In this work the construction characteristics and performances of a laser system operating with an e-beam sustained discharge are described. Operating with XeCl, the laser pulse energy is over 4 J. Details of the measurements on the system are also reported.

The longitudinal resistive microwave instability in storage rings has been identified in previous workshops as a key problem in heavy ion fusion. Here we show by means of computer simulation that the predictions from the linearized theory of instability are over-pessimistic in the case of non-relativistic ions. This is due to an early nonlinear saturation of the instability caused by the formation of a thin stabilizing tail of the momentum distribution, which provides enough Landau damping to suppress further growth. The main condition for this non-destructive self-stabilization lies in the slow resistive growth rate, as compared with the large coherent frequency shift induced by space charge. The important conclusion from this is a significant extension of the stable storage ring filling time to values that are comfortable from a design point of view. For the HIBALL reactor driver accelerator a safe storage time of 5 to 10 msec is expected, instead of only 1 msec according to the linearized theory e-folding times.

Radiation of a system of isomer nuclei due to an electromagnetic transition with change of momentum J2–J1 and directly connected to exchange of a magnetic interaction was investigated. Such an interaction may be a magnetic exchange interaction of the Ruderman-Kittel or Sull-Nakamura type as well as any other type of interaction resulting in nuclear ferromagnetism at T<Tc. The initial state of the system is prepared by the quick cooling technique at T lower than Tc, the nuclear ferromagnetic temperature. It is shown that this initial state has a full symmetric wave function (which is the eigenfunction of the whole Hamiltonian as well as operators R2, Rz, J2,JZ) and the maximum value of the cooperation number. This method of initial state preparation in this range of frequencies replaces the π/2-impulse technique in optics. The superradiance intensity of the system from a waveguide is found, assuming |κ| = const for angles from zero to the Bragg angle.

An analysis is made of the equation of state problems in inertial confinement fusion. After reviewing the need for compression for inertial confinement fusion along the lines of the classical self similarity model which is derived in a modified way with indications of the equation of state, the problems of the central core ignition are examined with respect to the equation of state. A basic difficulty is elaborated in the ‘scape goat diagram’. After describing alternative compression schemes such as non-linear force and cannon ball, the two temperature equation of state is developed with electronic and ionic contributions following the ideal gas, the Debye-Grüneisen equation of state, the solid-gas interpolation and the SESAME tables. A remarkable discrepancy for the isothermal diagrams is shown between the general result and the result based on the earlier McCarthy–Kalitkin scheme.

A heavy ion fusion (HIF) system, named HIBLIC (Heavy Ion Beam and LIthium Curtain) is conceptually designed. The driver system consists of RF linacs (RFQ linacs, IH linacs and Alvarez linacs), storage rings (one accumulator ring and three buncher rings) and beam transport lines with induction beam compressors. This accelerator complex provides 6 beams of 15 GeV208Pb1+ ions to be focused simultaneously on a target. Each beam carries 1·78 kA current with 25 ns pulse duration, i.e., the total incident energy on the target is 4 MJ, 160 TW per shot. Superconducting coils are used in most parts of the magnet system to reduce power consumption.

Focusing properties and mechanisms are experimentally investigated of an intense pulsed light-ion beam or a medium-mass ion beam extracted from racetrack type magnetically insulated diodes. Quantitative determinations are made for three factors that affect the focusing ability of the beam, i.e., local divergence angle, deviation angle from ideal trajectory and space-charge effect. Behaviour of electrons in an anodecathode gap as well as neutralizing process of the ion beam by electrons are studied in connection with beam focusing. It is found that there is a close correlation between ion yield and electron irradiation on the anode. By adopting a perforated cathode instead of a vane cathode to ensure good uniformity of electric field in the accelerating gap, we have succeeded in significantly reducing the divergence angle. Several new diagnostic techniques and methods have been developed, yielding information such as the time-resolved trajectory and profile or incident angle of the beam. Electron temperature of the anode plasma is theoretically anticipated from the ions observed experimentally. From an estimate of beam divergence due to a space-charge effect, it is suggested that ‘breakeven’ can be achieved without using conventional z-discharged plasma channels if a bunch of boron beams is utilized.

The experimental generation of fusion neutrons in low power and voltage deuterium RF discharges with plasma solitons is analyzed here on the basis of recently derived high internal electric fields present in non-uniform plasmas. Ion oscillation energies of 10 keV are derived and provide an explanation of the observed neutron generation rate of 105 per second.

Both broad and narrow band Nd glass laser beams with energies 1 to 3 joules and pulse width 150 ps were used in aluminium plane target experiments at laser irradiances 1 to 3 × 10 14 W cm −2 on target surfaces. The incident laser beams were angled at 0°, 7·2°, 14·4°, 21·6°, 28·8°, 36°, 43·2° to the target surface normal and the polarization was perpendicular or parallel to the incident plane (s or p polarization). The experiments showed that the maximum resonance absorption occurred near to incident angles of about 9° to 10° and the broadband resonance absorption was slightly smaller than that of the narrowband. At large incident angles the broadband absorption was larger than that of the narrowband.

