Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Improvement of lower hybrid current drive systems for high-power and long-pulse operation on EAST

  • M. Wang (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • L. Liu (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • L.M. Zhao (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • M.H. Li (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • W.D. Ma (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • H.C. Hu (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • Z.G. Wu (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • J.Q. Feng (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • Y. Yang (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • L. Zhu (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • M. Chen (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • T.A. Zhou (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • H. Jia (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • J. Zhang (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • L. Cao (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • L. Zhang (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • R.R. Liang (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • B.J. Ding (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • X.J. Zhang (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • J.F. Shan (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • F.K. Liu (Institute of Plasma Physics, Chinese Academy of Sciences) ;
  • A. Ekedahl (CEA, IRFM) ;
  • M. Goniche (CEA, IRFM) ;
  • J. Hillairet (CEA, IRFM) ;
  • L. Delpech (CEA, IRFM)
  • Received : 2022.02.15
  • Accepted : 2022.06.06
  • Published : 2022.11.25
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Abstract

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m2. Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 ℃, much below the permissible value of tungsten material (~1200 ℃). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-active-multijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5° toroidally from the 4.6 GHz LH system and is not magnetically connected.

Keywords

Acknowledgement

This work is supported by the Performance Improvement Project of EAST, Hefei Comprehensive National Science Center, the National Natural Science Foundation of China (Grant No. 11775259, 11805233, 11675214, 11175206 and 11275233), the National Magnetic Confinement Fusion Science Program of China (Grant No. 2015GB102003) and the Comprehensive Research Facility for Fusion Technology Program of China under Contract No. 2018 - 000052 - 73 - 01 - 001228.

