Tesis sobre el tema "Electrons de très haute énergie"
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Lemière, Anne. "Electrons reliques de très haute énergie dans les nébuleuses de pulsar : étude et identification d'une population de sources gamma du TeV avec H.E.S.S". Paris 7, 2006. http://www.theses.fr/2006PA077181.
Texto completoThe HESS experiment (High Energy Stereoscopic System) consist of four imaging atmospheric Cherenkov telescopes to study southern hemisphere astrophysical sources above 100 GeV. The first part of this thesis studies the extended sources observed along the Galactic plane with this instrument. A multi-resolution analysis based on wavelets has been adapted to the VHE (Very high Energy) data for a better study of morphology, and has been tested on Monte Carlo simulations. A rnorphological and spectral analysis has allowed the selection of sources with a powerful spatially-coincident pulsar and to make a list of pulsar wind nebulae candidates based on energetic criteria. The second part of this thesis investigates the origine of the asymmetric morphology of the nebulae by studying the interstellar medium and show that a majority of the PWN candidates have a matter gradient near the pulsar position which is compatible with the hypothesis of an asymmetric reverse shock. Finally, an energy-dependant morphological analysis is applied to HESS J1825-137, the archetypal VHE PWN, and reveals high-energy electrons near the pulsar and a hardening of the spectral index far from it : we propose to model this source with a time-dependent spectral rnodelling. This model reproduces very well the data with reasonable parameters. It allow us for the first time to constrain the time evolution of the magnetic field in a PWN together with the initial characteristics of the pulsar, and confirms the presence of relic electons in
Ronga, Maria Grazia. "Study and modelling of very high energy electrons (VHEE) radiation therapy". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST036.
Texto completoThe development of innovative methods capable of reducing the sensitivity of healthy tissue to radiation, while maintaining the effectiveness of the treatment on the tumour, is a central aspect of improving the effectiveness of radiotherapy in the treatment of cancer. Among possible developments and methodological innovations, the combination of ultra-high dose rate irradiation (FLASH) and very high energy electrons (VHEE) could make it possible to exploit the radiobiological advantages of the FLASH effect for the treatment of deep tumours. In particular, VHEEs in the 100 to 250 MeV energy range would be particularly interesting from a ballistic and biological point of view for the application of FLASH irradiation in radiotherapy. This thesis therefore studies the possible use of VHEEs in radiotherapy, and in particular their use at ultra-high dose rates, thus assessing the feasibility of FLASH-VHEE radiotherapy. Although promising, several aspects of this technique need to be studied before it can be used in a clinical context. The first part of this work studies the machine parameters required to meet the constraints of FLASH irradiation. To this end, an analytical model for calculating the dose based on Fermi-Eyges multiple scattering theory was developed and tested. This analytical model has also been used to design and optimise a double-scattering system for VHEE therapy, in order to obtain field sizes greater than 15x15 cm², and to assess the possible adaptation of conventional particle beam conformation methods for FLASH-VHEE therapy. The second part of this work focuses on VHEE treatment planning and the evaluation of clinical plans. Four representative clinical cases were studied, for which pencil-beam scanning (PBS) and double scattering (DS) treatment plans were calculated. The influence of beam energy on plan quality was studied and the PBS and DS techniques were compared. A temporal description of the irradiation was also carried out, as well as the incorporation of a FLASH modification factor when evaluating the plan and its effect on healthy tissue in FLASH mode. Finally, the estimation of doses from secondary particles and radiation protection issues were addressed. A calculation of the secondary dose due to Bremsstrahlung photons and neutrons from the two dose delivery systems was developed in water. The secondary particle dose received by various organs was also assessed in the context of intracranial treatments and in order to demonstrate the advantage of VHEE beams over proton beams in terms of out-of-field neutron dose. In summary, the fast analytical models parameterised in this study allow the dose distribution produced by a VHEE system to be estimated with good accuracy, providing important information for the potential design of a VHEE system. The results of this work could support the development of FLASH-VHEE radiotherapy
Mattei, Alvise. "Rayons cosmiques de très haute énergie : vers une nouvelle astronomie". Chambéry, 2006. http://www.theses.fr/2006CHAMS029.
Texto completoCosmic rays play an important role in the history of Physics, since more tan a century. Their spectrum extends by more than 10 orders of magnitude. The cosmic background radiation constrains the propagation distance and defines the class of Ultra High Energy Cosmic Rays (UHECR) which carry energy well beyond the pion production threshold, called cutoff GZK. Several experiments studied the UHECR to understand their nature and origin. The general aspects of this problems are analyzed in a critical flavor. I describe a method for the reconstruction of UHECR trajectories within the local universe, starting from the Galactic Magnetic Field (GMF). My code is able to back-propagate charged particles in a magnetic field. To determine the extragalactic magnetic field, I used a local universe map, taken from the catalog HyperLEDA. To verify the effects of these fields on UHECR trajectories, I back-propagate a beam of 40000 protons, 1 degree wide, towards the direction of Virgo cluster. The mean deviation is 0. 780. And grows up to 1. 30 for a frozen field model. These values are not negligible. I applied the same method to the triple event of AGASA experiment, added of a fourth event from HiRes. Through the plausible sources, I identified NGC3998, an Active Galactic Nucleus, of LINER type, a good candidate for acceleration. Finally, I worked also on a new kind of source: the charged black holes, which can be at the origin of UHECR emission. I sketch the acceleration mechanism and the expected flux, suggesting a correlation with gamma-ray bursts. So I propose a strategy of trajectory reconstruction, which can be improved with the next generation experiments (AUGER, SKA, LOFAR), as well as a new source to be searches through this new kind of astronomy
Jradi, Khalil. "Étude et réalisation de photodétecteurs de type APD Geiger pixellisés à très haute sensibilité pour l'astronomie gamma très haute énergie". Toulouse 3, 2010. http://thesesups.ups-tlse.fr/984/.
