Generation of sawtooth and square waveforms for heavy ion induction accelerator cells using impedance tapered PFN's

Abstract

The induction linear accelerator is a leading candidate for the acceleration of high current heavy ion beams to initiate inertial confinement fusion (ICF). To impart energy to the ion beam, it is necessary to generate well controlled ramped pulses at the beginning of the acceleration cycle and flat top pulses in later stages of the linac. The linac consists of many series induction cores similar to other previous induction accelerators but with the added requirement that the waveshapes are changing along the length of the accelerator in order to maintain longitudinal stability. It is highly desirable to generate these waveforms to be within a few percent of the ideal as required by physics so that a minimum of active modulators are applied to reach 1% of ideal. Since the induction cores are highly nonlinear, impedance tapered PFN's are used to generate both sawtooth and square pulses.