Report by the joint-core team for the establishment of technology bases required for the development of a development of fusion DEMO reactor / by Sakamoto, R., editor, Takenaga, H., editor, Tanaka, H., Tanigawa, H., Okano, K., Tobita, K., editor, Ushigusa, K., Kaneko, O., Sakamoto, Y., Yamada, H., editor, Ozaki, A., editor, Kasada, R., National Institute for Fusion Science