Very Low Impedance Pulse Forming Lines Built From Ferroelectric Tiles

A new approach to the construction of very low impedance pulse forming lines for application to low impedance loads such as z-pinches is being studied. The basic idea is to build parallel plate lines using tiles of barium titanate ceramic of the sort commonly used in "door-knob" high voltage ceramic capacitors. The tiles are typically 75 x 75 mm square and 25 mm thick and are metallised on the two square faces. The high dielectric constant of the ceramic means that lines can be built with impedances of around 2 Omega. In addition quite short lengths of line can be used to generate relatively long pulse lengths. For example a 2.5 m long line can generate a mus pulse. To achieve still lower impedances the lines can built as a folded, double pulse forming line and then run in parallel with many other lines1. It is hoped that very large currents could be generated by this technique sufficient to drive a substantial z-pinch plasma. The main concerns in using this approach to the construction of low impedance pulse forming lines are the breakdown strength of the tiles, their piezoelectric characteristics, the non-linearity of the dielectric constant of the tiles and the need to use very low inductance switching to avoid significant loss of pulse rise-time. By milling grooves into the sides of the tiles it has been possible to charge them, under oil, to a potential of 59 kV without breakdown.