Les accélérateurs de particules hyperfréquences sont au cœur de projets d’envergure aux visées scientifiques (comme l’European Spallation Source) ou énergétiques (comme le réacteur hybride MYRRHA). Pour ces applications, les cavités résonnantes composant ces accélérateurs doivent atteindre des champs accélérateurs très importants. Elles ont alors besoin d’une grande puissance RF. Le coupleur de puissance doit permettre d’injecter cette puissance dans la cavité tout en garantissant une grande fiabilité. L’étude d’un coupleur à 704,4MHz a été réalisée. Les comportements radiofréquences, thermiques et mécaniques ont été modélisés pour une puissance de 50kW en réflexion toutes phases. Les performances simulées permettent d’envisager son utilisation comme coupleur pour les cavités elliptiques de l’ADS MYRRHA. L’industrialisation d’un tel coupleur a également été étudiée. Cette étude a donné lieu à la fabrication de deux prototypes. L’étude d’un coupleur à 352MHz a également été réalisée afin de répondre aux exigences de la cavité SPOKE ESS. Un nouveau processus d’assemblage, impliquant une méthode de précontrainte de la céramique, sera exposé. Ce processus diminue le nombre d’étapes de fabrication et renforce mécaniquement la fenêtre du coupleur. Cette thèse a également permis la validation de l’extension aux ondes progressives d’un logiciel de simulation 3D du multipactor : Musicc3D. Les simulations et les mesures ont été favorablement comparées pour les coupleurs SPIRAL2 et XFEL. / Nowadays, the number of projects aiming at building high intensity proton linear accelerators is increasing thanks to a large field of applications: particles & nuclear physics, spallation sources and some applications in material sciences, biology and nuclear waste reprocessing. All these linear accelerator projects are based on superconducting technology that allows high accelerating gradients in continuous mode. The RF power coupler is one of the main components of the accelerator. It is designed to transmit the radio frequency power from the waveguide at room temperature to the cavity at 4 Kelvin with high reliability. In this thesis, a study of a 704.4MHz power coupler was carried out. The RF, thermal and mechanical behaviors of the coupler were simulated for 50kW full reflection continuous wave. This power coupler could be used as RF injector for MYRRHA elliptical cavities. The fabrication process has been established and two prototypes were build. A study of a 352MHz power coupler was also carried out to fulfill ESS Spoke cavities needs. The obtained design satisfies the specifications and lowers the maximum electric field in the power coupler window compared to existing design. Then a new fabrication process was developed using prestressed ceramic. Brazing operations have halved with this new process. It was shown that the prestressed could enhance the strengths ceramic. The last study in this thesis consisted in validating an extension to progressive waves of 3D simulation software of Multipacting, Musicc3D. The results obtained were favorably compared to the measurements for SPIRAL2 and XFEL power couplers.

No description available.

Le champ invariant de spin (ISF), et son évolution, informe en profondeur sur le comportement de la polarisation dans un accélérateur, permet de calculer la polarisation d'équilibre dans les accélérateurs d'éléctron, mais est également utile dans l'étude et la compréhension des machines protons. La luminosité croissante, le plus haute sensibilité des expériences et la prise en compte d'effet auparavant négligé rendent nécessaire l'amélioration de la précision du calcul de l'ISF. Le travail de cette thèse propose plusieurs méthodes de calcul numérique du Champ Invariant de Spin, basées sur l'intégration numérique de la trajectoire, permettant une précision accrue des effets de la dynamique orbitale sur la dynamique de spin, mais également de prendre en compte des effets souvent compliqués à étudier et habituellement négligés, comme la dynamique non linéaire, les effets faisceau-faisceau, etc. Ces effets n'ont pas été inclues, car l'élaboration des méthodes a demandé beaucoup de temps, mais ils sont une perspectives de recherche dans le domaine. L'algorithme intitulé stroboscopic averaging a été implémenté pour calculer l'ISF. Une implémentation "simple" conduit à des temps de calcul trop long pour être utile. Néanmoins, une implémentation "backward" permet de rendre le calcul de l'ISF en un point dépendant d'une unique trajectoire, et donc de paralèlliser le calcul. Il a été suggéré par ailleurs que le "spin tune" peut être calculé par analyse spectrale. Un algorithme a été implementé dans ce sens, et calcul la fréquence de précession du spin sur une trajéctoire donnée. Cette idée mène également à une méthode alternative de calcul de l'ISF. La combinaison de ces différentes méthodes permet une meilleure compréhension des effets en jeu dans la dynamique du spin. / Invariant Spin Field (ISF), and its evolution, gives an acute insight in the polarization behaviour of a polarized accelerator, allows to estimate the equilibrium polarization of electron accelerators, an is also useful in the design and understanding of proton machines. The increased luminosity of colliders, the higher precision of the experiments, the inclusion of previously neglected effects, marks a necessary step forward in ISF precision. The present thesis proposes different methods to compute Invariant Spin Field, based on particle tracking, allowing a better precision in the orbital dynamic effect on the spin dynamic, as well as the inclusion of effects complicated to study and usually neglected, such as non linear dynamic effects, Beam-Beam effect, etc. The inclusion of these different effects has not been done, because elaboration of new methods is quite demanding. This is a candidate for future research. We implemented the Stroboscopic Averaging algorithm to compute ISF. The "simple" implementation leads to a non-managable computing time, but the "backward" implementation solves the problem by making the computation of the ISF dependent on only one orbital trajectory, thus allowing a parallelisation of the algorithm. It has been suggested that the spin tune could be computed through a spectral analysis. We implemented an algorithm for this purpose, allowing us to compute the spin tune form the spin-orbit trajectory. Following these ideas, we also proposed new methods based on a prior knowledge of the spin tune, to compute ISF. Combining the different methods leads to a better understandings of the spin dynamic, as each method provides a different point of view.

