Victor Malka | Centre National de la Recherche Scientifique / French National Centre for Scientific Research (original) (raw)

Papers by Victor Malka

Physical Review Letters, 1998

The acceleration of electrons injected in a plasma wave generated by the laser wakefield mechanis... more The acceleration of electrons injected in a plasma wave generated by the laser wakefield mechanism has been observed. A maximum energy gain of 1.6 MeV has been measured and the maximum longitudinal electric field is estimated to 1.5 GV͞m. The experimental data agree with theoretical predictions when 3D effects are taken into account. The duration of the plasma wave inferred from the number of accelerated electrons is of the order of 1 ps. [S0031-9007(98)06766-0] PACS numbers: 41.75. Lx, 52.40.Nk, 52.75.Di The generation of large amplitude electric fields in plasmas by high-power lasers has been studied for several years in the context of high-field particle acceleration . The ponderomotive force of the laser excites a longitudinal electron plasma wave (EPW) with a phase velocity close to the speed of light [2]. Two mechanisms have been considered to excite the EPW.

Physics of Plasmas, 2012

ABSTRACT An integral back-transform has been developed to retrieve the polar magnetic component i... more ABSTRACT An integral back-transform has been developed to retrieve the polar magnetic component in a cylindrically symmetric plasma from a single projection. The formula is derived from parallel forward Radon transform (Abel transform) of a source-free vector field. Two numerical schemes are proposed to solve the backward transform. These schemes have been tested successfully with predefined plasma parameters. The practical application to the analysis of experimental Faraday rotation measurements is also presented, leading to the reconstruction of the transverse profile of the magnetic field.

Physics of Plasmas, 1996

Experimental and theoretical results on the stimulated Raman backscattering (SRS) reflectivity of... more Experimental and theoretical results on the stimulated Raman backscattering (SRS) reflectivity of a short laser pulse (120 fs) interaction with an optically ionized helium gas are presented. The reflectivity is measured as a function of the gas pressure from 1 to 100 Torr. A monodimensional (1-D) theoretical model, including the refraction induced during the ionization process, describes the dependence of

The all optical external injection scheme that we will use with two colliding laser pulses allows... more The all optical external injection scheme that we will use with two colliding laser pulses allows a way to stabilize the injection of electrons into the plasma wave, and to easily tune the energy of the output beam by changing the longitudinal position of the injection. The charge and relative energy spread are also controllable by tuning parameters such as the injection intensity and its polarization. We report here on the control of the e-beam parameters, on the e-beam parameters that will be used for the conception and design of the emittance meter and on the experimental arrangement on which emittance measurement experiments will be achieved.

ABSTRACT We demonstrate the generation of high quality electron beams resulting from the interact... more ABSTRACT We demonstrate the generation of high quality electron beams resulting from the interaction of ultrashort and ultraintense laser pulses with underdense plasmas. The electron energy distribution is quasi-monoenergetic and peaks at 170 MeV

Laser Acceleration of Electrons, Protons, and Ions II; and Medical Applications of Laser-Generated Beams of Particles II; and Harnessing Relativistic Plasma Waves III, 2013

ABSTRACT We report on an experimental demonstration of laser wake field electron acceleration usi... more ABSTRACT We report on an experimental demonstration of laser wake field electron acceleration using few-milijoule laser pulses tightly focused on a 100 μm scale gas target. Using a comparatively low energy pulse has the benefit of a more compact system with a high repetition rate (typically kHz), which can prove useful for both practical applications and better statistical studies of laser plasma interactions. A proof-of-principle experiment was conducted to demonstrate the applicability of such electron sources from laser plasma wake field accelerator for ultrafast electron diffraction.

Review of Scientific Instruments, 2001

... Focusing a laser pulse with a spherical or an axial lens onto the edge of the gas ... The bac... more ... Focusing a laser pulse with a spherical or an axial lens onto the edge of the gas ... The backing pressure is also limited, as the installation of an additional pump complicates the ... The resultingjet should be stable and quasistationary to simplify the synchronization of the valve and ...

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011

... Permissions & Reprints. Optimization of gamma-ray beams produced by a laser-plasma accele... more ... Permissions & Reprints. Optimization of gamma-ray beams produced by a laser-plasma accelerator. A. Ben-Ismaïl a , b , Corresponding Author Contact Information , E-mail The Corresponding Author , J. Faure a and V. Malka a. ...

Laser and Particle Beams, 2004

It is known that relativistic laser plasma interactions can already today induce accelerating fie... more It is known that relativistic laser plasma interactions can already today induce accelerating fields beyond some TV/m, which are indeed capable to efficiently accelerate plasma background electrons as well as protons. An introduction to the current state of the art will be given and possible applications of these optically induced charged particle sources will be discussed.

Stable and high quality electron beams are produced when two laser pulses collide in underdense p... more Stable and high quality electron beams are produced when two laser pulses collide in underdense plasmas. In addition to the improvement of the stability of the electron beam, the use of a second laser pulse allows the control of the electron beam parameters (energy, relative energy spread, and charge). The experimental features are well explained by the use of PIC simulations which underline physics processes which were not predicted by fluid model. This control is obtained by changing laser pulse energy, laser pulses polarization or electron density. With a total of 1 J laser energy, a 10 pC electron beam at 200 MeV with relative energy spread smaller than 1% has been measured for the first time. Using higher laser energy PIC simulations predicted that 3 GeV electron beam with 0.9% should be produced in this scheme after 3.8 cm propagation length. In collaboration with J. Faure and C. Rechatin, Laboratoire d'Optique Appliqu'ee, 'Ecole Nationale Sup'erieure de Te...

