"FINEMET^®" pulsed power cores use our newly developed nanocrystalline soft magnetic material"FINEMET^®" which has both high magnetic flux density and low loss properties. The cores are insulated by thin ceramics film which provides high voltage insulation between the ribbon layers. These cores are suitable for saturable cores and step-up transformer cores used in high voltage pulsed power supplies for Excimer lasers and accelerators, and for cavity cores used in induction linacs and RF accelerators.