Efficient laser-overdense plasma coupling via surface plasma waves and steady magnetic field generation (original) (raw)
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Physics of Plasmas, 2007
Two-dimensional ͑2D͒ particle-in-cell numerical simulations of the interaction between a high-intensity short-pulse p-polarized laser beam and an overdense plasma are presented. It is shown that, under appropriate physical conditions, a surface plasma wave can be resonantly excited by a short-pulse laser wave, leading to strong relativistic electron acceleration together with a dramatic increase, up to 70%, of light absorption by the plasma. Purely 2D effects contribute to enhancement of electron acceleration. It is also found that the angular distribution of the hot electrons is drastically affected by the surface wave. The subsequent ion dynamics is shown to be significantly modified by the surface plasma wave excitation.
High Intensity Laser Propagation though Overdense Plasmas
The Review of Laser Engineering, 2008
Significantly collimated fast electron beam with a divergence angle 10 (FWHM) is observed when an ultra-intense laser pulse (I ¼ 10 14 W/cm 2 , 300 fs) irradiates a uniform critical density plasma. The uniform plasma is created through the ionization of an ultra-low density (5 mg/c.c.) plastic foam by X-ray burst from the interaction of intense laser (I ¼ 10 14 W/cm 2 , 600 ps) with a thin Cu foil. 2D Particle-In-Cell (PIC) simulation well reproduces the collimated electron beam with a strong magnetic field in the region of the laser pulse propagation. To understand the physical mechanism of the collimation, we calculate energetic electron motion in the magnetic field obtained from the 2D PIC simulation. As the results, the strong magnetic field (300 MG) collimates electrons with energy over a few MeV. This collimation mechanism may attract attention in many applications such as electron acceleration, electron microscope and fast ignition of laser fusion. V C 2014 AIP Publishing LLC.
Interaction of Ultra Intense Laser with Overdense Plasma
Progress of Theoretical Physics Supplement, 2000
Three-dimensional particle-in-cell simulations of the interaction of an ultra-intense linearly-polarized laser light with an overdense plasma are presented. Intense laser radiation is shown to be unstable against modulation both in the direction of the laser propagation direction and in the direction perpendicular to the polarization direction. Growth rate of the instability has a maximum when laser frequency is of the order of the plasma frequency modified due to the relativistic increase of electron mass in the laser field. Analytical description of the instability is also presented.
Physics of Plasmas, 2004
The relativistic acceleration of electrons by the field of surface plasma waves created in the interaction between ultrashort high-intensity laser pulses with sharp-edged overdense plasmas has been investigated. It is shown that the initial phase of the wave experienced by the electrons play a leading part by yielding a well-defined peaked structure in the energy distribution function. This study suggests that resonant excitation of surface plasma waves could result in quasi-monokinetic energetic electron bunches. When the space charge field becomes too strong, this mechanism can evolve toward a true absorption process of the surface wave energy via an enhanced ''vacuum heating'' mechanism generalized to the case of surface plasma waves.
Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents
New Journal of Physics, 2018
The absorption of laser energy and dynamics of energetic electrons in dense plasma is fundamental to a range of intense laser-driven particle and radiation generation mechanisms. We measure the total reflected and scattered laser energy as a function of intensity, distinguishing between the influence of pulse energy and focal spot size on total energy absorption, in the interaction with thin foils. We confirm a previously published scaling of absorption with intensity by variation of laser pulse energy, but find a slower scaling when changing the focal spot size. 2D particle-in-cell simulations show that the measured differences arise due to energetic electrons recirculating within the target and undergoing multiple interactions with the laser pulse, which enhances absorption in the case of large focal spots. This effect is also shown to be dependent on the laser pulse duration, the target thickness and the electron beam divergence. The parameter space over which this absorption enhancement occurs is explored via an analytical model. The results impact our understanding of the fundamental physics of laser energy absorption in solids and thus the development of particle and radiation sources driven by intense laser-solid interactions.
