Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Perspective
  • Published:

Filamentary plasma eruptions and their control on the route to fusion energy

Nature Reviews Physics volume 2, pages 159–167 (2020)Cite this article

Subjects

Abstract

The tokamak is the most advanced approach to fusion and is approaching operation under power-plant conditions, promising sustainable, low-emission, baseload power to the grid. As the heating power of a tokamak is increased above a threshold, the plasma suddenly bifurcates to a state of high confinement, creating a region of plasma with a large pressure gradient at its edge. This bifurcation results in a repetitive sequence of explosive filamentary plasma eruptions called edge-localized modes (ELMs). ELMs on next-step tokamaks, such as ITER, will likely cause excessive erosion to plasma-facing components and must be controlled. We present what is understood about how ELMs form, their filamentary nature and the mechanisms that transport heat and particles to the first wall of the tokamak. We also discuss methods to control ELMs, including magnetic perturbations.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Currents and fields in a tokamak.
Fig. 2: Visible images of an edge-localized mode captured on the Mega Ampere Spherical Tokamak.
Fig. 3: Comparison of an edge-localized mode in simulation and experimental observation.
Fig. 4: Field lines traced in a JOREK simulation of a Joint-European-Torus-like plasma during an edge-localized mode.
Fig. 5: Suppression of edge-localized modes at the Axially Symmetric Divertor Experiment Upgrade tokamak using resonant magnetic perturbations.

Similar content being viewed by others

References

  1. Leonard, A. W. Edge-localized-modes in tokamaks. Phys. Plasmas 21, 090501 (2014).

    Article  ADS  Google Scholar 

  2. JET Team (prepared by Watkins, M. L.). Physics of high performance JET plasmas in DT. Nucl. Fusion 39, 1227–1244 (1999).

    Article  ADS  Google Scholar 

  3. Dudson, B. D. et al. Experiments and simulation of edge turbulence and filaments in MAST. Plasma Phys. Control. Fusion 50, 124012 (2008).

    Article  ADS  Google Scholar 

  4. Wagner, F. A quarter-century of H-mode studies. Plasma Phys. Control. Fusion 49, B1–B33 (2007).

    Article  ADS  Google Scholar 

  5. Connor, J. W. Edge-localized modes — physics and theory. Plasma Phys. Control. Fusion 40, 531–542 (1998).

    Article  ADS  Google Scholar 

  6. Suttrop, W. The physics of large and small edge localized modes. Plasma Phys. Control. Fusion 42, A1–A14 (2000).

    Article  ADS  Google Scholar 

  7. Loarte, A. et al. Characteristics of type I ELM energy and particle losses in existing devices and their extrapolation to ITER. Plasma Phys. Control. Fusion 45, 1549–1569 (2003).

    Article  ADS  Google Scholar 

  8. Cowley, S. C., Wilson, H., Hurricane, O. & Fong, B. Explosive instabilities: from solar flares to edge localized modes in tokamaks. Plasma Phys. Control. Fusion 45, A31–A38 (2003).

    Article  ADS  Google Scholar 

  9. Kirk, A. et al. Spatial and temporal structure of edge-localized modes. Phys. Rev. Lett. 92, 245002 (2004).

    Article  ADS  Google Scholar 

  10. Kirk, A. et al. Physics of ELM power fluxes to plasma facing components and implications for ITER. J. Nucl. Mater. 390–391, 727–732 (2009).

    Article  ADS  Google Scholar 

  11. Yun, G. S. et al. Two-dimensional visualization of growth and burst of the edge-localized filaments in KSTAR H-mode plasmas. Phys. Rev. Lett. 107, 045004 (2011).

    Article  ADS  Google Scholar 

  12. Freidberg, J. P. Ideal MHD (Cambridge Univ. Press, 2014) ISBN 978-1-107-00625-6.

  13. Connor, J. W., Hastie, R. J. & Taylor, J. B. High mode number stability of an axisymmetric toroidal plasma. Proc. R. Soc. Lond. A 365, 1–17 (1979).

    Article  ADS  MathSciNet  Google Scholar 

  14. Wilson, H. R., Cowley, S. C., Kirk, A. & Snyder, P. B. Magneto-hydrodynamic stability of the H-mode transport barrier as a model for edge localized modes: an overview. Plasma Phys. Control. Fusion 48, A71–A84 (2006).

