Railgun electric fields: Theory and experiment

Recent experiments were conducted and related three-dimensional theoretical predictions were made to identify sources of the electric held (E-field) n ear the ARL 15-mm and 50-mm square-bore railguns during the pulse discharge . This work was undertaken to better understand the results of earlier stud ies which reported measured E-field pulse shapes that resembled the muzzle voltage but whose magnitudes were much larger than those predicted on the b asis of quasi-static currents Rowing only in the rails and armature. In the se recent experiments, an armature was stationary in the bore of the railgu n while the E-field was measured. Peak currents for the 15-mm and 50-mm bor e railguns were 72 kA and 233 kA respectively. Two types of E-field probes were used to provide the measured data. The transient E-field data were mea sured at various locations along the length of the rail and with and withou t the power supply shorted at its output. As such, the dominant features of the E-field attributable to the coupling of the railgun with the breech an d power supply could be identified. Based on the analytical predictions and the measured E-field data, it is suspected that the high E-fields were cau sed by current sources within the power supply and railgun breech conductor systems.