Texto completoVery High Energy gamma ray astronomy uses till now exclusively as detector the Photomultiplier Tube (PMT) to collect weak light flux of atmospheric showers. But an alternative is now emerging: Avalanche Photodiodes polarized in Geiger mode called "Geiger-APD". The PMT is a detector designed in the 70's which presents many advantages but also suffers from several drawbacks: size, weight, cost, sensitivity to magnetic field but especially difficulty to realize its pixilation in matrix. Geiger-APDs are semi-conductor devices made of PN junction integrated in a special technology to detect very low light flux, thanks to the polarization beyond the avalanche voltage. Geiger-APD presents very high photoelectron gain (˜106) strongly dependant on the polarization voltage beyond avalanche. These photodiodes present many advantages with respect to PMT, mainly as concerns miniaturization for applications based on imaging, such as the detection of Cerenkov flashes in gamma ray astronomy. In this thesis, we present the study, the design and the realization of a technological structure, based on Silicon. This structure has shown reliability to detect weak luminous flux with breakdown voltage at 12V and dark current below 10pA at breakdown. We also developed several models, physical and electrical, necessary to the technological optimization, as well to the development of control and readout circuits, i. E. The basis of any imaging technology. The work presented here consists in the study, the design and the realization of a matrix of high sensitivity pixels. A project of a Cerenkov telescope based on this innovative technology is also presented
Garcon, Thibault. "Vers la radiodétection autonome des rayons cosmiques de très haute énergie". Phd thesis, Université de Nantes, 2010. http://tel.archives-ouvertes.fr/tel-00562591.
Texto completoGarçon, Thibault. "Vers la radiodétection autonome des rayons cosmiques de très haute énergie". Nantes, 2010. http://archive.bu.univ-nantes.fr/pollux/show.action?id=02d861a2-b295-46ec-a427-99001f4cd97a.
Texto completoThe radiodetection of extensive air showers, investigated for the first time in the 1960’s, obtained promising results but plagued by the technical limitations. At that time, H. R. Allan summed up the state of the art in an extensive review article whose conclusions and predictions are still used today. Set up in 2001 at the Nancay Observatory, the CODALEMA experiment was built first as a demonstrator and succesfully showed the feasibility of the radiodetection of extensive air showers. Radically modified in 2005, it allowed to obtain a clear energy correlation, and put in evidence an unambiguous signature of the geomagnetic origin of the electric field emission process associated to the air shower. The switch towards large areas is the next step of the technique’s development. Therefore, the autonomy of the detectors becomes essential. After test prototypes installed in 2006 at the Pierre Auger Observatory, a generation of new autonomous detectors was developed. Their first results will be presented. This work is also dedicated to the issues related to the radiodetection technique : the antenna response, the sensitivity, the surrounding effects, the monitoring of a big array. The determination of the shower characteristics independently of other detectors such as the lateral distribution, the energy correlation and the frequency spectrum of the radio transient will be discussed
Donnard, Jérôme. "Etude et conception d'un imageur β à très haute résolution spatiale". Nantes, 2008. http://www.theses.fr/2008NANT2130.
Texto completoThe b autoradiography is a widely used technique in pharmacology or biological fields. It is able to locate in two dimensions molecules labeled with beta emitters. The development of a gaseous detector incorporating micromesh called PIM in the Subatech laboratory leads to the construction of a very high spatial resolution apparatus dedicated to b imaging. This device is devoted to small analysis surface of a half microscope slide in particular of 3H or 14C and the measured spatial resolution is 20 µm FWHM. The recent development of a new reconstruction method allows enlarging the field of investigation to high energy beta emitters such as 131I, 18F or 46Sc. A new device with a large active area of 18x18 cm2 has been built with a user friendly design. This allows to image simultaneously 10 microscope slides. Thanks to a multi-modality solution, it retains the good characteristics of spatial resolution obtained previously on a small surface. Moreover, different kinds of samples, like microscope slides or scotches can be analysed. The simulation and experimentation work achieved during this thesis led to an optimal disposition of the inner structure of the detector. These results and characterization show that the PIM structure has to be considered for a next generation of b-Imager
Donnard, J. "Étude et conception d'un imageur bêta à très haute résolution spatiale". Phd thesis, Université de Nantes, 2008. http://tel.archives-ouvertes.fr/tel-00769792.
