The conversion of kinetic energy into heat is a possible approach to get the very high temperatures needed for controlled fusion. Various techniques leading to hypervelocities are considered. Some particular geometries and constitutions of liners allowing velocity amplification and superheating are described.

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.

In the Bennett-Nordsieck self-pinched regime of high power REB propagation in a neutral atmosphere, radial expansion is generally associated with transverse entropy generation caused by elastic electron-neutral multiple scattering: LN ∝ 1/s′⊥ elast, where LN is the Nordsieck length, the distance for one e-folding of beam radius, and where s′⊥ elast is the elastic collision space rate of transverse mean entropy per particle.

For ultrarelativistic beams (γ ≳ 100), the bremsstrahlung, which is the dominant energy loss process, also plays an essential rôle in the radial expansion.

A general treatment could be based on the proper time evolution equation of the beam electron pressure 4-tensor pλμ (λ, μ = 0, 1, 2, 3) where source terms linked to elastic, inelastic and bremsstrahlung collisions are introduced, as is also a closure relation. This approach is currently being studied at LPPG.

When the various implied scale lengths have clearly different orders of magnitude, a much simpler approximate description may be given.

In the λmbrems < z < λstrbrems propagation distance range, where λmbrems is the depth threshold beyond which bremsstrahlung scattering becomes multiple, and λstrbrems a characteristic distance for bremsstrahlung straggling, the rôle of bremsstrahlung in radial expansion is similar to that of elastic multiple scattering. The calculated s′⊥ brems/s′⊥ elast increases rapidly with both propagation distance and beam electron energy. For γ ≫ 103, the bremsstrahlung transverse entropy source term s′⊥ brems is no more negligible before s′⊥ elast.

In the z > λstrbrems propagation distance range, where bremsstrahlung straggling is dominant, an evaluation of its effect is deduced by applying the Haftel–Lampe–Aviles criterion to a statistical study of this straggling. A completely different estimation, based on an oversimplified version of the above-cited general thermodynamic method, gives a result which is in rather good agreement.

A model of quasars and their associated jets as phenomena of magnetic selfcompression is presented. Magnetic field self-compression, as observed in laboratory plasma focus devices, results in increases in energy density of more than 108 and in even larger increases in transferred power density. Our model, based on the scaling of these phenomena to astrophysical dimensions, avoids the problems of gravitationallyconfined approaches. It presents a mechanism by which the energy of a quasar is immediately derived from a volume nearly 106 times larger than the observed quasar radiating volume and is ultimately derived from the volume of an entire protogalactic plasma cloud. The model's predictions of quasar energy, radiated power, lifetime, dimensions, density and rotational velocity are in good agreement with observations. Part II of this paper extends the model to radio galaxies and briefly discusses the role of similar self-compression processes in the origin of filamentary super-clusters of galaxies.

A model of quasars and radio galaxies and their associated jets is further elaborated here. The model, presented in Part I of this paper, is based on magnetic selfcompression as the process involved in producing extremely high energy densities. In the present paper, the results derived in Part I are used to predict radiation spectra from quasars, and to extend the model to radio galaxies. The role of magnetic self-compression of magnetic vortices in the origin of filamentary superclusters of galaxies is briefly discussed.

Both temporally and spectrally resolved fine structures of 90° lateral (3/2)ω0 harmonic emission were experimentally observed. The existence of (3/2)ω0 harmonic filaments is attributed to formation from the moving filament bottom at its transient nc/4 surface. The double hump structure with its intense red hump of laterally emitted (3/2)ω0 spectrum can also be explained by a Doppler correction in addition to the thermal correction. Estimation of both red and blue spectral shifts with our simple model is qualitatively consistent with experimental results. Experiments showed that the (3/2)ω0 emission was evidently suppressed by using a broad band laser. This may be promising for superhot electron suppression.

A theoretical model of resonance absorption initiated by self-focusing filamentation is proposed on the bases of experiments on the 2ω0 time resolved spectrum, slow ion emission and filamentation of 3ω0/2 emission. A number of aspects of the experimental results can be well explained by this model.

Wavelength dependent absorption in laser-plasma interactions was investigated by measuring the energy spectra of freely expanding plasmas in their asymptotic stage of expansion. The experiments were performed with both 1·06- and 0·53-μm-wavelength light incident on flat tantalum targets. The experimental conditions were chosen adequately to ensure that inverse bremsstrahlung was the dominating absorption mechanism. As a result it is found that the absorption is enhanced at the shorter wavelength by a factor of 1·3. Primarily this leads to a higher ionisation state of the plasma and higher kinetic ion energies and temperatures, respectively, while the amount of ablated mass is approximately the same.

A simple model in two dimensions is developed and solved analytically taking into account the electric and magnetic fields in laser produced plasmas. The electric potential in this model is described by the non-linear differential equation

ψ = eφ/T, where eφ is the electric potential energy and T is the temperature in energy units. The physical branch ψ < 1, defined by the electron density n = no exp ψ, boundary conditions n (x = 0) = const and n (x = +∞) = 0, introduces a typical electrostatic double layer. The stationary solution of this model is consistent for − 3 ≲ ψ < 1, with electron temperatures in the KeV region and a ratio of the electric (E) to magnetic (B) fields of [E/106 v/cm]/[B/MGauss] ∼ 1.

A key issue in the design of an HIF reactor cavity is the transport of the heavy ion beam from final focusing, across the cavity, to the target. Previous estimates have indicated that streaming instabilities will disrupt the beam transport for a background chamber gas pressure of 10−4 to 10−1 torr. The most attractive liquid lithium first wall reactor cavity designs produce a background gas density in just this pressure range. A detailed analysis of the streaming instabilities has now demonstrated that the beam can be transported through this background. The important fact that had been neglected is that a mode with a given wave number will grow for only a small fraction of the transport time, due to the changing beam and electron densities during transport. This analysis opens wide an attractive window for reactor cavity design.

Application of Fourier theory to heat conduction due to laser irradiation at high power intensities (i.e. 1010 W/m2) gives errors of the order of 30 per cent at the upper end of the temperature rise time. This is caused by the assumptions made in the Fourier theory, since the heat flux through a given plane depends on the electron energy distribution through the material. On the scale of distance required to examine the problem, the material can no longer be considered as being a homogeneous continuum and when the power intensities of interest are concerned, the higher order terms in the heat transfer equation become important. Therefore, the problem requires to be examined in the quantum field. Application of electron kinetic theory to the problem enhances the solution within an accuracy greater than 90 per cent. The present theory introduces a new model for the conduction mechanism.

The effects of microscopic energy deposition in hot, dense plasmas and radiation transport in plasmas, on the interaction of ion beams with plane metal targets are investigated in this paper. In order to do this we analyze the plasma dynamics of ablatively accelerated plane metal foils. The physical analysis of these results is achieved by the derivation of solutions of the non-linear radiation conduction equation with boundary temperatures which increase in time. We illustrate, by means of numerical simulations, how range shortening due to plasma effects such as increased energy loss to excited electrons and an increased effective charge due to a reduction in the recombination rate, may be compensated for by radiation transport. The effect of radiation transport and detailed microscopic energy deposition on ion beam implosions, including hydrodynamic instability, is discussed.