FPGA Implementation of a General Space Vector Approach on a 6-Leg Voltage Source Inverter

A general algorithm of a Space Vector approach is implemented on a 6-leg VSI controlling a PM synchronous machine with three independent phases. In this last case, the necessity of controlling the zero-sequence current motivates the choice of a special family of vectors, different of this one used in Pulse Width Modulation (PWM) intersective strategy and in common Space Vector PWM (SVPWM). To preserve the parallelism of the algorithm and fulfill the execution time constraints, the implementation is made on a Field Programmable Gate Array (FPGA). Comparisons with more classical 2-level and 3-level PWM are provided.Fui8 within the SOFRACI projec

Performance Studies of Bulk Micromegas of Different Design Parameters

The present work involves the comparison of various bulk Micromegas detectors having different design parameters. Six detectors with amplification gaps of $64,~128,~192,~220 ~\mu\mathrm{m}$ and mesh hole pitch of $63,~78 ~\mu\mathrm{m}$ were tested at room temperature and normal gas pressure. Two setups were built to evaluate the effect of the variation of the amplification gap and mesh hole pitch on different detector characteristics. The gain, energy resolution and electron transmission of these Micromegas detectors were measured in Argon-Isobutane (90:10) gas mixture while the measurements of the ion backflow were carried out in P10 gas. These measured characteristics have been compared in detail to the numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed.Comment: arXiv admin note: text overlap with arXiv:1605.0289

Dynamics of polariton wave packets

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica de la Materia Condensada. Fecha de lectura: 20-07-2016This thesis is devoted to the theoretical study of the exciton-polariton wave packets and present joint theoretical and experimental results regarding their Rabi oscillations, their propagation and combination thereof. Quantitative description of the experimental data through a dissipative quantum-optical model allows us to identify and quantify the main channels of decay (including upper-polariton dephasing and incoherent pumping from an excitonic reservoir) along with the coupling mechanism of the exciting laser to the structure. Upgrading the dynamics to polarized fields, we propose the concept for a device that generates light that takes all the states of polarization (Full-Poincar´e beams), and implement it in the laboratory. In a purely theoretical exploration of the polariton packet dynamics, we introduce the notion of Self-Interfering Packets (SIP), that add a new member to the family of mechanisms that let particles emerge out of underlying fields, here powered by a mass-wall that folds back diffusion of the field onto itself. Finally, we consider the dynamics of vortices in coupled-fields and show the complex patterns of oscillations that result, both experimentally and theoretically.Esta tesis se ocupa del estudio teorico de los paquetes de ondas de polaritones de excitones, y en ella se presentan resultados teoricos y experimentales concernientes a sus oscilaciones de Rabi, su propagacion, y combinaciones de ambas. La descripcion cuantitativa de los datos experimentales, a partir de un modelo optico-cuantico disipativo, nos ha permitido identificar y cuantificar los principales canales de decaimiento (incluyendo el dephasing del polariton superior y el bombeo incoherente desde un reservorio de excitones), asi como los mecanismos por medio de los que un laser externo se acopla con la estructura. Al aumentar la complejidad en la dinamica de los campos involucrados, permitiendo que estos esten polarizados, hemos propuesto el concepto de un dispositivo que genera luz abarcando todos los estados de polarizacion (“haz completo de Poicare”), y el cual hemos implementado en el laboratorio. De forma completamente te´orica, hemos introducido la nocion de Paquetes Auto-Interferentes (PAI), añadiendo un nuevo mienbro a la familia de mecanismos a traves de los que particulas emergen de campos subyacentes, en este caso impulsado por un muro de masa que redirige el campo hacia si mismo. Finalmente, hemos considerado la dinamica de vertices en campos acoplados, y hemos mostrado tanto teorica como experimentalmente que de ellos surgen patrones complejos de oscilacio

Amphibia, Anura, Bufonidae, Melanophryniscus moreirae: distribution extension

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A Large Area Micromegas TPC for Tracking at the ILC

