The phenomenon of electric double layers in plasmas as a generalization of ambipolar effects and as an essential time dependent and oscillating phenomenon in the plasma interior, has emerged from studies in laser produced plasmas as well as from similar problems in space plasmas and their laboratory simulation experiments. While these results have been published occasionally in various places including the most prestigious journals and in small topical conferences, there was still a need to enter a more comprehensive presentation and overview into a referred journal.

A new method to focus a relativistic charged particle beam is suggested and studied. This idea is based on the use of the ponderomotive force which arises when a periodic electromagnetic field is created, as in the case of two crossed laser beams.

Recent experimental and theoretical research on intense pulsed particle beams involving the ETIGO Project at the Technological University of Nagaoka is reviewed. Experimentally, we review the following: (1) studies on local divergence angle in parameter space, (2) development of self-magnetically insulated “Plasma-Focus Diode,” (3) beam focusing by z-discharged plasma channel, (3) measurement of ablation process of beam-target interaction, (4) time-resolvable measurement of energy and species, (5) inductive postacceleration of highly neutralized ion beam, (6) construction of new pulse-power machine, and pulse-compression experiment by plasma erosion opening switch. A brief summary is also given on the development of 2.5-dimensional particle-in-cell computer simulation code.

Current driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur in extragalactic jets for estimated values of the carried currents. Strong plasma double layers, however, may exist within self-maintained density cavities. The relativistic double-layer-emitted electron and ion beams drive plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layeremitted electron beams may also emit polarized radio waves via a collectivebremsstrahlung process mediated by electrostatic two-stream instabilities.

Self-focusing of laser beams in plasma is studied analytically using the thermal (collision produced) and ponderomotive (nonlinear force produced) effects based on the model of Zakharov with solutions of the nonlinear Schrödinger equation. A basic difference appears if the electric field amplitude E is less than the threshold Eth (at which the electrodynamic energy density is equal to the gasdynamic pressure) from the contrary case, E > Eth.The length of the filamentation process is evaluated and results in large values for E below Eth.

Ponderomotive force initiated laser self focusing can be enhanced by relativistic electron motion in a laser plasma. We derive the nonlinear refractive index due to relativistic effects and find that relativistic self focusing becomes important for a 0·25 μm laser when the laser intensity exceeds 5 × 1018 W/cm2.

Double layers in plasmas can be created by different means. For example, a potential difference forms between two plasmas with different temperatures (Hultqvist 1971; Ishiguro et al. 1985), in a plasma jet flowing along a converging magnetic field (Serizawa & Sato 1984), in a quiescent plasma submitted to an external difference of potential or in a turbulent plasma carrying an electric current. The first three cases can be current-free, but not necessarily, although the numerical simulations have been made under such conditions for the first two points (Ishiguro et al. 1985; Serizawa & Sato 1984). Apart from the third case, which is mainly of interest for laboratory experiments, these double layers are good candidates for accelerating the auroral electrons to the few keV observed.

Fully electromagnetic, relativistic, two-dimensional, particle-in-cell (PIC) simulations of barrel-type and extractor-type Applied-B ion diodes have increased our confidence in the design of present and future diodes for the Particle Beam Fusion Accelerator II (PBFA II). In addition, the data from various experiments on Pro to I, Proto II, and PBFA I Applied-B ion diodes are inconsistent with previous models of diode operation, based on anode-cathode gap closure from expanding plasmas. A new model has been devised and applied to the PBFA II diode to explain the diode impedance and its time history, and to suggest methods for controlling the impedance.

An ion diode, where the insulating magnetic Bθ-field is produced by the diode current itself, has been investigated. Using a novel Thomson-parabola spectrometer that is capable of detecting up to 41 beam traces at a single shot and a carbon activation diagnostic the ion beam has been analyzed. The diode, operating at “KALIF”, delivers ion beams of 750 kA at energies of about 0·7 MeV. The focusing version of the diode shows a focus size of 1 cm2, the beam is neutralized to 98–99%, the proton content is about 60%.

This paper discusses the principles of reduction of quantum noise in optical radiation. The dynamics of photon number fluctuations in direct and cascade two-photon processes is investigated. The paper considers the cases of absorption and emission for the fields originally prepared in coherent and thermal states. It is shown that photon antibunching and bunching should occur for the passed radiation. The photon antibunching effect is only in definite time intervals of field interaction with resonance absorbing or emitting systems.

The possible cases of accumulation of photon antibunching effects are considered.

Double layers (i.e., electric fields parallel to B) form along auroral field lines in the Earth's magnetosphere. They form in order to maintain current continuity in the ionosphere in the presence of a magnetospheric electric field E with ∇. E ≠ 0. Features which govern the formation of the double layers are: 1) the divergence of E; 2) the conductivity of the ionosphere; and 3) the current-voltage characteristics of auroral magnetic field lines. Astrophysical situations where ∇. E ≠ 0 is applied to a conducting plasma similar to the Earth's ionosphere are potential candidates for the formation of double layers. The region with ∇. E ≠ 0 can be generated within, or along field lines connected to, the conducting plasma. In addition to ∇. E, shear neutral flow in the conducting plasma can also form double layers.

Various aspects of the pulsed power research program at Ecole Polytechnique are reviewed. Topics include a surface and a flashboard switch, the development of plasma guns for both switching and z-pinch diodes, and studies of beam control and synchronization.

High-power relativistic magnetrons operating in both S-Band and X-Band (4 GHz) and 8·5 GHz) have been developed with a variety of extraction methods. Using a six window radial extraction scheme, the S-Band magnetron produces ∼3·6 GW. The X-Band magnetron produces 0·05 GW with one radial extraction window. Axial extraction from all six vanes produced power in excess of 0·3 GW. Enhanced erosion and gap closure occur in the smaller X-Band resonator.

An experiment to study the physics of merging and of focusing ion beams is under development at the Lawrence Berkeley Laboratory. In this design, parallel beams of ions (C+, Al+, or Al++) are accelerated to several MV and merged transversely. The merged beams are then further accelerated and the growth in transverse and longitudinal emittance is determined for comparison with theory. The completed apparatus will be used to study problems associated with focusing ion beams to a small spot as required for heavy ion fusion. Details of the accelerator design and considerations of the physics of combining beams are presented.

We investigate the Fokker–Planck Equation (FPE) in which we retain electron–ion and electron–electron collision terms, as well as the inverse-bremsstrahlung absorption term. We exhibit asymptotic solutions, which are then used in a linear perturbation theory ‘à la Spitzer’, to calculate local transport coefficients. Their values can differ drastically from classical results, which in turn alters hydrocode simulations.

The Pseudospark is an axially symmetric, high-voltage gas discharge operating at pressures below 100 Pa. It is capable of producing pinched high current ion beams. Streak camera photographs of the operation of this discharge reveal that a pinch with a diameter of ∼1 mm occurs in the diode. The beam then expands to about 1 to 10 mm in a distance of 12 cm. The beam-target interaction shows a UV-emitting plasma corresponding to protons with a main energy of 100 keV and a current density of about 16 kA/cm2. Initial theoretical results for the pseudospark are given.

The formation of a double layer is proposed as the mechanism which produces the critical velocity phenomenon. We examine this hypothesis, qualitatively, and find that the double layer can be a very efficient mechanism for transferring the kinetic energy of the neutral gas into the kinetic energy of electrons which, in turn, will ionize the neutral gas if the critical velocity has been reached or exceeded.