The electromagnetic acceleration of a metallic ring carrying a high current, combined with the mutual interaction of a concentrical conductor carrying the same current, in the presence of a DC magnetic field, results in a converging beam of particles reaching a velocity above 1000 km/s. Lithium, gold, and uranium rings are considered and transient temperatures ranging from 108 to 1010 °K are expected. In the presence of deuterium and tritium fusion reactions will occur and the capture of the released neutrons may result in the synthesis of heavier elements. The considered device lends itself to a varied treatment allowing to consider velocities in the range of 2000 km/s.

The experimental study of the plasma projectile acceleration in the laser-induced cavity pressure acceleration (LICPA) scheme is reported. In the experiment performed at the kilojoule PALS laser facility, the parameters of the projectile were measured using interferometry, a streak camera and ion diagnostics, and the measurements were supported by two-dimensional hydrodynamic simulations. It is shown that in the LICPA accelerator with a 200-J laser driver, a 4-μg gold plasma projectile is accelerated to the velocity of 140 km/s with the energetic acceleration efficiency of 15–19% which is significantly higher than those achieved with the commonly used ablative acceleration and the highest among the ones measured so far for any projectiles accelerated to the velocities ≥100 km/s. This achievement opens the possibility of creation and investigation of high-energy-density matter states with the use of moderate-energy lasers and may also have an impact on the development of the impact ignition approach to inertial confinement fusion.

In inertial confinement fusion the target implosion non-uniformity is introduced by a driver beams’ illumination non-uniformity, a fuel target alignment error in a fusion reactor, the target fabrication defect, etc. For a steady operation of a fusion power plant the target implosion should be robust against the implosion non-uniformities. In this paper the requirement for the implosion uniformity is first discussed. The implosion uniformity should be less than a few percent. A study on the fuel hotspot dynamics is also presented and shows that the stagnating plasma fluid provides a significant enhancement of vorticity at the final stage of the fuel stagnation. Then non-uniformity mitigation mechanisms of the heavy-ion beam (HIB) illumination are also briefly discussed in heavy ion inertial fusion (HIF). A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to a radiation energy smoothing. In HIF a wobbling HIB illumination was also introduced to realize a uniform implosion. In the wobbling HIBs illumination, the illumination non-uniformity oscillates in time and space on a HIF target. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs’ illumination non-uniformity by its smoothing effect on the HIB illumination non-uniformity and also by a growth mitigation effect on the Rayleigh–Taylor instability.

Two spherically symmetric versions of a self-similar collapse are investigated within the framework of the Zakharov equations, namely, one relative to a vectorial electric field and the other corresponding to a scalar modeling of the Langmuir field. Singular solutions of both of them depend on a linear time contraction rate Ξ(t) = V(t* – t), where t* and V = – Ξ denote, respectively, the collapse time and the constant collapse velocity. We show that under certain conditions, only the scalar model admits self-similar solutions, varying regularly as a function of the control parameter V from the subsonic (V ≪ 1) to the supersonic (V ≫ 1) regime.

Starting from the Riemann-Silberstein formulation of classical electrodynamics the Schrödinger equation for the photon energy wave function is discussed. Hereafter, a propagator description of the space-time emission of a polychromatic photon from an atom is presented, paying particular attention to the near-field electrodynamics. When the atom is embedded in a solid-state plasma the photon emission process can be dramatically modified. Limiting the analyses to solid-state plasmas exhibiting translational and rotational symmetry, the near-field atom-photon-plasma interaction is studied paying particular attention to the plasmariton and plasmon excitation processes. It is shown that the transverse and longitudinal parts of the plasma-screened field propagator link in a direct manner to the free-photon propagator and the longitudinal near-field photon propagator. The necessity of keeping both the transverse and longitudinal parts of the plasma screening in a rigorous description of near-field electrodynamics is demonstrated.

