Propagation Of Relativistic Electron Beam Research Articles

Design and operational characteristics of a compact relativistic electron beam generator for the excitation of short wavelength lasers. (USA) (Japan)

Design and operational characteristics of a compact relativistic electron beam generator for the excitation of short wavelength lasers. (USA) (Japan)

Electron beam dynamics in combined guide and pump magnetic fields for free electron laser applications

The propagation of a cold relativistic electron beam in a free electron laser with an axial guide magnetic field is considered. The possibility of several steady-state helical trajectories for the electrons is shown, and the stability against perturbations and accessibility of such steady states is considered. Necessary and sufficient conditions for the stability are derived and indicate the importance of the transition region at the entrance of the laser. Possible modes of operation of the laser in different steady-state regimes are suggested and illustrated by numerical examples.

Design and operational characteristics of a compact relativistic electron beam generator for the excitation of short wavelength lasers

We have designed and constructed a compact and simple high current relativistic electron beam (REB) generator for the excitation of lasers in the short wavelength region. The REB generator mainly consists of Tesla transformer type high-voltage generator, water pulse forming line, cold cathode electron gun and provides the operational characteristics of 250 keV high energy, 15 kA high current and 15 ns pulse width electron beam.

Relativistic electron beam propagation along a wire

Reports experiments which show that the guiding properties of a vacuum tube for a relativistic electron beam are improved considerably by a thin insulated wire in the centre of the tube.

Relativistic electron-beam propagation in vacuum with ion acceleration

A self-pinched relativistic electron beam is injected through a thin foil into vacuum with no externally applied magnetic field. The beam is observed to propagate at currents well above the space-charge-limiting current (∼3 kA) but limited to the Alfven current (∼30 kA). Propagation results from charge neutralization of the beam by ions accelerated out of the anode plasma as confirmed by various ion diagnostics. Ions are collectively accelerated to greater than the electron energy. The experimental results are in qualitative agreement with a one-dimensional time-dependent computer simulation.

Vacuum propagation of solid relativistic electron beams

An investigation of equilibrium, stability, and space-charge- limiting current of a solid relativistic beam propagating along a finite external magnetic field has been carried out and compared with experiments. The concept of a rigid-rotor equilibrium is only approximately valid when the beam current is much less than the Alfvèn critical current. Typically, low-voltage beams rotate fastest at the beam edge whereas high-voltage beams rotate fastest near the beam axis. A limited investigation of the rigid rotor stability condition indicates, at worst, a weak instability may be present if the rigid-rotor equilibrium is artificially imposed, and no instability at all for a self-consistent equilibrium. Numerical solutions for the space-charge limiting current and relativistic factor on axis are presented and compared with two-dimensional, cylindrical, space- and time-dependent simulations. Analytical expressions for the limiting current are valid for ωc/ωb≳5, where ωc is the cyclotron frequency and ωb is the beam frequency. For external magnetic field strengths below this level, the limiting current increases monotonically with decreasing field strength until the beam collides with the drift tube. Expressions for foil scattering are also presented. The results are in good agreement with experiments.

Current multiplication during relativistic electron-beam propagation in plasma

During the passage of a highly relativistic electron beam through a plasma, the net current can be greater than the beam current. This current increase can be caused by momentum transferred from the beam to the plasma via the two-stream instability. The current gain at saturation of the two-stream instability is computed, and the theoretical results agree well with a one-dimensional computer simulation of the phenomenon. An equation is derived for the total plasma current, including both the current driven by the two-stream instability and the current driven by the beam-induced electric field.

Beam generation in foil-less diodes

A study is made of the generation of intense relativistic electron beams in rectangular and cylindrical foil-less diodes. The diode space charge is treated self-consistently. The electron emission from the cathode is assumed to be space-charge-limited. A strong axial magnetic field is assumed to prevent the electrons from reaching the anode surface(s) directly, and to constrain the electron motion to be approximately one-dimensional. A useful dimensionless measure of the diode potential φc is ε≈[mec2/(eφc)]1/2, with me and e the electron rest mass and charge, and c the speed of light. Properties of the diodes are first analyzed in the ultra-relativistic limit, ε=0, where the condition for space-charge-limited emission gives rise to a linear singular integral equation. This equation is solved for rectangular diode geometry, and the solutions are studied in detail. In particular, the diode impedance is independent of φc, and the beams are, in general, hollow. The beam particle kinetic energy flux, Γp, decreases as the beam width, b, increases; for b=a, Γp=0, where a is the diode width. A treatment of the diodes is then given for small but nonzero values of ε. For finite ε, there is a nonrelativistic Child–Langmuir sheath of thickness ≈εa at the cathode surface. For b=a, Γp is shown to be proportional to φc3/2.