Texto completoBarrau, Aurélien. "Astrophysique gamma de très haute énergie : étude du noyau actif de galaxie Mrk 501 et implications cosmologiques". Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10020.
Texto completode, Naurois Mathieu. "L'astronomie gamma de très haute énergie de H.E.S.S. à CTA. Ouverture d'une nouvelle fenêtre astronomique sur l'Univers non thermique". Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00687872.
Texto completoCore, L. "Recherche de neutrinos de ultra haute énergie à l'aide du telescope ANTARES". Phd thesis, Aix-Marseille Université, 2013. http://tel.archives-ouvertes.fr/tel-00969098.
Texto completoGuillard, Goulven. "Étude de la sensibilité du télescope à neutrinos ANTARES aux photons de très haute énergie — Contribution à l'étalonnage en temps du détecteur". Phd thesis, Université de Strasbourg, 2010. http://tel.archives-ouvertes.fr/tel-00555462.
Texto completoGuillard, Goulven. "Etude de la sensibilité du télescope à neutrinos Antares aux photons de très haute énergie : contribution à l'étalonnage en temps du détecteur". Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/GUILLARD_Goulven_2010.pdf.
Texto completoFrom the seafloor, the 900-odd photomultiplier tubes of the Antares neutrino telescope scrutinize the abysses attempting to discern, amid bioluminescence and marine radioactivity, Cerenkov photons emitted by muons from astrophysical neutrinos, and to distinguish these muons from those generated by air showers produced by cosmic rays. Antares has been collecting data since 2006 ; this feat of engineering has paved the way for submarine neutrino astronomy : Antares is expected to be the forerunner of a larger instrument, KM3NeT. A telescope’s performance is characterized in part by its angular resolution. In the case of Antares, the angular resolution is directly related to the time resolution of the detector’s elements. This manuscript presents a correction for one of the main sources of deterioration of this time resolution, the walk effect induced by the set up of a fixed threshold for triggering the photomultiplier tubes signal. This correction, implemented in the official software chain of the Antares collaboration, improves in particular the events reconstruction quality estimator. This implementation allows further optimizations. The author also attempts to evaluate, using a complete Monte-Carlo simulation, the possibility of using very high energy photon sources as calibrated muon beams in order to estimate the absolute pointing and the angular resolution of the telescope. Although limited by large uncertainties, it is demonstrated that the possibility to detect such sources is extremely small. In addition, it is shown that the atmospheric neutrino background induced by very high-energy photons is negligible
Lorentz, Matthias. "Caractérisation de la transparence de l'univers aux rayons gamma de très haute énergie avec H.E.S.S. et aspects associés en physique fondamentale et cosmologie". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS249/document.
Texto completoThe propagation of very high energy Ɣ rays in the universe depends on the properties of the extragalactic medium. Such TeV-scale photons travelling cosmological distances are -emitted through particle acceleration mechanisms in active galaxy nuclei- can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. This effect reduces the transparency of the universe to very high energy Ɣ rays but it also provides a unique opportunity to probe the properties of the extragalactic medium. In this thesis, data taken with the H.E.S.S. array of Cherenkov telescopes are analyzed and used to characterize the transparency of the universe to very high energy Ɣ rays. A independent measurement of the spectral energy distribution of the EBL with H.E.S.S. is presented. It is obtained by extracting the EBL absorption signal from the fit of spectral modulations in the high-quality spectra of a sample of bright blazars in the redshift range 0.03 < z < 0.28. The intensity of the EBL obtained in different spectral bands is presented together with the associated Ɣ-ray horizon. The obtained results are consistent with lower limits derived from galaxy counts and do not suggest an anomaly of the transparency of the universe to Ɣ rays with respect to current models of the extragalactic background light. Second-order processes affecting the propagation of very high energy Ɣ rays in the universe are also considered. Limits on Lorentz invariance violation at Planck scale are obtained from the spectral analysis of the active galaxy nucleus Mrk 501 observed during a high-flux state by H.E.S.S. in 2014, at large zenith angle. Finally, constraints on the extragalactic magnetic field properties are derived by considering the secondary Ɣ-ray emission expected from the simulation of electromagnetic cascades initiated by the absorption process for the distant active galaxy nucleus PG 1553+113 seen by H.E.S.S. and the Fermi Ɣ-ray space telescope. In this thesis some developments related to the calibration and analysis of H.E.S.S. data are also presented
Cibiel, Gilles. "Contribution à l'analyse d'amplificateurs microondes à très faible bruit de phase : application à la réalisation d'une source à très haute pureté spectrale en bande C". Toulouse 3, 2003. http://www.theses.fr/2003TOU30120.
