Advances in coherent power summation of independent Ka-band HPM oscillators

Recently we have demonstrated^1-2 that X-band and Ka-band microwave pulses from two identical relativistic subgigawatt backward wave oscillators can be phase-synchronized in the picosecond time scale with respect to the sharpened front of high-voltage nanosecond pulses supplying the cathodes of driving high-current electron accelerators. In the Ka-band experiment², two individual pulsed double forming lines switched by integrated spark gap were used to form such accelerating pulses. In this case, the fronts of accelerating voltage pulses were synchronized so accurately, as it followed from the spread of spatial spark location in the gap of integrated gas discharge switch. This feature of experiment² can be diminished when a single accelerating voltage pulse is split to feed two cathodes, as it was done earlier in the X-band experiment¹. In the report we present results of preliminary experiments with two independent subgigawatt Ka-band BWO oscillators when such HPM devices are driven by spit (2.5-3)-GW pulse from a single high-voltage supply source operating without spark gaps, at all. This source represents an all-solid-state SOS modulator, type S-500, equipped with a coaxial power divider and output transmitting lines with biased-saturated ferrites for precise controllable adjustment of the pulses steepness and delay.