The performance of the conduction cooled 2G HTS magnet wound without turn to turn insulation generating 4.1 T in 102 mm bore

Highlights: •Conduction cooled 2G HTS magnet with 102 mm RT bore was designed and assembled •22 double pancakes wound with no-insulation winding method. •Assembled coil generate 4.1 T at 10 K with operating current of 200 A. •No-insulation coil showed charging delay phenomenon. •Magnet quenched at 210 A by 0.15 A/s ramping but showed no degradation. -- Abstract: A large bore magnet coil wound without turn to turn insulation was fabricated and cooled down to 10 K by conduction cooling. The coil has room temperature bore of 102 mm in diameter and consists of 22 double pancakes wound with 2G HTS conductor on aluminium alloy bobbin. Tests for 22 double pancake coils were performed at 77 K for individual single DPC, coupled 2 DPCs, 4 DPCs, 8 DPCs and 22 DPCs. Tested DPCs were connected by splice joint and assembled coil structure was installed to the vacuum cryostat with radiation shield and cooled down to 10 K for 28 h. The coil generate 4.1 T when operating current ramped to 200 A by 0.1 A/s without quench. Test results agreed well with the designed performance showing field homogeneity of 0.021% for radial axis and 0.056% for vertical axis in 10 mm DSV at 4.1073 T. The magnet showed quench at 210 A when ramping rate was 0.15 A/s at 10 K. The results showed that without turn to turn insulation winding method is a possible option for making compact magnet coil with sufficient structural integrity, thermal and electrical stability at the same time