A two-dimensional simplified model of an HF chemical laser is introduced. Using an implicit finite difference scheme, the solution of two adjacent parallel streams with diffusion mixing and chemical reaction is generated. A contour of the mixing and reaction boundary is obtained without presupposition. The distribution of the HF(u) concentrations, gas temperature and the optical small signal gain (αu, J) on the flowing plane (X, Y) are presented. Compared with the solution solved directly from a set of Navier–Stokes equations, the results of these two methods agree with each other qualitatively. The influences of the different velocity, temperature (T0) and composition of the two streams on the small signal gain after the nozzle exit are investigated. It is interesting that for larger J with a fixed u, the peaks of αu, J—T0 profiles move towards higher T0. The computing method is simple and only a short computing time is needed.

Space-resolved spectra of line-shaped laser-produced magnesium plasmas in the normal direction of the target have been obtained using a pinhole crystal spectrograph. These spectra are treated by a spectrum analyzing code for obtaining the true spectra and fine structures of overlapped lines. The spatial distributions of electron temperature and density along the normal direction of the target surface have been obtained with different spectral diagnostic techniques. Especially, the electron density plateaus beyond the critical surface in line-shaped magnesium plasmas have been obtained with a fitting technique applied to the Stark-broadened Ly-α wings of hydrogenic ions. The difference of plasma parameters between those obtained by different diagnostic techniques is discussed. Other phenomena, such as plasma satellites, population inversion, etc., which are observed in magnesium plasmas, are also presented.

The article presents the multigroup kinetic approximation of radiation transport in hohlraum systems. The view factor-based method of numerical solution is proposed. Its advantages are a detailed account of the problem geometry and accurate handling of the solution angular anisotropy and discontinuities. The method is computationally efficient and easily parallelizable. Coupled to the kinetic + hydro description of the wall dynamics, it represents a powerful tool for integrated investigation of the systems with strongly inhomogeneous optical properties.

Intense laser light incident on solid targets has been shown to be a prolific source of harmonics. High harmonic intensities are characterized by a power-law spectrum Pm~m−p, where p denotes a spectral decay index and m is the harmonic number. Across a wide range of light intensity and target plasma density, particle-in-cell (PIC) simulations have shown p = 8/3, a value supported by the observation. However, the claim that this decay is universal has been contested and shown to break down in simulations when the incident light is P-polarized. Here weaker decays with p = 5/3 and at higher intensities p = 4/3 were observed. The distinction between the two regimes was attributed to the contribution to the spectrum from emission at the plasma frequency and its harmonics from Langmuir waves excited by the Brunel electrons generated when the incident light is P-polarized. In the present work, a single-particle model has been devised to lend support to a wide range of PIC data. The model incorporates a Langmuir electric field and is hybrid in the sense that we have made use of PIC output to guide our choice of field amplitudes in the Langmuir source. We find that the spectrum computed in this way shows generally satisfactory agreement with the corresponding PIC spectra, both in decay coefficient and spectral cut-off. At the highest intensities considered the emission from the convective bunching of electrons in high-amplitude Langmuir waves is itself superseded by Brunel electron bremsstrahlung and we have identified the regions of parameter space over which each of these sources is dominant. Interestingly, the same distinction has been drawn in a very different plasma regime where comparably complex spectra have been predicted in gamma-ray burst spectra from Langmuir turbulence produced in astrophysical jets.

A detailed investigation of many aspects of the physics of laser–plasma interaction at very high laser intensities is required in order to assess the feasibility and the promise of the fast ignitor scheme for inertial confinement fusion. Relevant results, obtained in a series of experiments carried out at the Rutherford Appleton Laboratory, Chilton (UK) and at the Centre d'Etudes Atomique, Limeil Valenton (France), are presented and discussed here. In particular, the formation of plasma channels was observed following the propagation of relativistically intense, ps laser pulses through underdense plasmas. The channels persist long after the interaction, and their expansion has been measured. Efficient guiding of ultraintense laser pulses, both through preformed density channels and through solid guides, has been demonstrated. Finally, indication of collimated fast electron propagation through solid targets has been obtained from the observation of filamentary ionization tracks in laser irradiated solid targets.

