Study on Mechanical Movements of HTS Coils Due to Winding and Thermal Effect

Structural concerns in high-temperature superconducting (HTS) magnets under high magnetic fields have received growing attention, yet the mechanical behavior during fabrication and cooling remains less studied. This work examines small-scale REBCO pancake coils by tracking turn displacement using surface markers applied during winding and thermal cycling. Reference lines drawn from the bobbin to the outer turns enabled direct visualization of azimuthal movement under varying winding tensions. Compared to theoretical predictions based on stiffness, REBCO coils showed displacements up to six times larger, while stainless steel coils aligned well with expected values. During thermal cycling, only REBCO coils wound at lower tension without full insulation exhibited measurable displacement near the inner turn after the first cooldown.