JAPANESE UNIVERSITIES ACTIVITIES FOR PFC DEVELOPMENT AND PMI STUDIES

Development of reliable plasma facing components (PFC) with active coo ling structures is required for divertor plates of fusion devices in o rder to remove a large heat flow to the divertor. It is also known tha t plasma material interactions (PMIs), i.e. fuel hydrogen recycling an d erosion of plasma facing material (PFM) determine the energy confine ment characteristics. The lifetime of PFCs is limited by the erosion o f PFMs. In Japanese universities, studies concerning PFCs and PMIs hav e been carried out so far for LHD and ITER. For the LHD divertor, both graphite/copper brazed components and mechanical joint components hav e been developed, and the heat load performance has been examined. For the particle control in LHD, a localized divertor called LID has been designed, the preliminary experiment was conducted in a small helical device, the CHS. In order to reduce the oxygen impurity level, boroni zation experiments have been conducted systematically, and properties such as oxygen gettering and hydrogen retention were clarified. In the TRIAM-1M tokamak, the damage of PFMs has been investigated using a su rface probe. Data on hydrogen retention, which determines the degree o f hydrogen recycling, have been accumulated for graphite, Li, B, B4C, SiC and W. Conditioning methods are also suggested. In this paper, the problems associated with PFCs and PMIs are pointed out and data recen tly obtained in Japanese universities and NIFS are briefly introduced. (C) 1998 Elsevier Science S.A. All rights reserved.