Measurement of the Magnetic Field Distribution in Railguns Using CMR-B-Scalar Sensors

One of the key points in understanding railgun behaviour is the current distribution in the rails. The current is strongly influenced by the fast moving projectile. Excessive current concentration near the contact interfaces leads to heating and wear-out effects of both, solid armatures and rails. If the magnetic field distribution around the conductors is known, conclusions concerning the current distribution can be drawn by using the Biot– Savart law. Precise measurements not only improve the understanding of the experiment but also serve as a validation for difficult “multi-physics” numerical analysis. To enable a precise measurement, magnetic field (B-field) sensors with small measurement volumes are needed. Furthermore, currently used high B-field sensors (> 1T) such as loop, Hall, magneto-optical or giant magnetoresistive sensors do not fulfill all the conditions like small size, accuracy or the usability under rough conditions (plasma, soot etc.) at the same time. A new kind of sensor, consisting of thin manganite films exhibiting the colossal magnetoresistance effect (CMR), is able to measure B-fields up to 40T under electromagnetic launch conditions [1]. A new generation of CMR-B-Scalar sensors, used for the experiments presented in this paper, has a very small volume and is therefore suitable to measure the B-field distribution close to the rails. An earlier paper [2] reported about the use