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Broadening of scrape-off layer width by turbulence spreading in the heavy hydrogen isotope plasmas

Y. J. Zhu1, J. Cheng1,*, Y. Xu1,†, L. W. Yan2, Y. He2, Q. Zou1, X. Chen1, J. Chen1, Z. S. Shi1 et al.

R. X. Huang1, Z. H. Huang2, W. C. Wang2, N. Wu2, Z. B. Shi2, X. Q. Ji2, and W. L. Zhong2

  • *Contact author: chengj@swjtu.edu.cn
  • †Contact author: xuyuhong@swjtu.edu.cn
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Phys. Rev. Research 8, 013290 – Published 17 March, 2026

DOI: https://doi.org/10.1103/c3r6-v2lk

Abstract

A significant enhancement of turbulence spreading across the last closed flux surface (LCFS) has been observed during the transition from hydrogen (H)- to deuterium (D)-dominated plasmas in the HL-2A tokamak. Experimental results show that boundary turbulence increases in D plasmas compared to H plasmas, while the E×B shear flow in the vicinity of the LCFS is accordingly reduced. It is found that fluctuations inside the LCFS are dominated by interchange turbulence, which spreads radially outward and penetrates the LCFS into the scrape-off layer (SOL), leading to a broader SOL width and a reduction of parallel heat flux. These findings highlight the significant contribution from turbulence spreading to the broadening SOL width and suggest a promising strategy for controlling exhaust heat load while maintaining good plasma confinement through isotope mass optimization in future fusion reactors.

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Phys. Rev. Research 8, 013290– Published 17 March, 2026
  • Received 24 August 2025
  • Accepted 17 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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