A linear hybrid kicker modulator for ETA-II

A new type of pulse modulator is being developed at Livermore that will rapidly split a high current electron beam into two halves, enabling each half to proceed along separate pathways. Each modulator will be capable of applying a /spl plusmn/10 kV, 200 A pulse onto a transmission line electrode structure with a rise time less than 10 ns, a pulse repetition frequency greater than 1 MHz, and a maximum pulse duration of 400 ns. The electrode structure, located inside the beam-transport pipe, generates an electromagnetic field that acts on part of the original beam to "kick" it in another direction. The true merit of this high-speed modulator will be its flexibility in pulse duration and shape. The electrodynamics involved in altering the beam\´s trajectory require the modulator to generate a time-varying pulse that is precisely tailored in amplitude. Consequently, the modulator is driven by an arbitrary waveform generator and must act more as a linear amplifier than as a simple switch. The requirements of high peak power and wide analog bandwidth (about 50 MHz) is addressed by merging a solid-state driver with an output stage of high-power vacuum tubes. Modulator development and performance data is presented as are the issues of beam-induced voltage and transit-time isolation that are considered when driving a beam load.