A Small D-dot for Use on Flux Compression Generators

Abstract

A D-dot voltage probe was designed and tested on a megajoule class flux compression generator (FCG) to measure the voltage on the generator load. Design calculations will be shown, along with experimental data taken from laboratory prototype testing as well as the explosive FCG experiment. The D-dot was terminated in a high impedance amplifier, so that the D-dot is mostly self-integrating (i.e. a capacitive divider). The amplifier limits the bandwidth of the probe to 40 MHz, which was sufficient for the transients expected in the experiment. The high sensitivity of this termination allows the use of a small, non-disturbing probe. The FCG D-dot data, combined with a measurement of the current using B-dot probes, can be used to calculate the dynamic impedance of the load. The load for the FCG was designed to be a static inductor, however, small load impedance changes on the order of 10's of μOhm are present as the conductors heat up and move apart at high current. This change in impedance of the load was modeled with ALE3D (multi-physics Lawrence Livermore code) [1] and compared to the measured voltage.