Measurement of Solid Armature's in Bore Velocity Using B-Dot Probes in Series Enhanced Railgun

The solid armatures displacement and velocity can be obtained by arranging B-dot probe arrays along the barrel of a series enhanced railgun. The moment of armature arrival can be determined by an evident change in the differential signals of B-dot probes while armature passing by. However, it is difficult or even impossible to pick up the arrival moment directly because of not only armature movement but also current variety, especially for the series enhanced railgun with currents in outer rails and connecting conductors. To eliminate the influence of current variety, the ratio function is introduced, which is the ratio of the differential signal integral to the current. The ratio function of armature B-dot probe will reach a maximum when the armature arrives, while the one of rail B-dot probe will reach the median. Three shots with same initial conditions, which adopted armature probe, rail probe and VISAR respectively, were carried on a series enhanced railgun. The well agreement with each other about displacement and velocity waveforms indicated that method and measurement were valid. The accuracy of B-dot method is mainly affected by probe size and position, railgun current distribution and electromagnetic noise.