to be in good agreement with a nonrelativistic calculation which included final-state-interactions.
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Niederhausen, Hans. „Measurement of the High Energy Astrophysical Neutrino Flux Using Electron and Tau Neutrinos Observed in Four Years of IceCube Data“. Thesis, State University of New York at Stony Brook, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10823307.
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The high-energy universe is known to be violent. Ultra High Energy Cosmic Rays (UHECRs) have been observed with kinetic energies exceeding 10 20 eV. Their origin, despite decades of observations, remains elusive. A unique probe of the sources and production mechanisms of these high energy cosmic rays can be neutrinos, since they are inevitably produced when high-energy protons interact. The IceCube Neutrino Observatory, located at the geographical South Pole in Antarctica, continuously monitors a total volume of 1 km 3 of clear Antarctic ice for neutrino interactions. For this purpose, a total of 5160 optical sensors (photomultiplier tubes) have been melted deep into the glacier at depths between 1450m and 2450m. In 2013 IceCube reported one of its biggest discoveries, the observation of highly energetic neutrinos that are consistent with a possible extra-galactic origin.
In this dissertation we use IceCube data (recorded from 2012 to 2015) to study the spectral properties of this astrophysical neutrino flux with focus on electron and tau neutrino flavors. We developed a new neutrino identification and muon background rejection method using state-of-the-art machine-learning techniques, more specifically multi-class gradient boosted decision trees. In addition to enlarging the number of detected neutrino events (>10x increase over previous works), we lowered the energy threshold to below 1 TeV and thereby greatly improved upon the control and treatment of systematic uncertainties. The sample contains ~400 astrophysical electron and tau neutrinos, which increases the significance of the original discovery to beyond 8 standard deviations. We find the astrophysical neutrino flux to be well described by a single power-law consistent with expectations from Fermi-type acceleration of high-energy particles at astrophysical sources and obtain leading constraints on its properties. We further studied the possibility of additional spectral complexity, which significantly increases measurement uncertainties. No evidence for such scenarios was found. Finally we searched for a contribution from atmospheric neutrinos related to heavy meson (charm) decay in Earth's atmosphere and derive a flux upper limit of 4.8 times the benchmark pQCD flux prediction at 90% confidence level, dominated by systematic uncertainties, especially related to photon transport in the glacial ice.
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Hollnagel, Annika [Verfasser], und Caren [Akademischer Betreuer] Hagner. „Energy reconstruction of electron neutrino events and muon neutrino-to-electron neutrino appearance search in the OPERA detector / Annika Hollnagel ; Betreuer: Caren Hagner“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1164158724/34.
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Tenti, Matteo <1982>. „Electron identification and reconstruction with the OPERA ECC bricks and search for muon neutrino to electron neutrino oscillations“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4294/1/TESI.pdf.
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The procedure for event location in OPERA ECC has been optimazed for penetrating particles while is less efficient for electrons.
For this reason new procedure has been defined in order to recover event with an electromagnetic shower in its final state not located with the standard one. The new procedure
include the standard procedure during which several electromagnetic shower hint has been defined by means of the available data. In case the event is not located, the presence of an electromagnetic shower hint trigger
a dedicated procedure. The old and new location procedure has been then simulated in order to obtain the standard location efficiency and the possible gain due to the new one for the events with electromagnetic shower. Finally a Data-MC comparison has been performed for the 2008 and 2009 runs for what concern the NC in order to validate the Monte Carlo. Then the expected electron neutrino interactions for the 2008 and 2009 runs has been evaluated and
compared with the available data.
22
Tenti, Matteo <1982>. „Electron identification and reconstruction with the OPERA ECC bricks and search for muon neutrino to electron neutrino oscillations“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4294/.
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The procedure for event location in OPERA ECC has been optimazed for penetrating particles while is less efficient for electrons.
For this reason new procedure has been defined in order to recover event with an electromagnetic shower in its final state not located with the standard one. The new procedure
include the standard procedure during which several electromagnetic shower hint has been defined by means of the available data. In case the event is not located, the presence of an electromagnetic shower hint trigger
a dedicated procedure. The old and new location procedure has been then simulated in order to obtain the standard location efficiency and the possible gain due to the new one for the events with electromagnetic shower. Finally a Data-MC comparison has been performed for the 2008 and 2009 runs for what concern the NC in order to validate the Monte Carlo. Then the expected electron neutrino interactions for the 2008 and 2009 runs has been evaluated and
compared with the available data.