    Article  ADS  Google Scholar 

  15. Bickerton, R. J., Connor, J. W. & Taylor, J. B. Diffusion driven plasma currents and bootstrap tokamak. Nat. Phys. Sci. 229, 110–112 (1971).

    Article  ADS  Google Scholar 

  16. Peeters, A. G. The bootstrap current and its consequences. Plasma Phys. Control. Fusion 42, B231–B242 (2000).

    Article  ADS  Google Scholar 

  17. Hegna, C. C., Connor, J. W., Hastie, R. J. & Wilson, H. R. Toroidal coupling of ideal magnetohydrodynamic instabilities in tokamak plasmas. Phys. Plasmas 3, 584–592 (1996).

    Article  ADS  Google Scholar 

  18. Connor, J. W., Hastie, R. J. & Wilson, H. R. Magnetohydrodynamic stability of tokamak edge plasmas. Phys. Plasmas 5, 2687–2700 (1998).

    Article  ADS  Google Scholar 

  19. Snyder, P. B. et al. Edge localized modes and the pedestal: a model based on coupled peeling–ballooning modes. Phys. Plasmas 9, 2037–2043 (2002).

    Article  ADS  Google Scholar 

  20. Burckhart, A. et al. Inter-ELM behaviour of the electron density and temperature pedestal in ASDEX upgrade. Plasma Phys. Control. Fusion 52, 105010 (2010).

    Article  ADS  Google Scholar 

  21. Dickinson, D. et al. Kinetic instabilities that limit β in the edge of a tokamak plasma: a picture of an H-mode pedestal. Phys. Rev. Lett. 108, 135002 (2012).

    Article  ADS  Google Scholar 

  22. Hatch, D. R. et al. Gyrokinetic study of ASDEX upgrade inter-ELM pedestal profile evolution. Nucl. Fusion 55, 063028 (2015).

    Article  ADS  Google Scholar 

  23. Snyder, P. B. et al. A first-principles predictive model of the pedestal height and width: development, testing and ITER optimization with the EPED model. Nucl. Fusion 51, 103016 (2011).

    Article  ADS  Google Scholar 

  24. Saarelma, S. et al. Integrated modelling of H-mode pedestal and confinement in JET-ILW. Plasma Phys. Control. Fusion 60, 014042 (2018).

    Article  ADS  Google Scholar 

  25. Maggi, C. F. et al. Pedestal confinement and stability in JET-ILW ELMy H-modes. Nucl. Fusion 55, 113031 (2015).

    Article  ADS  Google Scholar 

  26. Bowman, C. et al. Pedestal evolution physics in low triangularity JET tokamak discharges with ITER-like wall. Nucl. Fusion 58, 016021 (2018).

    Article  ADS  Google Scholar 

  27. Snyder, P. B. et al. Super H-mode: theoretical prediction and initial observations of a new high performance regime for tokamak operation. Nucl. Fusion 55, 083026 (2015).

    Article  ADS  Google Scholar 

  28. Zohm, H. Edge localized modes (ELMs). Plasma Phys. Control. Fusion 38, 105–128 (1996).

    Article  ADS  Google Scholar 

  29. Oyama, N. et al. Energy loss for grassy ELMs and effects of plasma rotation on the ELM characteristics in JT-60U. Nucl. Fusion 45, 871–881 (2005).

    Article  ADS  Google Scholar 

  30. Wilson, H. R. & Cowley, S. C. Theory for explosive ideal magnetohydrodynamic instabilities in plasmas. Phys. Rev. Lett. 92, 175006 (2004).

    Article  ADS  Google Scholar 

  31. Ham, C. J., Cowley, S. C., Brochard, G. & Wilson, H. R. Nonlinear stability and saturation of ballooning modes in tokamaks. Phys. Rev. Lett. 116, 235001 (2016).

    Article  ADS  Google Scholar 

  32. Ham, C. J., Cowley, S. C., Brochard, G. & Wilson, H. R. Nonlinear ballooning modes in tokamaks: stability and saturation. Plasma Phys. Control. Fusion. 60, 075017 (2018).

    Article  ADS  Google Scholar 

  33. Hutchinson, I. H. Principles of Plasma Diagnostics (Cambridge Univ. Press, 2002)

  34. Kirk, A. et al. Evolution of the pedestal on MAST and the implications for ELM power loadings. Plasma Phys. Control. Fusion 49, 1259–1275 (2007).

