Performance and transport in the ARC tokamak
- 1Massachusetts Institute of Technology
- 2Commonwealth Fusion Systems
- 3University of California-San Diego
Abstract
The ARC TM tokamak, a high-field ( BT = 11.4 T) fusion power plant, under development by Commonwealth Fusion Systems, is studied using a suite of integrated modelling tools to predict its fusion power generation ( Pfus ), transport and confinement properties. Analysis is based off an ARC operational point scoped first with zero-dimensional (0-D) plasma operational contour (POPCON) modelling to produce 1.13 GW of fusion power. A suite of integrated modelling tools (TRANSP, ASTRA and TORAX) were applied to predict the performance and kinetic profiles of the ARC design point, yielding a range of predicted performance spanning from ∼ 900 to 1300 MW in rough quantitative agreement with POPCON predictions. The sensitivity of these results to uncertain modelling inputs was probed using scans of pedestal boundary conditions around EPED-predicted values (total pressure and temperature ratios), tungsten concentration and seperatrix density around their nominal assumptions. Pedestal pressure and pedestal top (Ti/Te) play a large role in 1.5-dimensional performance predictions, able to modify the predicted Pfus by a factor of 2 within reasonable assumptions. High-fidelity core nonlinear gyrokinetic profile predictions, performed using CGYRO (Candy et al. 2016 J. Comput. Phys. , vol. 324, pp. 73–93) coupled with the PORTALS (Rodriguez-Fernandez et al. 2024 Nucl. Fusion , vol. 64, 076034; Phys. Plasmas , vol. 31, 2024, 062501) framework, yield substantially lower performance ( Pfus = 677 MW) compared with 0-D and medium-fidelity modelling for nominal assumptions, showing that there is non-negligible uncertainty between models and that future work on SPARC may help resolve discrepancies. Lower overall performance results from significantly reduced volume-averaged densities and temperatures, along with reduced levels of density and temperature peaking. Turbulence and transport are largely dominated by ion temperature gradient across the profile, confirmed by both linear stability and the response of the nonlinear fluxes to changes in gradients, with some impact of kinetic ballooning modes in the deep core. This work represents one of the most complete scoping of potential fusion power plant conditions performed to date. The extensive integrated modelling provides confidence in ARC performance approaching 1 GW, while nonlinear gyrokinetic modelling results in open questions into the physics of density and temperature peaking in fusion-power-plant-relevant operational space. A discussion of results and the role that the SPARC tokamak (Creely et al. 2020 J. Plasma Phys. , vol. 86, 865860502) will play in informing ARC design, performance and operation is presented.
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BibTeX
@article{howard2026performance,
title = {{Performance and transport in the ARC tokamak}},
author = {Nathan T. Howard and Pablo Rodriguez-Fernandez and J. Hall and M. Muraca and A. Saltzman and A. Ho and J.C. Hillesheim and Alexander J. Creely and T. Eich and Thomas A.J. Body and P.B. Snyder and C. HOLLAND},
journal = {Journal of Plasma Physics},
year = {2026},
month = jun,
doi = {10.1017/s0022377826101573},
url = {https://doi.org/10.1017/s0022377826101573},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Performance and transport in the ARC tokamak
AU - Nathan T. Howard
AU - Pablo Rodriguez-Fernandez
AU - J. Hall
AU - M. Muraca
AU - A. Saltzman
AU - A. Ho
AU - J.C. Hillesheim
AU - Alexander J. Creely
AU - T. Eich
AU - Thomas A.J. Body
AU - P.B. Snyder
AU - C. HOLLAND
PY - 2026
DA - 2026/06/01
JO - Journal of Plasma Physics
DO - 10.1017/s0022377826101573
UR - https://doi.org/10.1017/s0022377826101573
AB - The ARC ^TM tokamak, a high-field ( B_T = 11.4 T) fusion power plant, under development by Commonwealth Fusion Systems, is studied using a suite of integrated modelling tools to predict its fusion power generation ( P_fus ), transport and confinement properties. Analysis is based off an ARC operational point scoped first with zero-dimensional (0-D) plasma operational contour (POPCON) modelling to produce 1.13 GW of fusion power. A suite of integrated modelling tools (TRANSP, ASTRA and TORAX) were applied to predict the performance and kinetic profiles of the ARC design point, yielding a range of predicted performance spanning from ∼ 900 to 1300 MW in rough quantitative agreement with POPCON predictions. The sensitivity of these results to uncertain modelling inputs was probed using scans of pedestal boundary conditions around EPED-predicted values (total pressure and temperature ratios), tungsten concentration and seperatrix density around their nominal assumptions. Pedestal pressure and pedestal top (T_i/T_e) play a large role in 1.5-dimensional performance predictions, able to modify the predicted P_fus by a factor of 2 within reasonable assumptions. High-fidelity core nonlinear gyrokinetic profile predictions, performed using CGYRO (Candy et al. 2016 J. Comput. Phys. , vol. 324, pp. 73–93) coupled with the PORTALS (Rodriguez-Fernandez et al. 2024 Nucl. Fusion , vol. 64, 076034; Phys. Plasmas , vol. 31, 2024, 062501) framework, yield substantially lower performance ( P_fus = 677 MW) compared with 0-D and medium-fidelity modelling for nominal assumptions, showing that there is non-negligible uncertainty between models and that future work on SPARC may help resolve discrepancies. Lower overall performance results from significantly reduced volume-averaged densities and temperatures, along with reduced levels of density and temperature peaking. Turbulence and transport are largely dominated by ion temperature gradient across the profile, confirmed by both linear stability and the response of the nonlinear fluxes to changes in gradients, with some impact of kinetic ballooning modes in the deep core. This work represents one of the most complete scoping of potential fusion power plant conditions performed to date. The extensive integrated modelling provides confidence in ARC performance approaching 1 GW, while nonlinear gyrokinetic modelling results in open questions into the physics of density and temperature peaking in fusion-power-plant-relevant operational space. A discussion of results and the role that the SPARC tokamak (Creely et al. 2020 J. Plasma Phys. , vol. 86, 865860502) will play in informing ARC design, performance and operation is presented.
SN - 0022-3778
SN - 1469-7807
ER -