Theory of foil-less diode generation of intense relativistic electron beams

A study is made of the generation of intense hollow relativistic electron beams in a foil-less diode. A strong magnetic field is assumed so that the electron motion is one dimensional. Also, the electron motion is considered to be ultra-relativistic. The problem of the self-consistent space charge in the diode is reduced to a singular integral equation. This integral equation is solved and the nature of the solutions is discussed. The beam density increases at the beam edges and has a minimum in the beam interior. The diode impedance as a function of the beam thickness and geometry is discussed.

Collective Acceleration Investigations with the Ionization Front Accelerator

Part I of a three part program to demonstrate feasibility of the Ionization Front Accelerator (IFA) has been completed, and is successful. Experiments describing intense relativistic electron beam (IREB) propagation in Cs are reported. The threshold pressure for electron beam ionization of Cs is found to agree with earlier theoretical predictions. These results experimentally establish Cs as a feasible working gas for the IFA. Numerical simulation results are also reported which demonstrate controlled potential well motion and collective ion acceleration with the IFA.

Propagation of an unneutralized intense relativistic electron beam in a magnetic field

In this paper the results of a series of electron-beam vacuum propagation experiments are presented and compared with theoretical predictions. Important conclusions pertaining to time-dependent diode behavior, virtual cathode formation, and various equilibrium and stability criteria are reported.

Relativistic runaway electron beams in the Oak Ridge tokamak

The conditions for the generation and containment of relativistic electron beams in a tokamak discharge were studied by deliberately driving Ormak into a strong runaway regime. The experimental results show that beams with typical currents of 60 kA and mean electron energies of 3 MeV could be generated reproducibly and then contained safely over e-folding decay times of 35 msec without damaging the machine. The experiments substantially confirm and extend the results of previous modeling studies on runaway discharges. They also implicitly define the experimental conditions for the establishment of a steady, toroidal beam-plasma system that can be of interest for plasma physical studies.

3058. Propagation of an unneutralized intense relativistic electron beam in a magnetic field

3058. Propagation of an unneutralized intense relativistic electron beam in a magnetic field

The Poukey‐Rostoker‐Model of Relativistic Electron Beam Propagation: Further Comments

AbstractSeveral properties of the analytic one‐dimensional model of relativistic electron beam propagation published by POUKEY and ROSTOKER [1] are discussed in the more realistic case of a time‐dependent current. The general beam behaviour is similar to that in the case of constant current; the time that is necessary to build up the space charge wall and the potential well (typically ≈ 1 ns) and the sheath thickness (typically a few cm) are evaluated in the case of constant current growth rate.

Generation and extraction of microsecond intense relativistic electron beams

Generation and extraction of microsecond intense relativistic electron beams

Some aspects of high-current relativistic electron-beam generation

Some aspects of high-current relativistic electron-beam generation

Magnetic focusing of intense relativistic electron beams

Propagation and focusing of intense relativistic electron beams was investigated in an externally applied longitudinal magnetic field. Evidence is presented that propagation and focusing cannot accurately be described by a single particle adiabatic analysis even though the criteria for such an analysis seem to be fulfilled.

On the propagation of relativistic electron beams in finite-radius magnetized plasma columns

Presents a theoretical investigation of the electric and magnetic fields associated with a relativistic electron beam propagating in a finite-radius, magnetized plasma column enclosed by a larger conducting vacuum chamber. The results indicate electro-magnetic fields which can be significantly larger than in the case of beam propagation through an infinite plasma. Significant beam distortion and reflection may result when the beam density, nb, approaches the density of the plasma, n0, or when the beam length becomes excessive. It is suggested that the finite rise time of the beam energy may lead to a significant enhancement of these fields even when nb<<n0.

The Interaction between Intense Relativistic Electron Beam and Plasma

Intence relativistic electron beam generator, Reiden III, has been constructed forthe application of REB fusion research. The electron beam (500 ke V 80 kA) was generatedand focused onto the target. The spotsize on the target determined by a 3-channel X-raypinhole camera is as small as 1.5mm. The interaction of focused REB with denseplasma on the solid target was investigated. The experimental results shows theexistence of anomalonly strong interaction.

Generation and extraction of microsecond intense relativistic electron beams

The Physics International Pulserad 1140 has been modified so that a pulse length of 1.7 μsec can be obtained with a beam energy of 50 kJ. This modification involves substituting a pulse-forming network for the conventional Blumlein. This long-pulse generator has been used to study diode behavior on 1-μsec time scales. The dependence of impedance on voltage and anode–cathode spacing is discussed here. A semiempirical model has been developed. The diode time history and closure velocity are discussed in terms of this model.