Speaker
Description
A 12 mm-period, 0.6 m-long HTS undulator, employing staggered-array Gd-Ba-Cu-O (GdBCO) bulks and magnetized by a 7 T superconducting solenoid, is currently being fabricated at Zhangjiang Laboratory for deployment at the Shanghai Soft X-ray Free Electron Laser (SXFEL) facility [1-2]. Realizing an undulator field with an RMS phase error of only a few degrees requires approximately 100 half-moon-shaped GdBCO disks with highly uniform field trapping capabilities in the temperature range of 7 to 10 K. Preliminary magnetic assessments at 77 K are essential to expedite the selection of qualified GdBCO disks. A 2D magnetic field scanning system was developed to identify GdBCO disks with internal cracks, magnetized at 0.3 T at 77 K, while a magnetic levitation force measurement system screens disks with extreme superconducting performance. Twenty presorted GdBCO disks, selected based on their measured levitation forces, were assembled with ferromagnetic poles in a staggered-array configuration to construct a ten-period undulator model with a period length of 12 mm. The short undulator model was field-cooled at 77 K using an 0.3 Tesla electromagnet, with its magnetic properties characterized using a four-dimensional magnetic field measurement system. Based on the measured undulator field profile, the superconducting performance of each GdBCO disk was extrapolated, enabling their re-sorting and height adjustments of those ferromagnetic poles to achieve a more uniform undulator field. This study presents a comprehensive overview of the sample preparation process, magnetic characterization of individual GdBCO disks, and magnetic field optimization for the short-period HTS undulator model.
Key words: HTS undulator, RE-Ba-Cu-O bulk, Magnetic Field Optimization.
REFERENCES
[1] K. Zhang et al, 2025, IEEE Trans. Appl. Supercond., 35, 4100205
[2] D. Wei et al, 2024, IEEE Trans. Appl. Supercond., 34, 4100705