Une grande Chambre à Projection Temporelle (TPC) est un candidat pour la détection et la mesure des traces chargées auprès de l ILC, collisionneur linéaire d électrons et de positons de 31 km permettant d atteindre des énergies dans le centre de masse de 250 GeV à 1 TeV. Le travail de R&D décrit dans cette thèse porte sur un type nouveau de TPC, dont la lecture est assurée par des Micromégas à anode résistive. Ce dispositif permet de répartir le signal électrique sur plusieurs carreaux, même lorsque la charge est déposée sur un seul carreau. Il permet aussi de protéger l électronique, ce qui est utilisé dans notre prototype pour miniaturiser les cartes de lecture. Dans ce travail, des modules Micromégas ont été testés et caractérisés, dans un premier temps, en faisceau, un par un au centre de la chambre, puis 7 modules montés en même temps de façon à couvrir la surface. Egalement, des tests sur un banc équipé d une source de Fe ont permis de caractériser les 7 modules utilisés. Une résolution en position de 60 microns par ligne de carreaux est obtenue à petite distance de dérive. L uniformité est aussi évaluée, et des distorsions pouvant atteindre environ 500 microns sont observées. L ensemble des résultats démontre l adéquation de ce type de lecture à la TPC pour l ILC. La fraction de retour des ions est également mesurée à l aide d un détecteur de même géométrie et avec le même gaz que ceux utilisés dans ces tests, et la loi en rapport inverse des champs est validée à nouveau dans ces conditions. La même technique est appliquée à la réalisation d un imageur neutron, consistant en une TPC Micromégas plate précédée d un film convertisseur de 1mm d épaisseur. Les protons éjectés par les neutrons sont suivis à la trace dans le volume gazeux, ce qui permet de reconstruire avec une précision meilleure que le millimètre le point d origine du neutron.The study of the fundamental building blocks of matter necessitates always more powerful accelerators. New particles are produced in high energy collisions of protons or electrons. The by-products of these collisions are detected in large apparatus surrounding the interaction point. The 125 GeV Higgs particle discovered at LHC will be studied in detail in the next e e collider. The leading project for this is called ILC. The team that I joined is working on the R&D for a Time Projection Chamber (TPC) to detect the charged tracks by the ionization they leave in a gas volume, optimised for use at ILC. This primary ionization is amplified by the so-called Micromegas device, with a charge-sharing anode made of a resistive-capacitive coating. After a presentation of the physics motivation for the ILC and ILD detector, I will review the principle of operation of a TPC (Chapter 2) and underline the advantages of the Micromegas readout with charge sharing. The main part of this PhD work concerns the detailed study of up to 12 prototypes of various kinds. The modules and their readout electronics are described in Chapter 3. A test-bench setup has been assembled at CERN (Chapter 4) to study the response to a Fe source, allowing an energy calibration and a uniformity study. In Chapter 5, the ion backflow is studied using a bulk Micromegas and the gas gain is measured using a calibrated electronics chain. With the same setup, the electron transparency is measured as a function of the field ratio (drift/amplification). Also, several beam tests have been carried out at DESY with a 5 GeV electron beam in a 1 T superconducting magnet. These beam tests allowed the detailed study of the spatial resolution. In the final test, the endplate was equipped with seven modules, bringing sensitivity to misalignment and distortions. Such a study required software developments (Chapter 6) to make optimal use of the charge sharing and to reconstruct multiple tracks through several modules with a Kalman filter algorithm. The results of these studies are given in Chapter 7. The TPC technique has been applied to neutron imaging in collaboration with the University of Lanzhou. A test using a neutron source has been carried out in China. The results are reported in Chapter 8.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Experimental and numerical simulation of a TPC like set up for the measurement of ion backflow

Ion backflow is one of the effects limiting the operation of a gaseous detector at high flux, by giving rise to space charge which perturbs the electric field. The natural ability of bulk Micromegas to suppress ion feedback is very effective and can help the TPC drift volume to remain relatively free of space charge build-up. An efficient and precise measurement of the backflow fraction is necessary to cope up with the track distortion due to the space charge effect. In a subtle but significant modification of the usual approach, we have made use of two drift meshes in order to measure the ion backflow fraction for bulk Micromegas detector. This helps to truly represent the backflow fraction for a TPC. Moreover, attempt is taken to optimize the field configuration between the drift meshes. In conjunction with the experimental measurement, Garfield simulation framework has been used to simulate the related physics processes numerically

HARPO: a TPC as a gamma-ray telescope and polarimeter

A gas Time Projection Chamber can be used for gamma-ray astronomy with excellent angular-precision and sensitivity to faint sources, and for polarimetry, through the measurement of photon conversion to $e^+e^-$ pairs. We present the expected performance in simulations and the recent development of a demonstrator for tests in a polarized photon beam.Comment: SPIE Astronomical Telescopes + Instrumentation, Ultraviolet to gamma ray, Montr\'eal, Canada 2014. v2: note added in proof. Copyright 2014 SPIE. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibite