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.

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.

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.

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.

The mechanism of deflection of pulsed annular ion beams by toroidal magnetic fields is investigated. It is found that the ions of the annular beam obey the single particle orbits in the toroidal field. The polarization electric field, which is measured with an electric double probe in the annular beam inside the toroidal field, is found to be smaller than 1/10 of the value necessary for the force cancelling. It is reasonably concluded that the short-circuiting occurs via the toroidal magnetic field lines of force that have some rotational transform resulting from the helical winding of the toroidal coil.

A conical-pinched electron-beam diode has been studied with the objective of increasing the brightness of this inherently high current ion beam. Experiments and calculations are described that suggest it may be possible to obtain powers as high as 1013W/cm2 at 4MV from a carefully designed insulated-anode-type pinched-electron beam diode.

The current-neutralization fraction of a rotating and propagating light ion beam (LIB) injected into a low density plasma is investigated numerically. The beam space charge is essentially neutralized by a redistribution of the background plasma electrons in a time duration equal to the inverse of electron plasma frequency. When the density of the background plasma is comparable with that of the beam, incomplete current neutralization occurs because the strong magnetic field induced by the intense ion beam restricts the return plasma current.

In the simulation, the ion beam and the background plasma are treated as the fluids coupled with Maxwell's equations and Ohm's law, including the effect of the magnetic field on electrical conductivity. The calculations assume that the ion beam is injected in an unsteady fashion into the uniform plasma. It is found that the return current strongly depends on the density of the background plasma. The beam deceleration and the acceleration of the beam head and tail are also considered.

As the input power and energy content of Tokamaks are increased, the erosion rate of the first wall becomes larger, and a thick coating or cladding of low atomic number (Z) materials will be needed. Recently, the present authors prepared Si3N4–SiC films at alow temperature of 400°C by a plasma CVD method for the application to coating materials having high strength and wear resistance on metals and glasses. In this study, irradiation damage of the Si3N4–SiC films and 316 stainless steel (SUS-316) was investigated for the application to the first wall materials in a fusion reactor. The damage studies employed an intense pulsed light-ion beam (LIB) from the “ETIGO-I” device.

Experimental results are reported on an extractor for pulsed, high-intensity beams of intermediate mass ions. Aluminum and indium plasmas were generated using a metal vapor vacuum arc. A method for electrostatic separation of ions from electrons at the anode was utilized to generate constant current beams, insensitive to plasma flux variations.

A maximum extraction voltage of 30 kV was applied across a 1·6 cm gap. Voltage pulse length ranged from 10 to 50μsec. Peak current densities of 15 mA/cm2 and normalized emittance of εn<3χ10-7; π-m-rad were achieved for Al+ and In+ from a 20-cm2 anode. Ions were predominantly in the +1 ionization state with no observable species contamination. The technology may have application to the induction linac approach to Accelerator Inertial Fusion.

The Heavy-Ion Fusion Systems Assessment project is nearing completion of a two-year effort. The resulting system modelwill be used to set directions for future target design work.

Major uncertainties in target design were studied using thecost of electricity as a figure of merit. Net electric power was fixed at 1000 MW to eliminate large effects due to economies of scale. The system is relatively insensitive to target gain, factors of three changes in gain resulting in 8 to 12% changes in electricity cost. Possible increased peak power requirements pose only a small cost risk, but require many more beamlets for transport. A shortening ofthe required ion range causes both cost and beamlet difficulties. A factor of 4 decrease in the required range at a fixed driver energy increases electricity cost by 44% and raises the number of beamlets to 240. Finally, the heavy ion fusion system can accommodate large increases in target costs. Thus, to address the major uncertainties, target design should concentrate on requirements for ion range andpeak driver power.

Theoretical treatments of the stopping power are reviewed and problems necessary to extend these treatments to high temperature and high density materials are discussed. Physically important parameters which govern the stopping power properties are indicated. The average equilibrium charge for a gaseous medium is one of the important parameters in the stopping power and the charge-exchange processes involved are discussed. The effective charge is described in terms of a relation between the average equilibrium charge and the effective charge. The atomic energy levels for high density and high temperature matter are also included in the stopping power formula.

Actual calculations of the stopping power are made for Pb ions passing through the HIBLIC-target. Range profiles are estimated for Xe and U ions in an ionized Al target for temperatures T = 0 to T = 1290 eV using the Brueckner, Senbetu & Metzler (1982) theory based on a dielectric response function. Results are compared with those of Northcliffe & Schilling (1970), Ziegler (1980), and Hubert et al. (1980). In order to include dynamic local-field corrections in the dielectric function, a model is proposed similar to a two component plasma.

Inertial confinement fusion using light ion beams requires fast rise time, high power drivers. One technique to enhance a conventional pulsed power generator is to use a plasma erosion opening switch (PEOS) between the generator and the ion diode. Ideally, the PEOS conducts current until a current threshold is reached, then rapidly opens and delivers the inductively stored energy to the load on a short time scale. Experiments at the Naval Research Laboratory (NRL) used a PEOS to improve the Gamble II current rise time from 60 ns to 10 ns at 1 MA. Load voltages over 4 MV have been obtained (>2× the matched load voltage).

Based on these experiments and theoretical predictions, a PEOS system has been incorporated into the PBFA II experiment at Sandia National Laboratories (SNL). The PEOS on PBFA II is ultimately to provide a 6 to 8-MA, 30-MV pulse with 10-ns rise time into an “applied B” ion diode. This is a large extrapolation of present experiments. The PEOS system on PBFA II is described here and theoretical predictions are given.

The conference has shown some important advances toward the solution of problems required for inertial fusion. We can tentatively categorize as solved, or nearly solved, the following problems: Marx prefires, Marx jitter, gas-switch prefires, gas-switch jitter, power combination of multi-modules, high-current beam divergence (in barreltype, Applied-B/MID diodes), and preheat. In addition, there are a set of mature problems with promising solutions: pulsed power accelerator efficiency, ion sources, and the electron kinetics of an extractor ion diode. Newer problems that were addressed at the meeting but still require considerable work include: impedance control of efficient ion diodes, diagnostics for both beams and targets, the further development of target design tools and their experimental verification, targetfabrication processes to make the nearly perfect targets required for inertial fusion, channel formation and beam transport in those channels at the power levels required for fusion, and pulse-shaping.

For inertial confinement fusion (ICF) research, theories and simulations will continue to play an important role because research must cover all the sciences and technologies for extracting fusion energy. Experimental research is mainly concentrated on driver technology at the present stage.