The physical mechanisms of thermal flux limitation and thermal conduction inhibition in laser plasmas are analyzed. A numerical calculation accounting for the non-negative electron distribution function and pressure gradient has been given.

In 1982 to 83 a preliminary conceptual design of a heavy-ion-driven inertial fusion (HIF) system, called HIBLIC-I (Heavy Ion Beam and LIthium Curtain) was worked out (The Working Group on ‘HIBLIC-I’ 1984). Its principal aims are: (i) to find out the critical issues in this approach to fusion power plant, (ii) to assess its feasibility and (iii) to promote good collaboration between different fields (such as accelerator physics, plasma science and reactor technology) and of different institutions in Japan. (Obayashi 1981; Hirao 1982).

Spectral structure of various half harmonic (ω0/2, 3ω0/2 and 5ω0/2) emission from an inhomogeneous plasma is analyzed. Several interaction mechanisms are studied and the effects of plasmon refraction and reflection are included in the analysis. These modify earlier results of the homogeneous plasma model considerably and increase the number of possible coupling configurations. The predictions of results in the different lasertarget experiments are discussed.

Intense colinear laser beams ω0, k0 and ω1, k1, shone on a plasma with a frequency separation equal to the electron plasma frequency ωpe are capable of creating a large coherent longitudinal electric field EL = mcωpe/e of the order of 1 GeV/cm for a plasma density of 1018 cm-3 by the laser beat excitation of plasma oscillations. Accompanying favourable and deleterious physical effects using this process for a high energy beatwave accelerator are discussed: longitudinal dephasing, pump depletion, transverse laser diffraction, plasma turbulence effects, self-steepening, self-focusing, etc. The basic equation, the driven nonlinear Schrödinger equation, is derived to describe this system. Advanced accelerator concepts to overcome some of these problems are proposed, including various forms of the plasma fiber accelerator. An advanced laser architecture suitable for the beat-wave accelerator is suggested. Accelerator physics issues such as the luminosity are discussed. Applications of the present process to the current drive in a plasma and to the excitation of collective oscillations within nuclei are also discussed.

Our recent estimates are that the energy-gains for cryogenic single-shell targets are close to those of similar double-shelled targets. However, the peak-power requirements for single-shell targets are still about a factor of two higher.

The longitudinal dielectric response function of a relativistic gas consisting of charged bosons together with the corresponding antiparticles is obtained in the random phase approximation. The theory is renormalized and an analysis of the mode structure and damping properties of the plasma is carried out.

This paper reviews current trends in the technological design of electrical pulsed power generators of the 1 TW class. Using published data, design criteria for SIDONIX II, OWL II, KALIF and GAMBLE IIA are compared using a lumped circuit parameter. More precise predictions of machine performance are made with the GOST transmission line code. Code results show agreement to within 15% of the published experimental parameters. Electric stress limitations to power output are assessed for 1 TW level machines using empirical formulae and a finite element solution of Laplace's equation. The analysis is then used to study economic means of increasing output power so as to provide a multimodule approach to inertial confinement fusion at the 100 TW level.

From the neodymium glass laser system Novette with two beams of 74 cm diameter and 18 kJ energy per pulse output in the nanosecond range, the design, the steps of the construction, and results of the system are reported. The two beams are synchronized to 5 psec and conversion to green light up to 78% has been realized. Conversion to four times the laser frequency is measured with more than 25% conversion. Simulation and measurement of laser beam properties at several locations permit an analysis to define the final Nova configuration. About half of Novette's experiments were to study short wave length laser–plasma interactions for the then better coupling by inverse bremsstrahlung mechanisms for inertial confinement fusion with laser intensities up to 1017 W/cm2. Experiments were divided between high density implosion research and non-local thermodynamic equilibrium plasma conditions.

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.

Recently revised estimates of target gain have added additional optimistic inputs to the interface between targets, accelerators and fusion chamber beam transport. But it remains valid that neutralization of the beams in the fusion chamber is useful if ion charge state Z > 1 or if > 1 kA per beamlet is to be propagated. Some engineering and economic considerations favor higher currents.

We have proposed and calculated a ‘benchmark problem’ for inertial confinement fusion computer codes. The target and the input parameters for this problem together with the simulation results are presented in this paper. Users of other computer codes who are interested in a comparison between the results of different computer codes could easily run this test problem and use our results to ‘benchmark’ their code results.

A mechanism has been discussed before by Dragila and Hora where very short laser pulses in a homogeneous plasma can be absorbed without collisions by the action of time dependent nonlinear forces. The resulting absorption lengths are of interest for the study of femtosecond neodymium glass laser pulses or the sub-picosecond carbon dioxide laser pulses which are now available. A mathematically more rigorous treatment of this problem is presented where a nonlinear differential equation is derived for the general solution in the approximation of Klima and Petrzilka. The ordinary differential equation can be solved exactly. With reasonable initial conditions, the solutions are similar to those of Dragila and Hora and are evaluated numerically for cases of experimental interest.