Dissertation committee:
Ηλίας Γλύτσης, Καθηγητής, Σχολή Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών, ΕΜΠ
Νικόλαος Κανταρτζής, Καθηγητής, Τμήμα Ηλεκτρολόγων Μηχανικών και Μηχανικών Υπολογιστών, ΑΠΘ
Ιωάννης Κομίνης, Επίκουρος Καθηγητής, Σχολή Εφαρμοσμένων Μαθηματικών και Φυσικών Επιστημών, ΕΜΠ
Έκτωρ‐Εμμανουήλ Νισταζάκης, Αναπληρωτής Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Ιωάννης Γ. Τίγκελης, Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Εμμανουήλ Τσίλης, Επίκουρος Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Δημήτριος Φραντζεσκάκης, Καθηγητής, Τμήμα Φυσικής, ΕΚΠΑ
Summary:
In this thesis, we study the problem of the interaction between an electron beam and
the electromagnetic waves in complex waveguide structures with applications in
millimeter-wave oscillators. The study of the underlying physical phenomena has been
performed using the differential form of Maxwell equations and the appropriate
boundary conditions are applied. Due to the complexity of the geometry of the
structure, the solution of the corresponding electromagnetic problem has been
performed using a numerical code, which solves self-consistently the Maxwell
equations and the equations of motion. The code employs the FDTD method in
cylindrical coordinates for the electromagnetic part and the PIC one for the beam-wave
interaction. This code has been initially used for the study of cylindrical waveguides
without an electron beam (cold case) and then for the study with the presence of an
electron beam (hot case). These structures include waveguides with periodic axial
corrugations (with or without dielectric material) as well as with periodic azimuthal
corrugations. The field distributions have been derived and the dispersion
characteristics and the scattering parameters have been calculated. In addition, the
field distributions and the propagation characteristics have been found for the beamwave
interaction in a smooth and in an axially corrugated waveguide. Finally, a
parametric study has been performed for the effect of the geometrical and beam
properties on the interaction. The numerical results present very good agreement with
the theoretical ones as well as with those obtained by other in-house and commercial
codes.
Keywords:
Applied electromagnetism, Finite Difference Time Domain method, FDTD, Perfectly matched layer, PIC method, complex waveguide structures, beam-wave interaction.
