Design of 5.5 T High Homogeneity Calibration Superconducting Magnet System Based on Conduction Cooling

A 5.5 T superconducting magnet system with conduction cooling used for calibration has been designed by using NbTi/Cu wire. It provides a high homogeneity field of sixth-orders. The magnet system has a warm bore of 35 mm to ensure that the calibrated Hall probe can be easily inserted and positioned. The magnet is cooled down to superconducting state by a two-stage cryocooler with a capacity of 1.5 W at 4.2 K and is operated at 270 A. The magnet uses a combination of soft connection and cryogenic heat pipe (≤ 300 mL) for conduction cooling. It can be seen from the results that the magnetic field homogeneity does not exceed 15 parts per million (ppm) in φ20 mm × 20 mm at the central axis and about 5 ppm in φ10 mm × 10 mm at the central axis. The magnetic field deviation analysis was carried out in the article to provide guidance for coil manufacturing. At the same time, a supporting cryostat system was designed; the structure design and thermal analysis of the cryostat were carried out.