Cette thèse porte sur la caractérisation des champs magnétiques générés par l'interaction entre un laser d'intensité de 1017 W/cm2 à 1018 W/cm2 et de cibles solides, et leurs effets sur le faisceau d'électrons chauds. En effet, les différents champs magnétiques créés lors de cette interaction ont un rôle fondamental sur les caractéristiques du faisceau d'électrons chauds : sa source et son transport dans la matière. Des diagnostics de polarimétrie et d'interférométrie croisée ont été développés lors de cette thèse pour observer le champ magnétique en surface de la cible irradiée par laser et en particulier leurs évolutions spatiale et temporelle. Deux différents régimes ont été observés selon le contraste en intensité de l'impulsion laser : un possédant une montée rapide de champ magnétique suivie d'une décroissance plus lente créées par le déplacement des électrons chauds dans la matière, et un possédant une croissance plus lente de forme logarithmique créée par la pré-impulsion du laser par effet thermoélectrique. L'interprétation de nos résultats obtenues par ces diagnostics ont permis d'évaluer la résistivité du plasma. Cette résistivité nommée anormale dans la littérature se comprend en estimant l'influence du champ magnétique sur l'anisotropie du transport des électrons et donc sur la résistivité. Le dernier diagnostic permettant l'estimation du champ magnétique détaillé dans cette thèse est la déflectométrie protonique. Elle permet d'observer la déviation d'un faisceau de protons lors de sa propagation sous l'effet de champs électrique et magnétique. D'autres expériences se sont focalisées sur la divergence de ce faisceau d'électrons. Deux diagnostics principaux ont été utilisés : l'imagerie K α et l'imagerie du rayonnement de transition cohérente (C.T.R.) en face arrière de cibles. / This thesis concerns magnetic fields, generated by the interaction between strong laser pulse (intensity up to1018 W/cm2) and solid target, and their effects on the fast electron beam. Indeed, the various magnetic fields created during this interaction can inuence the divergence of the fast electron beam. The magnetic field createdduring this interaction have a fundamental role on the fast electron beam characteristics : its source and its transportin the material. Diagnotics of polarimetry and crossed interferometry were developed during this thesis to observethe on-surface magnetic field of the target, and in particular, their spatial and temporal evolutions. Two types oftemporal evolution of the magnetic field were observed according to the contrast in intensity of the laser pulse : afast rise of magnetic field followed by a slower decrease created by the travel of the fast electrons in the material,and a slower growth of logarithmic form created by the pre-pulse of the laser by thermoelectric effect. The interpretation of our results obtained by these diagnotics allowed us to estimate the resistivity of the plasma.This resistivity named "anomalously high resistivity" in the literature can be explained by taking into account theinuence of the magnetic field on the electrons transport (creation of an anisotropy) and thus on the resitivity.The last diagnotic allowing the estimation of the magnetic field detailed in this thesis is the proton deectometry. itallows to observe the deviation of a proton beam during its propagation under the inuence of electric and magneticfields. Other experiments were focused on the fast electron beam divergence. Two main diagnotics were used : the K α imaging and the coherent transition radiation (C.T.R) imaging at the rear side of solid targets. These diagnoticsallowed to estimate the fast electron beam divergence for two distinct energetic electron populations. The differenceof divergence coming from characteristics of both diagnotics (electrons in charge of the emissions in different energies). The diagnotics of on-surface magnetic fields of target irradiated by intense laser, such as the technics of polarimetry and crossed interferometry developed in this thesis, are dedicated to be combined with diagnotics determining the evolution of the radial size of the fast electron beam generated by the laser-matter interaction. Their simultaneous use, and the correlation between their respective data, should allow to establish experimentally, in the short term, the inuence of the on-surface magnetic fields on the fast electron beam initial characteristics, in particular the angular and energy distributions. Our results of polarimetry on the spatio-temporal evolution of the magnetic fields of surface establish the state of the art for this type of measures. There are possible improvements, in particular as regards their use in conditions of irradiation by lasers of intensities > 1018 W/cm2. These perspectives are also the object of discussions in this manuscript.

GeV electron bunches accelerated on a centimeter scale device exemplify the extraordinary advances of laser-plasma acceleration. The combination of high charges from optimized injection schemes and intrinsic femtosecond short bunch duration yields kiloampere peak currents. Further enhancing the current while reducing the energy spread will pave the way for future application, e.g. the driver for compact secondary radiation sources such as high-field THz, high-brightness x-ray or gamma-ray sources. One essential key for beam transport to a specific application is an electron bunch with high quality beam parameters such as low energy spread as well as small divergence and spot size. The inherent micrometer size at the plasma exit is typically sufficient for an efficient coupling into a conventional beamline. However, energy spread and beam divergence require optimization before the beam can be transported efficiently. Induced by the high peak current, the beam loading regime can be used in order to achieve optimized beam parameters for beam transport. / In this thesis, the impact of beam loading on the transverse electron dynamic is systematically studied by investigating betatron radiation and electron beam divergence. For this reason, the bubble regime with self-truncated ionization injection (STII) is applied to set up a nanocoulomb-class laser wakefield accelerator. The accelerator is driven by 150TW laser pulses from the DRACO high power laser system. A supersonic gas jet provides a 3mm long acceleration medium with electron densities from 3 × 10^18 cm^−3 to 5 × 10^18 cm^−3. The STII scheme together with the employed setup yields highly reproducible injections with bunch charges of up to 0.5 nC. The recorded betatron radius at the accelerator exit is about one micron and reveals that the beam size stays at the same value. The optimal beam loading, which is observed at around 250 pC to 300 pC, leads to the minimum energy spread of ~40MeV and a 20% smaller divergence. It is demonstrated that an incomplete betatron phase mixing due to the small energy spread can explain the experimentally observed minimum beam divergence.

Light Detection and Ranging (Lidar) is a kind of active sensor that emits a laser pulse and primarily measures the time of flight of the returning pulse and uses it to construct a 3D point cloud of the scene around the lidar sensor. The constructed point cloud is an essential asset for the control of autonomous vehicles, and especially today, an essential basis for the training of autonomous vehicle control models. However, it remains time-consuming, high-risk and expensive to acquire the amounts of data necessary to train the rather complex modern control models. As such, generating the point cloud through simulations becomes a natural solution. Yet, many lidar simulations today produce ideal point clouds, corrected only by random noise, without considering the physical reasons behind the imperfections visible in real lidar point clouds. The aim of this study was to investigate real-time simulation models for disturbances that may cause imperfections in lidar data. From a base investigation of lidar, disturbances were found, models were investigated and finally a real-time implementation of Atmospheric Effects and attenuation from Beam Divergence was evaluated. It was found that the implemented models could produce physically accurate lidar point placement while keeping the computational time low enough for real-time evaluation. However, to achieve correct separation of target hit rates under Atmospheric Effects, as high as 34% of the points had to be dropped. Additionally, the intensity of the return points could not be properly verified. From these results it can be concluded that, with additional verification and adjustment, the presented models can achieve good results for evaluation in real-time. The results of this study thus serve as a support for future developments of realistic real-time lidar simulations, for use in development of autonomous vehicle control models and implementation of digital twins.