Fast-ion physics in SPARC

S. D. Scott*, G. J. Kramer, E. A. Tolman, A. Snicker, J. Varje, K. Sarkimaki, J. C. Wright, P. Rodriguez-Fernandez

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

13 Citations (Scopus)
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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 (similar to 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 Alfven 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.

Original languageEnglish
Article number865860508
Number of pages27
JournalJournal of Plasma Physics
Issue number5
Publication statusPublished - Oct 2020
MoE publication typeA1 Journal article-refereed


  • fusion plasma
  • plasma simulation
  • plasma confinement


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  • Snicker Antti AT-palkka

    Snicker, A.


    Project: Academy of Finland: Other research funding

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