Coupling between High-Frequency Plasma Waves in Laser-Plasma Interactions
Physical Review Letters, 1995
Experimental evidence for the coupling between two electron plasma waves having nearly the same frequency but greatly differing in wave number is presented using time and wave-number resolved spectra of Thomson scattered light from the plasma. The qualitative features of the measured w͑t, k͒ spectra are predicted by a Lagrangian fluid description and reproduced in particle simulations. These show that the daughter waves generated in this mode coupling process take the energy preferentially from the large k wave without significantly affecting the small k plasma wave.
High Intensity Laser-Plasma Grating Interaction: surface wave excitation and particle acceleration
I first would like to thank my supervisors Michèle Raynaud of CEA/DSM and Caterina Riconda of Université Paris VI for their constant support and encouragement and for giving me the chance to work in an always friendly and stimulating environment. I owe my deepest gratitude to Anne Heron of CPHT for her invaluable support in the use and modification of the simulation code that I have used to perform the numerical study of laser-plasma grating interaction. I wish to thank Jean-Claude Adam and Denis Pesme of CPHT and all the collegues of LULI and LSI who constantly helped me whith their suggestion and remarks.
Ion dominated mechanism for coupling laser energy to plasma
arXiv: Plasma Physics, 2019
The well-known schemes (e.g. Brunel, resonance, JxB heating etc.,) of laser energy absorption in plasma are mediated through the lighter electron species. In this work a fundamentally new mechanism of laser energy absorption directly through the heavier ion species has been proposed. The mechanism relies on the difference between the ExB drifts of electron and ions in the oscillating electric field of the laser to create charge density perturbations in the presence of a strong external magnetic field. Particle - In - Cell (PIC) simulations using OSIRIS are carried out which provide clear support for this new absorption mechanism at work.
New Journal of Physics, 2020
The coupling of laser energy to electrons is fundamental to almost all topics 14 in intense laser-plasma interactions, including laser-driven particle and radiation 15 generation, relativistic optics, inertial confinement fusion and laboratory astrophysics. 16 We report measurements of total energy absorption in foil targets ranging in thickness 17 from 20 µm, for which the target remains opaque and surface interactions dominate, to 18 40 nm, for which expansion enables relativistic-induced transparency and volumetric 19 interactions. We measure a total peak absorption of ∼80% at an optimum thickness of 20 ∼380 nm. For thinner targets, for which some degree of transparency occurs, although 21 the total absorption decreases, the number of energetic electrons escaping the target 22 increases. 2D particle-in-cell simulations indicate that this results from direct laser 23 acceleration of electrons as the intense laser pulse propagates within the target volume. 24 The results point to a trade-off between total energy coupling to electrons and efficient 25 acceleration to higher energies. 26 1. Introduction 27 Energy absorption and coupling to electrons in dense targets irradiated by high intensity 28 laser pulses is fundamentally important to the development of ultra-bright sources of 29 high energy ions [1, 2], neutrons [3, 4], positrons [5, 6] and photons [7], to advanced 30 schemes for inertial confinement fusion [8], and in the generation of transient states of 31 warm dense matter [9, 10]. The efficiency with which laser energy is coupled to electrons within the plasma is a crucial aspect in optimising the properties of the particles and 33 radiation generated. The electrons accelerated by the laser directly produce photons and 34 positrons, and their displacement establishes the strong electrostatic fields responsible 35 for ion acceleration. The case of laser energy absorption and coupling to electrons in 36
Surface Oscillations in Overdense Plasmas Irradiated by Ultrashort Laser Pulses
Physical Review Letters, 2001
The generation of electron surface oscillations in overdense plasmas irradiated at normal incidence by an intense laser pulse is investigated. Two-dimensional (2D) particle-in-cell simulations show a transition from a planar, electrostatic oscillation at 2ω, with ω the laser frequency, to a 2D electromagnetic oscillation at frequency ω and wavevector k > ω/c. A new electron parametric instability, involving the decay of a 1D electrostatic oscillation into two surface waves, is introduced to explain the basic features of the 2D oscillations. This effect leads to the rippling of the plasma surface within a few laser cycles, and is likely to have a strong impact on laser interaction with solid targets.