Spontaneous Enhancement of Inward Impurity Pinch during Massive Impurity Injection in Tokamak Plasmas
Abstract
A spontaneous enhancement of inward impurity pinch is identified prior to the fast quench under massive impurity injection on the EAST tokamak. The transition is marked by a rapid shift of the magnetic-island rotation frequency toward the electron diamagnetic direction within a few hundred microseconds. An extended KDG model shows that the impurity-induced increase in bulk ion collisionality can drive a transition across banana regime, nonlinearly modifying the parallel viscosity and producing a radial electric field excursion of approximately -10 kV/m, consistent with experiment. The associated self-organized response of the plasma flow and electrostatic potential can modify the parallel friction and further strengthen the neoclassical inward impurity pinch. Projections for ITER disruption mitigation suggest that this mechanism is expected to enhance impurity penetration, thereby improving the overall effectiveness of mitigation.
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BibTeX
@misc{zeng2026spontaneous,
title = {{Spontaneous Enhancement of Inward Impurity Pinch during Massive Impurity Injection in Tokamak Plasmas}},
author = {L. Zeng and W. Xia and D. Hu and T. Tang and X. Zhu and S. Zhao and T. Shi and D. Chen and Y. Duan and L. Xu and G. Li and G. Zuo and J. Hu and X. Gao and Y. Sun and Z. Gao},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05850},
eprint = {2611.05850},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05850},
}
RIS
TY - UNPB
TI - Spontaneous Enhancement of Inward Impurity Pinch during Massive Impurity Injection in Tokamak Plasmas
AU - L. Zeng
AU - W. Xia
AU - D. Hu
AU - T. Tang
AU - X. Zhu
AU - S. Zhao
AU - T. Shi
AU - D. Chen
AU - Y. Duan
AU - L. Xu
AU - G. Li
AU - G. Zuo
AU - J. Hu
AU - X. Gao
AU - Y. Sun
AU - Z. Gao
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.05850
UR - https://arxiv.org/abs/2611.05850
AB - A spontaneous enhancement of inward impurity pinch is identified prior to the fast quench under massive impurity injection on the EAST tokamak. The transition is marked by a rapid shift of the magnetic-island rotation frequency toward the electron diamagnetic direction within a few hundred microseconds. An extended KDG model shows that the impurity-induced increase in bulk ion collisionality can drive a transition across banana regime, nonlinearly modifying the parallel viscosity and producing a radial electric field excursion of approximately -10 kV/m, consistent with experiment. The associated self-organized response of the plasma flow and electrostatic potential can modify the parallel friction and further strengthen the neoclassical inward impurity pinch. Projections for ITER disruption mitigation suggest that this mechanism is expected to enhance impurity penetration, thereby improving the overall effectiveness of mitigation.
ER -