T. Onodera et T. Hoashi, GENERALIZED REPRESENTATION OF BEAM COUPLING COEFFICIENT IN UNGRIDDED REENTRANT CAVITY, I.E.E.E. transactions on electron devices, 45(8), 1998, pp. 1858-1860
The Beam coupling coefficient and cavity voltage in an ungridded reent
rant cavity, in which the gap electric field varies in hyperbolic cosi
ne function and electrons move only along the axial direction, are der
ived from the analytical expressions of Kosmahl and Branch on electric
fields in the cavity.