Two-Dimensional Measurement Technique for Dynamic Magnetic Flux Density Distribution on the Surface of HTS Bulk

It is indispensable to the development of the superconductive electromagnetic machinery to measure the magnetic held precisely. In general, the scanning of a Hall probe over the HTS bulk is used for the measurement of the magnetic held. Because the Hall probe works mechanically, we need a long time before the measurement is completed. However, information about dynamic magnetic flux density distribution is not obtained. On the other hand, there is a method where several Hall elements placed on the HTS bulk surface measure the magnetic held. It is difficult to measure variation in the dynamic magnetic held by using a Hall element reacting with a delay, but a Hall element completes the measurement on the order of 1 ms. Instead, information about magnetic flux density distribution on the whole of the HTS bulk surface is not obtained. In this study, we have developed the measurement system of which dynamic magnetic flux density distribution is continuously measured using a Hall element to be placed on an HTS bulk surface in a short time. A new magnetic held sensor with 5 × 5 = 25 Hall elements forming a line at regular intervals can measure a magnetic held on the HTS bulk surface every about 1 ms. The 225 Hall elements require 900 electric wirings. On the other hand, our magnetic sensor needs only 76 wirings. We applied pulsed magnetic held to a two-dimensional magnetic held sensor with 5 × 5 = 25 Hall elements for operation verification. The sensor measured a dynamic variation of the magnetic flux density distribution every 0.5 ms. In future, we will clarify the details of the magnetic flux characteristic trapped to HTS bulk magnet by using the two-dimensional magnetic held sensor.