Second-harmonic generation by an obliquely incident s-polarized laser from an underdense plasma in the presence of a magnetic field has been investigated analytically. An expression for the relativistic factor γ has been obtained in the presence of magnetic field. The efficiency of second-harmonic radiation η has been obtained as a function of angle of incidence θ, normalized electric field amplitude of laser beam a0, normalized electron density ${\rm \omega} _{\rm p}^2 /{{\rm \omega} ^2}$, and magnetic field b. It is observed that γ increases with b. In turn, the conversion efficiency decreases with an increase in b. It is seen that the conversion efficiency is affected by the magnetic field due to the modified relativistic factor. In the absence of magnetic field, η increases with a0 and θ. However, in the presence of magnetic field, the conversion efficiency starts decreasing as the magnetic field is increased.

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.

The ab initio molecular dynamics (MD) simulations using an atom-centered density matrix propagation method are carried out in the first time to investigate the dissociative electron attachment (DEA) processes of adenine and its tautomer in the gas phase. Since the incoming electron are captured on the lowest π∗ anti-bond orbital, which is led to the different N–H bond, the C–H bond and the C–N bond are broken. The dominant anion observed in DEA dissociation process is the closed-shell dehydrogenated anion (Ade − H)−. The additional anions (Ade − NH2)− and (Ade − 2H)− are also obtained in ADMP simulation. The results are well consistent with the previous DEA experimental results. Thus, the ADMP method is used to gain a more intuitive and better understanding of the necessary dissociation process in the DEA experiment.

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.

We report the results of measurements aimed to check the phase lock of time-delayed, collinear, harmonic pulses and to verify the possibility of performing Ramsey-like spectroscopy in the XUV. We demonstrate that for harmonics of medium order and for the peak intensities available with our laser system, the generation of collinear phase-locked harmonic pulses is indeed possible and that such pulses can be used to achieve high-resolution spectroscopy in the short-wavelength region.

The main goals of the German program are the study of key issues of inertial fusion with intense beams of heavy ions. The completion of the new heavy-ion synchrotron and storage ring facility SIS/ESR at GSI opens new directions for experimental investigations on beam dynamics at high intensity and on beam/target interaction. In addition, new accelerator scenarios will be investigated based on non-Liouvillean beam-handling techniques.

High-temperature plasmas were produced by focusing 1·05 μm, 100 psec laser pulses onto Al layer targets at a mean irradiation of 3·1013 Watt/cm2. By means of simultaneous measurements of the thermal x-ray emission and the frequency-quadrupled laser pulse we observe a 20 ± 15 psec delay of the x-ray peak relative to the peak of the incident laser pulse. In addition, modulations on the trailing edge of the driving pulse appear strongly enhanced in the x-ray signature.

For real-time diffraction experiments in X-ray crystal research a simplified model is chosen to describe laser-generated plasmas. This enables a rough estimate of the optimum laser plasma parameters necessary to maximize the line emission of highly ionized species. Furthermore, the use of the hot electron spectrum of laser plasmas to generate ultrashort Kα-emission is discussed.

In this work, a new analytical potential for studying ions in excited configurations is presented, which is built up from a parametric potential for ions in a ground state. It is used to calculate atomic magnitudes of special importance in plasmas such as total energies, energy levels, and transition energies, for ions in excited configurations. The results are successfully compared with those obtained with both self-consistent or analytical models.

The ablation and acceleration of diamond-like high-density carbon foils irradiated by thermal X-ray radiations are investigated with radiation hydrodynamics simulations. The time-dependent front of the ablation wave is given numerically for radiation temperatures in the range of 100–300 eV. The mass ablation rates and ablation pressures can be derived or implied from the coordinates of ablation fronts, which agree well with reported experiment results of high-density carbon with radiation temperatures Trad in the range of 160–260 eV. It is also found that the $T_{{\rm rad}}^3$ scaling law for ablation rates does not apply to Trad above 260 eV. The trajectories of targets and hydrodynamic efficiencies for different target thicknesses can be derived from the coordinates of ablation fronts using a rocket model and the results agree well with simulations. The peak hydrodynamic efficiencies of the acceleration process are investigated for different foil thicknesses and radiation temperatures. Higher radiation temperatures and target thicknesses result in higher hydrodynamic efficiencies. The simulation results are useful for the design of fusion capsules.

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.

Discharge plasma channels have been investigated in recent years at Gesellschaft für Schwerionenforschung–Darmstadt (GSI) and at the Lawrence Berkeley National Laboratory in Berkeley, California, in a number of experiments. A short summary of the experimental work at Berkeley and GSI is given. Different initiation mechanisms for gas discharges of up to 60 kA were studied and compared. In the Berkeley experiments, laser ionization of organic vapors in a buffer gas was used to initiate and direct the discharge while at GSI, laser gas heating and ion-beam-induced gas ionization were tested as initiation mechanisms. These three initiation techniques are compared and the stability of the resulting discharge channels is discussed. A discharge current of 50 kA, a channel diameter well below 1 cm, a pointing stability better than 200 μm, and MHD stability of more than 10 μs have been demonstrated simultaneously in the recent experiments. These parameters are sufficient or close to the requirements of a reactor application depending on the details of the target design. The experimental results show that transport channels work with sufficient stability, reproducibility, and ion optical properties for a wide pressure range of discharge gases and pressures.

The problem of heavy-ion beam energy conversion into the plasma self-radiation of the spherical target is considered by using the radiative conductivity approximation. It is shown that there is a single parameter γ which determines the spherical ‘corona’ structure and has the meaning of the ratio: the ion range/the effective heat range. The conversion coefficient increases with the increase in the parameter γ and becomes ∼ 1, when γ ≃ 102. Typical beam and target parameters of modern HIF designs correspond to γ ≃ 10 and conversion coefficients >50%. Thus, at quasistationary stage of the ‘corona’ expansion the target acceleration and implosion regime is basically the radiative one.

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.

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.

We report time-dependent simulations of the evolution of atoms, molecules, and solids in the presence of intense electromagnetic radiation using the density functional theory. In the case of the ionic degrees of freedom we find that selective breaking of strong bonds may be possible at off-resonant infrared frequencies by a novel “concerted kick” mechanism. In the case of the electron response we find the following: free atoms and ions under intense infrared light respond with high harmonics in the X-ray regime; for a free molecule (Si2), we predict an unusual third harmonic response to a UV pulse centered at a frequency equal to the primary electronic excitation of the molecule; for a semiconductor (Si), we find several odd harmonics in response to a continuous wave of subgap infrared radiation. Prospects for future calculations are discussed.

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.