Texto completoThe aim of this theory is to present a methodology for the design of high spectral purity microwave sources, featuring state of the art performance both at low and high offset frequencies. The origin of oscillator phase noise is due to different fluctuations or perturbations. But, the main contributor to this noise is the microwave transistor. The study of microwave amplifiers dedicated to low phase noise applications is thus the main subject of this manuscript. It is interesting to study transistor phase noise instead of oscillator phase noise, because a device in open loop configuration is easier to model or to characterize than an oscillating device. Therefore, our study has been firstly based on experimental results obtained from a phase noise measurement bench which some special techniques have been implemented to characterize ultra low phase noise devices. Selecting the appropriate device and using this transistor in appropriate operating conditions are some keys of success in low phase noise oscillator design. This involves a good knowledge of the noise generation mechanisms. The transistor phase noise is indeed not entirely related to the device low frequency noise properties. .
Dubois, Florent. "L'astronomie γ de très haute énergie avec H. E. S. S. : Développement d'une analyse multi-variables et application à l'étude de nébuleuses de pulsar". Chambéry, 2009. http://www.theses.fr/2009CHAMS050.
Texto completoH. E. S. S. (High Energy Stereoscopic System) is one of the leading systems of four Imaging Atmospheric Cherenkov Telescopes that investigates very high energy (VHE) cosmic γ-rays in the 100 GeV to 100 TeV energy range. H. E. S. S. Is located in Namibia, near the Gamsberg mountain and operational since December 2003. The H. E. S. S. Experiment is mainly aimed to the observation of the southern sky including the galactic plan and the numerous astrophysics sources therein. Three analysis methods have been developed using various properties of the electromagnetic showers generated by the interaction of primary cosmic γ-rays within the Earth atmosphere. The first goal of this thesis was to combine the information from these methods for the selection and the energy and direction reconstruction of γ-ray events. The new analysis called Xeff improves significantly the quality of the selection and the precision of the reconstruction. This analysis has been afterwards applied to the study of pulsar wind nebulae like Vela X, GO. 9+0. 1 and MSH 15-52. New results were found concerning the source extension (Vela X) or spectral analysis (GO. 9+0. 1 and MSH 15-52) at TeV energies, thanks to additional data and to the improved efficiency of the new method. In 2010, a new phase will begin with the achievement of a fifth telescope dedicated to γ-ray observation from tens GeV. The calibration processes of the photomultipliers equipping the camera of the new telescope, as well as the results of the tests, are also described in this thesis
Marty, Arlette. "Propriétés statiques et dynamiques d'un transistor bipolaire à collecteur réalisé par implantation haute énergie développé en technologie VLSI CMOS". Toulouse, INSA, 1992. http://www.theses.fr/1992ISAT0030.
Texto completoFournier, Bertrand. "Modélisation des propriétés électrostatiques des complexes macromoléculaires à partir des données de diffraction des rayons X à très haute résolution". Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10074/document.
Texto completoX-ray diffraction allows to obtain information about atomic structure and charge density distribution of crystal-state compounds, which is of main interest for the understanding of their properties. Reaching experimentally charge density distribution description of macromolecular systems is rarely possible despite technical improvements. To get around this limit, the transferability of charge density distribution parameters is a reliable way to obtain for these systems estimated model and to deduce their electrostatic properties. Works introduced in this PhD thesis manuscript take part in the will of extending methods initially for study of small molecules to macromolecular systems. It is centered on the development of the MoPro software suite and of ELMAM database (Experimental Library of Multipolar Atom Model) for the study of electrostatic interaction energies in enzyme-inhibitor complexes’ active site. The study of fidarestat, an inhibitor of aldose reductase holoenzyme, performed using ultra-high resolution data, is exposed in this manuscript and allowed to improve ELMAM database for the study of electrostatic interaction in aldo-keto reductase holoenzyme complexes. Moreover, the legitimacy of using transferred charge density distribution models was discussed for the first time, thanks to statistical estimation of uncertainties on electrostatic interaction energies between enzyme and inhibitor
Zouari, Samuël. "Étude de l'origine de l'émission à très haute énergie au centre de notre galaxie et connexion possible avec Sgr A*, notre plus proche trou noir super-massif". Electronic Thesis or Diss., Université Paris Cité, 2023. http://www.theses.fr/2023UNIP7120.
