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.

A long-pulse high-confinement plasma regime in the Experimental Advanced Superconducting Tokamak

Abstract

High-performance and long-pulse operation is a crucial goal of current magnetic fusion research. Here, we demonstrate a high-confinement plasma regime known as an H-mode with a record pulse length of over 30 s in the Experimental Advanced Superconducting Tokamak sustained by lower hybrid wave current drive (LHCD) with advanced lithium wall conditioning. We find that LHCD provides a flexible boundary control for a ubiquitous edge instability in H-mode plasmas known as an edge-localized mode, which leads to a marked reduction in the heat load on the vessel wall compared with standard edge-localized modes. LHCD also induces edge plasma ergodization that broadens the heat deposition footprint. The heat transport caused by this ergodization can be actively controlled by regulating the edge plasma conditions. This potentially offers a new means for heat-flux control, which is a key issue for next-step fusion development.

Your institute does not have access to this article

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Internal view of EAST.
Figure 2: Demonstration of a high-confinement H-mode discharge over 30 s driven by LHCD with ICRH.
Figure 3: Demonstration of the effect of LHCD on ELM behaviour by modulating LCHD power in a series of target H-mode plasmas produced by ICRH with different edge safety factor, q95.
Figure 4: Contour plot of the magnetic perturbation spectrum with different q95.
Figure 5: Edge plasma conditions significantly influence the degree of the SHF induced by LHCD.

References

  1. Wesson, J. Tokamaks (Oxford Univ. Press, 2011).

    MATH  Google Scholar 

  2. Hawryluk, R. J. Results from deuterium-tritium tokamak confinement experiments. Rev. Mod. Phys. 70, 537–587 (1998).

    ADS  Article  Google Scholar 

  3. Keilhacker, M. et al. High fusion performance from deuterium-tritium plasmas in JET. Nucl. Fusion 39, 209–234 (1999).

    ADS  Article  Google Scholar 

  4. http://www.iter.org.

  5. Van Houtte, D. et al. Recent fully non-inductive operation results in Tore Supra with 6 min, 1 GJ plasma discharges. Nucl. Fusion 44, L11–L15 (2004).

    Article  Google Scholar 

  6. Tsitrone, E. Key plasma wall interaction issues towards steady state operation. J. Nucl. Mater. 363–365, 12–23 (2007).

    ADS  Article  Google Scholar 

  7. Loarte, A. et al. Progress in the ITER physics basis—Chapter 4: Power and particle control. Nucl. Fusion 47, S203–S263 (2007).

    Article  Google Scholar 

  8. Stangeby, P. C. The Plasma Boundary of Magnetic Fusion Devices (IOP, 2000).

    Book  Google Scholar 

  9. Wan, Y. Overview of steady state operation of HT-7 and present status of the HT-7U project. Nucl. Fusion 40, 1057–1068 (2000).

    ADS  Article  Google Scholar 

  10. Normile, D. Waiting for ITER, fusion jocks look EAST. Science 312, 992–993 (2006).

    Article  Google Scholar 

  11. Fuyuno, I. China set to make fusion history. Nature 442, 853–858 (2006).

    ADS  Article  Google Scholar 

  12. Wan, B. N. Recent experiments in the EAST and HT-7 superconducting tokamaks. Nucl. Fusion 49, 104011 (2009).

    ADS  Article  Google Scholar 

  13. Li, J. & Wan, B. N. Recent progress in RF heating and long-pulse experiments on EAST. Nucl. Fusion 51, 094007 (2011).

    ADS  Article  Google Scholar 

  14. Wagner, F. et al. Regime of improved confinement and high beta in neutral-beam-heated divertor discharges of the ASDEX tokamak. Phys. Rev. Lett. 49, 1408–1412 (1982).

    ADS  Article  Google Scholar 

  15. Zuo, G. Z. et al. Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST. Plasma Phys. Control. Fusion 54, 015014 (2012).

    ADS  Article  Google Scholar 

  16. Mansfield, D. K. et al. A simple apparatus for the injection of lithium aerosol into the scrape-off layer of fusion research devices. Fusion Eng. Design 85, 890–895 (2010).

    Article  Google Scholar 

  17. Majeski, R. et al. Enhanced energy confinement and performance in a low-recycling tokamak. Phys. Rev. Lett. 97, 075002 (2006).

    ADS  Article  Google Scholar 

  18. Apicella, M. et al. First experiments with lithium limiter on FTU. J. Nucl. Mater. 363–365, 1346–1351 (2007).

    ADS  Article  Google Scholar 

  19. Sánchez, J. et al. Impact of lithium-coated walls on plasma performance in the TJ-II stellarator. J. Nucl. Mater. 390–391, 852–857 (2009).

    ADS  Article  Google Scholar 

  20. Maingi, R. et al. The effect of progressively increasing lithium coatings on plasma discharge characteristics, transport, edge profiles and ELM stability in the National Spherical Torus Experiment. Nucl. Fusion 52, 083001 (2012).

    ADS  Article  Google Scholar 

  21. Ide, S. & the JT-60 Team, Overview of JT-60U progress towards steady-state advanced tokamak. Nucl. Fusion 45, S48–S62 (2005).

