Thermal energy mitigation and toroidal peaking effects in JET disruptions

Journal Article · 30 April 2025 · Physics of Plasmas

DOI: https://doi.org/10.1063/5.0261146 · OSTI ID:2563646

Stein-Lubrano, Ben  ^[1]; Sweeney, Ryan  ^[2]; Lovell, Jack  ^[3]; Baylor, Larry  ^[3]; Bonfiglio, D.  ^[4]; Carvalho, P.  ^[5]; Granetz, R. S.  ^[1]; Jachmich, S.  ^[6]; Joffrin, E.  ^[7]; Lehnen, Michael  ^[6]; Maggi, Costanza  ^[5]; Marmar, E. S.  ^[1]; Puglia, Paulo  ^[5]; Rice, J. E.  ^[1]; Sheikh, Umar  ^[8]; Shiraki, Daisuke  ^[3]; Silburn, Scott  ^[5]

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1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
2. Commonwealth Fusion Systems, Cambridge, MA (United States)
3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
4. Univ. di Padova (Italy). Consorzio RFX; Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Padova (Italy); Istituto Nazionale di Fisica Nucleare (INFN), Padova (Italy); National Research Council (CNR), Padova (Italy). Institute for Plasma Science and Technology (IPST)
5. UK Atomic Energy Authority (UKAEA), Culham (United Kingdom). Culham Centre for Fusion Energy (CCFE)
6. ITER Organization, St. Paul Lez Durance (France)
7. CEA, IRFM, Saint Paul Lez Durance (France)
8. Ecole Polytechnique Federale Lausanne (EPFL) (Switzerland)

Previous investigations on JET suggest half or less of plasma stored thermal energy W_th is radiated (f_rad,th ≲ 0.5) using either massive gas injection (MGI) or shattered pellet injection (SPI) disruption mitigation. We investigate whether the apparent incomplete f_rad,th is explained by radiation peaking near the injection plume. High toroidal peaking throughout the pre-thermal quench is found in argon–deuterium MGI on JET, with typically >3× higher radiation near the injector than toroidally distant. Previously unexplained toroidal bolometry measurements in neon–deuterium SPI are reproduced with similar peaking using the Emis3D radiation analysis code. These observations align with results from Alcator C-Mod and KSTAR. This peaking is not captured by previous JET studies that found poor thermal mitigation. Two sets of neon–deuterium SPI and two sets of argon–deuterium MGI are analyzed using Emis3D. In SPI, f_rad,th rises from no-plume estimates of 0.31 and 0.66 to lower bounds of 0.84 and 0.92, respectively, and f_rad,th ∼ 1 is possible. In MGI, the toroidal spread of the peaking feature is poorly constrained. f_rad,th up to 0.85 and 0.65 are possible using the largest possible spread, increasing from 0.42 and 0.28, although f_rad,th ∼ 1 does not appear to be reached. Revised mitigation estimates on JET suggest a lower melt risk to the divertor in mitigated disruptions on ITER and SPARC than previously thought. However, peaking near injectors could increase flash melting risk on nearby plasma facing components.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: European Union (EU); ITER Organization; Swiss State Secretariat for Education, Research, and Innovation (SERI); USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Grant/Contract Number: AC05-00OR22725; SC0014264
• OSTI ID: 2563646
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 4 Vol. 32; ISSN 1070-664X; ISSN 1089-7674
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English