23
Mohanmurthy, Prajwal. „Topics on electron,neutrino and axion scattering“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103161.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Physics, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 61-64).
Under the broad topic of scattering, in this thesis we particularly investigate Lorentz invariance using Compton Scattering at the Compton Polarimeter located in Hall-C at Thomas Jefferson National Accelerator Facility. The Mississippi State Axion Search, an axion search experiment which uses light shining through a wall technique is described in detail, including its instrumentation, initial tests and future impact. Furthermore, a novel method of detection of solar anti-neutrinos based on coherent neutrino scattering is described. Additionally, on the instrumentation side, development of a multi-purpose beam instrument based on synchrotron light to measure the electron beam polarization, beam profile and intensity at the future Electron Ion Collider is presented.
by Prajwal Mohanmurthy.
S.M.
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Holin, A. M. „Electron neutrino appearance in the MINOS experiment“. Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20223/.
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The MINOS experiment is a long-baseline neutrino oscillation experiment which sends a high intensity muon neutrino beam through two functionally identical detectors, a Near detector at the Fermi National Accelerator Laboratory in Illinois, 1km from the beam source, and a Far detector, 734km away, in the Soudan Mine in Minnesota. MINOS may be able to measure the neutrino mixing angle parameter sin{^2}2\theta{_1_3} for the first time. Detector granularity, however, makes it very hard to distinguish any \nu{_e} appearance signal events characteristic of a non-zero value of \theta{_1_3} from background neutral current (NC) and short-track \nu{_\mu} charged current (CC) events. Also, uncertainties in the hadronic shower modeling in the kinematic region characteristic of this analysis are relatively large. A new data-driven background decomposition method designed to address those issues is developed and its results presented. By removing the long muon tracks from \nu{_\mu}-CC events, the Muon Removed Charge Current (MRCC) method creates independent pseudo-NC samples that can be used to correct the MINOS Monte Carlo to agree with the high-statistics Near detector data and to decompose the latter into components so as to predict the expected Far detector background. The MRCC method also provides an important cross-check in the Far detector to test the background in the signal selected region. MINOS finds a 1.0-1.5 \sigma\nu{_e}-CC excess above background in the Far detector data, depending on method used, for a total exposure of 3.14x10{^20} protons-on-target. Interpreting this excess as signal, MINOS can set limits on sin{^2}2\theta{_1_3}. Using the MRCC method, MINOS sets a limit of sin{^2}2\theta{_1_3} < 0:265 at the 90% confidence limit for a CP-violating phase \delta = 0.
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Liu, Ji. „Electron Neutrino Appearance in the Nova Experiment“. W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1499449859.
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The NuMI off-Axis $\nu_e$ Appearance (NO$\nu$A) experiment is a long baseline, off-axis neutrino oscillation experiment. It is designed to search for oscillations of $\nu_\mu$ to $\nu_e$ by comparing measurements of the NuMI beam composition in two detectors. These two detectors are functionally identical, nearly fully-active liquid-scintillator tracking calorimeters and located at two points along the beam line to observe the neutrinos. The Near Detector (ND), situated \unit[1]{km} away from the proton target at Fermilab, measures neutrinos prior to oscillation. Then the Far Detector (FD), located 810 km away at Ash River, Minnesota, measures the neutrinos after they have traveled and potentially oscillated. The neutrino beam is generated at Fermi National Accelerator Laboratory in Batavia, Illinois by the Neutrinos at the Main Injector (NuMI) facility. By observing the $\nu_\mu\to\nu_e$ oscillation, NO$\nu$A is capable of measuring the neutrino mass hierarchy, CP violation and the octant of mixing angle $\theta_{23}$. This thesis presents the first measurement of $\nu_e$ appearance in the NO$\nu$A detectors with $3.52\times10^{20}$ protons-on-target (POT) data accumulated from February 2014 till May 2015. In this analysis the primary $\nu_e$ CC particle selection LID observes 6 $\nu_e$ like events in the far detector with a background prediction of $0.99\pm0.11$ (syst.), which corresponds to a $3.3\sigma$ excess over the no-oscillation hypothesis. This results disfavors $0.1\pi < \delta_{cp} < 0.5\pi$ in the inverted mass hierarchy at $90\%$ C.L with the reactor constrain on $\theta_{13}$.
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Baillie, Nathan Kidd. „Electron scattering from an almost free neutron in deuterium“. W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539623554.
