Achieving ignition in inertial confinement fusion requires significant heating and compression of the thermonuclear fuel. One of the most efficient ways to achieve such conditions is spherical compression of the target initiated by specially profiled laser pulses. Any irradiation asymmetries and target imperfections break the symmetry of the compression and are seeds for the growth of hydrodynamic instabilities. As a result, the initial small amplitudes grow significantly and break the effective target compression, which is critical for successful ignition. The paper numerically studies the evolution of ice–ablator small perturbations in a direct drive target. The simulations consider the target dynamics with two different numerical hydrocodes. As a result of Rayleigh–Taylor instability development during both acceleration and deceleration phases, the perturbations grow significantly and could violate the ignition if the initial amplitude is larger than the critical value of several hundred nm: for successful ignition, the amplitude should be compared or smaller than a 100 nm. The effect of perturbations propagating from the distributed interface to the internal smooth layers is also observed.

The development of hydrodynamic instabilities has a significant impact on the operation of laser fusion systems. During radiation compression, the shells of a target are accelerated, resulting in the growth of perturbations at their interfaces. In this paper, we study the influence of density perturbations on the stability of the contact boundary during accelerated motion. The analysis is performed in a two-dimensional planar formulation using the linear approximation and assuming a weak spatial dependence on the temperature near the contact boundary. Due to the consideration of small time intervals, the phenomenon of heat conduction is not taken into account. The cases of acceleration of a medium described by the Mie–Grüneisen equation of state (EoS) into a vacuum and of acceleration of two contacting media, each described by the ideal plasma EoS, are considered. The time dependence of the amplitude of the boundary perturbation on time is obtained. The obtained values are in agreement with the results of numerical analysis. It is shown that the boundary curvature occurs independently of the acceleration direction. The theoretical results are compared with numerical results for laser fusion systems.

The inertial confinement fusion has not been achieved yet. The reasons for this phenomenon are not fully understood. In our opinion, the main factor influencing the decrease in the yield is the evolution of hydrodynamic instabilities due to geometric inhomogeneities (surface roughness, the presence of asymmetric elements etc.). The perturbed density field can result from these inhomogeneities. The results of a theoretical study of the influence of density perturbations on the stability of the boundary under accelerated motion are presented in this paper. The performed numerical simulations are compared with theoretical results.

Low adiabat dynamics is necessary for efficient compression and achievement of ignition conditions in a laser fusion targets. In this case, any additional sources of target interior heating are undesirable. Parametric laser-plasma instabilities can lead to the generation of a noticeable amount of hot electrons with energies of tens to hundreds of keV, that could penetrate into the target before the front shock arrives. The paper presents a hydrodynamics consistent model for generation and propagation of such electrons. Our simulations show that up to 2

The interference contribution to the optical conductance (total transmittance) of a sample of a disordered Faraday medium is calculated. The suppression of wave interference in a magnetic field is shown to be due to helicity-flip scattering events. The magnetic field does not destroy the interference of waves with a given helicity, but suppresses it if the helicity changes along different parts of the wave trajectory. This leads to a decrease in the interference contribution to the conductance with increasing the magnetic field. A similar phenomenon, negative magnetoresistance, is known as a consequence of weak localization of electrons in metals with impurities. It is found that, as the magnetic field increases, the change in the interference correction to the optical conductance tends to a certain limiting value, which depends on the ratio of the transport mean free path to the helicity-flip scattering mean free path. We also discuss the possibility of controlling the transition to the regime of strong "Anderson" localization in the quasi-one-dimensional case by means of the field.

We study coherent backscattering (CBS) of light from a magnetoactive medium doped by Mie particles. A novel version of the CBS diffusion theory is developed, which takes into account both the Faraday effect and the effect of circular polarization memory specific to Mie scattering. The theory is based on a system of coupled diffusion equations for two slowly decaying cooperon modes arising from interference of waves with coinciding helicities. The impact of a magnetic field on CBS is shown to be controlled by the ratio of the helicity-flip scattering cross section to the transport scattering one. If this ratio is small, the CBS can exhibit unusual features first found experimentally by R. Lenke, R. Lehner, and G. Maret [Europhys. Lett. 52, 620 (2000)]. In the magnetic field parallel to the sample surface, the peak of coherent backscattering for circularly polarized light is shifted from the exact backward direction, while, for linearly polarized light, it splits in two ones for both co- and cross-polarization channels, and the backscattered waves acquire circular polarization. Saturation of the magnetic field dependence of the CBS cone occurs in the magnetic field normal to the surface. If the above ratio is close to unity (Rayleigh scattering) all these features disappear, and the effect of the magnetic field on the CBS angular profile is reduced to the universal law studied previously. The results obtained are in good quantitative agreement with the available Monte Carlo simulation and experimental data.

The ignition of laser-initiated inertial confined fusion (ICF) targets is still not reached, despite considerable efforts taken in this direction. The exact physical reasons for this failure are still questionable, but there are significant hints for the significant role of uncontrollable hydrodynamics instabilities, that prevent ignition. Many papers are devoted to such instabilities, special attention is paid to the Rayleigh-Taylor and Ritchmeyer–Meshkov instabilities of accelerated perturbed interfaces. In this paper we consider an alternative variant, when the interface is initially smooth and perturbations are given inside of one medium. During acceleration the perturbations are carried from medium interior to the interface even if conditions for the Rayleigh–Taylor instability are not fulfilled. This initiates the instability and mediums mixing. The effect may be important for ICF targets, where it is crucial to support target symmetry and purity of each layer during compression.

