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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Estudo da produção de quarks pesados no experimento STAR@RHIC / Study as production of heavy quarks in the STAR experiment at RHIC

Lima, Lucas Mafia 27 October 2011 (has links)
O plasma de quarks e glúons é uma previsão da cromodinâmica quântica e experimentos em aceleradores de alta energia têm encontrado evidências experimentais de sua criação em colisões de íons pesados relativísticos. Uma dessas evidências foi proposta por Matsui e Satz [1] que prevê a supressão de estados de heavy quarkonium na existência deste plasma. Este projeto tem como objetivo obter a seção de choque da produção de no experimento STAR em colisões p+p e d+Au com energia no centro de massa de 200GeV e calcular o fator de modificação nuclear Rab. Para tal, foi necessário reconstruir os através de seu decaimento leptônico. Os subdetectores do STAR utilizados foram o TPC e BEMC. Os valores encontrados para seção de choque foram de 3i=1 (nS)e-e+(nS)p+p= 84 ±9(stat)+18-19(sist)pb e 3i=1 (nS)e-e+(nS)d + Au = 41 ± 4(stat) +7-8(sist)nb para as produções pp2009 e dAu2008, respectivamente. Os valores se encontram compatíveis com os teóricos calculados pelo modelo de evaporação de cor. O Rab experimental vale 1.24 ± 0.18(stat)+0.35 0.38(sist). / The quark and gluon plasma is a prediction of QCD, and high energy experiments have studied evidences of its creation in relativistic heavy ion collisions. One of these evidences was proposed by Matsui and Satz [1] that provides a experimental signature of the creation of the plasma, observing an anomalous supression on the heavy quarkonium production. This project aims to get production cross section in the STAR experiment in collisions p+p and d+Au with energy in the center of mass of 200GeV and calculate the nuclear modification factor Rab. To this end, it was necessary to reconstruct the from his leptonic decay. The subsystems used in this analysis were the TPC, BEMC and the heavy quarkonia trigger system. The values for the cross sections were 3i=1 (nS)e-e+(nS)p+p= 84 ±9(stat)+18-19(sist)pb and 3i=1 (nS)e-e+(nS)d + Au = 41 ± 4(stat) +7-8(sist)nb for pp2009 and dAu2008 productions, respectively. These values are compatible with the theoretical calculated by the color evaporation model. The determined value for the factor Rab was 1.24 ± 0.18(stat)+0.35 0.38(sist).
72

Experimental Studies of Neutron Emission Induced by Heavy-Ion Scattering

Nadel-Turonski, Pawel January 2003 (has links)
<p>A beam of 250A MeV <sup>17</sup>O ions was scattered from argon and xenon targets. The large excess of fast neutrons compared with statistical model calculations that was observed earlier for xenon, was confirmed and found for argon as well. Analysis and calculations show that a considerable fraction of these neutrons can be interpreted as coming from direct knock-out reactions.</p><p>The angular distributions do not support the suggestion of using fast heavy ion scattering as a probe for the study of the neutron skin in nuclei. While the basic idea that a heavy projectile tends to sample the neutron wave function near the surface of the nucleus is sound, the measured neutron distribution is not as distinct as suggested by the previous experiment. This makes it difficult to distinguish direct reactions from other channels, such as semi-direct decay of giant resonances.</p><p>The improvements in the experimental methods have made the concept of using the CELSIUS storage and cooler ring as an internal magnetic spectrometer attractive for other of experiments presently being prepared.</p>
73

Experimental Studies of Neutron Emission Induced by Heavy-Ion Scattering

Nadel-Turonski, Pawel January 2003 (has links)
A beam of 250A MeV 17O ions was scattered from argon and xenon targets. The large excess of fast neutrons compared with statistical model calculations that was observed earlier for xenon, was confirmed and found for argon as well. Analysis and calculations show that a considerable fraction of these neutrons can be interpreted as coming from direct knock-out reactions. The angular distributions do not support the suggestion of using fast heavy ion scattering as a probe for the study of the neutron skin in nuclei. While the basic idea that a heavy projectile tends to sample the neutron wave function near the surface of the nucleus is sound, the measured neutron distribution is not as distinct as suggested by the previous experiment. This makes it difficult to distinguish direct reactions from other channels, such as semi-direct decay of giant resonances. The improvements in the experimental methods have made the concept of using the CELSIUS storage and cooler ring as an internal magnetic spectrometer attractive for other of experiments presently being prepared.
74

Análisis de los mecanismos de emisión y de las correlaciones angulares de los productos de interacción del 0-16 a 2,1 gev/a con núcleos de emulsión

