高温超伝導材料を利用した次世代NMR技術の開発;高電流密度コイル化技術の構築(4)-電磁力評価用REBCOコイル試験結果- (Development of the next-generation NMR technology using HTS materials; For achievement of HTS coil with high operating current density (4) - Experimental results of REBCO coils under electromagnetic forces -)