Self-consistent field theory of a helix traveling wave tube amplifier

• Published in: IEEE transactions on plasma science Vol. 20; no. 5; pp. 543 - 553
• Main Authors: Freund, J.P., Kodis, M.A., Vanderplaats, N.R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.1992; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Boundary conditions; Dielectrics; Dispersion; Electronic tubes, masers; Electronics; Equations; Exact sciences and technology; Propagation losses; Helical shape; Travelling wave tube; Amplifier; Boundary condition; Annular beam; Frequency characteristic; Phase velocity; Relativistic theory; Frequency; Field theory; Maxwell equation; Comparative study; Gain; Electrical characteristic
• ISSN: 0093-3813
• DOI: 10.1109/27.163592

A self-consistent relativistic field theory of a helix traveling wave tube (TWT) is presented for a configuration in which a thin annular beam propagates through a sheath helix enclosed within a loss-free wall. A linear analysis of the interaction is carried out, subject to the boundary conditions imposed by the beam, helix, and wall. A detrimental dispersion equation is obtained which implicitly includes beam space-charge effects without recourse to a heuristic model of the space-charge field. The equation is valid for arbitrary azimuthal mode number and is solved numerically for the azimuthally symmetric case. The coupled-wave Pierce theory is recovered in the near-resonant limit. Numerical comparisons between the complete dispersion equation and the Pierce model are described. A discrepancy is found between the Pierce and the field theory even for low currents in the nominally ballistic regime, owing to the dielectric effect of the beam on the helix modes.< >