Pencil-like mm-size electron beams produced with linear inductive voltage adders (LIVA)

This paper presents design, analysis, and first results of the high brightness electron beam experiments currently under investigation at Sandia. Anticipated beam parameters are: energy 12 MeV, current 35-40 kA, rms radius 0.5 mm, pulse duration 40 ns FWHM. The accelerator is SABRE, a pulsed LIVA modified to higher impedance, and the electron source is a magnetically immersed foilless electron diode. 20 to 30 Tesla solenoidal magnets are required to insulate the diode and contain the beam to its extremely small sized (1 mm) envelope. These experiments are designed to push the technology to produce the highest possible electron current in a submillimeter radius beam. Design, numercial simulations, and first experimental results are presented

Experiments investigating the generation and transport of 10--12 MeV, 30-kA, mm-size electron beams with linear inductive voltage adders

The authors present the design, analysis, and results of the high-brightness electron beam experiments currently under investigation at Sandia National Laboratories. The anticipated beam parameters are the following: 8--12 MeV, 35--50 kA, 30--60 ns FWHM, and 0.5-mm rms beam radius. The accelerators utilized are SABRE and HERMES III. Both are linear inductive voltage adders modified to higher impedance and fitted with magnetically immersed foil less electron diodes. In the strong 20--50 Tesla solenoidal magnetic field of the diode, mm-size electron beams are generated and propagated to a beam stop. The electron beam is field emitted from mm-diameter needle-shaped cathode electrode and is contained in a similar size envelop by the strong magnetic field. These extremely space charge dominated beams provide the opportunity to study beam dynamics and possible instabilities in a unique parameter space. The SABRE experiments are already completed and have produced 30-kA, 1.5-mm FWHM electron beams, while the HERMES-III experiments are on-going

The Light-ion Pulsed Power Induction Accelerator for the Laboratory Microfusion Facility (LMF)

In order to initiate ignition and substantial energy yield from an inertial confinement fusion target (ICF), a light-ion pulse of ~700 TW peak power and 15-20 ns duration is required. The preconceptual design presented provides this power. The HERMES-III technology of linear inductive voltage addition in a self-magnetically insulated transmission line (MITL) is utilized to generate the 25-36 MV peak voltage needed for lithium ion beams. The 15-20 MA ion current is achieved by utilizing many accelerating modules in parallel. The lithium ion beams are produced in two-stage extraction diodes. To provide the two separate voltage pulses required by the diode, a triaxial adder system is incorporated in each module. The accelerating modules are arranged symmetrically around the fusion chamber in order to provide uniform irradiation onto the ICF target. In addition, the modules are fired in a preprogrammed sequence in order to generate the optimum power pulse shape onto the target. In this paper we present an outline of the LMF accelerator conceptual design with emphasis on the architecture of the accelerating modules

HELIA - high energy linear induction accelerators

A novel approach to providing high voltage (>10 MV), high current (>200 kA), short duration (20-40 ns), particle beam pulses is described. The approach uses 1 MV Metglas isolated cavities driven by water pulse lines. These are stacked in series by using a magnetically insulated cathode stalk. Results from modeling of the cavity and cores and from a full sized single-cavity experiment are discussed. Plans for a four-cavity experiment to prove the principle of voltage addition by stacking cavities on a magnetically insulated transmission line are also described. The single-cavity experiments produced a 1.1 MV, 30 ns FWHM, 12 ns rise time, 250 kA electron beam. The HELIA pulsed power system and cavities are described. Particle-in-cell (PIC) computer simulations of the four-cavity experiment and the four-cavity conceptual design are discussed. 13 references, 14 figures

Computations of the spherical e. -->. i convertor

One proposed approach to the overlap/deposition problem for multi-channel electron beams is to place a thin hollow sphere in the overlap region and allow the incoming electrons to form a virtual cathode inside this sphere. The resulting electric field causes ions from the inner surface of the sphere to flow inward radially towards a target. The efficiency of this process is studied analytically and with a 1-D spherical, two-species electrostatic particle code. The maximum possible (power conversion) efficiency is concluded to be about 10 percent. Two-dimensional effects are briefly considered, and angular momentum in particular is found to be a possibly serious limitation