    Article  Google Scholar 

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

    ADS  Article  Google Scholar 

  23. Connor, J. W. et al. Magnetohydrodynamic stability of tokamak edge plasmas. Phys. Plasmas 5, 2687–2700 (1998).

    ADS  Article  Google Scholar 

  24. Hill, D. N. A review of ELMs in divertor tokamaks. J. Nucl. Mater. 241–243, 182–198 (1997).

    ADS  Article  Google Scholar 

  25. Shimada, M. et al. Progress in the ITER physics basis — Chapter 1: Overview and summary. Nucl. Fusion 47, S1–S17 (2007).

    Article  Google Scholar 

  26. Doyle, E. J. et al. Progress in the ITER physics basis — Chapter 2: Plasma confinement and transport. Nucl. Fusion 47, S18–S127 (2007).

    Article  Google Scholar 

  27. Ozeki, T. et al. Plasma shaping, edge ballooning stability and ELM behavior in DIII-D. Nucl. Fusion 30, 1425–1432 (1990).

    Article  Google Scholar 

  28. Stober, J. et al. Type II ELMy H modes on ASDEX Upgrade with good confinement at high density. Nucl. Fusion 41, 1123–1134 (2001).

    ADS  Article  Google Scholar 

  29. Sips, A. C. C. et al. Steady-state advanced scenarios at ASDEX Upgrades. Plasma Phys. Control. Fusion 44, B69–B83 (2002).

    Article  Google Scholar 

  30. Saibene, G. et al. Improved performance of ELMy H-modes at high density by plasma shaping in JET. Plasma Phys. Control. Fusion 44, 1769–1799 (2002).

    ADS  Article  Google Scholar 

  31. Maingi, R. et al. Comparison of small ELM characteristics and regimes in Alcator C-Mod, MAST and NSTX. Nucl. Fusion 51, 063036 (2010).

    ADS  Article  Google Scholar 

  32. Liang, Y. et al. Magnetic topology changes induced by lower hybrid waves and their profound effect on edge-localized modes in the EAST tokamak. Phys. Rev. Lett 110, 235002 (2013).

    ADS  Article  Google Scholar 

  33. Evans, T. E. et al. Edge stability and transport control with resonant magnetic perturbations in collisionless tokamak plasmas. Nature Phys. 2, 419–423 (2006).

    ADS  Article  Google Scholar 

  34. Loarte, A. Chaos cuts ELMs down to size. Nature Phys. 2, 369–370 (2006).

    ADS  Article  Google Scholar 

  35. Liang, Y. et al. Active control of type-i edge-localized modes with n = 1 perturbation fields in the JET tokamak. Phys. Rev. Lett. 98, 265004 (2007).

    ADS  Article  Google Scholar 

  36. Kirk, A. et al. Resonant magnetic perturbation experiments on MAST using external and internal coils for ELM control. Nucl. Fusion 50, 034008 (2010).

    ADS  Article  Google Scholar 

  37. Suttrop, W. et al. First observation of edge localized modes mitigation with resonant and nonresonant magnetic perturbations in ASDEX upgrade. Phys. Rev. Lett. 106, 225004 (2011).

    ADS  Article  Google Scholar 

  38. Schmitz, O. et al. Aspects of three dimensional transport for ELM control experiments in ITER-similar shape plasmas at low collisionality in DIII-D. Plasma Phys. Control. Fusion 50, 124029 (2008).

    ADS  Article  Google Scholar 

  39. Lunt, T. et al. First EMC3-Eirene simulations of the impact of the edge magnetic perturbations at ASDEX Upgrade compared with the experiment. Nucl. Fusion 52, 054013 (2012).

    ADS  Article  Google Scholar 

  40. Zou, X. L. et al. in Proc. 24th IAEA Fusion Energy Conference, October 8–13, San Diego PD/P8-08 (IAEA, 2012).

  41. Loarte, A. et al. Plasma detachment in JET Mark I divertor experiments. Nucl. Fusion 38, 331–371 (1998).

    ADS  Article  Google Scholar 

  42. Eich, T. et al. Inter-ELM power decay length for JET and ASDEX upgrade: Measurement and comparison with heuristic drift-based model. Phys. Rev. Lett. 107, 215001 (2011).

    ADS  Article  Google Scholar 

  43. Goldston, R. J. Heuristic drift-based model of the power scrape-off width in low-gas-puff H-mode tokamaks. Nucl. Fusion 52, 013009 (2012).

    ADS  Article  Google Scholar 

Download references

Acknowledgements

We would like to acknowledge the support and contributions from the rest of the EAST team and collaborators. This work was supported in part by the National Nature Science Foundation of China under Contract No. 11021565 and the National Magnetic Confinement Fusion Science Program of China under Contract Nos. 2010GB104001, 2010GB104002, 2011GB101000, 2011GB107001, 2012GB101001, 2013GB107003 and 2013GB106003, as well as the Thousand Talent Plan of China and Helmholtz Association in the frame of the Helmholtz-University Young Investigators Group VH-NG-410. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Author information

Authors and Affiliations

Authors

Contributions

All authors contributed to all aspects of this work.

Corresponding author

Correspondence to H. Y. Guo.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Li, J., Guo, H., Wan, B. et al. A long-pulse high-confinement plasma regime in the Experimental Advanced Superconducting Tokamak. Nature Phys 9, 817–821 (2013). https://doi.org/10.1038/nphys2795

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nphys2795

Further reading

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