Compact sources of high-energy particles and secondary radiation based on the interaction of high-power laser pulses with plasma targets are of interest due to a possibility of their application in a wide range of practical problems. One of the ways to optimize such sources is related to the possibility of controlling the preplasma of a solid target by changing the density gradient of the expanding plasma plume on the irradiated side. The problem of accelerating charged particles by a short laser pulse from targets with a preplasma generated by a nanosecond prepulse (additional pulse) of different intensity and duration is considered. Using self-consistent hydrodynamic/kinetic simulation, the efficiency of electron acceleration is shown to depend not only on the gradient of the preplasma density profile, but also on the focusing point of the laser pulse on this profile.

We report a study of electron beams and gamma radiation generation from targets with a preplasma and from targets with an extended plasma of near-critical density on the irradiated side. It is shown that for a laser pulse with an energy of about 1 J, a uniform layer of critical density makes it possible to generate a significantly larger number of high-energy electrons compared to targets with an exponentially decaying preplasma profile produced by the prepulse. The bremsstrahlung gamma radiation spectra of accelerated electron beams in a converter target are constructed, and the possibility of converting the laser pulse energy into gamma radiation energy (with photon energies above 1 MeV) at a level of 5

In this work, we study plasma that arises during the interaction of laser radiation with a target. Depending on the parameters of the laser pulse, the resulting plasma can have a significant impact on the efficiency of acceleration of charged particles.

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.

At present, a significant part of experiments on the interaction of high-power short laser pulses with solid targets is faced with the problem of target modification under the action of a nanosecond prepulse. In this paper, a series of hydrodynamic calculations of target irradiation with a nanosecond laser pulse is performed, which describes the plasma density profiles arising during the target expansion as a function of the parameters of the laser prepulse/additional pulse. The results obtained can make it possible to improve the efficiency of ion acceleration in the interaction of short laser pulses with a profiled plasma target.

The computational and theoretical analysis carried out in this article demonstrates the existence of a nontrivial mechanism for the compression of a submicron-sized gas bubble formed by a gas of classical ions and a gas of degenerate electrons. This mechanism fundamentally differs from conventional compression mechanisms. It is shown that taking into account the quantum effect of a large spatial scale in the distribution of electrons qualitatively changes the character of cumulative processes. Because of a large-scale electric field caused by quantum shell effects, the compression process is characterized by the formation of multiple shock waves. The values of gas temperature and pressure achieved during compression occur higher by two orders of magnitude as compared with the classical adiabatic regime. The analysis is carried out within the framework of the following model: the dynamics of the electron subsystem is described by equations of a quantum electron fluid, while the hydrodynamic approximation is adopted for the ionic subsystem. The large-scale effect is taken into account by means of effective external field acting on electrons. The theoretical analysis carried out within this approach clarifies the nature of the cumulative process in the system under consideration; some quantitative characteristics obtained with numerical simulation are presented. The possibility of experimental observation of this cumulative mechanism is analyzed. It is suggested that the manifestation of the effect can be observed during laser compression of a system of submicron targets by measuring the neutron yield.

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 September 2012 outburst of the type IIn supernova 2009ip was simulated using two independent codes, STELLA and FRONT. The UBVRI light curves obtained agree well with one another and with observational data. Special attention is given to the dynamics of the emerging dense shell, which determines the luminosity of the object and is used for the direct method of determining the distance to the supernova. Two-dimensional spectral radiation-hydrodynamics computations of the SN 2009ip model were carried out, which confirmed the conclusion about the stability of this shell on the times scales of the method application.

When a light beam enters a scattering-dominated medium, the radiation is isotropized. Part of the radiation goes backwards, leading to non-monotonicity in the radiation energy density profile inside this medium. There arises a local maximum at which the energy density at a scattering albedo ∼1 is severalfold greater than that without scattering at the same extinction. This effect is studied numerically in one-dimensional and two-dimensional simulations. It is demonstrated that a local maximum of the radiation energy density arises in the medium, whose value depends on the optical depth of the region. This effect can manifest itself, for example, when the radiation from a gamma-ray burst (GRB) enters heated regions in the interstellar medium. The presence of scattering in the GRB radiation generation region, near the front of strong shocks, affects the radiation pattern. The structure of such shocks is remarkable for the presence of a preshock preheating tail. Strong scattering in this region leads to the escape of a significant fraction of the radiation sideways and backwards in the shock reference frame, forming additional tails in the angular distribution of GRB radiation after the relativistic transformation to the laboratory frame. This effect is also studied numerically in three-dimensional simulations.

