Modeling Temperature Profiles in the Pedestal of NSTX with Reduced Models
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| Main Authors: | , , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866914412270452736 |
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| author | Li, P. -Y. Hatch, D. R. Leppin, L. A. Schmidt, J. Parisi, J. F. Lampert, M. Kotschenreuther, M. Mahajan, S. M. |
| author_facet | Li, P. -Y. Hatch, D. R. Leppin, L. A. Schmidt, J. Parisi, J. F. Lampert, M. Kotschenreuther, M. Mahajan, S. M. |
| contents | This paper describes new modeling capabilities for predicting H-mode pedestal profiles in spherical tokamaks. Temperature profiles for NSTX discharges 132543 and 132588 are modeled by coupling the \textsc{astra} transport solver with neoclassical transport and gyrokinetic-based reduced models for electron temperature gradient (ETG) and kinetic ballooning mode (KBM) instabilities. A quasi-linear surrogate model for ion-scale transport is developed using linear \textsc{gene} simulations, requiring only a single free parameter calibrated to one discharge. Time-evolving the temperatures with fixed density yields good agreement with experiments for both discharges. Systematic analysis of the transport mechanisms reveals that neoclassical transport is huge across the entire pedestal region for the ion channel. ETG turbulence is large in the plasma edge and low density gradient region, contributing substantially to the electron channel. However, KBM/MHD-like modes also drive significant transport in both the ion and electron thermal channels, making them essential for accurate pedestal modeling. Further refinements, including explicit $E \times B$ shear suppression and scaled ETG transport, produce quantitative but not qualitative improvements. This work lays the foundation for predictive modeling of future devices. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_20502 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Modeling Temperature Profiles in the Pedestal of NSTX with Reduced Models Li, P. -Y. Hatch, D. R. Leppin, L. A. Schmidt, J. Parisi, J. F. Lampert, M. Kotschenreuther, M. Mahajan, S. M. Plasma Physics This paper describes new modeling capabilities for predicting H-mode pedestal profiles in spherical tokamaks. Temperature profiles for NSTX discharges 132543 and 132588 are modeled by coupling the \textsc{astra} transport solver with neoclassical transport and gyrokinetic-based reduced models for electron temperature gradient (ETG) and kinetic ballooning mode (KBM) instabilities. A quasi-linear surrogate model for ion-scale transport is developed using linear \textsc{gene} simulations, requiring only a single free parameter calibrated to one discharge. Time-evolving the temperatures with fixed density yields good agreement with experiments for both discharges. Systematic analysis of the transport mechanisms reveals that neoclassical transport is huge across the entire pedestal region for the ion channel. ETG turbulence is large in the plasma edge and low density gradient region, contributing substantially to the electron channel. However, KBM/MHD-like modes also drive significant transport in both the ion and electron thermal channels, making them essential for accurate pedestal modeling. Further refinements, including explicit $E \times B$ shear suppression and scaled ETG transport, produce quantitative but not qualitative improvements. This work lays the foundation for predictive modeling of future devices. |
| title | Modeling Temperature Profiles in the Pedestal of NSTX with Reduced Models |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2603.20502 |