关键词: diocotron instability, macroscopic cold-fluid model, sheet electron beam

Abstract: This paper investigates the diocotron instability of an infinitely wide relativistic sheet electron beam in conducting walls propagating through a uniform magnetic field by using the macroscopic cold-fluid model  theory. Assuming low-frequency perturbations with long axial wavelengths, the eigenvalue equation and the dispersion relation are acquired for a sheet electron beam with sharp boundary profile and uniform density. The results  presented in this paper has developed the use of the macroscopic cold-fluid model theory by extending the parameter of the electron cyclotron frequency $\omega _{\rm c} $ to a wider usage range, which is restricted to be much  larger than the plasma frequency $\omega _{\rm p} $ in the previous research work. Theoretical analyses and numerical calculations indicate that the transport of the sheet electron beam will be completely stabilized by  augmenting the normalized beam thickness to a conductor gap larger than a threshold $\lambda _{\rm b} $, which is greatly dependent on the parameter ${\omega _{\rm c} }/{\omega _{\rm p}}$. The larger ${\omega_{\rm c} }/  {\omega _{\rm p} }$ is, the smaller $\lambda _{\rm b} $ will be needed. Moreover, the system parameters, including the wave number $k_x $ of the perturbations and the relativistic mass factor $\gamma _{\rm b} $, will also  influence the growth rate of diocotron instability obviously.

Key words: diocotron instability, macroscopic cold-fluid model, sheet electron beam