ThomX, un démonstrateur de source Compton compacte de rayons X d’énergie réglable entre 45 et 90 keV, est en construction sur le campus de l'Université Paris-Saclay à Orsay. La thèse s’inscrit dans le cadre de l’upgrade du linac de ThomX qui consiste à réaliser une section accélératrice compacte à fort gradient en bande S (3 GHz) pour porter les faisceaux de ThomX de 50 MeV à 70 MeV. Un accord de collaboration R&D est signé entre LAL et PMB-Alcen pour développer une structure accélératrice en cuivre (OFHC) compacte en bande S à fort gradient. Une étude électromagnétique, thermique et dynamique de faisceau a été effectuée au LAL pour proposer une géométrie optimale de la section accélératrice pour atteindre des gradients accélérateurs très élevés. PMB est en charge d’améliorer les processus de fabrication en commençant par la réalisation des prototypes pour valider les choix technologiques et ensuite fabriquer la section finale pour répondre aux spécifications demandées. Dans un premier temps une étude couplée électromagnétique-thermique-structurelle du canon HF a été effectuée en utilisant le Logiciel d'analyse des éléments finis 3D (ANSYS). Ensuite l’étude électromagnétique et l’optimisation de la géométrie des cellules accélératrices ainsi que la conception des coupleurs de puissance pour constituer les prototypes à impédance constante avec un certain nombre de cellules réduit et la section accélératrice compacte à gradient constant ont été effectuées en utilisant les logiciels CST MWS et HFSS. Puis une étude thermomécanique de la structure accélératrice a été réalisée avec ANSYS pour concevoir et optimiser le circuit de refroidissement pour extraire la chaleur générée par la puissance HF dissipée dans les parois de la structure et garantir une répartition uniforme de la température au long de la structure. Les simulations du vide ont été également réalisées avec le code Monte Carlo pour envisager la meilleure solution de pompage pour le prototype de cuivre et la section finale. En outre, les principales étapes suivies dans la fabrication du Canon HF au LAL et le prototype en aluminium à 7 cellules chez PMB-Alcen ont été présentées. Des tests HF bas niveau du prototype ont été effectués afin de valider la géométrie « processus d’usinage ». Compte tenu des résultats expérimentaux, des problèmes techniques et des contraintes technologiques ont été abordées et certaines solutions ont été proposées pour la fabrication des prototypes en cuivre et de la section finale. Les simulations de la dynamique des faisceaux du Linac de ThomX ont été effectuées en utilisant le code ASTRA. Le but est de réduire autant que possible la dispersion en énergie et l’emittance transverse du paquet d’électrons au point d’interaction avec les impulsions laser, pour préserver la pureté spectrale de rayons X produits. Un modèle aussi proche que possible des caractéristiques des composants réels, tels que le canon HF, la section accélératrice à onde progressive (OP) et les solénoïdes a été pris en compte dans les simulations. Des résultats importants ressortent de ces simulations concernant les paramètres du laser (taille et durée du spot), le champ magnétique maximal des solénoïdes pour la compensation de l'effet de charge espace, le déphasage entre l’onde RF et le laser et l'effet du champ électromagnétique sur la dynamique des électrons. Différentes options pour les paramètres de fonctionnement de la machine et une nouvelle configuration de la position des solénoïdes ont été proposées. L’optimisation des caractéristiques du paquet d’électrons a été obtenue en utilisant un algorithme génétique et les performances finales du faisceau d’électrons ont été mises en évidence. / The ThomX source should provide quasi-monochromatic high-quality X-rays (range 45-90 keV). The framework of the thesis is the electron beam linac energy upgrade from 50 MeV to 70 MeV necessary to achieve X-rays of 90 keV. For this purpose, the development of a compact high-gradient S-band electron accelerating structure is needed. It implies a research and development (R&D) activity at LAL in partnership with a French company (PMB-Alcen) in the High-Gradient (HG) technology of accelerating structures. The LAL-PMB-Alcen collaboration aims at the fabrication of a normal-conducting HG S-band structure by tackling the technological aspects that limit the achievement of high-gradient acceleration mostly due to vacuum RF breakdown and pulsed heating fatigue. Basically, the electromagnetic and thermal design of the HG S-band accelerating section has been performed at LAL. Meanwhile, PMB-Alcen was in charge to perform the fabrication, tuning and low power tests of prototypes and the final accelerating section. In this work, a fully coupled electromagnetic-thermal-structural finite element analysis on the THOMX RF gun has been performed with Ansys workbench. The HG accelerating section final regular cell dimensions and the power coupler design have been optimized. In particular, the electromagnetic simulation techniques and outcomes have been applied to constant impedance (CI) TW prototypes and also to a constant gradient (CG) final accelerating section. This allowed to verify the geometry choice, validate the fabrication procedure and check the fulfilment of the normal operating conditions. Moreover, a coupled thermo-mechanical study on a CI copper prototype has been performed. The water cooling system has been simulated to validate the capability to extract the heat generated by the dissipated power on the walls of the structure and guarantee a uniform temperature distribution along the section. Also, vacuum simulations have been performed on a 16-cells CI copper prototype and also on the final CG accelerating section. In addition, the main steps for the fabrication of the RF gun at LAL and a 7-cells aluminium prototype at PMB-Alcen have been presented. RF low power tests on the prototype have been performed in order to validate the 3D geometry design and the machining process. Taking into account the experimental results, mechanical problems and technological constraints have been tackled and some solutions have been proposed for the future copper prototype fabrication. Finally, beam dynamics simulations of the ThomX linac has been carried out by ASTRA code. The aim is to reduce as much as possible the energy spread and the transverse emittance to preserve the spectral purity of the produced X-rays, at the electron-photon interaction point. A model as close as possible to the characteristics of the real components, such as RF gun, TW section and solenoids has been considered. Important results came out from these simulations regarding laser parameters (spot size and duration), the maximum magnetic field of solenoids for high space charge effect compensation, dephasing between the RF and laser in the gun and effect of the travelling wave electromagnetic field on the particle dynamics. Different options for the parameter settings of machine operation and a new configuration of the solenoids position have been proposed. An optimization of the beam dynamics properties has been obtained by using a genetic algorithm and the ultimate performances of the electron beam have been highlighted.