Still unreachable sub-GeV scale laser-accelerated ion energies per nucleon, necessary for a number of practical applications, can be obtained using a new generation ultrashort-pulse laser XCELS. To accelerate ions to such energies, it is proposed to use low-density targets obtained, for example, as a result of pre-irradiation of a solid-state foil with an additional, longer laser pulse. Targets with controlled preplasma on the front side make it possible to significantly increase the efficiency of electron heating and subsequent acceleration of ions by the charge separation field from the rear side of the target. This, in general, classical acceleration mechanism is compared with the recently proposed mechanism of synchronized acceleration of ions by slow light. The PIC simulation of laser acceleration of protons is supplemented by hydrodynamic calculations to find the optimal preplasma profile, which allows high-energy particles to be most efficiently generated. The possibility of generation of a large number of protons with a 1 GeV energy-scale is demonstrated.

We compare the results of our computations of a simplified one-dimensional model for a type II supernova with a free expansion stage by the STELLA and FRONT codes that are based on different hydrodynamic approaches. We describe the problems that arise in numerical simulations of such supernovae on Eulerian grids using explicit schemes and possible ways of their solution. The profiles of physical quantities and the light curves of a model supernova obtained using these different approaches are shown to agree well with each other. We have also demonstrated that the light curve of such a type II supernova in the $$UX$$ band has a characteristic double-peaked structure. The amplitudes of both peaks virtually coincide between themselves, while the duration of the second peak is longer than that of the first one by orders of magnitude.

High gradients of electron temperature appear in plasma corona under direct laser irradiation of inertial confinement fusion targets. This results in nonlocality of heat transport. Such effect influence the efficiency of laser absorption, redistribute heat fluxes and could preheat plasma ahead the front shock wave, therefore alter the compression adiabat. Ignition requires a specially tuned compression dynamics, so such an effect should be taken into account. Target simulations with nonlocal models show the decrease of compression efficiency and hot-spot parameters degradation compared to local models: Spitzer–Härm model with and without flux-limiter.

The influence of neutrals on the development of multidimensional dense-shell instabilities in supernova remnants is investigated. We present a model in which the neutrals are described as a permanently present additional medium (with its own parameters: temperature, density, velocity, etc.) that interacts with the ion component through collisional processes. Within this model we have found that the presence of neutrals suppresses the growth of instabilities in the case where they dominate in the total density of the medium.

Nucleosynthesis at the deflagration stage of a white dwarf is considered. Burning calculations have been made with the previously developed hydrodynamic model implemented in the FRONT3D code including turbulence. The trajectories of passive particles used thereafter for nucleosynthesis simulations have been created through the hydrodynamic calculations. The abundances of elements from oxygen to iron and nickel calculated in the developed nucleosynthesis model are shown to be in agreement with both observations and calculations based on other models.

Radiation–matter interaction depends mainly on the state of matter (its density, temperature, etc.), and also on the radiation spectrum. The opacity of thick plasma also depends on plasma velocity—the Doppler effect shifts atomic lines. For the cases when there are many bound–bound transitions, i.e., the plenty of lines contribute to the opacity, the latter is enhanced when the plasma expands with a nonuniform velocity field. It is known as “expansion opacity” in the literature. Existing models are discrepant and predict diverse results in some cases. Here, we present a rigorous derivation of the effect and show that the effect is available for experimental study at modern laser facilities. The plasma created by a Cu target irradiated with an ∼100 J nanosecond laser pulse is rich in lines and has enough expansion velocity so that its opacity is increased in the spectral range ∼102−103 eV by the order of magnitude. The possible experimental measurement of the effect is briefly discussed.

Superluminous supernovae can be explained by the interaction of their ejecta with a dense circumstellar medium. The resulting shock boosts the radiative luminosity of the supernova by converting mechanical energy into radiative energy. Accurate modeling of the shock, which suffers high radiative losses, requires the use of radiation hydrodynamics. High-precision methods have a large computational cost, so approximations are generally used. In this paper, we describe the implementation of the M1 approximation of radiation transfer using the hydrodynamics code, front . Basic tests show good agreement with reference solutions and with results from other codes. Additional tests were undertaken to show some cases where the M1 method produces unphysical results, such as in the regions where the light beams intersect each other. Tests with outgoing rays are also presented to validate the use of the M1 approach in supernova simulations. Further, a simple initial model for a superluminous supernova was created to study the shock-interacting mechanism. It is shown that the M1 approach correctly reproduces both the bolometric light curve of the supernova in one-dimensional, spherically symmetric simulations, as well as the dynamics of the thin dense layer that arises in this scenario due to extreme radiative cooling. The thin layer is unstable in multidimensional simulations, but the perturbations do not drastically change the photosphere’s parameters at the beginning of the simulation and do not strongly affect the light curve during the first 50 days.