  Focusing on traveling wave tube (TWT) applications, the interaction impedance
between an electron beam and electromagnetic modes in three distinct, but
related, corrugated waveguides that operate at millimeter waves is investigated
together with the role of glide symmetry. Two waveguide structures have glide
symmetry, and the irreducible Brillouin zone is related to half of the period,
leading to a wide band linearity, i.e., nondispersive, property of the
dispersion diagram. The investigation on the modes with longitudinal electric
field that can be excited shows that the bottom-top glide (BT Glide) symmetric
corrugated waveguide has a wide band interaction impedance, hence it is a good
candidate for millimeter wave TWT amplifiers. Furthermore, the backward
electromagnetic mode in such BT Glide slow wave structure is not $z$ polarized,
eliminating the {risk} of backward wave oscillations.
