The interaction between the core and pedestal of tokamak plasma plays a pivotal role in optimizing the performance of future fusion reactors. Recent research published on March 18, 2025, explored the prediction of kinetic profiles—specifically electron temperature and density—using innovative modeling techniques on the Experimental Advanced Superconducting Tokamak (EAST) device.
The study focused on using the REPED model, which applies empirical observations to predict pedestal structures for type-III edge-localized mode (ELM) H-modes. By coupling the REPED model with the TGYRO transport module, researchers aimed to accurately predict the kinetic profiles from the core of the plasma to the separatrix, where the plasma transitions to the edge.
Previous modeling efforts using the REPED model have shown promising results for type-I ELM plasmas. The current study expands this analysis to include type-III ELMs, which have distinct characteristics defined by their inverse relationship between ELM frequency and heating power. Through comprehensive validation against experimental results from EAST, the research provided significant insights for predicting plasma behavior under H-mode operation.
The REPED model’s strength lies not just in predicting the size and structure of the plasma pedestal but also how changes affect overall core confinement. The research established the scaling relationship between the pedestal width and poloidal pedestal beta, allowing for refined predictions of plasma behavior. These insights are particularly important as they signify how advancing our predictive capabilities can aid the long-term goal of achieving sustainable fusion energy.
The team validated their approach against various type-III ELMs, ensuring their predictions aligned closely with experimental measurements. During these tests, they observed discrepancies, particularly concerning electron density profiles, highlighting the conductivity changes due to impurity seeding during the discharge process.
Chaotong Yang and Kai Li, key contributors to the study, emphasized the model's applicability by stating, "The predicted 00T_{e} and 00T_{i} profiles are in good agreement with experimental measurements; differences were observed in the core 00n_{e} profile because of the H-mode discharge with the impurity seeding." This highlights both the practical successes of the REPED model and the challenges faced when attempting to achieve perfect calibration with real-world data.
The study also explored how ideal magnetohydrodynamic (MHD) constraints could be applied to understand type-III ELM behavior. The authors noted, "We understand type-III ELMs should be described by resistive MHD; here we apply ideal MHD constraints to test the extent to which the ideal MHD can predict the pedestal structure of the type-III ELMs using the REPED model." This approach allowed for quicker simulations, which could aid researchers when attempting real-time profile predictions during experiments.
Overall, the findings indicate significant progress toward achieving more accurate kinetic profile predictions for plasma discharges, with the REPED model validating its reliability through empirical testing. By providing the means to efficiently predict these structures, researchers are laying the groundwork for enhanced operation of tokamaks, potentially guiding future designs for more effective and reliable fusion reactors.
This study was supported by the National Natural Science Foundation of China under Grant No. 12205157, illustrating collaborative efforts dedicated to advancing the research capabilities of fusion technology.
