Generation Of Intense Ion Beams Research Articles

Generation and Measurements of Ion Species from Vacuum Arcs

We have measured the ion flux for different electrode materials in a vacuum arc. The vacuum arc has a point-plane geometry. The ion species in the generated plasma are identified using a time-of-flight (TOF) spectrometer. Ion species that have been generated to date include D+, Mg+, Mg++, Al+, Al++, Al+++, Ti+, Ti++, Ni+, Ni++, Cu+, Cu++, Zn+, Zn++, and In+. We found that in all cases, the ion flux measured is directly proportional to the interelectrode gap spacing and to the arc current. Typical current densities measured were ~300 mA · cm-2 at a distance of 10 cm from the gap for 150-?s pulse. The study will be used for the development of a multiple-arc array source for application to intense ion beam generation.

Light-ion beams for inertial confinement fusion

Inertial confinement fusion requires the generation and focusing of several megajoules of energy at > 100 TW power and > 100 TW·cm−2 power density onto a target for approximately 10 ns. Lasers and particle beam drivers have been developed for this purpose. Lightion beams offer the potential for a cost-effective, efficient and versatile driver with excellent energy deposition and no significant preheat. The research and development to date has emphasized technology development of the driver. Advances in pulsed power technology, magnetically insulated power flow, intense ion beam generation, focusing and transport, and ion beam deposition have led to the Particle Beam Fusion Accelerator II at Sandia National Laboratories which will begin operation in January 1986. This accelerator has the potential for achieving ignition of thermonuclear fuel in the laboratory.

Numerical simulation of ion beam propagation in Z-pinch plasma channels

Propagation of intense ion beams in preformed z-pinch plasma channels, a scenario of interest for inertial confinement fusion devices, has been studied with a 2½-dimensional (r, z, vr, vθ , vz; ∂/∂θ = 0) hybrid simulation model. In the code, ions are represented by particles and electrons by an inertialess thermal fluid which obeys a generalized Ohm's law. Fields are solved in the quasi-neutral Darwin approximation. Several collisional and atomic processes are included. The simulations of this paper are performed with collisional effects scaled down by a factor of ten. The results are then extrapolated to estimate that propagation efficiencies in the 70% range are possible using 5–7 MeV, 1–2 MA proton beams with initial divergences in the range of 1.5° to 7° in a 4-m hydrogen channel. Current neutralization in excess of 99% is found, and no gross axisymmetric instabilities are observed.

Comments on ‘‘Propagation of intense ion beams in straight and tapered z-discharge plasma channels’’

A comment is presented on the propagation of intense ion beams in straight and tapered z−discharge plasma channels.(AIP)

Reply to the comments of F. Winterberg

A reply to the comment on the propagation of intense ion beams in straight and tapered z−discharge plasma channels is presented.(AIP)

Intense ion beams

CONTENTS Introduction 576 1. Generation of intense ion beams in reflex systems 577 a) Symmetrical reflex systems 577 b) Asymmetrical reflex systems 578 c) Reflex triode with a massive dielectric anode 579 d) Comparison with experiment 579 2. Generation of intense ion beams in magnetically insulated diodes 580 a) Magnetically insulated diodes with a drift electron flux 580 b) Magnetically insulated diodes with Larmor electron orbits 581 c) Comparison with experiment 581 3. Generation of intense ion beams in diodes with a pinched electron beam 582 a) Analytical and numerical models 582 b) Comparison with experiment 584 4. Transport and focusing of intense ion beams 584 a) Mechanisms of neutralization and transport of intense ion beams 585 b) Ballistic focusing of intense ion beams 586 c) Electromagnetic focusing of intense ion beams 587 5. Application of intense ion beams 587 a) Ion-beam-driven controlled thermonuclear fusion 587 b) Ion rings for Astron–type devices 589 c) Neutron sources based on intense ion beams 590 d) Laser pumping with intense ion beams 590 Conclusion 591 References 591

Propagation of intense ion beams in straight and tapered z-discharge plasma channels

A preformed z-discharge plasma channel can be used to transport focused ion beams appropriate for a pellet fusion device. During transport, the beam can be compressed axially by time-of-fight bunching when appropriate ion accelerating voltage waveforms are employed. Single-particle orbits in such channels are expressible in terms of simple harmonic functions for small ion injection angles. In this work, orbit analysis is used to investigate how nonuniformities or tapering of the channel and electric fields present in the channel affect radial beam confinement and power multiplication by bunching.

Intense ion-beam neutralization in free space

Electron neutralization is a key feature in the propagation of intense ion beams. A one-dimensional sheath solution is given that demonstrates how electrons are captured by a transient ion beam emerging into a field-free vacuum. Conditions for space-charge and current neutralization are discussed. The importance of the electron distribution in determining the minimum spot size of a focused ion beam is considered.

Microsecond-pulse insulation and intense ion beam generation in a magnetically insulated vacuum diode

The insulation and ion generation characteristics of coaxial magnetically insulated diodes were tested using microsecond voltage pulses from a Marx generator with magnetic fields ranging up to 20 kG, voltages of 150–300 kV, and gap widths of 0.3–0.9 cm. Voltage standoff was observed for up to 4 μsec when using graphite or metallic electrodes. With plasma-producing nylon filament anodes, high-energy ion beam pulse lengths of up to 2 μsec and total charge generation densities of up to 7.5 μA sec/cm2 were obtained.

Generation of Intense Ion Beams in Pulsed Diodes

The generation of high-current (\ensuremath{\sim}${10}^{5}$ A) pulsed ion beams with ion energy in the range 0.5-10 MeV appears to be possible by modifications of present electron-beam technology.