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Davoine X.,CEA DAM Ile-de-France | Beck A.,CEA DAM Ile-de-France | Lifschitz A.,CNRS Physics, Gas, and Plasmas Laboratory | Malka V.,Ecole Polytechnique - Palaiseau | Lefebvre E.,CEA DAM Ile-de-France
New Journal of Physics

The present paper elaborates on the cold injection scheme, which was recently proposed in the context of laser wakefield acceleration (Davoine et al 2009 Phys. Rev. Lett. 102 065001). This scheme allows one to inject a bunch of electrons into a laser wakefield, which is possible thanks to the collision between the main and a counter-propagating laser pulse. Unlike in the conventional colliding pulse schemes, in this process, a beatwave is created during the collision, which allows the injection of electrons with negligible heating. In this paper, we show that the injection of on-axis electrons observed in simulations is well described by a one-dimensional (1D) model, as long as conditions given here are satisfied. Injection of off-axis electrons is also influenced by transverse effects, but the basic mechanisms remain the same. Then, a comparison with the conventional colliding pulse schemes shows that each scheme can occur in different regimes. In particular, cold injection proves to be more interesting regarding the energy spread issue. Indeed, the simulations demonstrate that electron bunches with sub-MeV absolute energy spreads can be injected, leading, after acceleration, to electrons at several GeV and relative energy spread below 1%. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft. Source

Berger G.,CNRS Physics, Gas, and Plasmas Laboratory
2011 7th Asia-Pacific International Conference on Lightning, APL2011

Demonstration of the analogy between lightning and electricity reached its maturity with the personal involvement of Benjamin Franklin in 1746 and the epistolary publication of his innovating ideas through his friend Peter Collinson. A first wave of experiments on lightning was triggered by the translation into French of the ideas of Franklin (Dalibard, Delor, Buffon and Jacques de Romas). The famous kite experiment was invented by Franklin and Romas independently. Romas produced very long sparks in front of enthusiastic crowds (first success in 1753). Franklin and Romas argued about the priority of this invention which prefigured the modern conception of the lightning rod. The tradition only retained the name of Franklin, which is justified as regards to his great talent but rather unfair to the memory of Romas which led with obstinacy research works on the nature and effects of lightning. © 2011 IEEE. Source

Mochalskyy S.,CNRS Physics, Gas, and Plasmas Laboratory | Lifschitz A.F.,CEA Cadarache Center | Minea T.,CEA Cadarache Center
AIP Conference Proceedings

The development of a high performance negative ion (NI) source constitutes a crucial step in the construction of Neutral Beam Injector (NBI) of the future fusion reactor ITER. NI source should deliver 40 A of H- (or D -), which is a technical and scientific challenge, and requires a deeper understanding of the underlying physics of the source and its magnetic filter. The present knowledge of the ion extraction mechanism from the negative ion source is limited and concerns magnetized plasma sheaths used to avoid electrons being co-extracted from the plasma together with the NI. Moreover, due to the asymmetry induced by the ITER crossed magnetic configuration used to filter the electrons, any realistic study of this problem must consider the three spatial dimensions. To address this problem, a 3D Particles-in-Cell electrostatic collisional code was developed, specifically designed for this system. Binary collisions between the particles are introduced using Monte Carlo Collision scheme. The complex orthogonal magnetic field that is applied to deflect electrons is also taken into account. This code, called ONIX (Orsay Negative Ion eXtraction), was used to investigate the plasma properties and the transport of the charged particles close to a typical extraction aperture [1].This contribution focuses on the limits for the extracted NI current from both, plasma volume and aperture wall. Results of production, destruction, and transport of H- in the extraction region are presented. The extraction efficiency of H- from the volume is compared to the one of H- coming from the wall. © 2011 American Institute of Physics. Source

Touil B.,Universite Ibn Khaldoun | Bendib A.,University of Science and Technology Houari Boumediene | Bendib-Kalache K.,University of Science and Technology Houari Boumediene | Deutsch C.,CNRS Physics, Gas, and Plasmas Laboratory
Laser and Particle Beams

The dispersion relation of electrostatic waves with phase velocities smaller than the electron thermal velocity is investigated in relativistic temperature plasmas. The model equations are the electron relativistic collisionless hydrodynamic equations and the ion non-relativistic Vlasov equation, coupled to the Poisson equation. The complex frequency of electrostatic modes are calculated numerically as a function of the relevant parameters kλ De and ZT e/T i where k is the wavenumber, λDe, the electron Debye length, T e and T i the electron and ion temperature, and Z, the ion charge number. Useful analytic expressions of the real and imaginary parts of frequency are also proposed. The non-relativistic results established in the literature from the kinetic theory are recovered and the role of the relativistic effects on the dispersion and the damping rate of electrostatic modes is discussed. In particular, it is shown that in highly relativistic regime the electrostatic waves are strongly damped. Copyright © Cambridge University Press 2016 Source

Britun N.,University of Mons | Minea T.,CNRS Physics, Gas, and Plasmas Laboratory | Konstantinidis S.,University of Mons | Snyders R.,University of Mons | Snyders R.,Materia Nova
Journal of Physics D: Applied Physics

The physical and chemical aspects of plasma-surface interaction in high-power impulse magnetron sputtering (HiPIMS) discharges are overviewed. The data obtained by various plasma diagnostic methods representing the important sputtering discharge regions, namely the cathode vicinity, plasma bulk, and substrate vicinity, are reported. After a detailed introduction to the problem and description of the plasma characterization methods suitable for pulsed magnetron discharge analysis, an overview of the recent plasma diagnostics achievements in both non-reactive and reactive HiPIMS discharges is presented. Finally, the conclusions and perspectives suggesting possible directions and research strategies for increasing our knowledge in this domain are given. © 2014 IOP Publishing Ltd. Source

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