Texto completoAt the Centre of our Galaxy lies a supermassive black hole named Sgr A*. The HESS experiment has been observing the region in very high energy gamma rays, and has detected a compact source HESS J1745-290, compatible in position with the black hole, as well as a diffuse emission, interpreted as a proof of an excess of energetic particles, freshly injected by a PeVatron. The key to understanding the origin of the diffusion emission is the establishment of an association between Sgr A* and the central source : its possible extension, its spectral behaviour and its possible time variations. Indeed, there are two objects compatible with the position of HESS J1745-290, which could theoretically emit very high energy gamma rays : Sgr A* and the pulsar nebula G359,95. This thesis will investigate these questions from a theoretical perspective and then through the analysis of the many data HESS has gather on the Galactic Centre (GC). This work will also allow to offer prospects for the first years of CTA observing the GC. By using gamma ray emission model relying on the interaction between cosmic rays and molecular clouds, and by incorporating a spatial description of the target gas, we were able to model the temporal evolution of the gamma ray flux at TeV energies from a injection spectrum of protons, a hypothesis on their diffusion speed and a particle injection scenario (2 massive flares 100 and 200 years ago). We find that the flux variations corresponding to our assumptions are of the order of 10 to 15% during the HESS observation period. With regard to the analysis of HESS data we begin with the practical application of the spectro-morphological analysis (or 3D analysis) recently developed for HESS, applied to the Galactic Center. This allows us to obtain the first intrinsic spectrum of the HESS J1745-290 source, i.e separated from any contribution from the diffuse emission. We also re-estimate of the amplitude of the systematic errors of HESS on the spectral parameters, using in particular the new numerical tools developed within the framework of the python library gammapy. The separation of the contributions from HESS J1745-290 and the diffuse emission is what allows us to better study the temporal evolution of the central source. Indeed, monitoring a source over fifteen years is made difficult by the many changes (instrumental, climatic, etc.) experienced by the HESS system. We therefore use the diffuse emission as a reference to monitor more precisely the intrinsic variations of the HESS J1745-290 source. However, we do not observe any sign of variability over the period 2004-2019. To estimate the sensitivity of HESS to temporal variations, and in order to determine the evolution scenarios that we can already exclude, we simulated HESS data, using the response functions of the instrument and different models of temporal evolution. We find that the variation in flux of HESS J1745-290 over a single year is detectable if it is greater than 30%. Then, for a linear decrease in flux between 2004-2019, HESS is able to detect it if it is greater than 30% over 16 years. We deduce that the particle injection model developed previously is not excluded by the observations of HESS. Finally, using predictive instrument functions for CTA, we were able to make predictions about CTA's performance with respect to the observation of HESS J1745-290 : we determine that CTA will have sufficient angular resolution to determine whether this gamma source is associated with Sgr A* or G359.95-0.4. In addition, CTA's sensitivity to low flux variations will confirm or invalidate the temporal evolution scenario studied in our work
Martraire, Diane. "Étude du pouvoir de discrimination des primaires initiant les grandes gerbes atmosphériques avec des réseaux de détecteurs au sol : analyse des rayons cosmiques de ultra haute énergie détectés à l’observatoire Pierre Auger, Estimation des performances pour la detection de gamma de très haute énergie du future observatoire LHAASO". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112276/document.
Texto completoDuring the past century, ultra-high-energy cosmic rays (UHECR), those with an energy larger than 1018 eV, remain as a mystery: What are cosmic rays? Where do they come from? How do they attain their huge energy? When these charged particles strike the earth's atmosphere, they dissipate their energy by generating a shower of secondary particles whose development is significantly different depending on the nature of the primaries. The Pierre Auger observatory, with its hybrid structure and huge size network of ground detectors, can shed some light into these questions.The study of the composition of UHECR was performed with the Pierre Auger apparatus. This is crucial both to understand the hadronic interactions, which govern the evolution of showers, and to identify their sources. It can help to understand the origin of the energy spectrum cut-off: is it the GZK cut-off or the exhaustion of sources? These reasons motivate the first part of this thesis: the development of a method to extract the muonic component of air showers and deduce the implications on the composition of UHECR at the Pierre Auger observatory. The results of this method show a dependence of the composition with the distance to the axis of the shower, which could help to improve the hadronic models. The determination of the muon component is limited by the surface detector setup.The second part is devoted to the new observatory in China, LHAASO. This project focuses on the study of gamma rays with an energy higher than 30 TeV, which probe the acceleration of protons in the galaxy, providing indirect information on cosmic rays. Moreover, the observatory studies cosmic rays between 10 TeV and 1 EeV, one of the regions where the energy spectrum presents a break. This region requires the ability to discriminate gamma rays and cosmic rays. For this reason, one of the detectors of LHAASO, the KM2A, was simulated and its power of discrimination gamma/hadron evaluated
Chalmé-Calvet, Raphaël. "Étalonnage du cinquième télescope de l'expérience H.E.S.S. et observation du Centre Galactique au delà de 30 GeV". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066504/document.
Texto completoThe phase II of the H.E.S.S. experiment (High Energy Stereoscopic System) consists of five imaging atmospheric Cherenkov telescopes to study the southern astrophysical sources above 30 GeV. This thesis present the detector as well as the analysis chain, with a deep look on the fifth telescope commissioned on July 2012. The calibration method are described in detail. Then, an analysis based on a semi-analytical model of the electromagnetic shower development in the atmosphere is explained. A tool to reconstruct the energy spectrum of the very high energy gamma ray sources is presented. The methods of gamma ray selection among the hadron background are studied. Especially, the development of a new variable using the temporal data of the fifth telescope for the background rejection is shown. A systematic study of the analysis performances and of the selection cuts is accomplished, in order to reach the lowest energy threshold while keeping control of the background subtraction. The Galactic Centre has long been observed by H.E.S.S., which has detected a bright and punctual source at very-high energy as well as a diffuse emission along the Galactic plan. The Galactic Centre observations performed by the phase II of H.E.S.S. during the year 2014 are presented. A spectral reconstruction of the central source is performed
Dufreneix, Stéphane. "Etablissement de références dosimétriques dans les faisceaux de rayons X de hautes énergies et de très petites sections (< 1cm²) pour la radiothérapie". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112416/document.
