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Title: MHD stability and disruptions in the SPARC tokamak

Abstract

SPARC is being designed to operate with a normalized beta of $$\beta _N=1.0$$ , a normalized density of $$n_G=0.37$$ and a safety factor of $$q_{95}\approx 3.4$$ , providing a comfortable margin to their respective disruption limits. Further, a low beta poloidal $$\beta _p=0.19$$ at the safety factor $q=2$$ surface reduces the drive for neoclassical tearing modes, which together with a frozen-in classically stable current profile might allow access to a robustly tearing-free operating space. Although the inherent stability is expected to reduce the frequency of disruptions, the disruption loading is comparable to and in some cases higher than that of ITER. The machine is being designed to withstand the predicted unmitigated axisymmetric halo current forces up to 50 MN and similarly large loads from eddy currents forced to flow poloidally in the vacuum vessel. Runaway electron (RE) simulations using GO+CODE show high flattop-to-RE current conversions in the absence of seed losses, although NIMROD modelling predicts losses of $${\sim }80$$  %; self-consistent modelling is ongoing. A passive RE mitigation coil designed to drive stochastic RE losses is being considered and COMSOL modelling predicts peak normalized fields at the plasma of order $$10^{-2}$ that rises linearly with a change in the plasma current. Massive material injection is planned to reduce the disruption loading. A data-driven approach to predict an oncoming disruption and trigger mitigation is discussed.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [1]; ORCiD logo [3]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [3];  [1]; ORCiD logo [4];  [5]; ORCiD logo [6]; ORCiD logo [1]; ORCiD logo [5]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [3];  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  2. Commonwealth Fusion Systems, Cambridge, MA (United States)
  3. Chalmers Univ. of Technology, Göteborg (Sweden)
  4. Fiat Lux, San Diego, CA (United States)
  5. General Atomics, San Diego, CA (United States)
  6. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1705065
Grant/Contract Number:  
SC0014264; AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Plasma Physics
Additional Journal Information:
Journal Volume: 86; Journal Issue: 5; Journal ID: ISSN 0022-3778
Publisher:
Cambridge University Press
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; fusion plasma; plasma instabilities; runaway electrons

Citation Formats

Sweeney, R., Creely, A. J., Doody, J., Fülöp, T., Garnier, D. T., Granetz, R., Greenwald, M., Hesslow, L., Irby, J., Izzo, V. A., La Haye, R. J., Logan, N. C., Montes, K., Paz-Soldan, C., Rea, C., Tinguely, R. A., Vallhagen, O., and Zhu, J.. MHD stability and disruptions in the SPARC tokamak. United States: N. p., 2020. Web. https://doi.org/10.1017/s0022377820001129.
Sweeney, R., Creely, A. J., Doody, J., Fülöp, T., Garnier, D. T., Granetz, R., Greenwald, M., Hesslow, L., Irby, J., Izzo, V. A., La Haye, R. J., Logan, N. C., Montes, K., Paz-Soldan, C., Rea, C., Tinguely, R. A., Vallhagen, O., & Zhu, J.. MHD stability and disruptions in the SPARC tokamak. United States. https://doi.org/10.1017/s0022377820001129
Sweeney, R., Creely, A. J., Doody, J., Fülöp, T., Garnier, D. T., Granetz, R., Greenwald, M., Hesslow, L., Irby, J., Izzo, V. A., La Haye, R. J., Logan, N. C., Montes, K., Paz-Soldan, C., Rea, C., Tinguely, R. A., Vallhagen, O., and Zhu, J.. Tue . "MHD stability and disruptions in the SPARC tokamak". United States. https://doi.org/10.1017/s0022377820001129. https://www.osti.gov/servlets/purl/1705065.
@article{osti_1705065,
title = {MHD stability and disruptions in the SPARC tokamak},
author = {Sweeney, R. and Creely, A. J. and Doody, J. and Fülöp, T. and Garnier, D. T. and Granetz, R. and Greenwald, M. and Hesslow, L. and Irby, J. and Izzo, V. A. and La Haye, R. J. and Logan, N. C. and Montes, K. and Paz-Soldan, C. and Rea, C. and Tinguely, R. A. and Vallhagen, O. and Zhu, J.},
abstractNote = {SPARC is being designed to operate with a normalized beta of $\beta _N=1.0$ , a normalized density of $n_G=0.37$ and a safety factor of $q_{95}\approx 3.4$ , providing a comfortable margin to their respective disruption limits. Further, a low beta poloidal $\beta _p=0.19$ at the safety factor $q=2$ surface reduces the drive for neoclassical tearing modes, which together with a frozen-in classically stable current profile might allow access to a robustly tearing-free operating space. Although the inherent stability is expected to reduce the frequency of disruptions, the disruption loading is comparable to and in some cases higher than that of ITER. The machine is being designed to withstand the predicted unmitigated axisymmetric halo current forces up to 50 MN and similarly large loads from eddy currents forced to flow poloidally in the vacuum vessel. Runaway electron (RE) simulations using GO+CODE show high flattop-to-RE current conversions in the absence of seed losses, although NIMROD modelling predicts losses of ${\sim }80$  %; self-consistent modelling is ongoing. A passive RE mitigation coil designed to drive stochastic RE losses is being considered and COMSOL modelling predicts peak normalized fields at the plasma of order $10^{-2}$ that rises linearly with a change in the plasma current. Massive material injection is planned to reduce the disruption loading. A data-driven approach to predict an oncoming disruption and trigger mitigation is discussed.},
doi = {10.1017/s0022377820001129},
journal = {Journal of Plasma Physics},
number = 5,
volume = 86,
place = {United States},
year = {2020},
month = {9}
}

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