A compact modulator for RF source development

A compact, low repetition rate, pulse-modulator is being developed for use as a driver in high power microwave experiments. A single stage of the modulator consists of a 16 Ω pulse forming network in a Blumlein configuration driving a 3:1 coaxial ferrite loaded pulse transformer. The output of the transformer is a 100 kV, 150 ns (FWHM) pulse, with a 70 ns flat top (±1.0%), into a matched load. A second device, driven with a different pulse line, gives a 130 ns flat top pulse. To obtain the flat top requires tuning with a reactive circuit in the transformer primary. We plan to stack transformer modules in series to obtain a 500 kV, 1 kA modulator. A second stage is currently being built and various stacking techniques are being investigated