Texto completoThe French primary standard dosimetry laboratory “Laboratoire National Henri Becquerel” is in charge of the establishment of dosimetric standards for ionizing radiation beams. Absolute dose measurements are thus available for X-Ray beams used in radiotherapy for field sizes between 10 and 2 cm. Since the miniaturization of absolute dosimeters is not possible for smaller field sizes, a dose area product (DAP) has been suggested as a substitute to the absorbed dose at a point.In order to measure a DAP with dosimeters which sensitive surface is larger than the beam, a graphite calorimeter with a sensitive surface of 3 cm diameter was designed, built and tested. An ionization chamber with the same diameter was realized and tested to transfer the dosimetric references to the end users. Its calibration factor in terms of DAP was determined in circular beams of 2, 1 and 0.75 cm diameter with an uncertainty smaller than 0.7 %. The two-Dimension relative dose distribution was measured thanks to a diamond dosimeter, a PinPoint ionization chamber and gafchromic films, using a specific protocol.Both approaches, respectively based on a PDS and an absorbed dose to water at a point, were in good agreement in the 2 cm beam. Correction factors determined from Monte Carlo simulations and measured dose distributions were needed for this comparison. The calibration factor of the large ionization chamber in the 1 and 0.75 cm diameter beams were in good agreement within the uncertainties but a gap of -2.6 % was found with the one established in the 2 cm diameter beam. As a result, the DAP can be used if the sensitive surface is much larger than the beam section
Jakoncic, Jean. "Étude structurale de métalloprotéines à centres [2Fe-2S]. Cas d’une ferrédoxine et d’une dioxygénase impliquée dans biodégradation des hydrocarbures aromatiques. Cristallographie des protéines à très haute énergie. Méthodes de phasage d’une protéine modele à 55 keV". Grenoble 1, 2007. http://www.theses.fr/2007GRE10012.
Texto completoMETALLOPROTEINS CONTAINING FE-S CLUSTERS PLAY AN IMPORTANT ROLE lN NATURE AS THEY ARE INVOLVED lN ESSENTIAL PHYSIOLOGICAL FUNCTIONS INCLUDING PHOTOSYNTHESIS, RESPIRATION, AND NITROGEN FIXATION. LN THIS THESIS, A [2FE-2S] FERREDOXIN INVOLVED lN FE-S CLUSTER BIOGENESIS, AND A BACTERIAL DIOXYGENASE PLAYING A CRITICAL ROLE lN AROMATIC HYDROCARBON BIODEGRADATION WERE SUBJECTED TO STRUCTURAL ANALYSIS BY SYNCHROTRON X-RA Y CR YSTALLOG RAPHY. THE STRUCTURE OF A FERREDOXIN FROM THE PHOTOSYNTHETIC BACTERIUM RHODOBACTER CAPSULATUS WAS SOLVED lN BOTH ITS OXIDlZED AND REDUCED STATES. SUBTLE STRUCTURAL CHANGES WERE OBSERVED UPON REDUCTION, ESPECIALLY lN THE VICINITY OF THE [2FE-2S] CLUSTER. THESE CHANGES ARE DISCUSSED lN COMPARISON WITH THOSE DESCRIBED FOR FERREDOXINS WITH SIMILAR STRUCTURES BUT DIFFERENT FUNCTIONS. A MORE COMPLEX METALLOPROTEIN, BELONGING T0 A LARGE FAMILY OF BACTERIAL DIOXYGENASES, WAS STUDIED FOR ITS ABILITY TO OXIDIZE POL YCYCLIC AROMATIC HYDROCARBONS (PAHS). THIS MULTICOMPONENT ENZYME, ISOLATED FROM A PAH-DEGRADING SPHINGOMONAS STRAIN, CONSISTS OF A NAD(P)H-OXIDOREDUCTASE, A [2FE-2S] FERREDOXIN, AND A TERMINAL OXYGENASE. THE TERMINAL OXYGENASE COMPONENT, CALLED PhnI, CONSISTS OF SIX SUBUNITS ASSEMBLED INTO AN ALPHA3B ET A3 HEXAMER, AND CONTAINS ONE RIESKE-TYPE [2FE-2S] CLUSTER AND ONE FE(II) ION PER ALPHA SUBUNIT, WHICH WERE IDENTIFIED BY THEIR CHARACTERISTIC EPR SIGNATURE. THE ENZYME SHOWED AN EXCEPTIONALLY BROAD SUBSTRATE SPECIFICITY, AS IT COULD HYDROXYLATE A WIDE RANGE OF PAHS MADE OF TWO TO FIVE FUSED RINGS, INCLUDING THE CARCINOGENS, BENZ[A]ANTHRACENE AND BENZO[A]PYRENE WlTH NAPHTHALENE AS SUBSTRATE, STEADY STATE KINETICS SHOWED TH AT THE ENZYME HAD A LOW APPARENT KM (092 MICRO-MOLE) AND A SPECIFICITY CONSTANT OF 2. 0 MICRO-MOLE¯¹. SECOND¯¹. THE PHN1 PROTEIN WAS CRYSTALLIZED AND ITS THREEDIMENSIONAL STRUCTURE WAS DETERMINED AT 1. 85 ANGSTROM RESOLUTION. LN SPITE OF MODERATE SEQUENCE SIMILARITY WITH HOMOLOGOUS DIOXYGENASES, THE 3D POL YPEPTlDE FOLD W AS FOUND TO BE VER Y SIMlLAR, MOST OF THE DIFFERENCES BEING OBSERVED NEAR THE SUBSTRATE BINDING POCKET. MANY PROTEIN CR YSTALS, ESPECIALLY THOSE OF FE-S PROTEINS, HAVE BEEN SHOWN TO UNDERGO X-RA Y RADIATION DAMAGE, LEADING TO ARTIFACTS lN PROTEIN STRUCTURE DETERMINATIONS. AS AN ATTEMPT TO SOLVE THE PROBLEM, ULTRA-HIGH ENERGY X-RA YS (55 KEY: 0. 22 ANGSTROM), WHICH ARE ONLY SLlGHTLY ABSORBED BY PROTEINS, WERE USED FOR THE FIRST TIME TO DETERMINE THE 3 D STRUCTURE OF A MODEL PROTEIN? LYSOZYME. BEAMLINE SPECIFITIES AS WELL AS OPTIMUM ENERGY WERE DETERMINED. POTENTIAL APPLICATIONS FOR STRUCTURAL BIOLOGY ARE DISCUSSED
Aubert, Pierre. "Calcul haute performance pour la détection de rayon Gamma". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV058/document.
