Optimizing the Super H-mode pedestal to improve performance and facilitate divertor integration
M. Knölker, P.B. Snyder, T.E. Evans, T. M. Wilks, D. Eldon, B. A. Grierson, A.E. Jaervinen, Xiang Jian, F. M. Laggner, J. McClenaghan, A.G. McLean, T.H. Osborne, C. Paz-Soldan, F. Scotti, W.M. Solomon
Abstract
Access to Super H-mode is demonstrated for moderately shaped plasmas in agreement with EPED [Snyder et al., Phys. Plasmas 16, 056118 (2009)] predictions. In particular, Super H-mode is realized in a DIII-D shape that is accessible to the JET tokamak. The reduced triangularity of the JET-compatible shape compared to previous Super H-mode plasma shapes does not prevent deep ascension into the so-called Super H-mode “channel.” Operationally, access is enabled and optimized by delaying the neutral beam power injection and, thus, protracting the L–H transition. In highly shaped DIII-D plasmas, the injection of nitrogen sufficient for the establishment of a radiative divertor is shown to be possible during Super H-mode without pedestal degradation. Due to its increased stored energy and radiative divertor integration capabilities, Super H-mode is a promising candidate as operating regime for JET, ITER, and future fusion reactors.