Applications of laser wakefield accelerator-based light sources

Laser-wakefield accelerators (LWFAs) were proposed more than three decades ago, and while they promise to deliver compact, high energy particle accelerators, they will also provide the scientific community with novel light sources. In a LWFA, where an intense laser pulse focused onto a plasma forms an electromagnetic wave in its wake, electrons can be trapped and are now routinely accelerated to GeV energies. From terahertz radiation to gamma-rays, this article reviews light sources from relativistic electrons produced by LWFAs, and discusses their potential applications. Betatron motion, Compton scattering and undulators respectively produce x-rays or gamma-rays by oscillating relativistic electrons in the wakefield behind the laser pulse, a counter-propagating laser field, or a magnetic undulator. Other LWFA-based light sources include bremsstrahlung and terahertz radiation. We first evaluate the performance of each of these light sources, and compare them with more conventional approaches, including radio frequency accelerators or other laser-driven sources. We have then identified applications, which we discuss in details, in a broad range of fields: medical and biological applications, military, defense and industrial applications, and condensed matter and high energy density science

Rayonnement synchrotron base sur l'interaction laser-plasma en regime relativiste

Lors de l'interaction entre un laser femtoseconde ultra intense (50 TW) et un jet de gaz, des electrons du plasma peuvent etre pieges et acceleres par sillage laser dans une cavite ionique. Au cours de leur acceleration, ils effectuent egalement des oscillations transverses et, comme dans un synchrotron mais a petite echelle, ces electrons en mouvement vont produire un faisceau de rayons X polychromatiques et ultrabrefs, le rayonnement Betatron. Apres la mise en evidence experimentale de ce mecanisme en 2004, l'objectif de la these a ete de caracteriser spectralement et spatialement la source. Ces etudes ont egalement permis de determiner les proprietes des trajectoires electroniques dans la cavite. Apres un bref rappel des proprietes theoriques de la source X-Betatron, la caracterisation experimentale du rayonnement X et des trajectoires electroniques est presentee. Trois spectrometres ont ete developpes pour caracteriser le spectre de la source X-Betatron entre 1 et 10 keV : un spectrometre a filtres et deux spectrometres a cristaux haute resolution. Trois methodes experimentales, reposant sur les proprietes spectrales et spatiales de la source, ont permis de caracteriser les trajectoires electroniques dans la cavite acceleratrice. Cette source de rayons X ouvre des perspectives nouvelles dans le domaine des applications. Sa polychromaticite permettra notamment de realiser des experiences d'absorption X resolues en temps a l'echelle femtoseconde

DEVELOPMENT OF LASER BASED SYNCHROTRON X-RAY SOURCE

International audienceBy focusing an ultraintense laser onto a helium gaz jet, a collimated beam of ultrafast broadband X-ray radiation can now be generated. The X-ray radiation results from the betatron oscillations of relativistic electrons in the laser created plasma channel. Thus, just as in a synchrotron, the spectral and flux properties of the X-ray beam can be linked to the electron beam through the plasma wiggler strength. The radiation has been observed within 1-10 keV with filters and presents a divergence of as low as 20 mrad. In addition, this source possesses the unique properties to be ultrafast and perfectly synchronized with the laser system, which opens the way toward new types of pump probe experiments

Imaging Electron Trajectories in a Laser-Wakefield Cavity Using Betatron X-Ray Radiation

International audienceWe demonstrate that betatron x-ray radiation accurately provides direct imaging of electrons trajectories accelerated in laser wakefields. Experimental far field x-ray beam profiles reveal that electrons can follow similar transverse trajectories with typical excursions of 1.5  μm±0.5  μm in the plane of laser polarization and 0.7  μm±0.2  μm in the plane perpendicular

Analysis of wakefield electron orbits in plasma wiggler

International audienceIn relativistic laser plasma interaction, electrons can be simultaneously accelerated and wiggled in an ion cavity created in the wake of an intense short pulse laser propagating in an underdense plasma. As a consequence of their motion, the accelerated electrons emit an intense x-ray beam called laser produced betatron radiation. Being an emission from charged particles, the features of the betatron source are directly linked to the electrons trajectories. In particular, the radiation is emitted in the direction of the electrons velocity. In this article we show how an image of electrons orbits in the wakefield cavity can be deduced from the structure of x-ray spatial profiles