Application of a Hall sensor for pulsed magnetic field measurement in the FAT-CM FRC experiments

Abstract

Collisional merging experiments of a field-reversed configuration (FRC) plasma at the super-Alfvénic velocity have been conducted in the FAT (FRC Amplification via Translation)-CM (Collisional Merging) device. In the experiments, two FRCs are collided and merged in a confinement section with a quasi-static confinement magnetic field. Therefore, it is necessary to measure the high-frequency pulsed magnetic field superposed on a quasi-stationary signal. The magnetic field is generally measured by a magnetic coil probe in the pulse discharge experiments; however, in such measurements, errors arise in the low-frequency band in the conducted FRC experiments. Therefore, a Hall sensor has been applied for low-frequency magnetic field measurements in the FAT-CM experiments. Calibration of the Hall sensor involves confirming that the sensor has a sufficient response speed and linear characteristics for the magnetic field with a rising time of approximately 240 µs and that its output voltage does not saturate up to a magnetic field of 0.7 T. Combination of the Hall sensor and the magnetic coil probe ensures a comprehensive measurement of the magnetic field in the range of FAT-CM experiments. In this study, accurate magnetic measurements were performed in a collisional merging experiment in the FAT-CM device by using a combined magnetic diagnostic system.

Measurement System for Short-Pulsed Magnetic Fields

“…However, as the measured signal in this case is proportional to the derivative of the magnetic pulse, to obtain the real magnetic pulse shape, the signal has to be integrated. This leads to error accumulation throughout the integration period [ 7 ]. Other measurement techniques are based on the Hall effect [ 8 ], and several magnetoresistivity effects such as anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunneling magnetoresistance (TMR) [ 9 , 10 , 11 ].…”