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_⊥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 β_N ≅ 3.0 and H_98(y,2) ≈ 1.35. It is also demonstrated that q_⊥p could be reduced ≈50% by extending the parallel connection length (L_||-XPT) in the scrape-off layer between the X-point and divertor targets over a variety of the RD and non-RD environments tested