Paper  Title  Page 

THPAS085  Kinetic Equilibrium and Stability Properties of 3D HighIntensity Charged Particle Bunches  3681 


Funding: Research supported by the U. S. Department of Energy. In 3D highintensity bunched beams, the collective effects associated with strong coupling between the longitudinal and transverse dynamics are of fundamental importance. A direct consequence of this coupling is that the particle dynamics does not conserve transverse energy and longitudinal energy separately, and there exists no exact kinetic equilibrium which has an anisotropic energy in the transverse and longitudinal directions. The strong coupling also introduces a mechanism for the electrostatic Harristype instability driven by strong temperature anisotropy, which exists naturally in beams that have been accelerated to large velocities. The selfconsistent VlasovMaxwell equations are applied to highintensity bunched beams, and a generalized lownoise deltaf particle simulation algorithm is developed for bunched beams with or without energy anisotropy. Systematic studies are carried out that determine the particle dynamics, the approximate equilibrium, and stability properties under conditions corresponding to strong 3D nonlinear spacecharge force. Finite bunchlength effects on collective excitations and anisotropydriven instabilities are also investigated. 

FRPMS092  Kinetic Description of Nonlinear Wave and Soliton Excitations in Coasting Charged Particle Beams  4291 


Funding: Research supported by the U. S. Department of Energy.
This paper makes use of a onedimensional kinetic model based on the VlasovMaxwell equations to describe nonlinear wave and soliton excitations in coasting charged particle beams. The kinetic description makes use of the recentlydeveloped gfactor model [1] that incorporates selfconsistently the effects of transverse density profile shape at moderate beam intensities. The nonlinear evolution of wave and soliton excitations is examined for disturbances both moving faster and moving slower than the sound speed, incorporating the important effects of wave dispersion [2]. Analytical solutions are obtained for nonlinear traveling wave pulses with and without trapped particles, and the results of nonlinear perturabtive particleincell simulations are presented that describe the stability properties and longtime evolution.
[1] R. C. Davidson and E. A. Startsev, Phys. Rev. ST Accel. Beams 7, 024401 (2004).[2] R. C. Davidson, Phys. Rev. ST Accel. Beams 7, 054402 (2004). 

FRPMS093  Numerical Studies of the Electromagnetic Weibel Instability in Intense Charged Particle Beams with Large Temperature Anisotropy Using the Nonlinear BEST Darwin Deltaf Code  4297 


Funding: Research supported by the U. S.Department of Energy. A numerical scheme for the electromagnetic particle simulation of highintensity chargedparticle beams has been developed which is a modification of the Darwin model. The Darwin model neglects the transverse induction current in Ampere?s law and therefore eliminates fast electromagnetic (light) waves from the simulations. The model has been incorporated into the nonlinear deltaf Beam Equilibrium Stability and Transport(BEST) code. As a benchmark, we have applied the model to simulate the transverse electromagnetic Weibeltype instability in a singlespecies chargedparticle beam with large temperature anisotropy. Results are compared with previous theoretical and numerical studies using the eighenmode code bEASt. The nonlinear stage of the Weibel instability is also studied using BEST code, and the mechanism for nonlinear saturation is identified. 