ABSTRACT
Representative source parameters for BWOs and the multiwave devices are shown in Table 8.1. For reasons that are perhaps more historic than physics based, these devices have been optimized for gigawatt-level power output from the S-band up to 60 GHz, with a peak power of 15 GW exiting the slow-wave structure of an MWCG at a frequency just below 10 GHz. All of the major devices in this class operate at an impedance around 100
Ω
, so that voltages approaching, and exceeding, 1 MV are required for a microwave output in the gigawatt range. Output modes for the BWO and MWCG are usually TM
, with an annular intensity pattern, unless a mode converter
is added downstream. The MWDG and RDG operate in higher-order radial modes with more complicated mode patterns. One of the TWTs with an internal mode converter had a plane-wave-like TE
output. MWCGs, MWDGs, and RDGs were all developed as large-cross-section
devices, with diameters of a few to 10 wavelengths or more. Their strengths are large power production and long-duration/high-energy output pulses, but their large size and the mass and power demand of their magnetic field coils are drawbacks.