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The Barely off-Shell Nucleon Structure (BoNuS) experiment measured electron scattering from neutrons bound in deuterium nuclei at Jefferson Lab's Hall B with the intent of obtaining the ratio Fn2/Fp2 at high Bjorken x. The Fn2 structure function is difficult to obtain due to nature's lack of a free neutron target. Previous experiments have measured inclusive scattering from atomic nuclei, but extracting Fn2 from these data requires knowledge of inclusive scattering from the proton and corrections for nucleon binding and Fermi motion. In BoNuS we restrict our analysis to neutron scattering events tagged by a backward-going low-energy recoil proton. This selects loosely bound neutrons that are nearly on their mass-shell and have few final state interactions with the recoil proton. The recoil protons were detected in a Radial Time Projection Chamber (RTPC) using gas electron multipliers (GEMs) in a cylindrical geometry around the target. The production data were taken at three beam energies: 2.140 GeV, 4.223 GeV and 5.262 GeV with an additional set of calibration data taken at 1.099 GeV. The kinematic coverage includes the invariant mass, W, from the quasi-elastic peak up to 3.0 GeV and momentum transfer, Q 2, from 0.2 GeV2 up to approximately 3.0 GeV 2. The final experimental observations presented here are the tagged/untagged cross section ratios, corrected for a number of physical processes and backgrounds. The ratio enables us to ignore many complications arising from a typical absolute cross section measurement. An extraction of Fn2/Fp2 for x up to 0.75 is made and compared with previous data These data are important because they can provide a model independent measurement of neutron structure.
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Lafont, Fabien. „Développement du détecteur d'électrons SECOND dédié à la mesure du temps de vie du neutron dans l'expérience HOPE“. Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY065/document.
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Sous réserve d’une énergie cinétique suffisamment faible, un neutron libre peut être piégé matériellement ou magnétiquement de sorte à garantir son confinement au sein d’un volume défini. Cette caractéristique permet l’étude de plusieurs paramètres, notamment de son temps de vie moyen. L’expérience HOPE, piège magnétique de neutrons ultra-froids mis en œuvre à l’Institut Laue Langevin à Grenoble, vise à fournir une valeur précise de ce temps de vie au travers de différentes méthodes. L’une d’entre elles consiste à observer les électrons émis par la décroissance bêta du neutron. Le détecteur SECOND a été spécifiquement conçu pour permettre le comptage de ces électrons au sein de l’expérience HOPE. La grande difficulté de ce projet réside dans le faible taux de comptage des électrons attendu, qui nécessite la discrimination des rayonnements parasites. Dans ce but, SECOND est constitué de deux étages de détection, dont le principal, un phoswich de scintillateurs plastiques, a donné des résultats probants lors de premiers tests fonctionnels à basse température ; la différenciation des événements induits par des muons cosmiques est efficace dans 98 % des cas, et tout porte à croire qu’elle sera considérablement améliorée par l’utilisation d’un système d’acquisition adapté à l’application souhaitéeConsidering a low enough kinetic energy, a free neutron can be materially or magnetically trapped in a defined volume. This trapping allows experimenters to study the neutron and its characteristics, and in this case, to measure its mean lifetime. The HOPE experiment commissioned at Laue Langevin Institute in Grenoble is aimed at providing a 1 %- accuracy value. One way to measure lifetime is to record every single neutron beta decay occurring in the trap by counting the emitted electrons. The detector SECOND has been specifically designed to fulfill this goal within HOPE but also to discriminate other types of particles that induce false events. The latter argument is the reason for the two detection stages SECOND is composed of. The plastic scintillators phoswich constitutes the main part of the detector and has been successfully operated during preliminary tests at low temperature. The rejection rate of cosmic muons events is about 98 %, and this value can be drastically enhanced using a more suitable data acquisition system
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FERRARIO, ALBERTO. „Atmospheric neutron induced soft errors on electronic devices“. Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28334.
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Soft errors at sea level, originating from scattered particles in the atmosphere or alpha-emitting contaminants in chip materials, are a known source of disturbances in SRAM's and, to a lesser extent, in DRAM's. Relatively less is known about the sensitivity of Floating Gate memories, one of the most pervasive type of memory. An extensive literature covers the effects of heavy ions on floating gate cells, but little data obtained with particles matching the terrestrial neutron environment are available.
The purpose of this thesis is to investigate atmospheric neutron effects on floating gate cells in NAND Flash memories. Experimental data were obtained with neutron irradiation on commercial devices from different vendors. Irradiation was performed at the line of the ISIS facility at the Rutherford Appleton Laboratory, in Didcot, UK, using a wide-energy neutron beam. The VESUVIO neutron spectrum reasonably reproduces the terrestrial environment, with several orders of magnitude of acceleration.
