Dielectric studies in the development of high energy density pulsed power capacitors

In an effort to increase the energy density of high voltage capacitors to greater than 5 J/cm³ for compact pulsed power sources, high dielectric constant materials with high dielectric strength are under continued development at the University of Missouri. The materials are modified versions of composites recently developed for compact dielectric-loaded antennas. While the composites for antennas were developed specifically for use at 100s of MHz to several GHz, the requirements of capacitor applications present unique challenges. In particular, the leakage current must be minimized to efficiently store the energy for long periods of time, and the dielectric losses must be considered at relatively low frequencies up to several 10s of MHz. This paper details the dielectric properties of the materials under development for high energy density pulsed power capacitors. The dielectric constant and loss are reported under low electric field conditions at frequencies relevant for capacitor applications. The leakage current under high electric field conditions is presented, and the dielectric constant under high electric field conditions is calculated from analysis of the fast discharge of sample capacitors charged to high voltage. Finally, projections are provided on how the materials may be scaled from small capacitors for dielectric evaluation to full-size prototypes.