EURISOL sera la source de prochaine génération pour la production de faisceaux intenses d'ions exotiques. Son complexe accélérateurs se compose d'un linac primaire, des ensembles cibles et sources et d'un linac de post-accélération qui fournit les ions radioactifs aux différentes aires expérimentales. L'étude menée dans ce mémoire concerne l'accélérateur primaire : un linac RF supraconducteur capable d'accélérer plusieurs types d'ions (D+, 3He2+ et H

In this conceptual report the idea to establish an European Positron Source for Applied Research ("EPOS") based on new LINAC facilities in Germany (ELBE/Rossendorf or TTF-DESY/Hamburg) is considered. The report contains not only the outline of obvious applications in atomic physics, materials science and surface physics, but also several new methodical developments which are only possible with an intense positron beam. This opportunity will also allow the use and further development of imaging techniques being of special interest for industrial applications.

The focus of this thesis is to improve upon the existing neutron cross section data for rhenium (Re) in the energy range 0.01 eV to 1 keV. Neutron transmission and capture yield measurements were performed using natural rhenium samples at the Rensselaer Polytechnic Institute Gaerttner Linear Accelerator Center. Measurements were performed using the time of flight method, in which neutron energies are differentiated using the elapsed times between neutron emission from a pulsed neutron source and the subsequent detector interactions. Transmission measurements were performed using ⁶Li glass scintillation detectors. Capture measurements were performed utilizing a 16-segment NaI(Tl) multiplicity detector. Most measurements were performed at a flight path length of 25 meters, with one set of experiments (thermal transmission) performed at 15 meters. The experiments used several metallic, elemental rhenium samples of various thicknesses, ranging from 1 mil to 100 mils. (1 mil = 0.001 inch = 0.0254 mm) Following the reduction of the experimental data, SAMMY was used to perform the data analysis. SAMMY is a shape-fitting Bayesian analysis code that determines resonance parameters by fitting neutron time of flight data using the Reich-Moore approximation of R-matrix theory. The combined transmission and capture yield data analysis determined resonance parameters for rhenium resonances in the energy range of 0.01 eV to 1 keV. The updated rhenium resonance parameters are compared to previously published parameters and ENDF/B-VII.1. / text

No description available.

