The linear theory of a cold relativistic electron beam propagating parallel to an external magnetic field and through cold, homogeneous plasma is investigated. electromagnetic dispersion relation solved numerically compared with analytical predictions based on the electrostatic approximation. It found that effects are important for determining entire unstable spectrum. However, except strong regime, maximum growth rates corresponding frequencies in agreement those predicted by In regime...

Uniform density electron beam flow in a one-dimensional Pierce diode is alternately stable and unstable as the width increased. Each stability transition corresponds to an equilibrium bifurcation involving either static nonuniform or steady oscillatory configuration. The equilibria, although nonlinear, are evaluated analytically their properties derived. Details of solutions determined numerically from integral equations relating transit time electrons electric field at entrance plane. As...

An investigation of equilibrium, stability, and space-charge- limiting current a solid relativistic beam propagating along finite external magnetic field has been carried out compared with experiments. The concept rigid-rotor equilibrium is only approximately valid when the much less than Alfvèn critical current. Typically, low-voltage beams rotate fastest at edge whereas high-voltage near axis. A limited rigid rotor stability condition indicates, worst, weak instability may be present if...

Particle-in-cell (PIC) simulations of relativistic flowing plasmas are key interest to several fields physics (including, e.g., laser-wakefield acceleration, when viewed in a Lorentz-boosted frame) but remain sometimes infeasible due the well-known numerical Cherenkov instability (NCI). In this article, we show that, for plasma drifting at uniform velocity, NCI can be eliminated by simply integrating PIC equations Galilean coordinates that follow (also known as comoving coordinates) within...

A Kruskal-like extension of the Taub-NUT (Newman, Unti, Tamburino) metric is given, clearly exhibiting unusual properties this metric. The new incompatible with Misner and Taub, referred to as space, also further non-Hausdorff latter that has been proposed by various authors. geodesic incompleteness these extensions discussed.

The generalized Kerr solution is tentatively accepted as the description for state of a charged rotating mass which has undergone complete gravitational collapse. Mass accretion by such system demonstrated to damp out rotation. Even most favorable selective capture matter leaves angular momentum bounded ${m}^{2}$, precisely upper limit that geometry can accommodate without change character. Mach's principle, exemplified rotation inertial frames, employed obtain approximate expressions...

Representing the electrodynamics of relativistically drifting particle ensembles in discrete, co-propagating Galilean coordinates enables derivation a Particle-In-Cell algorithm that is intrinsically free numerical Cherenkov instability for plasmas flowing at uniform velocity. Application method shown by modeling plasma accelerators Lorentz-transformed optimal frame reference.

The pseudo-spectral analytical time-domain (PSATD) particle-in-cell (PIC) algorithm solves the vacuum Maxwell's equations exactly, has no Courant time-step limit (as conventionally defined), and offers substantial flexibility in plasma particle beam simulations. It is, however, not free of usual numerical instabilities, including Cherenkov instability, when applied to relativistic This paper presents several approaches that, combined with digital filtering, almost completely eliminate...

The scattering of self-pinched particle beams propagating in gas is investigated using Moliere’s treatment multiple scattering. Nordsieck lengths significantly longer than those predicted on the basis less accurate formalisms are obtained numerically. An improved analytic expression for length derived and agrees well with numerical results. Experimental data beam expansion from ASTRON experiment show good agreement simulations evolution a thin annular due to studied, found acquire Bennett...

Necessary and sufficient conditions are derived for the analytic extendability of a static two-dimensional space-time. For all allowed cases, explicit extensions determined together with their corresponding Penrose-Carter diagrams. Extensions classified further discussed in terms these diagrams, special consideration given to question bifurcate Killing horizons. The application results four-dimensional relativistic space-times is illustrated specific examples.

A set of four, coupled, first-order differential equations describing the normal modes a cylindrically symmetric, cold fluid, unneutralized, relativistic electron beam arbitrary radial profile is derived. Effects rotation and equilibrium fields are treated exactly. The found to have singular points for radially inhomogeneous wherever eigenfrequency equals cyclotron or Doppler resonance frequencies. resulting branch cuts in dispersion function give rise secularly decaying contributions...

The addition of helical quadrupole focusing to a modified betatron configuration is shown give rise an electromagnetic instability under certain conditions. arises from three-wave coupling between the field, transverse mode on beam, and transverse-electric waveguide mode. An analytic dispersion relation derived. Several features are confirmed using three-dimensional computer simulations.

Growth rates of negative mass instabilities in conventional and modified betatrons are calculated by analytic methods performing three-dimensional particle simulations. In contrast to earlier work, toroidal corrections the field equations included model. As a result, good agreement with numerical simulations is obtained. The show that nonlinear development can seriously disrupt beam.

Recently extremely large supersonic amplitude ion waves have been observed in simulations of backscatter instabilities, electron beam interactions, and Langmuir waves, which break an unconventional symmetrical x-type manner. The conditions necessary for this type breaking to support theory are presented.