Electron beam halo formation in high-power periodic permanent magnet focusing klystron amplifiers

Pakter, Renato; Chen, Chiping

doi:10.1109/27.887658

Cited by 10 publications

(1 citation statement)

References 17 publications

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“…33) (l % 2), which is a realistic value in some applications. 40 Our first aim here is to determine if and when an analogous symmetry breaking instability occurs for bunched beams.…”

Section: Spherical Beammentioning

confidence: 99%

Nonlinear stability in the transport of intense bunched beams

et al. 2016

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The paper investigates the nonlinear coupling of envelope modes of oscillation for intense bunched beams. Initially, the analysis concentrates on the case of spherically symmetric beams for which longitudinal and transverse focusing forces are assumed to be the same. It is investigated how externally induced spherically symmetric breathing oscillations may nonlinearly drive the growth of ellipsoidal modes which can break the spherical beam symmetry. Next, a more general case in which the focusing forces are not symmetric such that the matched beam already presents an ellipsoidal shape is studied. It is found that depending on the parameters of the system, even a very small mismatch amplitude can drive an instability, which leads to an effective coupling of longitudinal and transversal envelope oscillations by means of the space-charge forces. Use is made of Poincar e plots and the stability index of periodic orbits to perform a detailed analysis of the location of the instability in the parameter space and how it affects the beam transport. Selfconsistent numerical simulations are performed in order to verify the onset of the nonlinear instability and its effect on the evolution of the RMS size and emittance of the beam.

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“…33) (l % 2), which is a realistic value in some applications. 40 Our first aim here is to determine if and when an analogous symmetry breaking instability occurs for bunched beams.…”

Section: Spherical Beammentioning

confidence: 99%

Nonlinear stability in the transport of intense bunched beams

et al. 2016

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Beam confinement in periodic permanent magnet focusing klystrons

Hess

Chen

2002

Physics Letters A

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Nonlinear coupling between breathing and quadrupole-like oscillations in the transport of mismatched beams in continuous magnetic focusing fields

2006

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A nonlinear analysis of the transport of breathing beams considering nonaxisymmetric perturbations is performed. It is shown that large-amplitude breathing oscillations of an initially round beam may couple nonlinearly to quadrupole-like oscillations, such that the excess energy initially constrained to the axisymmetric breathing oscillations is allowed to flow back and forth between breathing and quadrupole-like oscillations. In this case, the beam develops an elliptical shape with a possible increase in its size along one direction as the beam is transported. This is a highly nonlinear phenomenon that occurs for large mismatch amplitudes on the order of 100% and is found to be particularly relevant for space-charge-dominated beams with K≳k0ϵ, where K is the beam perveance, k0 is the vacuum phase advance per unit axial length, and ϵ is the emittance of the beam. A simple model based on mapping techniques is used to clarify the mechanism that leads to the energy exchange between the modes and is tested against results from direct integration of the envelope equations.

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Electron beam halo formation in high-power periodic permanent magnet focusing klystron amplifiers

Cited by 10 publications

References 17 publications

Nonlinear stability in the transport of intense bunched beams

Nonlinear stability in the transport of intense bunched beams

Beam confinement in periodic permanent magnet focusing klystrons

Nonlinear coupling between breathing and quadrupole-like oscillations in the transport of mismatched beams in continuous magnetic focusing fields

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