A Geant4-based code has been developed to simulate the irradiation of three technological floating gate cells. With Matlab data post processing, simulations have provided physical informations about the interactions between incident neutrons and chip materials.
Finally, a relation between experimental data and simulations has been studied. The thesis is organized as follows:
Chapter 1 gives an overview of radiations effects. Different sources of neutrons,
like space environments, terrestrial environments, but also man-made radiation facilities are introduced. The second part of Chapter 1 is focused on
radiation effects on CMOS technology, with attention on single event effects.
Chapter 2 is a brief survey of Flash technology. The Chapter explains the basic
principles and operation of non-volatile memories, with attention on the cell array architecture. The multi level cell memories are also introduced. Then, the reliability problems of industry-standard Flash Cell and scaling issues of the latest Flash structures are presented.
Chapter 3 contains the experimental work of this thesis. In the first part, general
published data of ionizing radiation on
floating gate cell are given. Hence,
experimental data of neutron radiation on commercial Flash memories at the
Isis facility are presented, focusing on the Cross Section and the Threshold
Voltage shift.
Chapter 4 presents the simulation work. After an introduction of the general
concepts of the Geant4 toolkit, the chapter explains the developed simulation tool in terms of 3D Geometry, Materials, Sensitive Detector and
the simulated Particles Spectrum. Data obtained from simulations and
analysed, in all their components, are exposed, suggesting a relation with
the experimental data.
Appendices gives the reader details of the Geant4 source code implemented for
this work. In particular, the descriptions of the Sensitive Detector and the
Physic List are reported.
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Ruan, Chong-yu. „From neutrinos to liquid clusters, structure investigations by electron scattering and related methods /“. Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Deniz, Muhammed. „Measurement Of Sm Electro-weak Parameters In Reactor Antineutrino-electron Scattering In Texono Experiment“. Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608386/index.pdf.
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In this thesis a search for electron type neutrino-electron scattering cross-section and Weinberg
Angle measurements were performed at KS Nuclear Power Station with 200 kg CsI(Tl) scintillating crystal detector located at a distance of 28 m from the 2.9 GW reactor core giving total flux of 6:52X10^12 cm^-2s^-1 in average at
the experimental site. New analysis techniques and background suppression methods were developed. In the region of 3-8 MeV a measurement of SM cross section of (1:235+-0.577) XR_SM and Weinberg Angle of 0:264 +-0.075
which is quite consistent with the SM value of 0.23120(15)were obtained. These are the best results with wold wide level sensitivities at untested low energy region by using reactor anti-neutrinos.
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Dong, Chuang. „Structure et formation des quasicristaux et des phases cristallines approximantes dans les alliages Ti-Fe, Al-Cu-Fe(-Cr), Al-Cu-Co(-Si) et Al-Pd-Mn“. Vandoeuvre-les-Nancy, INPL, 1991. http://docnum.univ-lorraine.fr/public/INPL_T_1991_DONG_C.pdf.
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Nous avons analysé par microscopie électronique à transmission et par diffraction des neutrons les alliages quasicristallins suivants: Ti2Fe, Al65Cu20Fe15, Al71Pd19Mn10, Al65Cu20Fe10Cr5, Al65Cu17,5 et Al63Cu17,5Si2. Toutes ces études abordent deux aspects différents de ces alliages : les phases quasicristallines et leurs approximants cristallins. Dans le premier aspect, nous avons étudié la structure et la formation des phases icosaédriques Ti-Fe, Al-Cu-Fe et Al-Pd-Mn. Les mécanismes de croissance ont été identifiés. Les vitesses de croissance de ces quasicristaux sont très faibles par rapport à celles des cristaux. En ce qui concerne le deuxième aspect, nous nous sommes attachés à l'étude des approximants de la phase décagonale dans les alliages Al65Cu20Fe10Cr5 et Al63Cu17,5Co17,5Si2. Nous avons pu relier la phase décagonale à ses approximants en mettant en évidence les mêmes types d'unités structurales. Nous avons aussi mis l'accent sur la phase de type CsCl qui peut être la structure de base pour toutes les structures quasicristallines et cristallines étudiées dans ce travail
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Toner, Ruth Bushnell. „Measuring θ₁₃ via muon neutrino to electron neutrino oscillations in the MINOS experiment“. Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/265528.
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One of the primary goals in neutrino physics at the present moment is to make a measurement of the neutrino oscillation parameter B13 . This parameter, in addition to being unknown, could potentially allow for the introduction of CP violation into the lepton sector. The MINOS long-baseline neutrino oscillation experiment has the ability to make a measurement of this parameter, by looking for the oscillation of muon neutrinos to electron neutrinos between a Near and Far Detector over a distance of 735 km. This thesis discusses the development of an analysis framework to search for this oscillation mode. Two major improvements to pre-existing analysis techniques have been implemented by the author. First, a novel particle ID technique based on strip topology, known as the Library Event Matching (LEM) method, is optimized for use in MINOS. Second, a multiple bin likelihood method is developed to fit the data. These two improvements, when combined, increase MINOS' sensitivity to sin2(W13 ) by 27% over previous analyses. This thesis sees a small excess over background in the Far Detector. A Frequentist interpretation of the data rules out B13 = 0 at 91 %. A Bayesian interpretation of the data is also presented, placing the most stringent upper boundary on the oscillation parameter to date, at sin2 (2B13 ) < 0.09(0.015) for the Normal (Inverted) Hierarchy and 6cp = 0.
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Yang, Tingjun. „A study of muon neutrino to electron neutrino oscillations in the MINOS experiment /“. May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Liu, Qiang. „Synthesis, characterization and investigation on the magnetic and electronic structure of strontium iron oxides“. Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14772/document.
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Les diverses perovskites de strontium-fer présentent de très fortes corrélations entre la structurecristalline et les phénomènes d’ordre de lacunes d’oxygènes, de charge, de spin et d’orbitales. Danscette thèse, nous avons réalisé une étude systématique des relations entre les ordres de charges etles ordres de spins selon les différents environnements cristallographiques rencontrés pour lescations Fe3+ et Fe4+ dans la phase Sr4Fe4O11, pour le cation Fe3+ dans les phases Sr3Fe2O6 et Sr2Fe2O10et pour le cation Fe2+ dans la phase SrFeO2. Les synthèses des phases polycristallines furent réaliséesvia des voies « solide » ou « sol-gel » en complément de la synthèse de cristaux préparés à l’aide d’unfour à image à fusion de zone verticale pour les phases Sr4Fe4O11 et Sr2Fe2O10. La qualité cristalline etchimique des oxydes fut contrôlée par diffraction de rayons X sur poudre et spectroscopieMössbauer alors que l’étude de la structure électronique de chaque phase a été réalisée à l’aide despectroscopie d’absorption de rayons X. Finalement, les structures magnétiques des phases Sr3Fe2O6et Sr4Fe4O11 sont aussi présentéesThe relationship of the crystallographic, magnetic, and electronic structure have long been of highinterest in research. Strontium iron oxides have structural, charge, spin, and orbital degrees offreedom, and thus give rich information to study for the condensed matter scientists. In this thesis,we have systematically studied the strontium iron oxides based on the freedom of the iron charge:Fe3+ and Fe4+ mixed valence compound SrFeO2,75 , Fe3+ compound Sr3Fe2O6 and SrFeO2,5 with differentcoordination around Fe3+ and Fe2+ compound SrFeO2. The synthesis of the polycrystalline compoundsare through either solid state reaction or sol-gel method. Single crystals of SrFeO2,75 and SrFeO2,5have been prepared by floating zone furnace. The purity of all the compounds is checked by lab x-raydiffraction and Mössbauer spectroscopy. Electronic structures have been studied by x-ray absorptionspectroscopy for all these compounds. Special efforts have been used to investigate the magneticstructure of SrFeO2,75 and Sr3Fe2O6
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Versari, Federico <1992>. „Measurement of the atmospheric electron and muon neutrino flux with the ANTARES neutrino telescope“. Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9664/1/PhD_Thesis____.pdf.
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This thesis presents a combined measurement of the energy spectra of atmospheric electron and muon neutrinos in the energy range between around 100 GeV and 50 TeV with the ANTARES neutrino telescope. The analysis uses 3012 days of detector livetime in the period from 2007 to 2017, and selects 1016 neutrino interacting in (or close to) the instrumented volume of the detector, yielding shower-like events and starting track events. The contamination by atmospheric muons is suppressed at the level of a few per mill by different steps in the selection analysis, including a Boosted Decision Tree classifier. The distribution of reconstructed events is unfolded in terms of electron and muon neutrino fluxes and the derived energy spectra are compared with previous measurements.
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Bay, Muhammet Fatih. „Study Of Electron Identification In The Opera Detector“. Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609649/index.pdf.
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The OPERA experiment is designed to perform first direct observation
of $nu_{tau}$ appearance in an almost pure $nu_{mu}$ beam. The
OPERA detector is a hybrid set-up which combines a lead/emulsion
target with various electronic detectors. It is located in Gran
Sasso Laboratory (LNGS), 730 km away from CERN where neutrino beam
is produced. A good electron identification in the ECC brick would
also allow OPERA to search for $nu_{mu}rightarrownu_{e}$
oscillations. We have studied electron identification in the
Emulsion Cloud Chamber (ECC) brick which was exposed to CERN SPS H4
electron beam. Emulsion scanning was performed in LNGS scanning
laboratory. FEDRA framework was used for the data analysis. In
total, we have found 30 electron showers in the brick. The
characteristics of each shower have been studied. The background
base-track contamination in the shower was estimated as $20pm 4$.
This is mainly due to shower overlap of electrons and passing
through cosmic rays.
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Ewings, Russell A. „Neutron and X-ray scattering studies of strongly correlated electron systems“. Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489436.
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In this thesis results of x-ray scattering and neutron scattering experiments on several strongly correlated transition metal oxides are presented. The prototypical charge ordered cuprate La1.48Nd0.4Sr0.12CuO4 was investigated using polarised neutron scattering. The results show that several proposed schemes for the magnetic order in this class of materials may be ruled out, however the data are consistent with one-dimensional stripe-like magnetic order. X-ray diffraction was used to show that the charge order is insensitive to an applied magnetic field, but might be affected by the existence of superconductivity. The magnetic excitations were also studied, and at low energies a gap in the magnetic fluctuations was observed and there is tentative evidence that this is related to magnetic anisotropy. The spin state transition in LaCoO3 was investigated using neutron inelastic scattering, and excitations reminiscent of those observed in ferromagnets above their critical temperatures were observed. The debate surrounding the nature of the excited spin state, S=1 or S=2, could not be resolved, however. The nature of the spin excitations in La0.82Sr0.18CoO3 was investigated using polarised neutrons and it was found that at low energies the excitations take the form of spin-waves. At higher energies this mode becomes heavily damped, and several possible damping mechanisms for this are discussed. Finally, the multiferroic material DyMn2O5 was studied using x-ray resonant scattering. A complex, temperature dependent, magnetic structure was found using a Dy resonance, which reflects an underlying order of the Mn ions. The measurements were in agreement with a theory of multiferroics based on acentric spin-density waves.
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Castellan, John-Paul Adrian Gaulin B. D. „X-ray and neutron diffraction studies of strongly correlated electron systems“. *McMaster only, 2007.
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Jillings, Christopher James. „The electron scattering reaction in the Sudbury Neutrino Observatory“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0006/NQ42947.pdf.
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Sowrey, Frank Edward. „Electronic and magnetic coupling in triangular metal clusters“. Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338298.
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41
Miranda, P. M. C. „Contributions to the search for a neutron EDM“. Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375844.
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The work described in this thesis was carried out at the Institut Laue Langevin, Grenoble, France as a member of the group searching for the electric dipole moment (EDM) of the neutron. The first chapter is an introduction to ultra-cold neutrons (UCN) and their use in the search for an EDM. In chapter two a description is given of the data acquisition procedure and the data analysis method as well as a discussion of the various sources of spurious EDM signals. The data taken by the author yielded the result I-fe/e = ( -3.7 ± 5.4 )xl0-25 cm, which together' with all the other data previously and subsequently collected on PN5 gives I-fe/e = ( -3.7 ± 5.4 )xlO- 25 cm. The third chapter contains some calculations, based on a simple model of the polarizer's properties, of the time dependence of the polarized UCN density in the apparatus during a data ~cquisition cycle. It. also includes the results of the experiments made in an attempt to determine experimentally the model's parameters. The other two chapters are concerned with the problem of transferring efficiently UCN from the 0.6 K volume of the 4He superthermal source to thf! 300 K EDM apparatus without allowing the heat transfer by radiation to overload the source's refrigerator. The possibility of using metal coated polypropylene windows to achieve this aim is investigated in the fourth chapter. In chapter five the infra-red transmission of the stainless steel neutron guides is estimated by calculation and then determined experimentally with a view to using lengths of cold guides to attenuate the radiation heat transfer from the apparatus to the source.
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Seydaliev, Marat Radikovich. „Development and Test of a GEM-Based TEPC for Neutron Protection Dosimetry“. Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14607.
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The effective dose equivalent, H (or the effective dose, E ) to an individual is the primary limiting quantity in radiation protection. However, techniques for measuring H for neutrons have not been fully developed. In this regard a new tissue equivalent proportional counter (TEPC) based on a gas electron multiplier (GEM) for measuring H*(10), which is a conservative estimate of H, for neutrons was designed and constructed.
The deposited energy distribution for two different neutron sources (a Cf-252 source and a AmBe source) was measured using the new TEPC. The measurements were performed using two different proportional gases: P-10 gas and a propane-based tissue equivalent gas at various pressures. A computer simulation of the new TEPC, based on the Monte Carlo method, was performed in order to obtain the pulse height distributions for the two neutron sources. The simulated results and the measured results were compared. Results show that the experimental results agree with the computational results within 20% of accuracy for both Cf-252 and AmBe neutron sources.
A new model GEM-based TEPC was developed for use in obtaining H*(10). The value of H*(10) for the Cf-252 source and for the AmBe source using experimental measurements was obtained. These results are presented in this study. The study shows that the GEM-based TEPC can successfully estimate H*(10). With these results and some refinements, this GEM-based TEPC can directly be used as a neutron rem meter.
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Gilkes, Kai William Reginald. „Tetrahedral carbon : studies using high resolution transmission electron microscopy and neutron scattering“. Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281952.
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Giganti, Claudio. „Particule Identification in the T2K TPCs and study of the electron neutrino component in the T2K neutrino beam“. Paris 11, 2010. http://www.theses.fr/2010PA112334.
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Cette thèse est consacrée à la mesure de l'apparition du neutrino électronique avec l'expérience T2K. T2K est une expérience pour la mesure des oscillations de neutrinos installée au Japon. Le faisceau de neutrinos est produit par un accélérateur à JPARC et les neutrinos sont observés avant l'oscillation dans un détecteur proche, ND280, et après l'oscillation dans un détecteur lointain, SuperKamiokande. L'objectif de cette thèse est la mesure, avec le détecteur proche, de la composante intrinsèque de neutrinos électroniques dans le faisceau. Les TPC constituent le détecteur principal utilisé pour cette mesure. La première partie de la thèse décrit la méthode utilisée pour l'identification des particules (PID) : la méthode est basée sur la mesure de la moyenne tronquée de la charge déposée par les particules traversant le milieu gazeux. Les capacités de PID des TPC ont été testées avec des données en faisceau prises à TRIUMF avec un faisceau composé d'électrons, muons et pions ayant une impulsion jusqu'à 400 MeV. L'analyse de ces données confirme que la résolution sur l'énergie déposée dans la TPC est de l'ordre de 7%. Avec les premières données de l'expérience T2K une première mesure de la composante de neutrinos électroniques a été faite. Pour effectuer l'analyse, interactions de neutrinos dans ND280 ont été sélectionnées : cet échantillon est principalement composé par des interactions de neutrinos muoniques car les neutrinos électroniques sont de l'ordre de 1 % du nombre total de neutrinos dans le faisceau. La sélection avec le PID des neutrinos électroniques et muoniques, a permis une première mesure de la composante des neutrinos électroniques dans le faisceau de T2KThis thesis is devoted to the measurement of the electron neutrino appearance with the T2K experiment. T2K is a long baseline neutrino oscillation experiment that is taking data in Japan. The neutrino beam is produced by an accelerator in JPARC and neutrinos are observed in a Near Detector, ND280, before the oscillation and in the far detector, SuperKamiokande, after the oscillation. The aim of this thesis is the measurement of the intrinsic electron neutrino component of the beam with the Near Detector. The main detector used in this measurement is the ND280 TPC. The first part of the thesis describes the method developed for the particle identification in the TPCs: the PID method is based on the measurement of the truncated mean of the charge deposited by the particles crossing the gas. The PID capabilities of the TPCs have been tested analyzing the beam test data: these data have been taken at TRIUMF where we had a beam composed by electrons, muons and pions with momenta up to 400 MeV/c: the analysis of these data confirmed that the resolution on the deposited energy in the TPCs was of the order of 7%. When the first data of the T2K experiment were available, a first measurement of the electron neutrino component in the near detector has been done. To perform the analysis, a sample of neutrino interactions in ND280 was selected: this sample was mainly composed by muon neutrino interactions as the electron neutrino is expected to be 1 % of the total number of neutrinos in the beam. The selection of both, electron and muon neutrinos, allowed a first measurement of the electron neutrino component in the T2K beam
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Orrell, John Laurence. „A search for an electron antineutrino signal in the Sudbury Neutrino Observatory /“. Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9794.
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Evans, Alan Charles. „The study of condensed matter by deep inelastic neutron scattering“. Thesis, University of Warwick, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387343.
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Gérard, Pascale. „Contribution à l'étude magnétostatique des systèmes intermétalliques R(Co1-xNix)5“. Grenoble 1, 1992. http://www.theses.fr/1992GRE10041.
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Une etude de l'evolution du magnetisme des electrons 3d dans le systeme y(co#1##xni#x)#5 (entre le fort ferromagnetisme itinerant associe au compose yco#3 et le paramagnetisme de pauli caracteristique du compose yni#5) est effectuee. On montre qu'aux fortes concentrations en nickel, les instabilites du magnetisme s'instaurent de maniere inhomogene, en fonction des environnements locaux. On precise ensuite les anisotropies associees a ce magnetisme. Elles revelent le caractere du magnetisme itinerant du sous-reseau (co#1##xni#x). Une etude de la coercivite magnetique, associee aux defauts d'echange et d'anisotropie introduits par la substitution du nickel au cobalt, est egalement menee sur les composes monocristallins du systeme riches en nickel. Cette coercivite est interpretee dans un modele de parois flexibles ancrees sur les clusters de faible densite d'aimantation. Nous considerons ensuite l'influence sur le magnetisme 3d, associe au sous-reseau (co#1##xni#x), d'une terre rare magnetique isotrope. Cette etude est realisee sur le systeme gd(co#1##xni)#5. Elle permet d'apprehender l'effet de champ d'echange, associe au gadolinium, sur la stabilite relative du magnetisme du sous-reseau 3d, et de mettre en evidence experimentalement une anisotropie des interactions d'echange entre les sous-reseaux 3d et 4f. Nous presentons enfin une etude par diffraction de neutrons polarises et non polarises du compose yco#3ni#2. Une determination fine de la structure cristallographique de ce compose est realisee. On met en evidence une repartition non aleatoire des atomes de cobalt et de nickel dans les deux types de sites qu'ils occupent. Une carte de la densite d'aimantation moyenne dans ce compose est etablie. Elle met en evidence l'existence d'une polarisation des electrons 5d, mediateurs des interactions d'echange 3d-4f, et permet en outre, d'evaluer la contribution orbitale au magnetisme du compose
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Ronchi, Emanuele. „Neural Networks Applications and Electronics Development for Nuclear Fusion Neutron Diagnostics“. Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-108583.
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This thesis describes the development of electronic modules for fusion neutron spectroscopy as well as several implementations of artificial neural networks (NN) for neutron diagnostics for the Joint European Torus (JET) experimental reactor in England. The electronics projects include the development of two fast light pulser modules based on Light Emitting Diodes (LEDs) for the calibration and stability monitoring of two neutron spectrometers (MPRu and TOFOR) at JET. The particular electronic implementation of the pulsers allowed for operation of the LEDs in the nanosecond time scale, which is typically not well accessible with simpler circuits. Another electronic project consisted of the the development and implementation at JET of 32 high frequency analog signal amplifiers for MPRu. The circuit board layout adopted and the choice of components permitted to achieve bandwidth above 0.5 GHz and low distortion for a wide range of input signals. The successful and continued use of all electronic modules since 2005 until the present day is an indication of their good performance and reliability. The NN applications include pulse shape discrimination (PSD), deconvolution of experimental data and tomographic reconstruction of neutron emissivity profiles for JET. The first study showed that NN can perform neutron/gamma PSD in liquid scintillators significantly better than other conventional techniques, especially for low deposited energy in the detector. The second study demonstrated that NN can be used for statistically efficient deconvolution of neutron energy spectra, with and without parametric neutron spectroscopic models, especially in the region of low counts in the data. The work on tomography provided a simple but effective parametric model for describing neutron emissivity at JET. This was then successfully implemented with NN for fast and automatic tomographic reconstruction of the JET camera data. The fast execution time of NN, i.e. usually in the microsecond time scale, makes the NN applications presented here suitable for real-time data analysis and typically orders of magnitudes faster than other commonly used codes. The results and numerical methods described in this thesis can be applied to other diagnostic instruments and are of relevance for future fusion reactors such as ITER, currently under construction in Cadarache, France.
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Mannix, Daniel. „X-ray and neutron scattering studies of f-electron multilayers and single crystals“. Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263708.
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Saeed, Azmat. „A high resolution electron microscopy and neutron scattering investigation of some amorphous materials“. Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358768.
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