During the last decades, it was demonstrated that magnetic field sensors based on nanostructured lanthanum manganite films exhibiting the colossal magnetoresistance (CMR) phenomenon could be used for high pulsed magnetic field measurement in very small volumes (10-2 mm³) [1]. These sensors are capable of measuring the magnetic field magnitude independent of the magnetic field direction (CMR-B-scalar sensors) [2]. They were used for the measurement of magnetic field distribution [3] and diffusion processes in railguns [4]. It was showed that they are a suitable instrument for measuring the field with high resolution in both time and space. In all these experiments the pulse duration of magnetic field was 1-100 milliseconds.
However, in some processes the significantly shorter magnetic pulses with high amplitude should be measurement. Magnetic Pulse Welding (MPW) is one of this process. The MPW is a collision welding process, which uses a high velocity impact to join two metals that are accelerated by short (about 20 – 30 μs) strong (~10 T) magnetic field. The measurement of the intensity and dynamics of the magnetic field at different positions during the electromagnetic forming or welding process is not only required for the calculation of the magnetic pressure, which influences the acceleration, but can also provide additional information about the processes that take place during the MPW. Therefore, the magnetic field sensors, which are capable to measure these fields, should be designed and tested.
Short pulsed high magnetic field generation system for electromagnetic welding and forming was designed for testing the CMR-B-scalar sensors. It consisted of capacitor bank, spark-gap switch and a Bitter coil. A 50 μF capacitor charged up to 9 kV was discharged throughout 5 winding Bitter coil and the magnetic pulse of about 25 μs with amplitude of 5 T was generated inside the coil. The tested sensor was positioned inside of the coil (or in the field shaper) and the output signal was recorded by a measuring module. It was found that this kind of sensor is easy installed to the measuring position, because due to diminished anisotropy the CMR-B-scalar sensor does not require an exact orientation with respect to the magnetic field direction. Moreover, it is very small and thus can be applied for measuring the magnetic field locally. In addition, the measurement module of the system has a sufficient time resolution to measure fast magnetic field changes. However, some problems concerning the "loop" effect (induced parasitic signal due to electromotive forces) and electromagnetic noises should be resolved to obtain output signal of sensor with higher accuracy. The possibility to use these sensors for the measurement of magnetic field dynamics during magnetic pulse forming of metal tube will be demonstrated.