Results for the energy spectra of the electrons scattered on a potential in the presence of a bichromatic field of frequencies ω and 2ω are obtained based on 1D numerical integration of the time dependent Schrödinger equation. Both the perturbative and the nonperturbative regimes are investigated for low scattering energies and a laser frequency that is close to that of CO2 lasers. Special attention is paid to the influence of the relative phase between the harmonic and the laser field on the features of the laser-assisted signals.

Experimental results are presented on the focusing of an intense microsecond relativistic electron beam. The beam is generated in a high-voltage quasi-planar diode (E = 600–800 keV, τ = 3–5 μsec). It is then magnetically – focused by longitudinal injection into a magnetic mirror. The total energy of the beam is about 50 kJ. The focusing chamber is filled with argon under a pressure varying from 3 × 10−5 to 1 torr. The results include investigations of beam focusing under various conditions, the dynamics of the return current in the plasma as well as the influence of the reflected beam electrons on the operation of the accelerator diode. A 20-fold focused beam with a 4 cm diameter, 46 kJ energy content, and current density up to 3 kA/cm2 was obtained.

A new method of intense relativistic electron beam modulation at frequencies up to ∼1 GHz is suggested. Current modulation is provided by using the azimuthal magnetic field of the beam to control the beam reflection from the magnetic mirror. The results of computer simulations for a 2-MeV, 20–50-kA beam are presented.

The knowledge of the properties of atoms in high-temperature/density plasmas is of deep interest in many fields of physics. Theoretical studies and interpretation of the inertial confinement fusion experiments is one of the examples. On the basis of the density functional formalism, a model of matter at extreme conditions is presented. Application of the model is illustrated by examples of average ionization state and equation of state calculations.

Atomic modeling of high-Z partially ionized plasma is essential for simulating radiation hydrodynamics of laser-produced plasma. A collisional-radiative model based upon an average atom model is used to calculate plasma opacity and emissivity. Because line radiations are most dominant in such plasma, the detail configuration accounting (DCA) for electronic state is required. We propose a statistical method to carry out the DCA with the use of the average population of bound electrons. Further modeling of line group made of the same transition from ions in different change states is discussed by considering the detail structure (hierarchy) of the line group.

Analytical study of the linear stability of one-dimensional double layers in nonmagnetized plasmas based on the solution of the Vlasov–Poisson system is presented. Electromagnetic effects are not included. A self-consistent equilibrium electrostatic potential Φ0(z) that monotonically increases from a low level at z = − ∞ to a high level at z = + ∞ is assumed. We model this potential as a piecewise continuous function of z and we assume that Φ0(z) has constant values for − ∞ z ≤ 0 and L ≤ z < ∞, L being the thickness of the double layer. The BGK states for the Vlasov–Poisson system provide an explicit expression for the velocity distribution of the reflected electrons required for the particular double layer configuration. The stability of the double layers is studied via the linearized Vlasov and Poisson equations using the WKB approximation.

The intrinsically nonperturbative “vacuum persistence probability” P for e + e− production in the overlap region of a pair of high-intensity lasers is estimated in the context of three models, each of which adapt and simplify the exact Fradkin representation for the logarithm of the fermion determinant in the fields of the crossed lasers. In each case, one finds for P an expression resembling Schwinger's 1951 result for the probability of pair production in a constant electric field, proportional to an exponential factor which contains an essential singularity and hence does not admit a perturbative expansion about zero coupling. Qualitative estimates of these models suggest that realistic yields for this form of e + e− production must await lasers of intensity 1029 W/m2. The possibility of producing a quark–antiquark pair in this way is noted, in particular, with temporary, but large separations of the qq.

A study of the effects of photoionization of a laser-produced plasma has been carried out by modeling the fluorescence of resonance lines due to cascades. The photoionization source is the X-ray M-band emission of a laser-produced high-Z plasma and it perturbs a ground state He-like aluminum plasma. Simulations have been performed to study the conditions necessary to maximize the fluorescence and guide future experiments. A collisional-radiative model is used to determine the optimal temperature and density of the pumped plasma, while hydrodynamic models are used to produce realistic plasma gradients and explore the optimum time delay of the photopumping.