[en] Radiation emission from thin solid targets irradiated by short-intense laser pulses has been re-examined. Free electrons in the material are driven by the applied external radiation field and harmonics are generated by the electronic response to the crystal lattice force. Recent work on this phenomenon has drawn attention to a flat spectral profile featured by a sudden cut-off at high harmonic order. In the present work we report a number of effects that may in practice have a bearing on the emission. A model was modified by introducing a more general expression for the lattice force that by sharpening or by smoothing the potential in turns allow the strength of the electronic perturbation to be varied. Results from the computed emission reported here show that the pulse shape and the intensity of the laser light may modify the spectral characteristics. For infinite plane waves the obtained emission spectra are in accordance with a recent theoretical model. (Author)

[en] Electron Cyclotron Resonance (ECR) plasma devices have an important place among the electrode less cold plasma sources, due to their potential applications in industry. Many different devices of this type are now under research around the world. This paper deals with the design description of a microwave ECR plasma source, in which an overdense plasma will be generated, making use of the plasma Eigen modes to induce wave conversion. (Author). 12 refs, 7 figs

[en] A radiation resonance effect observed in the reflection spectra from overdense plasmas illuminated by femtosecond laser pulses at normal incidence is reported from particle-in-cell simulations. Harmonic emission at multiple orders of the fundamental is found to exhibit resonance phenomena, with the number of resonances and power emitted depending on the electron plasma density. For relatively low laser intensities the reflected light at the laser frequency shows prominent resonant emission around specific values of the plasma density, mainly at 4, 16, and 36 times critical. For increasing laser intensities, strong harmonic emission around 4 and 16 times critical dominates the reflection spectra. In the case of the third laser harmonic, the emission is found to be resonant about those densities and presents, additionally, a distinctive resonant region around nine times critical. A simple radiation model for the power of the third harmonic was proposed confirming a resonant effect dependent on the electron plasma density. For higher harmonic numbers, weak radiation resonances persist in the emission spectra, with their number increasing with order. The resonance effect reported in this paper is found to occur at densities that approximately satisfy n_e/n_c=4n², where n_e and n_c are the plasma and the critical density, respectively, and n is an integer. For the third harmonic, the second resonance corresponds to n=1.5

[en] Recent work on the irradiation of thin solid targets by short-pulse high intensity laser light has drawn attention to the high order of harmonics that may be generated. Results reported here examine how the spectrum of harmonics is affected by the choice of the lattice potential and by the pulse length and intensity of the laser light. (author). 4 refs, 6 figs

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[en] In this paper the average energy and the magnetic moment conservation laws in the Drift Theory of charged particle motion are obtained in a simple way. The approach starts from the energy and magnetic moment conservation laws and afterwards the average is performed. This scheme is more economic from the standpoint of time and algebraic calculations than the usual procedure of Bogolyubov's method. (Author)

[en] High-order harmonic emission from the interaction of intense femtosecond laser pulses with super-critical plasmas characterized by a rippled density profile at the vacuum-plasma interface has been observed from particle-in-cell (PIC) simulations. A plasma simulation box several laser wavelengths in extent was prepared with a rippled density of a fraction of a laser wavelength. Emission spectra at the very initial stage of the interaction were recorded with spectral characteristics dissimilar to those previously reported in the literature. The reflected light spectra were characterized by a strong emission at the plasma line and by a series of harmonics at multiples of the ripple frequency. Harmonic spectra were obtained for different values of the plasma ripple frequency. In all cases the harmonics were emitted at the precise multiple harmonic number of the ripple frequency. Another important feature apparent from the simulations was that the emission peaks appeared to havea complex structure as compared with those for unrippled plasmas. For the cases when the plasma was rippled the peaks that corresponded to the multiples of the rippled density typically showed a double peak for the first few harmonics. The reflected emission plots for the main laser pulse showed strong emission at the plasma frequency and at multiples of that frequency as reported by the authors in the literature. (Author)

[en] The investigation of the laser interaction with plasma has been carried out mainly in laboratories of Europe, Japan and United States during the last decades. This studies concern the propagation of intense light laser in a non homogeneous plasma, the radiation absorption and the generation of suprathermal electrons, among others. Numerical simulations made by Denavit, for radiation pulses for up of 10²⁰ W/cm² on solid targets, have allowed to observe the generation of ionic crash fronts with high propagation speeds. In this work it is expanded the study of this effect through algorithms of particles simulation. (Author)

[en] An analytical model for the description of the movement of a charged particle in the interaction of an electromagnetic pulse elliptically polarized propagating along of a static and homogeneous external magnetic field in a plasma starting from the force equation is presented. The method allows to express the solution in terms of the invariant phase, obtaining differential equations for the trajectory of the accelerated particle by means of an electromagnetic pulse of arbitrary amplitude and modulated by an encircling Gaussian. The numerical solutions reported in this work can find varied applications, for example in the physics of the interaction laser-plasma, in the acceleration of particles, in hot plasma and in radiative effects. (Author)