Experiments employing a pulsed relativistic electronbeam 0-typet oscillator, which drives two 0-type amplifiers, operating at levels of a few hundred megawatts in the Xband are described. A second configuration of oscillatoramplifier was also designed, fabricated and cold-tested, but experiments using it have not yet been performed.In the first configuration a backward-wave oscillator (BWO) drives two independent travelling-wave amplifiers (TWT) , with each slow-wave structure having its own independent relativistic electron beam. The microwaves are coupled, using matched sections of TE-mode waveguide, from the upstream end of the BWO into the upstream ends of the amplifiers, with each amplifier having its own output window and waveguide. TWT gain is typically 10 to 25 dB, depending upon the number of ripple sections in its slow-wave structure (10 to 20) and upon the electron beam parameters. Spontaneous oscillations occurred occasionally at the highest gains. The field emission cathodes of the BWO and TWT's were all connected to the same pulse-forming line to eliminate problems with the timing of pulses.In the second configuration the same electron beam passes through both the BWO and the TWT structures. Two versions of this configuration eçist, one in which both the electromagnetic wave and the beam spacecharge wave are coupled from oscillator to amplifier, and one in which the structures are separated by a region that is cut off to the electromagnetic wave, and only the beam wave is coupled through. This configuration permits the use of high modes in large-diameter waveguide, to allow large powers to be generated without electrical breakdown.Experimental results showing power output, pulse distortion, 'gain, and output matching are presented. A brief discussion of the pulse -shortening syndrome, and the apparent absence of it in TWT's also is given. The results of experiments are compared to computer calculations where possible.
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