    Article  ADS  Google Scholar 

  35. Vianello, N. et al. Direct observation of current in Type-I edge-localized-Mode filaments on the ASDEX upgrade tokamak. Phys. Rev. Lett. 106, 125002 (2011).

    Article  ADS  Google Scholar 

  36. Beurskens, M. N. A. et al. Pedestal and scrape-off layer dynamics in ELMy H-mode plasmas in JET. Nucl. Fusion 49, 125006 (2009).

    Article  ADS  Google Scholar 

  37. Eich, T. et al. ELM divertor peak energy fluence scaling to ITER with data from JET, MAST and ASDEX upgrade. Nucl. Mater. Energy 12, 84–90 (2017).

    Article  Google Scholar 

  38. Becoulet, M. et al. Edge localized mode physics and operational aspects in tokamaks. Plasma Phys. Control. Fusion 45, A93–A113 (2003).

    Article  Google Scholar 

  39. Alladio, F., Mancuso, A. & Micozzi, P. Rotating twisted filaments buoyancy: comparison between the convective region of the sun and the edge of a tokamak plasma. Plasma Phys. Control. Fusion 50, 124019 (2008).

    Article  ADS  Google Scholar 

  40. Evans, T. E. et al. A conceptual model of the magnetic topology and nonlinear dynamics of ELMs. J. Nucl. Mater. 390, 789–792 (2009).

    Article  ADS  Google Scholar 

  41. Rack, M. et al. Thermoelectric currents and their role during ELM formation in JET. Nucl. Fusion 52, 074012 (2012).

    Article  ADS  Google Scholar 

  42. Freethy, S. J. et al. Electron kinetics inferred from observations of microwave bursts during edge localized modes in the mega-amp spherical tokamak. Phys. Rev. Lett. 114, 125004 (2015).

    Article  ADS  Google Scholar 

  43. Galdon-Quiroga, J. et al. Beam-ion acceleration during edge localized modes in the ASDEX upgrade tokamak. Phys. Rev. Lett. 121, 025002 (2018).

    Article  ADS  Google Scholar 

  44. Galdon-Quiroga, J. et al. Velocity space resolved absolute measurement of fast ion losses induced by a tearing mode in the ASDEX Upgrade tokamak. Nucl. Fusion 58, 036005 (2018).

    Article  ADS  Google Scholar 

  45. Pamela, S. J. P. et al. Nonlinear MHD simulations of edge-localized-modes in JET. Plasma Phys. Control. Fusion 53, 054014 (2011).

    Article  ADS  Google Scholar 

  46. Pamela, S. J. P. et al. Recent progress in the quantitative validation of JOREK simulations of ELMs in JET. Nucl. Fusion 57, 076006 (2017).

    Article  ADS  Google Scholar 

  47. Snyder, P. B. et al. Pedestal stability comparison and ITER pedestal prediction. Nucl. Fusion 49, 085035 (2009).

    Article  ADS  Google Scholar 

  48. Bécoulet, M. et al. Non-linear MHD modelling of edge localized modes dynamics in KSTAR. Nucl. Fusion 57, 116059 (2017).

    Article  ADS  Google Scholar 

  49. Huysmans, G. T. A. & Czarny, O. MHD stability in X-point geometry: simulation of ELMs. Nucl. Fusion 47, 659–666 (2007).

    Article  ADS  Google Scholar 

  50. Ebrahimi, F. Nonlinear reconnecting edge localized modes in current-carrying plasmas. Phys. Plasmas 24, 056119 (2017).

    Article  ADS  Google Scholar 

  51. Kirk, A. et al. Evolution of filament structures during edge-localized modes in the MAST tokamak. Phys. Rev. Lett. 96, 185001 (2006).

    Article  ADS  Google Scholar 

  52. Mink, A. F. et al. Nonlinear coupling induced toroidal structure of edge localized modes. Nucl. Fusion 58, 026011 (2018).

    Article  ADS  Google Scholar 

  53. Pamela, S. J. P. et al. Non-linear MHD simulations of ELMs in JET and quantitative comparisons to experiments. Plasma Phys. Control. Fusion 58, 014026 (2016).

    Article  ADS  Google Scholar 

  54. Kirk, A. et al. Recent progress in understanding the processes underlying the triggering of and energy loss associated with type I ELMs. Nucl. Fusion 54, 114012 (2014).

