We aim to develop a persistent-mode 1.3 GHz (30.5 T) NMR magnet with a REBCO layer-wound (LW) insert, a Bi-2223 LW midsert and LTS LW outsert. Protection of the REBCO insert is of great importance and we have employed intra-layer no-insulation (LNI) method in a magnet design ,. In the present work, we developed a model magnet similar to the 1.3 GHz NMR magnet, i.e. REBCO/Bi-2223/LTS magnet, to demonstrate 30 T high field generation and protection of the REBCO insert from a thermal runaway. A LNI REBCO coil (i.d. 17.6 mm : o.d. 70 mm : length 40.1 mm) and a Bi-2223 coil (i.d. 80 mm : o.d. 124 mm : length 384 mm) were connected in series and charged in the cold bore of a 17.2 T LTS magnet. We achieved the center magnetic field of 30 T at the REBCO/Bi-2223 coil current of 265.6 A without normal voltage and discharged the coils. We made a charging test again and continued to increase the current of the REBCO/Bi-2223 coil. The REBCO coil eventually showed a thermal runaway at 289.6 A in 31.4 T which resulted in no degradation of the REBCO coil. These results provide a promising prospect of the 1.3 GHz NMR magnet with an LNI REBCO insert.
1] H. Maeda et al., IEEE Trans. Appl. Supercond. 29 (2019) 4602409
 Suetomi et al 2019 SuST 32 045003
This work is supported by the JST Mirai-Program Grant Number JPMJMI17A2.