Divertor shaping with neutral baffling as a solution to the tokamak power exhaust challenge
K. Verhaegh, J. Harrison, D. Moulton, B. Lipschultz, N. Lonigro, Nicola Lonigro, Peter G. Ryan, C. Theiler, T. Wijkamp, D. Brida, C. Cowley, Gijs Derks, R.S. Doyle, F. Federici, B. Kool, O. Février, A. Hakola, S. Henderson, H. Reimerdes, A. Thornton, N. Vianello, M. Wischmeier, Marco Wischmeier, Lingyan Xiang, the EUROfusion Tokamak Exploitation Team, D. Abate, J. Adamek, M. Agostini, C. Albert, F. C. P. Albert Devasagayam, S. Aleiferis, E. Alessi, J. Alhage, S. Allan, J. Allcock, M. Alonzo, G. Anastasiou, E. Andersson-Sunden, C. Angioni, Y. Anquetin, L. Appel, G. M. Apruzzese, M. Ariola, C. Arnas, J. F. Artaud, W. Arter, O. Asztalos, L. Aucone, M. H. Aumeunier, F. Auriemma, J. Ayllon, E. Aymerich, A. Baciero, F. Bagnato, L. Bähner, F. Bairaktaris, P. Balázs, L. Balbinot, I. Balboa, M. Balden, A. Balestri, M. Baquero Ruiz, T. Barberis, C. Barcellona, O. Bardsley, M. Baruzzo, S. Benkadda, T. Bensadon, E. Bernard, M. Bernert, H. Betar, R. Bianchetti Morales, J. Bielecki, R. Bilato, P. Bilkova, W. Bin, G. Birkenmeier, R. Bisson, P. Blanchard, A. Bleasdale, V. Bobkov, A. Boboc, A. Bock, K. Bogar, P. Bohm, T. Bolzonella, F. Bombarda, N. Bonanomi, L. Boncagni, D. Bonfiglio, R. Bonifetto, M. Bonotto, D. Borodin, I. Borodkina, T. O. S. J. Bosman, C. Bourdelle, C. Bowman, S. Brezinsek, D. Brida, F. Brochard
Abstract
Exhausting power from the hot fusion core to the plasma-facing components is one fusion energy’s biggest challenges. The MAST Upgrade tokamak uniquely integrates strong containment of neutrals within the exhaust area (divertor) with extreme divertor shaping capability. By systematically altering the divertor shape, this study shows the strongest evidence to date to our knowledge that long-legged divertors with a high magnetic field gradient (total flux expansion) deliver key power exhaust benefits without adversely impacting the hot fusion core. These benefits are already achieved with relatively modest geometry adjustments that are more feasible to integrate in reactor designs. Benefits include reduced target heat loads and improved access to, and stability of, a neutral gas buffer that ‘shields’ the target and enhances power exhaust (detachment). Analysis and model comparisons shows these benefits are obtained by combining multiple shaping aspects: long-legged divertors have expanded plasma-neutral interaction volume that drive reductions in particle and power loads, while total flux expansion enhances detachment access and stability. Containing the neutrals in the exhaust area with physical structures further augments these shaping benefits. These results demonstrate strategic variation in the divertor geometry and magnetic topology is a potential solution to one of fusion’s power exhaust challenge. Power exhaust is one of the biggest challenges stopping fusion energy. This article shows experimental evidence for strategically shaping the power exhaust region as a solution to this challenge, utilising physics understanding to strike a balance between engineering complexity and power exhaust benefits, consistent with reduced models and simulations.