EPL (Europhysics Letters), 2008

... with their injection velocity parallel to the propagation axis (r(0) = r0 and dr/dt(0) = 0). ... more ... with their injection velocity parallel to the propagation axis (r(0) = r0 and dr/dt(0) = 0). An analytic solution to this differential equation exists and under the assumption √ 2γ0β0E0/Ez ≫ 1, the output angle θ ≈ vr/vz ≈ c−1 dr/dt simplifies to ... [22] Tsung FS, Ren C., Silva LO, Mori ...

Applied Physics Letters, 2011

ABSTRACT Gamma-ray beams with optimal and tuneable size, temperature, and dose are of great inter... more ABSTRACT Gamma-ray beams with optimal and tuneable size, temperature, and dose are of great interest for a large variety of applications. These photons can be produced by the conversion of energetic electrons through the bremsstrahlung process in a dense material. This work presents the experimental demonstration of 30 mu m resolution radiography of dense objects using an optimized gamma-ray source, produced with a high-quality electron beam delivered by a compact laser-plasma accelerator. (C) 2011 American Institute of Physics. [doi:10.1063/1.3604013]

Since its creation, LULI has given an important contribution to laser plasma physics and Inertial... more Since its creation, LULI has given an important contribution to laser plasma physics and Inertial Confinement Fusion studies. We will review some major results obtained these last two years with a 600 ps laser chain and with the recent 100-TW, 300fs ultra-intense laser chain. These result cover a wide spectrum of laser plasma physics research such as laser plasma interaction,

An experiment has been performed with the LULI Multi-TeraWatt Laser. The acceleration of electron... more An experiment has been performed with the LULI Multi-TeraWatt Laser. The acceleration of electrons injected in a plasma wave generated by the laser wakefield mechanism has been observed with a maximum energy gain of 1.5 MeV. It has been shown that the electrons deflected during the interaction, could scatter on the walls of the experimental chamber and fake a high

Procedia Engineering, 2004

Nonlinear Thomson scattering radiation has been observed from relativistic laser plasma interacti... more Nonlinear Thomson scattering radiation has been observed from relativistic laser plasma interaction. We found that this radiative process is dominant for very high intensity at which point the relativistic scattering of the laser light originates from MeV energy electrons inside the plasma

New Journal of Physics, 2011

Betatron X-ray radiation in laser-plasma accelerators is produced when electrons are accelerated ... more Betatron X-ray radiation in laser-plasma accelerators is produced when electrons are accelerated and wiggled in the laser-wakefield cavity. This femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt range has been observed at different interaction regime using high power laser from 10 to 100 TW. However, none of the spectral measurement performed were at sufficient resolution, bandwidth and signal to noise ratio to precisely determine the shape of spectra with a single laser shot in order to avoid shot to shot fluctuations. In this letter, the Betatron radiation produced using a 80 TW laser is characterized by using a single photon counting method. We measure in single shot spectra from 8 to 21 keV with a resolution better than 350 eV. The results obtained are in excellent agreement with theoretical predictions and demonstrate the synchrotron type nature of this radiation mechanism. The critical energy is found to be Ec = 5.6 ± 1 keV for our experimental conditions. In addition, the features of the source at this energy range open novel perspectives for applications in time-resolved X-ray science.

We have produced polychromatic x-ray radiation by linear and non-linear Thomson scattering of an ... more We have produced polychromatic x-ray radiation by linear and non-linear Thomson scattering of an intense femtosecond laser on relativistic electrons accelerated in a helium plasma. The principle is the following. When relativistic electrons are submitted to a strong femtosecond laser pulse they experience strong accelerations and emit a femtosecond burst of nonlinear Thomson scattering radiation. This was demonstrated in the

An experimental study of shocks with astrophysical relevance is performed with the high energy de... more An experimental study of shocks with astrophysical relevance is performed with the high energy density laser of the LULI, at the Ecole Polytechnique. The peculiarity of these shocks is the strong coupling between radiation and hydrodynamics which leads to a structure governed by a radiative precursor. A new experiment has been performed this year where we have observed shocks identified

Harnessing Relativistic Plasma Waves as Novel Radiation Sources from Terahertz to X-Rays and Beyond, 2009

A wide-band spectral diagnostic system based on dispersion property of the Zinc Selenide prism, a... more A wide-band spectral diagnostic system based on dispersion property of the Zinc Selenide prism, a crystalline material highly dispersive in the near-to-far infrared spectral range, has been studied and developed for the laser wakefield acceleration experiment at LOA for the measurement of few femto-seconds long electron beam. The extensive PIC simulation studies of the colliding-beam LWFA have shown very short electron beam duration of less than 10 femtoseconds. The prism spectrometer diagnostic with highly sensitive Mercury Cadmium Telluride infrared detector and the diffraction-grating spectrometer with a high-resolution imaging visible camera together have the spectral range coverage and resolution capable of detecting ultra-short Coherent Transition Radiation (CTR) generated by interaction of bunch charges with a 100 microns thickness aluminum foil. The beam profile of asymmetric shape then could be extracted from the CTR spectrum by inverse Fourier transformation with Kramers-Kronig relation. The diagnostic system has been tested and calibrated for characterization of blackbody source spectrum and spectral responsivity. The measurement of electron beam duration of few femtoseconds has yet been convincingly shown with high resolution, and the measurements of this kind have important implication in understanding and subsequent successful operation of the future FEL light source with a highly mono-energetic LWFA beam source.

New Journal of Physics, 2010

In this study, electrons were injected into a laser plasma accelerator using colliding laser puls... more In this study, electrons were injected into a laser plasma accelerator using colliding laser pulses. By varying the parameters of the injection laser pulse, the amount of charge accelerated in the plasma wave could be controlled. This external control of the injected load was used to investigate beam loading of the accelerating structure and especially its influence on the electron beam energy and energy spread. Information on the accelerating structure and bunch duration was then derived from these experimental observations.