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Touil B.,Université 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 | Year: 2016

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

Pointu A.M.,University Paris - Sud | Pointu A.M.,CNRS Physics, Gas, and Plasmas Laboratory | Stancu G.D.,CNRS Physics, Gas, and Plasmas Laboratory | Stancu G.D.,École Centrale Paris
Plasma Sources Science and Technology | Year: 2011

The kinetic mechanisms of creation and loss of transported species in a flowing afterglow apparatus at atmospheric pressure were studied by optical emission spectroscopy over some tens of cm. The feeding gas was nitrogen containing up to 12.5 ppm of NO flowing at 1333 cm s-1 in an afterglow tube of 8 mm diameter. The absolute concentration dependences versus axial distance were measured for four excited species: O(1S), N( 2P), N2(B,v′ = 0) and N2(A). They are all related by linear dependence laws, this being explained by the fact that N 2(A) contributes linearly to the creation of O(1S), N(2P), N2(B, v′ = 0). Quantitative measured dependences allowed us to estimate creation and loss rates. © 2011 IOP Publishing Ltd.

Cassou K.,University Paris - Sud | Daboussi S.,University Paris - Sud | Daboussi S.,CNRS Physics, Gas, and Plasmas Laboratory | Daboussi S.,Tunis el Manar University | And 9 more authors.
Optics Letters | Year: 2014

We show that a significant enhancement of the photon flux produced by high harmonic generation can be obtained through guided configuration at high laser intensity largely above the saturation intensity. We identify two regimes. At low pressure, we observe an intense second plateau in the high harmonic spectrum in argon. At relatively high pressure, complex interplay between strongly time-dependent ionization processes and propagation effects leads to important spectral broadening without loss of spectral brightness. We show that the relevant parameter for this physical process is the product of laser peak power by gas pressure. We compare source performances with high harmonic generation using a gas jet in loose focusing geometry and conclude that the source developed is a good candidate for injection devices such as seeded soft x-ray lasers or free electron lasers in the soft x-ray range. © 2014 Optical Society of America.

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 | Year: 2010

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.

Lifschitz A.F.,Laboratoire dOptique Appliquee | Revel A.,CNRS Physics, Gas, and Plasmas Laboratory | Caillault L.,CNRS Physics, Gas, and Plasmas Laboratory | Minea T.,CNRS Physics, Gas, and Plasmas Laboratory
Nuclear Fusion | Year: 2014

Non-ohmic heating will be used in the experimental nuclear fusion reactor ITER to reach thermonuclear temperatures. Two heating mechanism will be implemented, i.e. microwaves resonant with ion and electron cyclotron frequencies and energetic neutral beam injection, which contributes also to the current drive. Each one of the two neutral beam injector planned for ITER will deliver 16 MW of 1 MeV D0 beam. In the injector, negative ions D - coming from a 40 A negative ion source are electrostatically accelerated to 1 MeV, and stripped of their extra electron by collision with a target gas in a structure known as the neutralizer. Residual charged particles are deflected after the neutralizer in an electrostatic ion dump (E-RID). The ionization of the deuterium buffer gas filling the neutralizer induced by the D- beam creates a rarefied plasma which is expected to efficiently screens the Coulomb repulsion of the beam. Moreover, this plasma can eventually escape from the neutralizer and move back in the accelerator, towards the accelerating grids and the negative ion source. The transport of the beam through the neutralizer and the RID and the related plasma properties were studied using a 3D electrostatic particle-in-cell code called OBI-3 (Orsay Beam Injector 3 dimensional). Particle-particle and particle-wall collisions are treated using the Monte Carlo collision approach. Simulations show that the secondary plasma effectively screens the beam space charge preventing beam transverse expansion. Plasma ions created in the neutralizer form an upstream current with a magnitude of ∼0.5% of the negative ion current. Gas breakdown leading to arc formation in the RID was not observed. Finally, results for the propagation of non-ideal beams coming from simulations of the extraction and consecutive acceleration taken from Revel et al 2013 Nucl. Fusion 53 073027 are presented. © 2014 IAEA, Vienna.

Mochalskyy S.,CNRS Physics, Gas, and Plasmas Laboratory | Lifschitz A.F.,CEA Cadarache Center | Minea T.,CEA Cadarache Center
AIP Conference Proceedings | Year: 2011

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.

Delmas O.,Center Laser Of Luniversite Paris Sud | Delmas O.,CNRS Physics, Gas, and Plasmas Laboratory | Delmas O.,Amplitude | Pittman M.,Center Laser Of Luniversite Paris Sud | And 16 more authors.
Optics Letters | Year: 2014

We have investigated a new scheme for laser plasma transient collisional soft x-ray lasers based on the use of an additional laser to produce the preplasma. Soft x-ray emission measurements made for different solid targets are presented and discussed. A significant enhancement of the SXRL emission as compared to double-pulse single-beam grazing incidence (DGRIP) using the same pump laser is reported for 13.9- and 32.6-nm SXRL wavelengths. © 2014 Optical Society of America

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

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.

Gadonna K.,CNRS Physics, Gas, and Plasmas Laboratory | Leroy O.,CNRS Physics, Gas, and Plasmas Laboratory | Silva T.,University of Lisbon | Leprince P.,CNRS Physics, Gas, and Plasmas Laboratory | And 2 more authors.
EPJ Applied Physics | Year: 2011

A hydrodynamic model was developed to simulate the flow and the heat transfer with the gas/plasma system produced by a microwave-driven (500-900 W at 2.45 GHz) axial injection torch, running in atmospheric pressure helium at 3-9 L min-1 input gas flows. The model solves the Navier-Stokes' equations, including the effect of the plasma upon the momentum and the energy balance, in order to obtain the spatial distributions of the gas velocity and temperature. The model predicts average gas temperatures of 2500-3500 K, in the same range of those obtained by optical measurements. Simulations show that the plasma influences the gas flow path and temperature, promoting an efficient power transfer. © EDP Sciences, 2011.

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 | Year: 2014

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.

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