Experimental study on fast electron generation during internal crash

Mai, Chaowei; Hu, Liqun; Xu, Liqing; Luo, Z.P.; Lin, Shiyao

doi:10.1088/2058-6272/abeda1

Cited by 2 publications

(2 citation statements)

References 27 publications

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“…2015; Mai et al. 2021). To illustrate that it is conceivable to get significant reverse runaway beams in disruptions with an intact edge region, we return again to the alternative scenario detailed in Appendix A, but now, unlike in the case studied in figure 2, with an intact edge region outside .…”

Section: Resultsmentioning

confidence: 99%

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Runaway dynamics in tokamak disruptions with current relaxation

2022

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The safe operation of tokamak reactors requires a reliable modelling capability of disruptions, and in particular the spatio-temporal dynamics of associated runaway electron currents. In a disruption, instabilities can break up magnetic surfaces into chaotic field line regions, causing current profile relaxation, as well as a rapid radial transport of heat and particles. Using a mean-field helicity transport model implemented in the disruption runaway modelling framework Dream, we calculate the dynamics of runaway electrons in the presence of current relaxation events. In scenarios where flux surfaces remain intact in parts of the plasma, a skin current is induced at the boundary of the intact magnetic field region. This skin current region becomes an important centre concerning the subsequent dynamics: it may turn into a hot ohmic current channel, or a sizeable radially localized runaway beam, depending on the heat transport. If the intact region is in the plasma edge, runaway generation in the countercurrent direction can occur, which may develop into a sizeable reverse runaway beam. Even when the current relaxation extends to the entire plasma, the final runaway current density profile can be significantly affected, as the induced electric field is reduced in the core and increased in the edge, thereby shifting the centre of runaway generation towards the edge.

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Section: Resultsmentioning

confidence: 99%

“…2015; Mai et al. 2021), such as large sawteeth. However, we are not aware of any clear observation of a significant reverse runaway electron beam.…”

Section: Resultsmentioning

confidence: 99%

Runaway dynamics in tokamak disruptions with current relaxation

2022

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Observation of nonthermal electrons further acceleration and long-lasting associated with magnetic reconnection and turbulence bursting in tokamak plasma

Mai,

Xu,

Lin

et al. 2024

Nucl. Fusion

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Vital to magnetized plasma performance, the acceleration of nonthermal electrons significantly influences the current drive of radio frequency (RF) waves in plasma. In EAST, we observed nonthermal electrons initially <215 keV in energy, being locally accelerated to 600 keV within 100 milliseconds, which corresponds to the total growth time of the magnetic island. Surprisingly, these fast electrons (FE) lasted for 1.4 seconds, several times longer than the estimated relaxation time of 0.26 seconds, and exceeded 1/10 of the discharge length. Turbulence generation at island’s X point is attributed to the unexpected confinement and repopulation of FEs. This phenomenon may have positive implications for the steady-state long pulse H mode operation in EAST, especially regarding non-inductive current sustainment. For future RF electron heating-dominant devices, the mechanisms elucidated in this study have immediate implications for optimizing RF current drive efficiency.

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Experimental study on fast electron generation during internal crash

Cited by 2 publications

References 27 publications

Runaway dynamics in tokamak disruptions with current relaxation

Runaway dynamics in tokamak disruptions with current relaxation

Observation of nonthermal electrons further acceleration and long-lasting associated with magnetic reconnection and turbulence bursting in tokamak plasma

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