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.

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%.

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.

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.

This paper presents a survey of selected results of laboratory experiments and numerical simulations of plasma double layers. Emphasis is given to discrimination between features peculiar to the experimental or numerical investigation and results which may have general implications for double layers in space similar to that of laser or particle beam produced plasma. The discussion concentrates on certain aspects pertaining to dynamics, structure, and stability of double layers considering the effects of boundary conditions (trapped particles, Bohm conditions, and applied potentials), waves and turbulence, collisions, and volume ionization.

Recent progress in research on Light Ion Beams-Inertial Confinement Fusion (LIB-ICF) at ILE, Osaka University is summarized. We report on pulsed power compression using PEOS, a super high voltage source, on diode physics, on beam trajectory control for focusing, on beam-target interactions and on a conceptual reactor design (Rokko I) in this article.

The free expansion of a heated mass of uniform gas (e.g. a laser produced plasma) can be modelled by self-similar motion with a linear velocity gradient. Using a series of numerical solutions we have shown that a reasonable representation is obtained by the use of a matching parameter relating the scale lengths in the prototype and its model, and that the representation improves as the ratio of the heating and disassembly times increases. In this paper we re-examine these two inferred results, and re-derive them on an analytic basis. The extension of the theory to multi-structured bodies shows that such systems of symmetric form allow self-similar motion, as does the particular case of an asymmetric one-dimensional foil. The case of isothermal foils is examined in detail to illustrate the derivation of the matching conditions.

A harmonic generator of submillimeter wavelength radiation, operating on a relativistic electron beam, is proposed. The device is shown to operate on principles of parametric interactions, under the particular conditions of an electric-quadrupole pump field which is propagating synchronously with the electron beam. Using a fluid model, it is shown that a cascade of parametric sum and difference frequencies in the transverse beam modes should occur, with each harmonic component growing convectively along the beam. The physical effect, termed the “sonic condition”, has been observed previously on a non-relativistic device emitting output radiation in the UHF range. A realization for relativistic beams is proposed, using an FEL structure as the parametric pump, a closed waveguide synchronous pump region and an output coupling of the gyrotron type. Possible advantages over the present state-of-the-art for high-power submillimeter electron-beam devices are discussed.

Pinched electron beams emit high power microwaves by formation of a virtual cathode. Radiation occurs simultaneously with pinching or slightly thereafter. Observations of strong electrostatic fields and the partitioning of current into reflexing and transmitting populations at the same time that microwaves are emitted indicate virtual cathode formation. Microwaves originate mainly from the virtual cathode side of the anode. A two-dimensional model for the electron flow in the presence of a virtual cathode is presented. The model allows for electron reflexing and velocity distribution spread. Solutions with strong radial flow agree closely with microwave measurements, and result in the microwave frequency scaling linearly with diode current.

Diode experiments that trigger the anode plasma formation by external radiation have been carried out with the goal of producing a pure beam of metallic ions. The anode of a race-track-type MID, which is coated with a sodium film in situ by vapor deposition, is synchronously irradiated by radiation emitted from a vacuum diode. Pure beams of Na+ are extracted only under operation with the radiation trigger. The current density reaches the Child–Langmuir limit.

Polarization dependent light absorption in laser produced plasmas of small focal diameters (28 μm full 1/e2 width) has been investigated simultaneously in five different channels of observation: specular reflection of the laser light, second harmonic (2ω) generation, charge and velocity distribution of the emitted ions and ablation pressure to the target. The experiments have been performed using a Nd-YAG mode locking pulse (λ = 1·06 μm, λ = 45 ps) which has been focused onto plane, thick plexiglass (C8H5O2) n disks to intensities up to 1014 W/cm2. As a result of the small focal spot size, a very small density scale length of 0·6 μm is derived from the resonance curves, consistently, for all channels of diagnostics.

Ultrahigh axial magnetic fields have been compressed and measured in a gas-puff Z pinch. A 0·5-MA, 2–cm-radius annular gas-puff Z pinch with a 3-minute repetition rate was imploded radially onto an axial seed field, causing the field to compress. Axial magnetic field compressions up to 180 and peak magnetic fields up to 1·6 MG were measured. Faraday rotation of an argon laser (515·4 nm) in a quartz fiber on axis was the principal magnetic field diagnostic. Other diagnostics included a nitrogen laser interferometer, x-ray diodes, and magnetic field probes.

The magnetic field compression results are consistent with simple snowplow and self-similar analytic models, which are presented. The axial magnetic fields strongly affect the Z pinch dynamics. Even small axial fields help stabilize the pinches, some of which exhibit several stable radial bounces during a current pulse.

The method of compressing axial fields in a gas-puff Z pinch is extrapolable to the order of 100 MG. Scaling laws are presented. Potential applications of ultrahigh axial fields in Z pinches are discussed for x-ray lasers, inertial confinement fusion, and collimated sources of gamma radiation.