Texto completoThe new generation research experiments will introduce huge data surge to a continuously increasing data production by current experiments. This increasing data rate causes upheavals at many levels, such as data storage, analysis, diffusion and conservation.The CTA project will become the utmost observatory of gamma astronomy on the ground from 2021. It will generate hundreds Peta-Bytes of data by 2030 and will have to be stored, compressed and analyzed each year.This work address the problems of data analysis optimization using high performance computing techniques via an efficient data format generator, very low level programming to optimize the CPU pipeline and vectorization of existing algorithms, introduces a fast compression algorithm for integers and finally exposes a new analysis algorithm based on efficient pictures comparison
Lenain, Jean-Philippe. "Rayonnement gamma des Noyaux Actifs de Galaxies observé aux Très Hautes Énergies avec H.E.S.S.: Études multi-longueurs d'onde et modélisation de processus radiatifs". Phd thesis, Observatoire de Paris, 2009. http://tel.archives-ouvertes.fr/tel-00431288.
Texto completoCharbonnier, Aldée. "De la recherche de matière noire à l'émission diffuse de rayons gamma dans l'expérience H.E.S.S". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2010. http://tel.archives-ouvertes.fr/tel-00553807.
Texto completoLaffon, Hélène. "Optimisation logicielle des performances instrumentales de H. E. S. S. Pour l'analyse des sources ténues de rayonnement gamma : Application à l'étude de l'objet HESS J1832-092". Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/docs/00/77/09/59/ANNEX/Soutenance_Laffon.pdf.
Texto completoH. E. S. S. (High Energy Stereoscopic System) is an array of very-high energy gamma-ray telescopes located in Namibia. These telescopes take advantage of the atmospheric Cherenkov technique using stereoscopy, allowing to detect gamma-rays between 100 GeV and a few tens of TeV. The location of the H. E. S. S. Telescopes in the Southern hemisphere allows to observe the central parts of our galaxy, the Milky Way. Tens of new gamma-ray sources were thereby discovered thanks to the galactic plane survey strategy. After ten years of fruitful observations with many detections, it is now necessary to improve the detector performance in order to detect new sources by increasing the sensitivity and improving the angular resolution. The aim of this thesis consists in the development of advanced analysis techniques allowing to make sharper analysis. An automatic tool to look for new sources and to improve the subtraction of the background noise is presented. It is optimized for the study of weak sources that needs a very rigorous analysis. A combined reconstruction method is built in order to improve the angular resolution without reducing the statistics, which is critical for weak sources. These advanced methods are applied to the analysis of a complex region of the galactic plane near the supernova remnant G22. 7-0. 2, leading to the detection of a new source, HESS J1832-092. Multi-wavelength counterparts are shown and several scenarii are considered to explain the origin of the gamma-ray signal of this astrophysical object
Laffon, Hélène. "Optimisation logicielle des performances instrumentales de H.E.S.S. pour l'analyse des sources ténues de rayonnement gamma : Application à l'étude de l'objet HESS J1832-092". Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00770959.
Texto completoSala, Leo Albert. "Low-energy Electron Induced Chemistry in Supported Molecular Films". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS438/document.
