Modeling the characteristics of a magnetically switched pulse-forming line

Abstract

Recent developments in magnetic switching technology have enabled linear induction accelerators to operate at high repetition rates. These accelerators provide high-average-power electron beams for many applications. However, some applications, such as free-electron lasers, also require a beam with a very narrow energy spread. As a result, the characteristics of the waveform driving the induction cell are very critical. Several accelerator systems at Lawrence Livermore National Laboratory use three-stage magnetic pulse compressors in which the final stage consists of a pulse-forming line (PFL) followed by a saturable output reactor. Ideally, the PFL forms a pulse with the required rise time and flatness. Unfortunately, traveling waves introduced on the PFL during the charging process as well as output switch performance may degrade the pulse shape. To understand the effect of these factors upon the output pulse shape, we have used the computer code SPICE to model the final stage. The model simulates PFL dynamics under various conditions and includes a first-order model of the saturable output reactor. Discussed in this paper are the saturable inductor model and results obtained with the final stage compression model.