A megawatt class electron linear accelerator (e-linac) will be constructed at TRIUMF as part of the new ARIEL facility which will produce rare ion beams for the study of nuclear structure and astrophysics, and material science. The 50MeV, 10mA, continuous wave e-linac will drive gamma ray induced fissioning of a Uranium target for the production of neutron rich beam species. View Screens located at a number of places along the e-linac beam-line will acquire two dimensional images of the transverse electron beam profiles, providing measurements of the size, position, and shape of the incident e-linac beam. The design of the View Screens will be presented, based on design studies and simulations performed to evaluate the performance of the View Screens under various operating conditions. These studies include GEANT simulations of the energy loss and scattering of the electron beam as it passes through the scintillation and Optical Transition Radiation beam targets, the subsequent thermal response of the targets, and a ray tracing optics simulation to optimize the configuration of the imaging optics. Bench test have been performed on the resulting optics design to evaluate the imaging characteristics, verifying fulfillment of the design requirements. Construction of a prototype View Screen device is currently underway, with beam tests scheduled for Fall 2011. A total of 14 View Screens will be constructed and installed along the e-linac beam-line. / Graduate

Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2018-02-01T17:49:29Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Aline Dantas de Oliveira.pdf: 7187935 bytes, checksum: 2f865a50020bf3264c45bd86c0acd251 (MD5) / Made available in DSpace on 2018-02-01T17:49:29Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Aline Dantas de Oliveira.pdf: 7187935 bytes, checksum: 2f865a50020bf3264c45bd86c0acd251 (MD5) Previous issue date: 2016-08-24 / CNPQ / Os tumores do Sistema Nervoso Central (SNC) representam o segundo grupo de neoplasias mais frequentes na infância. A técnica radioterápica crânio-espinhal é considerada padrão para pacientes diagnosticados com meduloblastoma e outros tumores cerebrais com tendências a disseminação liquórica. Este tratamento é realizado com dois campos craniais bilaterais e um ou dois campos espinhais póstero-anterior, com o paciente deitado em decúbito ventral e imobilizado com o auxílio de uma máscara termoplástica. É possível encontrar registros de pacientes pediátricos com sequelas radioinduzidas após serem submetidos a tratamentos radioterápicos do SNC, o que justifica a importância de avaliações dosimétricas. Modelos Computacionais de Exposição (MCE) são desenvolvidos com a finalidade de realizar avaliações dosimétricas e são compostos, em sua maioria, por um fantoma antropomórfico, um código Monte Carlo e um algoritmo de fonte radioativa. Neste trabalho foram desenvolvidos MCEs para os campos do tratamento crânio-espinhal e a distribuição de dose em órgãos e tecidos radiossensíveis foi avaliada por meio da dose absorvida/kerma incidente no ar. Foi desenvolvido um fantoma mesh feminino nomeado SARA (Simulador Antropomórfico para Dosimetria das Radiações Ionizantes em Adolescentes). O algoritmo da fonte Acelerador Linear (linac) foi implementado no código de usuário do EGSnrc e a sua distribuição de fótons foi dada por arquivos espaços de fase. Os resultados dosimétricos validam o acoplamento do fantoma a fonte desenvolvida e são parciais, visto que, o fantoma SARA ainda não possui os tecidos ósseos radiossensíveis segmentados. / The tumors of the Central Nervous System (CNS) represent the second group of most common cancer in childhood. The cranial spinal radiation treatment is considered standard for patients diagnosed with medulloblastoma and others brain tumors with tendency to liquoric dissemination. This treatment is performed with two bilateral cranial fields and one or two posterior-anterior spinal fields with the patient lying in prone position and immobilized with the help of a thermoplastic mask. It is possible to find records of pediatric patients with radiation-induced sequelae after undergoing radiotherapy treatment of CNS which justify the importance of dosimetric evaluations. Exposure Computational models (ECMs) are developed in order to perform dosimetric evaluations and are composed mostly by an anthropomorphic phantom, a Monte Carlo code and radioactive source algorithms. In this work ECMs for the cranial spinal treatment fields were developed and dose distribution in radiosensitive organs and tissues by means of absorbed dose/kerma incident in the air was evaluated. A female mesh phantom named SARA (Simulador Antropomórfico para Dosimetria das Radiações Ionizantes em Adolescentes - Anthropomorphic Simulator for Dosimetry of Ionizing Radiation in Adolescents) was developed. The Linear Accelerator (linac) source algorithm was implemented in the EGSnrc user code and its distribution of photons was given by phase spaces files. The dosimetric results validate the coupling of the phantom to the developed source and are partial since the SARA phantom does not yet have the segmented radiosensitive bone tissues.