Texto completoHigh-energy irradiation of condensed matter leads to the production of copious amounts of low-energy (0-20 eV) secondary electrons. These electrons are known to trigger various dissociative processes leading to observed damages including erosion and chemical modifications. The resulting reactive species within the condensed media can also lead to the synthesis of new molecules. This has implications in several applications most especially in the design of lithographic methods, focused beam-assisted deposition, as well as in astrochemistry. In all these applications, it is important to identify the processes induced by low-energy electrons, study the reactive fragments and stable molecules produced to determine possibilities of controlling them, and generate quantitative data to gauge the efficiencies of these processes. The approach developed for this PhD work consists of directly irradiating surfaces and interfaces using low-energy electrons and studying the processes that arise. The responses of different model molecular films (of varying thickness) were studied as a function of incident electron energy and dose. In favorable cases, methodologies proposed herein can be used to estimate effective cross sections of observed processes. Three complementary surface-sensitive techniques were utilized for this purpose. To characterize the deposited films and formed residues, the High Resolution Electron-Energy Loss Spectroscopy (HREELS) and Temperature Programmed Desorption (TPD) were used. Neutral fragments (as opposed to their often-detected ionic counterparts) desorbing under electron irradiation were monitored using a mass spectrometer in a technique called Electron Stimulated Desorption (ESD).Within the context of surface functionalization, the grafting of sp2-hybridized carbon centers on a polycrystalline hydrogenated diamond substrate was realized through electron irradiation of a thin layer of benzylamine precursor deposited on its surface. At 11 eV, the dominant mechanism is proposed to be neutral dissociation of the precursor molecules. The effective cross section of the grafting process was estimated in only a single measurement from the HREELS map of the sample surface, taking advantage of the electron beam profile. Within the context of astrochemistry, on the other hand, the responses of crystalline and amorphous NH3 ices were studied under electron impact. The desorption of intact NH3 was observed which resulted in the direct erosion of the film proceeding through a mechanism consistent with desorption induced by electronic transitions (DIET). Different fragmentation and recombination processes were also observed as evidenced by detected neutral species like NHx (x=1,2), N2, and H2. Aside from desorption, a wealth of chemical processes was also observed at 13 eV. Temporal ESD at this energy allowed for the estimation of the effective cross section of NH3 desorption and observing the delayed desorption of N2 and H2. TPD analysis of the residues also provided evidence of N2H2 and N2H4 synthesis in the film. These results can help explain the observed discrepancies in abundances of NH3 and N2 in dense regions in space. Lastly, this PhD work will present prospects for these electron-induced processes to be constrained spatially in microscopic dimensions for lithographic applications. The feasibility of the procedure utilizing Low-Energy Electron Microscope (LEEM) was demonstrated on a terphenylthiol self-assembled monolayer (TPT SAM) specimen. Spots of 5 μm in diameter with different work functions were imprinted on the surface using energies from 10-50 eV. Electron-induced reactions in thin-film resists (PMMA, poly(methyl methacrylate)) were also studied at low-energy identifying opportunities for energy- and spatially-resolved surface modification
Fiasson, Armand. "Recherche de l'origine des rayons cosmiques par l'étude d'associations de vestiges de supernova et de nuages moléculaires avec HESS et validation du circuit d'échantillonnage de HESS II". Phd thesis, Montpellier 2, 2008. http://www.theses.fr/2008MON20083.
Texto completoThe H. E. S. S. Telescope (High energy Stereoscopic System), located in Namibia, is currently the most efficient observatory of very high energy (VHE) gamma-ray sources. It consists in 4 large diameter telescopes working in stereoscopic mode and allows an unequaled survey of the galactic plane at these extreme wavelenghts. The H. E. S. S. Experiment showed the presence of high energy particles up to 100 TeV within supernova remnant. This astrophysical objects are believed to be the main particle accelerator within the Galaxy. However, the nature hadronic or leptonic of these particles remains unclear. This thesis presents a new observationnal approach in order to show hadronic particles acceleration through diffusive shock within supernova remnants. A search of supernova remnants associated with molecular clouds has been led within the HESS source catalog and the H. E. S. S. Observations. An analysis of the new VHE gamma-ray source in Monoceros and its interpretation are presented. Then, the analysis and interpretation of new observations of the unidentified source HESS J1745-303 are presented. Finally, the multi-wavelength analysis of the new source HESS J1714-385, coincident with the supernova remnant CTB 37A is presented. Moreover, I have shown a gamma-ray excess towards OH masers, which are believed to indicate association between supernova remnant and molecular clouds. A contribution to the H. E. S. S. Phase II building is also presented. This second phase consists in the building of a fifth telescop at the center of the existing system. The series tests of the new camera sampling system are reported
Fiasson, Armand. "Recherche de l'origine des rayons cosmiques par l'étude d'associations de vestiges de supernova et de nuages moléculaires avec HESS et validation du circuit d'échantillonnage de HESS II". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2008. http://tel.archives-ouvertes.fr/tel-00660134.
Texto completoDubois, Florent. "L'astronomie gamma de très haute énergie avec H.E.S.S. Développement d'une analyse multi-variables et application à l'étude de nébuleuses de pulsars". Phd thesis, 2009. http://tel.archives-ouvertes.fr/tel-00518172.
Texto completoMasbou, Julien. "Étude de la sensibilité de H.E.S.S. 2 en dessous de 300 GeV et recherche indirecte de matière noire dans les données de H.E.S.S". Phd thesis, 2010. http://tel.archives-ouvertes.fr/tel-00623972.
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