Application of the radiating divertor approach to innovative tokamak divertor concepts

We survey the results of recent DIII-D experiments that tested the effectiveness of three innovative tokamak divertor concepts in reducing divertor heat flux while still maintaining acceptable energy confinement under neon/deuterium-based radiating divertor (RD) conditions: (1) magnetically unbalanced high performance double-null divertor (DND) plasmas, (2) high performance double-null Snowflake (SF-DN) plasmas, and (3) single-null H-mode plasmas having different isolation from their divertor targets. In general, all three concepts adapt well to RD conditions, achieving significant reduction in divertor heat flux (q(perpendicular to p)) and maintaining high performance metrics, e.g., 50-70% reduction in peak divertor heat flux for DND and SF-DN plasmas that are characterized by beta(N) congruent to 3.0 and H98((y,2)) approximate to 1.35. It is also demonstrated that q(perpendicular to p) could be reduced approximate to 50% by extending the parallel connection length (L parallel to-XPT) in the scrape-off layer between the X-point and divertor targets over a variety of the RD and non-RD environments tested. (C) 2014 Elsevier B.V. All rights reserved.