The TRIUMF view screen system encompases a set of devices which individually image, and produce measurements of, the transverse profile of an accelerated electron beam. A control system is an essential component of the overall diagnostic device. The system requirements were compiled from those produced by the TRIUMF laboratory and from those based on the needs of the individual diagnostic devices. Based on the requirements, a control system was designed and implemented with a combination of industrial electrical and mechanical hardware, and a variety of software components. One component of the image reconstruction algorithm was validated with experimental data; the accuracy and precision of beam profile measurements was evaluated through simulation studies. Although it was not possible to demonstrate the satisfaction of requirements relating to alignment, it was shown that all other requirements were satisfied. / Graduate / 0798 / 0752 / 0605

Les travaux de thèse décrits dans ce manuscrit s’intéressent à la modélisation et lecontrôle de procédés cryogéniques associés à un LINAC supraconducteur. Les élémentsconstituants le système cryogénique du LINAC (cryomodules, vannes, tuyaux,...) sontmodélisés sous forme d’objets inter-connectables. Ces mêmes objets sont utilisés pourmodéliser le système cryogénique de l’accélérateur SPIRAL2. La justesse de ces modèlesest évaluée à travers des comparaisons entre simulations non-linéaires et mesures expérimentales.Une fois la capacité de prédiction des modèles validée, ces derniers sont utiliséspour synthétiser des lois de commande. Tout particulièrement, une commande linéairequadratique ainsi qu’un filtre de Kalman étendu ont été réalisés pour les cryomodulesde SPIRAL2. Enfin, la réalisation d’une commande hiérarchisée appliquée au cas d’unréfrigérateur cryogénique est étudiée. Une méthode est proposée pour le contrôle de plusieurssous-systèmes inter-connectés et régulés par des contrôleurs PID, LQ et MPC. / The thesis works describe in this manuscript deal with the modelling and the control ofLINAC cryogenic process. The components of the LINAC cryogenic system (cryomodule,valves, pipes,...) are modeled as interconnectable objects. Those same objects are usedto model the SPIRAL2 cryogenic system. The model trueness is evaluated through comparisonbetween experimental and simulated data. Once the model prediction capabilityhas been validated, the models are used to synthetized control laws. More specifically, alinear quadratic command and an extended Kalman filter has been realized for the SPIRAL2cryomodule. Finally, a hierarchical control for a cryogenic refrigerator has beenstudied. A method is proposed for the control of multiple interconnected subsystemsregulated through PID, LQ and MPC controllers.

In this conceptual report the idea to establish an European Positron Source for Applied Research ("EPOS") based on new LINAC facilities in Germany (ELBE/Rossendorf or TTF-DESY/Hamburg) is considered. The report contains not only the outline of obvious applications in atomic physics, materials science and surface physics, but also several new methodical developments which are only possible with an intense positron beam. This opportunity will also allow the use and further development of imaging techniques being of special interest for industrial applications.