A.M. Bashkirev – Post-graduate Student, Department «Physics», Volgograd State Technical University
A.G. Shein – Dr. Sc. (Phys.-Math.), Professor, Department «Physics», Volgograd State Technical University
D.G. Kovtun – Ph. D. (Phys.-Math.), Associate Professor, Department «Physics», Volgograd State Technical University
One of the important and urgent issues of modern plasma physics and high-power electronics is the study of oscillatory and wave processes in intense beams of charged particles. In particular, this task is about the study of positive ions impact on dynamics of an electron beam.
In case of an electron beam with a virtual cathode, the neutral gas ionization processes by electron beam are especially interested. In fact, an electron speed in an intense, especially in relativistic beam is significantly higher than the maximum of ionization coefficient rate. However, at occurrence of a virtual cathode, an electron speed in an area of virtual cathode is significantly reduced and may coincide with the maximum of ionization coefficient rate. As a result, the processes of virtual cathode formation and neutral gas ionization are self-consistent, and the distribution of ionized gas is substantially inhomogeneous.
Previously, the occurrence of generation intensity fluctuation with a stable rate as in relativistic beam, extending in a gas-filled interaction space has been demonstrated. However, the question about the ability to control the pulse frequency and conditions of the generation mode remains open. A series of numerical experiments aimed at identifying this dependencies were performed within this work.
Based on the numerical modeling results of relativistic electron beam in gas-filled interaction space: the influence of several system parameters on pulse generation frequency was researched, as well as the limits of pulse mode occurrence were defined. In particular, dependences of pulse frequency from the strength of current flow, the neutral gas pressure, flow rate, and the external magnetic field strength were built. The possibility of smooth adjustment of the pulse frequency in a wide range by changing the external longitudinal magnetic field strength was demonstrated. Also, there was demonstrated the ability to control the oscillation amplitude by changing the neutral gas pressure.
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