Activities of research and development on repetitive induction
voltage modulators in the Tokyo Institute of Technology–High
Energy Accelerator Research Organization group are presented
along with a discussion of the magnetic response of ferro-magnetic
materials to fast magnetization and a transient beam loading
in the modulators. The modulator is composed of independently
driven modules switched by field effect transistors. To make
waveform control, the induced voltages are stacked and synthesized
in the induction unit. A proof-of-principle experiment shows
that the module elements are successfully operated up to megahertz
levels with good reproducibility. For the evaluation of magnetic
core response, magnetic characteristics are investigated over
a wide range of parameters, and an empirical core loss scaling
is derived at minor-hysteresis loops. Using the prototype induction
module, we have also investigated the effect of beam loading.
Results indicate that the effect depends not only on the impedance
of the driving circuit but on nonlinearity of the magnetic-core
response. This means that the response of the induction modulator
depends on the time scale of domain motion and operating point
in the B-H plane of magnetic materials. Based on the progress
of the component technology in the induction accelerator and
database of magnetic materials, a system design has been developed.
Repetitive induction voltage modulator for heavy ion fusion