Orientador: Carlos Ourivio Escobar / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-05T00:48:53Z (GMT). No. of bitstreams: 1 Gomes_RicardoAvelino_D.pdf: 22856845 bytes, checksum: ff49da476ee952e261dde1c21ce27f56 (MD5) Previous issue date: 2005 / Resumo: Apresentamos uma investigação sobre o decaimento semileptônico ?0??+µ - ?µ. Observamos este decaimento pela primeira vez com nove eventos identificados, utilizando para tal a linha de feixe e os detectores do experimento KTeV no Fermilab. O decaimento é normalizado pelo modo ?0??+e- ?e, resultando em uma razão das taxas de decaimento G(?0??+µ - ?µ)/G(?0??+e- ?e) igual a ( 1,8+0,7-0,5(estat.) ± 0,2(sist.) ) x 10-2 com 68,27% C.L., que se tomou a medida oficial da colaboração KTeV: Em uma análise independente, também utilizamos o decaimento dominante ?0? ?p0(???p-) como modo de normalização, o que corroborou o resultado principal. Realizamos ainda, uma nova medida da razão de ramificação do modo ?0??+e- ?e com base em 1139 eventos e normalizada pelo decaimento ?0??p0(???p-). Os resultados estão em pleno acordo com o modelo a quarks com simetria SU(3) de sabor / Abstract: We report an investigation of the semileptonic decay ?0??+µ - ?µ. This decay was observed for the first time with nine identified events using the KTeV beam line and detector at Fermilab. The decay is normalized to the ?0 beta decay mode and yields a value for the ratio of decayrates G(?0??+µ - ?µ)/G(?0??+e- ?e) igual a ( 1,8+0,7-0,5(stat.) ± 0,2(syst.) ) x 10-2 at the 68,27% confidence level, being the official measurement of KTeV Collaboration. We also used the dominant decay ?0? ?p0(???p-) as normalization mode in an independent analysis which corroborated with the main result. In addition, a new measurement of the ?0??+e- ?e branching ratio is presented, based on 1139 events and normalized to the ?0??p0(???p-) decay mode. The results are in agreement with the SU(3) flavor symmetric quark model / Doutorado / Física das Particulas Elementares e Campos / Doutor em Ciências

This project has investigated the muon background of the SHiP experiment to determine whether it can boost the experiment sensitivity to visible Dark Photon decay. Using Fermi-Weizsäcker-Williams approximation to muon scattering we found the probability of muons generating massive photons, using Bremsstrahlung and direct lepton pair production as an estimation of the frequency of muon EM-interactions. In this work we only considered muons with momenta above 10 GeV/c. The number of visible Dark Photon decays was calculated for a range of the coupling constant and photon mass. The resulting range that promised visible decay has already been excluded by previous experiments, but the method could be used to further investigate enhanced production of Dark Photons from muons and electrons, and possibly also production of Axion-like particles. The work could also be used to estimate sensitivities of other experiments using muons.

19 Dec 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 1993" Ning Yang. 12/19/2004. Report is also available in paper and microfiche from NTIS.

Thesis; Thesis information not provided; 1 Feb 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "JLAB-PHY-03-39" "DOE/ER/40150-2763" Silvia Niccolai. 02/01/2003. Report is also available in paper and microfiche from NTIS.

Thesis (Ph.D.); Submitted to The University of California at Berkeley, Berkeley, CA (US); 1 Sep 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--55022" Prilliman, Gerald Stephen. USDOE Director. Office of Science. Office of Basic Energy Sciences (US) 09/01/2003. Report is also available in paper and microfiche from NTIS.

Thesis (Ph.D.); Submitted to Univ. of California, Davis, CA (US); 17 Sep 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "UCRL-TH-207378" Gibson, D J. 09/17/2004. Report is also available in paper and microfiche from NTIS.

A Penning-type surface-plasma negative hydrogen (H^-) ion source has been delivering beam at the ISIS pulsed spallation neutron and muon facility for over thirty years. It is one of the most powerful and well-renowned H^- sources in the world. Although long-term experience has allowed the source to be operated reliably and set up in a repeatable way, it is treated as something of a 'black box': the detailed plasma physics of why it works has always been unclear. A vacuum Vessel for Extraction and Source Plasma Analyses (VESPA) has been developed to understand the ISIS ion source plasma and improve the beam extracted from it. The VESPA ion source is operated in a completely new regime whereby the analysing sector dipole magnet housed inside a refrigerated 'cold box', presently used on ISIS, is replaced by an on-axis extraction system. The new extraction system incorporates a novel einzel lens with an elliptical aperture. This is the first demonstration of an elliptical einzel being used to focus an asymmetric H^- ion beam. With the dipole magnet removed, the ion source has been shown to produce 85 mA of H^- beam current at normal settings; of which 80 mA is transported through the new einzel lens system, with a normalised RMS emittance of 0.2 π mm mrad. Optical emission spectroscopy measurements have shown a plasma density of 10¹⁹ m^–3, an H₂ dissociation rate of 70%, an almost constant electron temperature of 3.5 eV and an atomic temperature which linearly increases above the electron temperature. In support of these principal measurements, rigorous particle tracking, electrostatic and thermal simulations were performed. In addition, a suite of new equipment was manufactured by the author. This includes a fast pressure gauge, a temperature controller, a high voltage einzel lens circuit, a fast beam chopper and a caesium detection system.