References

  1. O. Naito and the JT-60 Team, Steady state plasma performance on JT-60U, Plasma Phys. Contr. Fusion 35 (1993) B215. 
  2. JET Team (presented by Soldner F. X.), 1994 (Proc. 15th Int. Conf. Seville, 1994), Plasma Physics and Controlled Nuclear Fusion Research, vol. 1, IAEA, Vienna, 1995, p. P423. 
  3. H.D. Van, et al., Recent fully non-inductive operation results in Tore Supra with 6 min, 1 GJ plasma discharges, Nucl. Fusion 44 (2004) L11. 
  4. G. Zhuang, et al., Progress of the CFETR design, Nucl. Fusion 59 (2019), 112010. 
  5. J.F. Shan, et al., A new 4 MW LHCD system for EAST, in: Proceedings of the 23rd IAEA Fusion Energy Conference, Daejon, Korea, 2010. 
  6. F.K. Liu, et al., Development of 4.6 GHz lower hybrid current drive system for steady state and high performance plasma in EAST, Fusion Eng. Des. 113 (2016) 131-138.  https://doi.org/10.1016/j.fusengdes.2016.10.020
  7. J.P. Qian, et al., Integrated operating scenario to achieve 100-second, high electron temperature discharge on EAST, Plasma Sci. Technol. 18 (2016) 457. 
  8. B.N. Wan, et al., Recent advances in EAST physics experiments in support of steady-state operation for ITER and CFETR, Nucl. Fusion 59 (2019), 112003. 
  9. X.Z. Gong, et al., Integrated operation of steady-state long-pulse H-mode in experimental advanced superconducting tokamak, Nucl. Fusion 59 (2019), 086030. 
  10. L. Liu, et al., 4.6-GHz LHCD launcher system of experimental advanced superconducting tokamak, Fusion Sci. Technol. 75 (2019) 49-58.  https://doi.org/10.1080/15361055.2018.1516416
  11. M.H. Li, et al., Lower hybrid current drive experiments with different launched wave frequencies in the EAST tokamak, Phys. Plasmas 23 (2016), 102512. 
  12. B.J. Ding, et al., Correlation between the onset of parametric instability of lower hybrid waves and modification in edge plasma current profile on EAST, Nucl. Fusion 58 (2018), 126015. 
  13. M.H. Li, et al., Experimental investigation on spectral broadening of lower hybrid waves with different frequencies in the EAST long-pulse plasmas, Plasma Phys. Contr. Fusion 61 (2019), 065005. 
  14. L. Zhang, et al., A fast-time-response extreme ultraviolet spectrometer for measurement of impurity line emissions in the Experimental Advanced Superconducting Tokamak, Rev. Sci. Instrum. 86 (2015), 123509. 
  15. P. Jacquet, et al., Heat loads on JET plasma facing components from ICRF and LH wave absorption in the SOL, Nucl. Fusion 51 (2011), 103018. 
  16. K.K. Kirov, et al., Operation and coupling of LH waves with the ITER-like wall at JET, Plasma Phys. Contr. Fusion 55 (2013), 115008. 
  17. A. Ekedahl, et al., Operational limits during high power long pulses with radiofrequency heating in Tore Supra, Nucl. Fusion 49 (2009), 095010. 
  18. J. Mailloux, et al., Strong toroidal asymmetries in power deposition on divertor and first wall components during LHCD on TdeV and Tore Supra, J. Nucl. Mater. 241-243 (1997) 745-749.  https://doi.org/10.1016/S0022-3115(96)00598-3
  19. M. Goniche, et al., Enhanced heat flux in the scrape-off layer due to electrons accelerated in the near field of lower hybrid grills, Nucl. Fusion 38 (1998) 919. 
  20. K.M. Rantamaki, et al., Estimation of heat loads on the wall structures in parasitic absorption of lower hybrid power, Nucl. Fusion 40 (2000) 1477. 
  21. J. Hillairet, et al., ALOHA: an advanced LOwer hybrid antenna coupling code, Nucl. Fusion 50 (2010), 125010. 
  22. B.J. Ding, et al., Effect of edge plasma density on hot spot in LHCD plasma in EAST, Nucl. Mater.Energy 27 (2021), 100992. 
  23. M. Goniche, et al., Lower hybrid current drive experiments on Tore Supra in the ergodic divertor configuration, Plasma Phys. Contr. Fusion 46 (2004) 899. 
  24. J.S. Hu, et al., First results of the use of a continuously flowing lithium limiter in high performance discharges in the EAST device, Nucl. Fusion 56 (2016), 046011. 
  25. J. Gunn, et al., Measurement of lower hybrid hot spots using a retarding field analyzer in Tore Supra, J. Nucl. Mater. 390e391 (2009) 904. 
  26. L.L. Zhang, et al., A tungsten guard limiter for EAST 4.6 GHz lower hybrid waveguide antennas, Fusion Eng. Des. 136 (2018) 447-453.  https://doi.org/10.1016/j.fusengdes.2018.02.093
  27. M.H. Li, et al., Design of a PAM launcher and comparative analysis with the old FAM launcher for 2.45 GHz LHCD system on EAST, Fusion Eng. Des. 147 (2019), 111250. 
  28. A. Ekedahl, et al., 39th EPS Conference & 16th International Congress on Plasma Physics, Stockholm, Sweden, Comparison of Fast Electron Generation in Front of Passive-Active and Fully-Active Multijunction LH Launchers in Tore Supra, 36F, ECA, 2012. paper P2.088. 
  29. A. Ekedahl, L. Colas, M.L. Mayoral, et al., AIP Conference Proceedings, Density Convection Near Radiating ICRF Antennas and its Effect on the Coupling of Lower Hybrid Waves, vol. 694, 2003, p. 259. 
  30. K.K. Kirov, et al., Effects of ICRF induced density modifications on LH wave coupling at JET, Plasma Phys. Contr. Fusion 51 (2009), 044003. 
  31. C. Lau, et al., Effects of ICRF power on SOL density profiles and LH coupling during simultaneous LH and ICRF operation on Alcator C-Mod, Plasma Phys. Contr. Fusion 55 (2013), 095003. 
  32. D.A. D'Ippolito, et al., Analysis of RF sheath interactions in TFTR, Nucl. Fusion 38 (1998) 1543. 
  33. M. Becoulet, et al., Edge plasma density convection during ion cyclotron resonance heating on Tore Supra, Phys. Plasmas 9 (2002) 2619. 
  34. E.H. Kong, et al., Study and optimization of lower hybrid wave coupling in the experimental advanced superconducting (EAST) tokamak, Plasma Phys. Contr. Fusion 55 (2013), 065007. 
  35. J. Roth, et al., Tritium inventory in ITER plasma-facing materials and tritium removal procedures, Plasma Phys. Contr. Fusion 50 (2008), 103001.