    Article  ADS  Google Scholar 

  55. Huysmans, G. T. A., Pamela, S. J. P., van der Plas, E. & Ramet, P. Non-linear MHD simulations of edge localized modes (ELMs). Plasma Phys. Control. Fusion 51, 124012 (2009).

    Article  ADS  Google Scholar 

  56. Henneberg, S. A., Cowley, S. C. & Wilson, H. R. Explosive ballooning mode instability in tokamaks: modelling the ELM cycle. 41st EPS Conference, Berlin, Germany P1.066 (2014).

  57. Henneberg, S. A., Cowley, S. C. & Wilson, H. R. Interacting filamentary eruptions in magnetised plasmas. Plasma Phys. Control. Fusion 57, 125010 (2015).

    Article  ADS  Google Scholar 

  58. Brodrick, J. P. et al. Testing nonlocal models of electron thermal conduction for magnetic and inertial confinement fusion applications. Phys. Plasmas 24, 092309 (2017).

    Article  ADS  Google Scholar 

  59. Snyder, P. B. et al. ELMs and constraints on the H-mode pedestal: peeling–ballooning stability calculation and comparison with experiment. Nucl. Fusion 44, 320–328 (2004).

    Article  ADS  Google Scholar 

  60. Herrmann, A. Overview on stationary and transient divertor heat loads. Plasma Phys. Control. Fusion 44, 883–903 (2002).

    Article  ADS  Google Scholar 

  61. Lang, P. et al. ELM pace making and mitigation by pellet injection in ASDEX Upgrade. Nucl. Fusion 44, 665–677 (2004).

    Article  ADS  Google Scholar 

  62. Baylor, L. R. et al. Reduction of edge-localized mode intensity using high-repetition-rate pellet injection in tokamak H-mode plasmas. Phys. Rev. Lett. 110, 245001 (2013).

    Article  ADS  Google Scholar 

  63. Futatani, S. et al. Non-linear MHD modelling of ELM triggering by pellet injection in DIII-D and implications for ITER. Nucl. Fusion 54, 073008 (2014).

    Article  ADS  Google Scholar 

  64. Lang, P. T. et al. ELM control strategies and tools: status and potential for ITER. Nucl. Fusion 53, 043004 (2013).

    Article  ADS  Google Scholar 

  65. Degeling, A. W. et al. Magnetic triggering of ELMs in TCV. Plasma Phys. Control. Fusion 45, 1637 (2003).

    Article  ADS  Google Scholar 

  66. Lang, P. T. et al. Frequency control of type-I ELMs by magnetic triggering in ASDEX Upgrade. Plasma Phys. Control. Fusion 46, L31–L39 (2004).

    Article  Google Scholar 

  67. de La Luna, E. et al. Understanding the physics of ELM pacing via vertical kicks in JET in view of ITER. Nucl. Fusion 56, 026001 (2015).

    Article  Google Scholar 

  68. Gerhardt, S. P. et al. First observation of ELM pacing with vertical jogs in a spherical torus. Nucl. Fusion 50, 064015 (2010).

    Article  ADS  Google Scholar 

  69. Jayhyun Kim et al. ELM control experiments in the KSTAR device. Nucl. Fusion 52, 114011 (2012).

    Article  ADS  Google Scholar 

  70. Garzotti, L. et al. Investigating pellet ELM triggering physics using the new small size pellet launcher at JET. 37th EPS Conference, Dublin, Ireland P2.131 (2010).

  71. Jakubowski, M. et al. Overview of the results on divertor heat loads in RMP controlled H-mode plasmas on DIII-D. Nucl. Fusion 49, 095013 (2009).

    Article  ADS  Google Scholar 

  72. Viezzer, E. Access and sustainment of naturally ELM-free and small-ELM regimes. Nucl. Fusion 58, 115002 (2018).

    Article  ADS  Google Scholar 

  73. Evans, T. E. et al. Suppression of large edge-localized modes in high-confinement DIII-D plasmas with a stochastic magnetic boundary. Phys. Rev. Lett. 92, 235003 (2004).

    Article  ADS  Google Scholar 

  74. Suttrop, W. et al. Experimental conditions to suppress edge localised modes by magnetic perturbations in the ASDEX Upgrade tokamak. Nucl. Fusion 58, 096031 (2018).