Ruiz Jimeno, Alberto 03 June 1978 (has links)
The interactions, with emulsion nuclei, of O-16 ions accelerated at 2.1 GeV/nucleon in the Berkeley accelerator, are analyzed. A phenomenological study of the events, particularly reaction cross sections and multiplicities is exposed to nuclear theories with nucleons acting individually and collectively An study of the angular distributions of the reaction products and their correlations, particularly in the transversal space, is shown. Finally, a discussion of the present parton model of the nucleon structure is done, comparing it with the experimental results.
75

Etude des effets singuliers produits par les particules énergétiques chargées de l’environnement radiatif spatial sur les capteurs d’images CMOS / Study of Single Event Effects induced by highly energetic charged particles of the space environment in CMOS image Sensors

Lalucaa, Valérian 12 December 2013 (has links)
Ce mémoire de thèse traite des effets singuliers produits par les milieux radiatifs sur les capteurs d’images CMOS. Le travail se concentre sur les effets provoqués par les ions lourds sur les capteurs utilisant des pixels 3T à photodiode standard et des pixels 4T et 5T à photodiodes pincées. Dans un premier temps, l’étude se concentre sur l’environnement spatial et l’architecture des capteurs. La comparaison avec la littérature met en évidence les effets les plus critiques sur les capteurs : le SEL et les SET. Les capteurs testés expérimentalement valident les travaux théoriques. Les SET sont comparés aux simulations de l’outil de modélisation STARDUST, et montrent un bon accord pour toutes les puces et les ions. Il est expliqué pourquoi les SET sur les puces 3T sont insensibles aux variations de conception de la photodiode, et pourquoi l’utilisation d’un substrat épitaxié diminue grandement les SET. Une méthode de réduction des SET est implémentée avec succès sur les puces 4T et 5T, et le composant responsable du latchup est identifié. L’ensemble des mécanismes explorés permet de connaitre les paramètres importants pour durcir les imageurs. / This thesis studies the single event effects of space environment in CMOS image sensors (CIS). This work focuses on the effects of heavy ions on 3T standard photodiode pixels, and 4T and 5T pinned photodiode pixels. The first part describes the space radioactive environment and the sensor architecture. The most harmful events (SEL and SETs) are identified thanks to the scientific literature. The experimentally tested sensors agree with the theoretical work. SETs are compared to STARDUST simulations with a good agreement for all ions and sensors. The work explains why the SETs on 3T pixels are insensitive to the various photodiode designs, and they are decreased when an epitaxial substrate is used. A method using anti-blooming was successfully used in 4T and 5T pixels to prevent the spread of the SETs. The mechanism of latchup in 4T pixel sensors is described. All the identified mechanisms are very useful to provide hardening methods for the CISs.
76

Estudo da produção de quarks pesados no experimento STAR@RHIC / Study as production of heavy quarks in the STAR experiment at RHIC

Lucas Mafia Lima 27 October 2011 (has links)
O plasma de quarks e glúons é uma previsão da cromodinâmica quântica e experimentos em aceleradores de alta energia têm encontrado evidências experimentais de sua criação em colisões de íons pesados relativísticos. Uma dessas evidências foi proposta por Matsui e Satz [1] que prevê a supressão de estados de heavy quarkonium na existência deste plasma. Este projeto tem como objetivo obter a seção de choque da produção de no experimento STAR em colisões p+p e d+Au com energia no centro de massa de 200GeV e calcular o fator de modificação nuclear Rab. Para tal, foi necessário reconstruir os através de seu decaimento leptônico. Os subdetectores do STAR utilizados foram o TPC e BEMC. Os valores encontrados para seção de choque foram de 3i=1 (nS)e-e+(nS)p+p= 84 ±9(stat)+18-19(sist)pb e 3i=1 (nS)e-e+(nS)d + Au = 41 ± 4(stat) +7-8(sist)nb para as produções pp2009 e dAu2008, respectivamente. Os valores se encontram compatíveis com os teóricos calculados pelo modelo de evaporação de cor. O Rab experimental vale 1.24 ± 0.18(stat)+0.35 0.38(sist). / The quark and gluon plasma is a prediction of QCD, and high energy experiments have studied evidences of its creation in relativistic heavy ion collisions. One of these evidences was proposed by Matsui and Satz [1] that provides a experimental signature of the creation of the plasma, observing an anomalous supression on the heavy quarkonium production. This project aims to get production cross section in the STAR experiment in collisions p+p and d+Au with energy in the center of mass of 200GeV and calculate the nuclear modification factor Rab. To this end, it was necessary to reconstruct the from his leptonic decay. The subsystems used in this analysis were the TPC, BEMC and the heavy quarkonia trigger system. The values for the cross sections were 3i=1 (nS)e-e+(nS)p+p= 84 ±9(stat)+18-19(sist)pb and 3i=1 (nS)e-e+(nS)d + Au = 41 ± 4(stat) +7-8(sist)nb for pp2009 and dAu2008 productions, respectively. These values are compatible with the theoretical calculated by the color evaporation model. The determined value for the factor Rab was 1.24 ± 0.18(stat)+0.35 0.38(sist).
77

Fragmentação nuclear em colisões de íons pesados a energias relativísticas / Nuclear fragmentation in collisions of heavy ions to relativistic energies

Rogerio Gregorio Burgugi 31 August 2009 (has links)
Foi investigada a correlação entre a energia transversa (ET) produzida e a energia de partículas neutras (En) emitidas em colisões de íons de 28Si (plab=14.6 GeV/c por nucleon) com alvos de Al, Cu e Pb, estudadas pelo Experimento 814 no acelerador AGS do Laboratório Nacional de Brookhaven. A correlação entre a energia transversa e a energia dianteira produzida em colisões com emissão dos fragmentos 2H, 3H, 3He, 4He, 6He, 5Li e 6Li também foi investigada. Foi observado que a energia En dianteira produzida pelas partículas neutras tem uma forte dependência com a energia transversa ET produzida na colisão. Uma parametrização eficiente dos dados é obtida utilizando um modelo estatístico que relaciona o numero de espectadores da colisão com o numero de nêutrons detectados na região dianteira. As distribuições de momento desses fragmentos foram investigadas através do modelo de Goldhaber e os seus respectivos parâmetros 0 foram calculados para os eventos referentes as colisões de 28Si com alvos de Al, Cu e Pb. / We carried out a study of the forward neutral energy (En) and its correlation with the produced transverse energy (ET ) in collisions of 28Si ions (plab=14.6 GeV/c per nucleon) with Al, Cu, and Pb targets, investigated by Experiment 814 at the Brookhaven AGS. The correlation of the produced transverse energy with forward neutral energy from fragments 2H, 3H, 3He, 4He, 6He, 5Li and 6Li was also investigated. We find that the forward neutral energy En has a strong dependence on transverse energy ET produced in the collision. An efficient parametrization of this data set is accomplished through the use of a statistical model which relates the number of spectators in the collision to the number of neutrons detected in the forward direction. Momentum distributions of the fragments were investigated through the use of the Goldhaber model and the 0 parameter was calculated to each of the fragments in reactions of 28Si with Al, Cu and Pb targets.
78

A seção de choque total de reação de íons pesados e a transparência nuclear / Total cross-section of heavy ion reactions and nuclear transparency

Ricardo Affonso do Rego 12 December 1984 (has links)
Foi calculado microscopicamente a seção de choque total de reação para os sistemas ANTPOT. 12 C + ANTPOT. 12 C, ANTPOT. 1-2 C+ ANTPOT. 40 Ca, ANTPOT. 12 C + ANTPOT. 90 Zr, ANTPOT. 12 C + ANTPOT. 208 Pb, ANTPOT. 40 Ca + ANTPOT. 40 Ca, ANTPOT. 40 Ca + ANTPOT. 208 Pb, ANTPOT. 90 Zr + ANTPOT. 90 Zr, ANTPOT. 90 Zr + ANTPOT. 208 Pb e ANTPOT. 208 Pb + ANTPOT. 208 Pb numa ampla faixa de energia. Foi usada a expressão WKB para a defasagem imaginária, na representação do parâmetro do impacto. A parte imaginária do potencial óptico foi construída, usando o primeiro termo da teoria de espalhamento múltiplo, incorporando na sua expressão o principio de Pauli. A inclusão da interação nuclear e coulombiana mostrou ser importante. Os resultados teóricos não se apresentam em bom acordo com os poucos dados experimentais existentes, a baixas energias. Este resultado foi atribuído a fraca absorção contida no potencial imaginário, que contém o processo de knock-out quase-livre como mecanismo dominante de reação. / The total reaction cross section of the systems 12C +12C, 12C + 40Ca, 12C + 90Zr, 12C + 208 Pb, 40Ca + 40Ca, 40Ca + 208Pb, 90Zr + 90Zr, 90 Zr + 208 Pb and 20B Pb + 208 Pb for a wide range of energies has been calculated microscopically. A WKB expression for the imaginary part of the optical potential has been constructed by using the first term of multiple scattering theory with the effect of Pauli blocking incorporated into it. The inclusion of the nuclear and Coulomb interactions is shown to be important. The theoretical results do not show very good agreement with the experimental data at lower energies. This is attributed to the weak absorption contained in the imaginary potential of the tpApB interaction, wich contained only quasi-free knock-out as the dominant reaction mechanism.
79

Identificação de elétrons com um detector de radiação de transição em colisões de íons pesados relativísticos / Electron identification with a transition radiation detector in relativistic heavy ion collisions

