Interaction Of High Power Laser Beam Research Articles

Modeling the ponderomotive interaction of high-power laser beams with collisional plasma: the FDTD-based approach.

The ponderomotive interaction of high-power laser beams with collisional plasma is modeled in the nonrelativistic regime and is simulated using the powerful finite-difference time-domain (FDTD) method for the first time in literature. The nonlinear and dissipative dielectric constant function of the collisional plasma is deduced that takes the ponderomotive effect into account and is implemented in the discrete framework of FDTD algorithms. Maclaurin series expansion approach is applied for implementing the obtained physical model and the time average of the square of light field is extracted by numerically evaluating an integral identity based on the composite trapezoidal rule for numerical integration. Two numerical examples corresponding to two different types of laser beams, Gaussian beam and vortex Laguerre-Gaussian beam, propagating in collisional plasma, are presented for specified laser and plasma parameters to verify the validity of the proposed FDTD-based approach. Simulation results show the anticipated self-focusing and attenuation phenomena of laser beams and the deformation of the spatial density distributions of electron plasma along the beam propagation path. Due to the flexibility of FDTD method in light beam excitation and accurate complex material modeling, the proposed approach has a wide application prospect in the study of the complex laser-plasma interactions in a small scale.

Magnetic Reconnection in Plasma under Inertial Confinement Fusion Conditions Driven by Heat Flux Effects in Ohm’s Law

In the interaction of high-power laser beams with solid density plasma there are a number of mechanisms that generate strong magnetic fields. Such fields subsequently inhibit or redirect electron flows, but can themselves be advected by heat fluxes, resulting in complex interplay between thermal transport and magnetic fields. We show that for heating by multiple laser spots reconnection of magnetic field lines can occur, mediated by these heat fluxes, using a fully implicit 2D Vlasov-Fokker-Planck code. Under such conditions, the reconnection rate is dictated by heat flows rather than Alfvènic flows. We find that this mechanism is only relevant in a high β plasma. However, the Hall parameter ωcτei can be large so that thermal transport is strongly modified by these magnetic fields, which can impact longer time scale temperature homogeneity and ion dynamics in the system.

Nonlinear laser spectroscopy of gases, gas flows, and low-temperature plasmas

The potentialities of gas analysis by the methods of active Raman spectroscopy based on coherent four-proton interaction of high-power laser beams with the resonance cubic nonlinearity .are examined. Particular attention is paid to the possibility of measuring the parameters of gas discharges, flows, and flames, and also to the detection of low-level impurities in gases. A comparison is made with the traditional methods of spontaneous Raman spectroscopy. We show that the coherent methods of optical gas analysis possess a number of important advantages over the traditional methods, and show promise in many scientific and technical applications. The review is based on materials published in the scientific literature in the past two or three years, and on materials of domestic and international conferences on laser spectroscopy and gas diagnostics during recent years.