Space-charge wavelengths in electron beams

Branch, G.M.; Mihran, T.G.; Neugebauer, W; Pohl, W.J.

doi:10.1109/t-ed.1967.15961

Cited by 8 publications

(1 citation statement)

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“…However, it is not trivial to compute R using the sheath helix model, and most authors studying linear beam tubes simply use the values for R from the Branch and Mihran model [13]- [15]. Furthermore, experimental work has also been performed in [16], [17] aiming at determining the reduced plasma frequency in linear beam tubes. To date, there is a lack of literature available to provide a robust method that can be easily used to verify or find the reduced plasma frequency in complex structures.…”

Section: Introductionmentioning

confidence: 99%

Reduced Plasma Frequency Calculation Based on Particle-In-Cell Simulations

Mealy¹,

Marosi²,

Capolino³

2022

Preprint

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We propose a scheme to calculate the reduced plasma frequency of a cylindrical-shaped electron beam flowing inside of a cylindrical tunnel, based on results obtained from Particle-in-cell (PIC) simulations. In PIC simulations, we modulate the electron beam using two parallel, non-intercepting, closely-spaced grids which are electrically connected together by a single-tone sinusoidal voltage source. The electron energy and the beam current distributions along the length of the tunnel are monitored after the system is operating at steadystate. We build a system matrix describing the beam's dynamics, estimated by fitting a 2 × 2 matrix that best agrees with the first order differential equations that govern the physics-based system. Results are compared with the theoretical Branch and Mihran model, which is typically used to compute the plasma frequency reduction factor in such systems. Our method shows excellent agreement with the theoretical model, however, it is also general. Our method can be potentially utilized to determine the reduced plasma frequencies of electron beams propagating in differentlyshaped beam tunnels, where no theoretical model yet exists, such as the case of a cylindrical or elliptical electron beam propagating inside of a metallic beam tunnel of cylindrical, square, or elliptical cross-section. It can be applied also to electron beams composed of multiple streams.

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