Bruno Rodrigues Lenzi 14 August 2007 (has links)
Este trabalho descreve o desenvolvimento de um simulador para as câmaras de expansão temporal / detectores de radiação de transição (TEC / TRD) do experimento PHENIX, instalado no Colisor de Íons Pesados Relativisticos (RHIC) do Laboratório Nacional de Brookhaven (BNL) nos EUA. O programa do RHIC prevê a produção e caracterização de um estado da matéria conhecido como plasma de quarks e glúons (QGP), através de colisões entre prótons, dêuterons e íons pesados com energias de centro de massa sqrt(s_NN) entre 20 e 200 GeV. O PHENIX, um dos quatro experimentos instalados no acelerador, é especializado na medida de sinais eletrofracos provenientes das colisões e o TEC / TRD é o único subsistema do PHENIX capaz de identificar elétrons de forma eficiente para momentos acima de 5 GeV/c. Um simulador para reprodução da resposta do detector à passagem de partículas foi desenvolvido e comparado a dados de um detector proporcional monofilar construído no Laboratório de Instrumentação e Partículas da USP, e aos dados do próprio TEC / TRD. Os resultados mostram um acordo razoável entre medidas e simulações. O uso do simulador deverá permitir o estudo de novos métodos e melhoras na capacidade de identificação de elétrons do sistema. / The present work describes the development of a simulator for the Time Expansion Chambers / Transition Radiation Detectors (TEC / TRD) of the PHENIX experiment, installed at the Relativistic Heavy Ion Collider (RHIC) of Brookhaven National Laboratory (BNL). The main goal of the RHIC project is the production and study of a state of matter known as Quark Gluon Plasma (QGP), through collisions of protons, deuterons and heavy ions at center of mass energies sqrt(s_NN) ranging between 20 and 200 GeV. PHENIX, one of the four experiments of the accelerator, is dedicated to measuring electroweak signals arising from the collisions, and TEC / TRD is the only subsystem capable of identifying efficiently electrons with momenta above 5 GeV/c. A simulator to reproduce the detector response to the passage of particles was developed and compared to data from a single wire proporcional counter and from TEC / TRD itself. The results show reasonable agreement between measurements and simulations. The use of the simulator allows studies of new methods and possibly improvements in the electron identification capability of the system.
80

Etude du profil en profondeur des modifications induites par irradiation aux ions sur substrat de saphir et du film mince GaN / Damage depth profile of modifications induced in alpha-Al2O3 substrate and GaN thin film under swift heavy ions

Ribet, Alexis 04 October 2019 (has links)
La famille des matériaux semiconducteurs III-N présente des propriétés adéquates pour diversesapplications que ce soit dans le domaine de l’optique ou de l’électronique. Certaines de ces applicationsconsistent à intégrer ces matériaux dans des environnements hostiles et notamment soumis à l’actiond’ions lourds à différentes énergies. Lors de cette thèse, le travail consistait tout d’abord à comprendrel’évolution microstructurale sous irradiation du substrat alpha-Al2O3, puis du film mince GaN, afin d’établirun profil de l’évolution de l’endommagement en fonction de la profondeur. Un comportement assezsimilaire concernant l’évolution des paramètres de maille a été observé pour les deux matériaux. Dansla direction parallèle à la trajectoire du faisceau d’ions, une importante augmentation du paramètre demaille a été mise en évidence tandis que peu de variations ont été relevées perpendiculairement à latrajectoire du faisceau d’ions. Les formations de couche amorphe pour l’alpha-Al2O3 et de couche fortementendommagée pour le GaN ont été observées en surface. Les épaisseurs de ces couches augmentent enfonction de la fluence, associé à l’augmentation des contraintes résiduelles au sein du matériau. Al’aide d’hypothèses et des différents résultats obtenus, deux profils d’endommagement en profondeuront été proposés. D’autre part, la nanoindentation a montré que les paramètres de dureté et de moduled’élasticité évoluent fortement sous irradiation en fonction de la fluence. / Nitride semiconductors are attractive materials for the development of optical and electronic devices.Some of these applications can expose materials to extreme environments and especially radiation ofheavy ions at different energies. In this thesis, the study focused first on behaviour evolution underirradiation of alpha-Al2O3 and then of GaN thin film, in order to establish a profile of damage evolution asfunction of the depth. Concerning lattice parameter, a similar behaviour was observed for both materials.An important increase of lattice parameter parallel to ion beam was highlighted while few variations wasnoted for the lattice parameter perpendicular to ion beam. Formation of amorphous layer for alpha-Al2O3and highly disordered layer for GaN were observed in surface. Layers thicknesses increase as functionof the fluence with an increase of residual stresses in material. Using different results and assumptions,two damage profiles as function of the depth have been proposed. In addition, nanoindentation hasshown hardness and modulus of elasticity parameter evolve highly under irradiation as function of thefluence.

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