The purpose of the present paper is to investigate the generation of soft X-ray emission from an anharmonic collisional nanoplasma by a laser–nanocluster interaction. The electric field of the laser beam interacts with the nanocluster and leads to ionization of the cluster atoms, which then produces a nanoplasma. Because of the nonlinear restoring force in an anharmonic nanoplasma, the fluctuations and heating rate of, as well as the power radiated by, the electrons in the nanocluster plasma will be notably different from those arising from a linear restoring force. By comparing the nonlinear restoring force state (which arises from an anharmonic cluster) with that of the linear restoring force (in harmonic clusters), the cluster temperature specifically changes at the resonant frequency relative to the linear restoring force, while the variation of the anharmonic cluster radius is almost identical to that of the harmonic cluster radius. In addition, it is revealed that a sharp peak of X-ray emission arises after some picoseconds in deuterium, helium, neon and argon clusters.
In this study, the influence of a helical magnetic wiggler on the nonlinear interaction of a laser beam with a lattice of metallic nanoparticles is investigated. Coupling of the static magnetic field of the wiggler to the field of the laser wave, and therefore a change in the electric field intensity of the pumped wave, leads to the formation of a nonlinear force in the interaction region. As a consequence, the nonlinear force enhances the plasmonic oscillations of the electronic cloud of each nanoparticle causing electron density modulation, which improves the self-focusing property of the laser beam. Using a perturbative method, the nonlinear dispersion plasmonic and body waves are obtained from the interaction of a laser beam with a lattice of nanoparticles in the presence of a helical magnetic wiggler. We investigate the effects of nanoparticle size, their separations and wiggler field strength on the evolution of the transverse profile of the laser beam in both incident linearly polarized and circularly polarized waves. The numerical results indicate that in the linear polarization for all branches of plasmonic and body waves (except for the low-frequency middle branch), laser bandwidth decreases with increasing nanoparticle separation length, which improves the self-focusing property. Moreover, with enhancement of the normalized wiggler field strength, the laser amplitude transverse profile for all branches of plasmonic and body waves (except for the low-frequency middle branch) decreases, which leads to beam focusing. For left and right circular polarization, it is found that with an increase in the nanoparticle separation length, the laser amplitude transverse profile for all branches of plasmonic and body waves (except for the low-frequency middle branch) increases, which leads to beam defocusing. Furthermore, with enhancement of the normalized wiggler field strength, the laser amplitude transverse profile decreases for body waves and the low-frequency lower branch of plasmonic waves, which gives rise to the beam focusing, whereas it increases for the low-frequency middle and upper branches of plasmonic waves, which leads to the beam defocusing.
In this paper, generation of terahertz (THz) radiation by the beating of two super-Gaussian laser beams in a nanocluster plasma is investigated, theoretically. The electric field of laser beams interacts with the nanocluster, leads to the ionization of the cluster atoms, and produces nanoplasma. Interaction of laser beams with the electronic clouds of nanoplasma generates ponderomotive force that leads to the creation of a macroscopic electron current at the beat frequency, which can generate THz radiation. The THz wave equations and THz efficiency in the nanoplasma medium were analytically derived and then numerically discussed. The effects of the density and radius of nanoclusters, the laser beam width, and intensity of super-Gaussian lasers on the THz radiation efficiency have been investigated in the nanoplasma-based THz emitter. The results indicated when the beat-wave frequency approaches the effective plasmon frequency of the nanoplasma, the maximum value of the field amplitude of THz radiation is acquired. In addition, it was found that the best situation that can be obtained is the THz radiation occurring at frequency
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