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Title: Fast-ion physics in SPARC

Abstract

Potential loss of energetic ions including alphas and radio-frequency tail ions due to classical orbit effects and magnetohydrodynamic instabilities (MHD) are central physics issues in the design and experimental physics programme of the SPARC tokamak. The expected loss of fusion alpha power due to ripple-induced transport is computed for the SPARC tokamak design by the ASCOT and SPIRAL orbit-simulation codes, to assess the expected surface heating of plasma-facing components. We find good agreement between the ASCOT and SPIRAL simulation results not only in integrated quantities (fraction of alpha power loss) but also in the spatial, temporal and pitch-angle dependence of the losses. If the toroidal field (TF) coils are well-aligned, the SPARC edge ripple is small (0.15–0.30 %), the computed ripple-induced alpha power loss is small ( ~0.25% ) and the corresponding peak surface power density is acceptable ( 244 kW m-2 ). However, the ripple and ripple-induced losses increase strongly if the TF coils are assumed to suffer increasing magnitudes of misalignment. Surface heat loads may become problematic if the TF coil misalignment approaches the centimetre level. Ripple-induced losses of the energetic ion tail driven by ion cyclotron range of frequency (ICRF) heating are not expected to generate significantmore » wall or limiter heating in the nominal SPARC plasma scenario. Because the expected classical fast-ion losses are small, SPARC will be able to observe and study fast-ion redistribution due to MHD including sawteeth and Alfvén eigenmodes (AEs). SPARC's parameter space for AE physics even at moderate Q is shown to reasonably overlap that of the demonstration power plant ARC (Sorbom et al., Fusion Engng Des., vol. 100, 2015, p. 378), and thus measurements of AE mode amplitude, spectrum and associated fast-ion transport in SPARC would provide relevant guidance about AE behaviour expected in ARC.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3];  [4]; ORCiD logo [4]; ORCiD logo [5]; ORCiD logo [3]; ORCiD logo [3]
  1. Commonwealth Fusion Systems, Cambridge, MA (United States)
  2. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  4. Aalto Univ., Espoo (Finland)
  5. Chalmers Univ. of Technology, Gothenburg (Sweden)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE; Commonwealth Fusion Systems; National Science Foundation (NSF); Academy of Finland
Contributing Org.:
INFUSE programme
OSTI Identifier:
1668281
Grant/Contract Number:  
AC02-05CH11231; RPP005; 1122374; 324759
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:
fusion plasma; plasma simulation; plasma confinement

Citation Formats

Scott, S. D., Kramer, G. J., Tolman, E. A., Snicker, A., Varje, J., Särkimäki, K., Wright, J. C., and Rodriguez-Fernandez, P. Fast-ion physics in SPARC. United States: N. p., 2020. Web. doi:10.1017/s0022377820001087.
Scott, S. D., Kramer, G. J., Tolman, E. A., Snicker, A., Varje, J., Särkimäki, K., Wright, J. C., & Rodriguez-Fernandez, P. Fast-ion physics in SPARC. United States. doi:10.1017/s0022377820001087.
Scott, S. D., Kramer, G. J., Tolman, E. A., Snicker, A., Varje, J., Särkimäki, K., Wright, J. C., and Rodriguez-Fernandez, P. Tue . "Fast-ion physics in SPARC". United States. doi:10.1017/s0022377820001087. https://www.osti.gov/servlets/purl/1668281.
@article{osti_1668281,
title = {Fast-ion physics in SPARC},
author = {Scott, S. D. and Kramer, G. J. and Tolman, E. A. and Snicker, A. and Varje, J. and Särkimäki, K. and Wright, J. C. and Rodriguez-Fernandez, P.},
abstractNote = {Potential loss of energetic ions including alphas and radio-frequency tail ions due to classical orbit effects and magnetohydrodynamic instabilities (MHD) are central physics issues in the design and experimental physics programme of the SPARC tokamak. The expected loss of fusion alpha power due to ripple-induced transport is computed for the SPARC tokamak design by the ASCOT and SPIRAL orbit-simulation codes, to assess the expected surface heating of plasma-facing components. We find good agreement between the ASCOT and SPIRAL simulation results not only in integrated quantities (fraction of alpha power loss) but also in the spatial, temporal and pitch-angle dependence of the losses. If the toroidal field (TF) coils are well-aligned, the SPARC edge ripple is small (0.15–0.30 %), the computed ripple-induced alpha power loss is small ( ~0.25% ) and the corresponding peak surface power density is acceptable ( 244 kW m-2 ). However, the ripple and ripple-induced losses increase strongly if the TF coils are assumed to suffer increasing magnitudes of misalignment. Surface heat loads may become problematic if the TF coil misalignment approaches the centimetre level. Ripple-induced losses of the energetic ion tail driven by ion cyclotron range of frequency (ICRF) heating are not expected to generate significant wall or limiter heating in the nominal SPARC plasma scenario. Because the expected classical fast-ion losses are small, SPARC will be able to observe and study fast-ion redistribution due to MHD including sawteeth and Alfvén eigenmodes (AEs). SPARC's parameter space for AE physics even at moderate Q is shown to reasonably overlap that of the demonstration power plant ARC (Sorbom et al., Fusion Engng Des., vol. 100, 2015, p. 378), and thus measurements of AE mode amplitude, spectrum and associated fast-ion transport in SPARC would provide relevant guidance about AE behaviour expected in ARC.},
doi = {10.1017/s0022377820001087},
journal = {Journal of Plasma Physics},
number = 5,
volume = 86,
place = {United States},
year = {2020},
month = {9}
}

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