Emittance Growth and Image Formation in a Nonuniform Space-Charge-Dominated Electron Beam

Reiser, M.; Chang, C. R.; Kehne, D.; Low, Kain Lu; Shea, T. K.; Rudd, H.; Haber, I.

doi:10.1103/physrevlett.61.2933

Cited by 42 publications

(18 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent experiments and simulation studies suggest that such modes can play a deleterious role in intense beam transport. [33][34][35][36][37][38][39][40][41][42][43][44] In general, an analysis of collective modes in intense nonneutral beams requires knowledge of the beam distribution function in six-dimensional phase space in order to carry out numerical simulations using the distribution function as an initial condition, or to perform analytical studies of equilibrium and stability properties using kinetic theory. Although analytical studies provide valuable insight regarding parametric behavior, such kinetic analyses can become quite complex, even under highly idealized assumptions.…”

Section: Introductionmentioning

confidence: 99%

Warm-fluid description of intense beam equilibrium and electrostatic stability properties

Lund

Davidson

1998

Physics of Plasmas

View full text Add to dashboard Cite

A nonrelativistic warm-fluid model is employed in the electrostatic approximation to investigate the equilibrium and stability properties of an unbunched, continuously focused intense ion beam. A closed macroscopic model is obtained by truncating the hierarchy of moment equations by the assumption of negligible heat flow. Equations describing self-consistent fluid equilibria are derived and elucidated with examples corresponding to thermal equilibrium, the Kapchinskij–Vladimirskij (KV) equilibrium, and the waterbag equilibrium. Linearized fluid equations are derived that describe the evolution of small-amplitude perturbations about an arbitrary equilibrium. Electrostatic stability properties are analyzed in detail for a cold beam with step-function density profile, and then for axisymmetric flute perturbations with ∂/∂θ=0 and ∂/∂z=0 about a warm-fluid KV beam equilibrium. The radial eigenfunction describing axisymmetric flute perturbations about the KV equilibrium is found to be identical to the eigenfunction derived in a full kinetic treatment. However, in contrast to the kinetic treatment, the warm-fluid model predicts stable oscillations. None of the instabilities that are present in a kinetic description are obtained in the fluid model. A careful comparison of the mode oscillation frequencies associated with the fluid and kinetic models is made in order to delineate which stability features of a KV beam are model-dependent and which may have general applicability.

show abstract

Section: Introductionmentioning

confidence: 99%

Warm-fluid description of intense beam equilibrium and electrostatic stability properties

Lund

Davidson

1998

Physics of Plasmas

View full text Add to dashboard Cite

show abstract

“…We first consider a quincunx distribution as used in previous work on space-charge-dominated beam physics [10]. Such a pattern can easily be generated by intercepting the photocathode drive laser with a mask.…”

Section: Simulation Of Perturbed Beamsmentioning

confidence: 99%

Impact of transverse irregularities at the photocathode on the production of high-charge electron bunches

Rihaoui

Bohn

Piot

et al. 2007

2007 IEEE Particle Accelerator Conference (PAC)

View full text Add to dashboard Cite

The properties of electron beams produced in a photoinjector are strongly dependent on the initial conditions, i.e. the photocathode drive laser shape and its uniformity. We explore the impact of well-defined transverse laser perturbations on the evolution of the electron beam both in configuration and velocity spaces and especially investigate how certain types of perturbations evolve as the beam propagates in the Argonne Wakefield Accelerator facility. Numerical simulations performed with IMPACT-T are presented. Finally preliminary experimental results aimed at validating our simulations are discussed.

show abstract

“…Such halos have been observed in existing machines, such as the LANSCE proton linac [1]. Furthermore, the evolution of beam halo has been studied in experiments at the University of Maryland [2]. In the design of next-generation accelerators, it is very important to understand the physics of the beam halo.…”

Section: Introductionmentioning

confidence: 99%

Beam halo studies using a three-dimensional particle-core model

Qiang

Ryne

2000

Phys. Rev. ST Accel. Beams

View full text Add to dashboard Cite

In this paper we present a study of beam halo based on a three-dimensional particle-core model of an ellipsoidal bunched beam in a constant focusing channel including the effects of nonlinear rf focusing. For an initially mismatched beam, three linear envelope modes -a high frequency mode, a low frequency mode, and a quadrupole mode-are identified for an azimuthally symmetric bunched beam. The high frequency mode has three components all in phase; the low frequency mode has the transverse components in phase and the longitudinal component 180 ± out of phase; the quadrupole mode has no longitudinal component, and the two transverse components in the mode are 180 ± out of phase. We also study the case of an ellipsoidal bunched beam without azimuthal symmetry and find that the high frequency mode and the low frequency mode are still present but the quadrupole mode is replaced by a new mode with transverse components 180 ± out of phase and a nonzero longitudinal component. Previous studies, which generally addressed the situation where the longitudinal-to-transverse focusing strength is roughly 0.6 or less, conclude that the oscillation of the high frequency mode is predominantly transverse, and that of the low frequency mode is predominantly longitudinal. In this paper we present a systematic study of the features of the modes as a function of the longitudinal-to-transverse focusing strength ratio. We find that, when the ratio is greater than unity, the high frequency mode may contain a significant longitudinal component. Thus, excitation of the high frequency mode in this situation can be responsible for the formation of longitudinal beam halo. Furthermore, while previous studies have observed halo amplitudes roughly 2-3 times the matched beam edge, for the present parameters we observe much larger amplitudes (5 times or more). This is due to the fact that the longitudinalto-transverse focusing ratio used here is greater than that of previous studies. The finding of large transverse halo amplitude can have significant impact on the design of high-intensity ion accelerators where the longitudinal-to-transverse focusing ratio is slightly greater than unity in some parts of the linac.

show abstract

Emittance Growth and Image Formation in a Nonuniform Space-Charge-Dominated Electron Beam

Cited by 42 publications

References 4 publications

Warm-fluid description of intense beam equilibrium and electrostatic stability properties

Warm-fluid description of intense beam equilibrium and electrostatic stability properties

Impact of transverse irregularities at the photocathode on the production of high-charge electron bunches

Beam halo studies using a three-dimensional particle-core model

Contact Info

Product

Resources

About