    Article  ADS  Google Scholar 

  75. Jeon, Y. M. et al. Suppression of edge localized modes in high-confinement KSTAR plasmas by nonaxisymmetric magnetic perturbations. Phys. Rev. Lett. 109, 035004 (2012).

    Article  ADS  Google Scholar 

  76. Sun, Y. et al. Nonlinear transition from mitigation to suppression of the edge localized mode with resonant magnetic perturbations in the EAST tokamak. Phys. Rev. Lett. 117, 115001 (2016).

    Article  ADS  Google Scholar 

  77. Liu, Y. et al. Modelling of plasma response to resonant magnetic perturbation fields in MAST and ITER. Nucl. Fusion 51, 083002 (2011).

    Article  ADS  Google Scholar 

  78. Wade, M. R. et al. Advances in the physics understanding of ELM suppression using resonant magnetic perturbations in DIII-D. Nucl. Fusion 55, 023002 (2015).

    Article  ADS  Google Scholar 

  79. Paz-Soldan, C. et al. The effect of plasma shape and neutral beam mix on the rotation threshold for RMP-ELM suppression. Nucl. Fusion 59, 056012 (2019).

    Article  ADS  Google Scholar 

  80. Willensdorfer, M. et al. Field-line localized destabilization of ballooning modes in three-dimensional tokamaks. Phys. Rev. Lett. 119, 085002 (2017).

    Article  ADS  Google Scholar 

  81. Federici, G., Loarte, A. & Strohmayer, G. Assessment of erosion of the ITER divertor targets during type I ELMs. Plasma Phys. Control. Fusion. 45, 1523 (2003).

    Article  ADS  Google Scholar 

  82. Pankin, A. Y. et al. Modelling of ELM dynamics for DIII-D and ITER. Plasma Phys. Control. Fusion 49, S63–S75 (2007).

    Article  ADS  Google Scholar 

  83. Dudson, B. D. et al. Simulation of edge localized modes using BOUT++. Plasma Phys. Control. Fusion 53, 054005 (2011).

    Article  ADS  Google Scholar 

  84. Whyte, D. G. et al. I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod. Nucl. Fusion 50, 105005 (2010).

    Article  ADS  Google Scholar 

  85. Burrell, K. H. et al. Discovery of stationary operation of quiescent H-mode plasmas with net-zero neutral beam injection torque and high energy confinement on DIII-D. Phys. Plasmas 23, 056103 (2016).

    Article  ADS  Google Scholar 

  86. Kamada, K. et al. Pedestal characteristics and extended high-βp ELMy H-mode regime in JT-60U. Plasma Phys. Control. Fusion 44, A279–A286 (2002).

    Article  Google Scholar 

  87. Kirk, A. Nuclear fusion: bringing a star down to Earth. Contemp. Phys. 57, 1–18 (2016).

    Article  ADS  Google Scholar 

  88. Pamela, S. et al. Resistive MHD simulation of edge-localized modes for double-null discharges in the MAST device. Plasma Phys. Control. Fusion 55, 095001 (2013).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

The authors gratefully acknowledge the comments on this manuscript given by Samuli Saarelma, William Morris and Jack Connor. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement no. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This work has been part-funded by the RCUK Energy Programme (grant number EP/P012450/1). To obtain further information on the data and models underlying this paper, please contact PublicationsManager@ukaea.uk. Simulations published in this review have benefited from the support of EUROfusion on the Marconi HPC cluster (CINECA, Italy), as well as the support of PRACE on the MareNostrum HPC cluster (BSC, Spain).

Author information

Authors and Affiliations

  1. UKAEA – CCFE, Culham Science Centre, Abingdon, UK

    Christopher Ham, Andrew Kirk, Stanislas Pamela & Howard Wilson

  2. York Plasma Institute, Department of Physics, University of York, Heslington, UK

    Howard Wilson

Authors
  1. Christopher Ham
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Andrew Kirk
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Stanislas Pamela
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Howard Wilson
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

All authors contributed to all aspects of this Perspective.

Corresponding author

Correspondence to Christopher Ham.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Reviewer information

Nature Reviews Physics thanks F. Jenko and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ham, C., Kirk, A., Pamela, S. et al. Filamentary plasma eruptions and their control on the route to fusion energy. Nat Rev Phys 2, 159–167 (2020). https://doi.org/10.1038/s42254-019-0144-1

Download citation

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/s42254-019-0144-1

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing