Electromagnetic Waves Dispersion and Interaction of an Annular Beam-Ion Channel System in Plasma Waveguide

Jixiong Xiao,Jun Chen,Zhijiang Wang,Changhai Liu

doi:10.1155/2017/8141549

Abstract

A linear theory for the electromagnetic properties and interactions of an annular beam-ion channel system in plasma waveguide is presented. The dispersion relations for two families of propagating modes, including the electrostatic and transverse magnetic modes, are derived. The dependencies of the dispersion behavior and interaction for different wave modes on the thickness of the annular beam and betatron oscillation frequency are studied in detail by numerical calculations. The results show that the inner and outer radii of the beam have different influences on propagation properties of the electrostatic and electromagnetic modes with different betatron oscillation parameters. In the weak ion channel situation, the two types of electrostatic waves, that is, space charge and betatron modes, have no interaction with the transverse magnetic modes. However, in the strong ion channel situation, the transverse magnetic modes will have two branches and a low frequency mode emerged as the new branch. In this case, compared with the solid beam case, the betatron modes not only can interact with the high frequency branch at small wavenumber but also can interact with the low frequency branch at large wavenumber.

Highlights

Plasma filling has a variety of advantages in increasing the space charge limited current, overall energy conversion efficiency, and radiation bandwidth dramatically [1,2,3] and it has been widely used in many plasma microwave radiation sources, such as traveling-wave tubes (TWT) [4], backward-wave oscillators (BWO) [5], klystrons [6], and gyrotrons [7]
As a relativistic electron beam (REB) passes through the preformed plasma, the beam front will push out the plasma electrons continuously by the space charge force induced by beam electron, leaving the almost immobile positive ions to form the so-called ion channel
The electron beam can transport reliably with the guidance of the focus force of the ion channel. This new focusing method has been experimentally demonstrated in plasma wave tubes (PWT) [12], free electron lasers (FEL) [13], and charged particle accelerators [14] successfully

Summary

Introduction

Plasma filling has a variety of advantages in increasing the space charge limited current, overall energy conversion efficiency, and radiation bandwidth dramatically [1,2,3] and it has been widely used in many plasma microwave radiation sources, such as traveling-wave tubes (TWT) [4], backward-wave oscillators (BWO) [5], klystrons [6], and gyrotrons [7]. Compared with the vacuum electronic devices, the EM dispersion characteristic and beam-wave energy transfer mechanism will become more complex [8]. As it is the basis of the application of any plasma electronics devices, the EM dispersion behavior and interaction in such plasma apparatus have always been research hot spots in the past two decades. The electron beam can transport reliably with the guidance of the focus force of the ion channel. This new focusing method has been experimentally demonstrated in plasma wave tubes (PWT) [12], free electron lasers (FEL) [13], and charged particle accelerators [14] successfully. Mirzanejhad et al have presented the dispersion characteristics of the space charge waves in a uniform and rigid rotation REB in ion channel without betatron oscillations [19]

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Conclusion