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Ion temperature measurement by laser‐induced fluorescence spectroscopy in panta
摘要： A laser-induced ?uorescence spectroscopy system was developed in a linear magnetized helicon plasma at Kyushu University. The thermal Doppler broadening on velocity distribution function follows the Maxwell distribution, and the averaged central ion temperature was evaluated to be ～0.36 eV. The effect of Zeeman splitting was observed for a more accurate assessment of the measurement and is consistent with the calculation. The temperature ratio of electrons and ions, T i /T e, was evaluated to be ～0.1. The result is valuable for evaluating the nonlinear processes of the plasma turbulence. ? 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
关键词： plasma ion temperature measurement,laser-induced ?uorescence,linear magnetized plasma
更新于2025-09-19 17:13:59
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Direct electron acceleration with a linearly polarized laser beam in a two-dimensional magnetized plasma channel
摘要： We examine the electron acceleration induced by an ultra-relativistic intensity laser–plasma interaction in a two-dimensional plasma channel in the presence of a self-generated transverse magnetic field. We find that the electron dynamics is strongly affected by the laser pulse polarization angle, plasma density, and magnetic field strength. We investigate in detail, the dependencies of the electron acceleration in terms of different parameters and find excellent agreement with non-magnetized plasma in the absence of the magnetic field. The numerical results show that the self-generated magnetic field plays a constructive role in the electron acceleration process. It is shown that electron acceleration is more affected by self-generated magnetic field for the laser radiations with large polarization angles. The numerical results show the maximum enhancement for electron acceleration for a laser radiation with polarization angle θ = π/2.
关键词： filamentation instability,two-fluid model,Electron beams,magnetized plasma
更新于2025-09-19 17:13:59
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Propagation of circularly polarized laser in strongly magnetized over-dense collisional plasma
摘要： Permittivity of a circularly polarized (CP) laser in magnetized collisional plasma is obtained in simpli?ed form. The propagation of a CP laser in magnetized homogeneous over-dense collisional plasma was investigated, and characteristics such as attenuation length, speci?c energy deposition and blue shift are obtained. Potential applications in ?elds such as inertial con?ned fusion are discussed.
关键词： energy deposition,collisional plasma,permittivity,inertial con?ned fusion,attenuation length,blue shift,circularly polarized laser,magnetized plasma
更新于2025-09-16 10:30:52
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Second harmonic generation by circularly polarized laser beam propagating in obliquely magnetized plasma
摘要： An analytical study of intense radiation generation at second harmonic frequency, by a circularly polarized laser beam propagating in plasma, in presence of an obliquely applied magnetic field, has been presented. Considering a mildly relativistic regime, a perturbation scheme is used for evaluation of transverse components of current density. The current density oscillating at twice the fundamental frequency of the laser field, drives the second harmonic radiation. The amplitude of the circularly polarized second harmonic radiation is derived and its variation with obliqueness of the applied magnetic field is graphically depicted.
关键词： obliquely magnetized plasma,perturbation scheme,mildly relativistic regime,second harmonic generation,circularly polarized laser beam
更新于2025-09-12 10:27:22
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Magnetosonic wave-aided terahertz emission by nonlinear mixing of lasers in plasmas
摘要： A scheme of phase-matched terahertz generation by beating two co-propagating lasers in magnetized plasma, in the presence of a magnetosonic wave (MSW), is developed. The beat frequency ponderomotive force of the lasers imparts an oscillatory drift to electrons. The electron drift velocity couples with the electron density perturbation associated with the MSW to produce an irrotational nonlinear current ? × (cid:1)J NL = 0. The beat current density resonantly excites a THz (Terahertz) radiation when the phase-matching conditions are satisfied. The MSW mediates the phase matching. At 9.6 and 10.6 μm wavelengths, and background magnetic field of 285 kG, one may achieve normalized THz wave amplitude of the order of 10?6 and one obtains the ratio of THz power to pump power of the order of 10?3.
关键词： terahertz radiation,phase-matching condition,Magnetized plasma,ponderomotive nonlinearity,resonant excitation
更新于2025-09-12 10:27:22
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Generation of terahertz radiation from beating of two intense cosh-Gaussian laser beams in magnetized plasma
摘要： An analytical and numerical study has been carried out for the generation of terahertz (THz) radiation by beating of two intense cosh-Gaussian laser beams (decentered Gaussian beams) in the rippled density magnetized plasma under the relativistic–ponderomotive regime. In this process, both laser beams exert a relativistic–ponderomotive force on plasma electrons at the beat frequency and impart them an oscillatory velocity in the presence of a static magnetic field. Due to coupling between this nonlinear oscillatory velocity with density ripple, nonlinear current is generated that excites the THz radiation at the different frequency. Higher-order paraxial-ray approximation (non-paraxial theory) has been used in this study. The effects of the decentered parameter, magnetic field, and density ripple on the THz radiation generation in ripple density magnetized plasma have been investigated. Further, the effect of beating of laser beams on the THz field amplitude and the efficiency of THz radiation have been studied. The amplitude and efficiency of the emitted radiation are found to be highly sensitive to the decentered parameter, magnetic field, and density ripple. It has been found that the amplitude and efficiency of the generated THz radiation increase significantly with increasing the values of decentered parameter, magnetic field, and density ripple.
关键词： relativistic–ponderomotive nonlinearity,magnetized plasma,cross-focusing,terahertz radiation,Cosh-Gaussian laser beams
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [AIP Publishing INTERNATIONAL CONFERENCE ON PHOTONICS, METAMATERIALS & PLASMONICS: PMP-2019 - Noida, India (14–16 February 2019)] INTERNATIONAL CONFERENCE ON PHOTONICS, METAMATERIALS & PLASMONICS: PMP-2019 - Stabilization of plane polarized Alfven waves by anomalous Doppler resonance
摘要： This work presents non-linear decay of plane polarized Alfven wave via anomalous Doppler resonance with an electron beam in a magnetized plasma. First order perturbation theory has been employed to derive the expressions for dispersion relation of Alfven waves and their growth rate. Numerical calculations have also been carried out for growth rate and unstable mode frequencies for typical plasma parameters. There exists two modes of wave propagation, one having frequency < ωci corresponds to Alfven wave, and the other has frequency approaching ωce which corresponds to electron cyclotron wave. The waves interact with the electron beam via normal and anomalous Doppler resonance. The normal resonance interaction increases the frequency of plane polarized Alfven wave but shows no growth or decay in amplitude. However, in anomalous resonance interaction the frequency remains unchanged and the wave stabilizes. The variation of frequency and growth rate with magnetic field and number density of plasma electrons is also discussed in the present paper. The phase velocity and the unstable frequency of the wave decrease with an increase in the number density of plasma electrons. The results of our work are applied to explain some of the experimental observations.
关键词： anomalous Doppler resonance,magnetized plasma,Alfven waves,growth rate,electron beam
更新于2025-09-11 14:15:04