Recent discrete model for small-signal analysis of traveling-wave tubes

• Published in: Physica scripta Vol. 94; no. 5; pp. 55601 - 55608
• Main Authors: Minenna, Damien F G, Terentyuk, Artem G, André, Frédéric, Elskens, Yves, Ryskin, Nikita M
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.05.2019
• Subjects: Classical Physics; dispersion relation; Electromagnetism; Engineering Sciences; equivalent circuit; Kuznetsov discrete model; model reduction; Physics; Pierce model; Plasma Physics; traveling-wave tube; wave-particle interaction; Frequency domain; Impedances; Dispersion relation; Coupled mode; Time domain; Traveling-wave tube (TWT); Wave-particle interaction; Pierce model; Kuznetsov discrete model; Band edge; Equivalent circuit; Gel'fand transform; Model reduction; Passband
• ISSN: 0031-8949; 1402-4896
• DOI: 10.1088/1402-4896/ab060e

The numerical simulations of the wave-particle interaction, as it occurs in particular in traveling-wave tubes, require new tools especially to investigate near the band edges of those devices. We propose a new approach (not limited to traveling-wave tubes) using field decomposition allowing an important reduction of degrees of freedom: the discrete model. To assess its validity, we compare it in a small-signal regime with Pierce's four-wave theory. For both models, we take the same simplified fluid model and we express the associated circuit-beam impedances. We show analytically and with a numerical example that the newly developed reduced model is very close to the Pierce model, especially where the latter is well established. Small deviations do occur at the edges of the amplification band, where Pierce's model is known to lose its accuracy while the reduced model offers a valid physical interpretation.