The ignition is still unachieved in current schemes of inertial confinement fusion (ICF) despite significant efforts in this direction. The reason for it is unclear as the dynamics of target combine a lot of physical processes that are crucial for successful ignition. One possible limiting factor is known for a long time – hydrodynamic instabilities and mixing. Current work consider the effect of initial roughness on compression efficiency of ICF targets. The roughness is set on the ice–ablator boundary (outer ice interface). First, some analytical results on stability of accelerated perturbed interface are presented. Second, numerical simulations of ICF target show the influence of initial perturbations on hot–spot conditions and ice–ablator mixing.

We present the results of a theoretical study of underwater pulse propagation. The vector radiative transfer equation (VRTE) underlies our calculations of the main characteristics of the scattered light field in the pulse. Under the assumption of highly forward scattering in seawater, three separate equations for the basic modes are derived from the exact VRTE. These three equations are further solved both within the small-angle approximation and numerically. The equation for the intensity is analyzed for a power-law parametrization of the wings of the sea water phase function. The distribution of early arrival photons in the pulse, including the peak intensity, is calculated. Simple relations are also presented for the variance of the angular distribution of radiation, the effective duration of the signal and other parameters of the pulse. For linearly and circularly polarized pulses, the temporal profile of the degree of polarization is calculated for actual data on the scattering matrix elements. The degree of polarization is shown to be described by the self-similar dependence on some combination of the transport scattering coefficient, the temporal delay and the source-receiver distance. Our results are in agreement with experimental and Monte-Carlo simulation data. The conclusions of the paper offer a theoretical groundwork for application to underwater imaging, communication and remote sensing.

The problem of two semi-infinite plates under impact is studied both theoretically and numerically. Initially, one plate has the perturbed density field with uniform distribution of pressure. We demonstrate that various regimes of instabilities development in plates are guided by the appropriate initial conditions. A viscosity effect on instabilities growth is analyzed. Particularly, the minimal wavelength of an initial perturbation, for which viscosity effect is negligible, is obtained. The performed numerical simulations support our theoretical insights.

Unpolarised light propagation is considered in a circularly dichroic medium with optically isotropic Mie-particles. The degree of passed radiation polarisation is calculated under the assumption that multiple scattering in such a system occurs in the spatial diffusion regime. It is shown that introducing Mie particles into a homogeneous sample with natural optical activity can noticeably enhance the observed circular dichroism, namely, increase a difference between the intensities of right- and left-handed polarised light passed through the medium. If the first Kerker condition is fulfilled for Mie particles, then the effect can be almost ten times stronger as compared to the case of a homogeneous sample.

We study the long-range spatial correlations between intensity fluctuations in speckles formed by multiply scattered light. The correlation function between intensity fluctuations at the opposite boundaries of the slab are analyzed under the conditions of circular polarization memory. It shown that, until the scattered light is depolarized completely, the polarization and scalar contributions to the correlation function are of the same order of magnitude. As the slab thickness increases, their ratio falls off in inverse proportion to the thickness.

The problem of multiple scattering of polarized light in a two-dimensional medium composed of fiberlike inhomogeneities is studied. The attenuation lengths for the density matrix elements are calculated. For a highly absorbing medium it is found that, as the sample thickness increases, the intensity of waves polarized along the fibers decays faster than the other density matrix elements. With further increase in the sample thickness, the off-diagonal elements which are responsible for correlations between the cross-polarized waves disappear. In the asymptotic limit of very thick samples the scattered light proves to be polarized perpendicular to the fibers. The difference in the attenuation lengths between the density matrix elements results in a nonmonotonic depth dependence of the degree of polarization. In the opposite case of a weakly absorbing medium, the off-diagonal element of the density matrix and, correspondingly, the correlations between the cross-polarized fields are shown to decay faster than the intensity of waves polarized along and perpendicular to the fibers.

The problem of small-angle multiple-scattering of circularly polarized light in a two-dimensional medium with large fiberlike inhomogeneities is studied. The attenuation lengths for elements the density matrix are calculated. It is found that with increasing the sample thickness the intensity of waves polarized along the fibers decays faster than the other density matrix elements. With further increase in the thickness, the off-diagonal element which is responsible for correlation between the cross-polarized waves dissapears. In the case of very thick samples the scattered field proves to be polarized perpendicular to the fibers. It is shown that the difference in the attenuation lengths of the density matrix elements results in a non-monotonic depth dependence of the degree of polarization.

We show that a disordered ensemble of dielectric particles near the Mie resonances has anomalous depolarizing properties. Under the first Kerker condition the depolarization length of circularly polarized light reaches its peak value, and can be ten times greater than the transport mean free path. The second Kerker condition is shown to be satisfied as the refractive index of particles increases. In this case, the depolarization length is minimum and almost coincides with the mean free path.

The problem of the interaction of a shock wave with an anisotropic entropy perturbation field has been solved including second-order corrections to hydrodynamic quantities. It has been shown that nonlinear interactions between acoustic waves result in the localization of acoustic perturbations behind the shock front. This effect is observed when sound attenuation is absent in the linear approximation. The problem of the propagation of the shock wave in an incident sample, where the spatially anisotropic density perturbation field initially exists, has been numerically solved in application to the collision of two plates. Numerical calculations confirm the results of the theoretical analysis.

We study how the effect of circular polarization memory in a disordered ensemble of resonant Mie particles reveals itself in mesoscopic intensity fluctuations. It is shown that polarization of light enhances the fluctuations. In the vicinity of the first Kerker point, sharp changes in the depolarization rate result in a quasiresonant dependence of the variance of transmission coefficient fluctuations on the wavelength of light.