Results from a study of a relativistic X-Band backward-wave oscillator
(RBWO) with 3-GW output microwave power are presented. The RBWO was d
riven by the high-current electron accelerator SINUS-7. The dependence
of radiated microwave pulse duration on microwave power was obtained,
Pulse shortening occurring at the higher power levels is probably att
ributable to explosive electron emission from the slow wave structure
(SWS), An increase in the cross section of the electrodynamic structur
e seems to be a way to increase the microwave pulse duration. Experime
ntal results from a moderately oversized X-band RBWO using a resonance
reflector are described. This tube can be operated,vith a low externa
l magnetic field.