Noise study of open-loop direct current-current transformer using magneto-resistance sensors

This paper presents a detailed noise analysis study for an open-loop Direct Current-Current Transformer using magnetic field sensors. The device is intended to be used for ion-beam measurements in the `Facility of Antiproton and heavy Ion Research' in Germany. The device is used for real-time ion-beam measurements in particle accelerators. The main objective is to measure the particles stored inside the accelerator for long time durations that cannot be detected by classical transformers [2]. Commercial magnetic field sensors are used to measure the magnetic field generated by the ion-beam. Magneto-resistance effect sensors are used to sense the magnetic field, in specific Giant and Tunneling Magneto-Resistance sensors. The noise of the sensor determines the minimum detectable signal of the instrument. A detailed theoretical noise study is given, followed by noise measurements for different sensor types. The measured minimum detectable magnetic field of the device is 16nT at very low frequencies which corresponds to 128μA current resolution.