Experimental observation of hot tail runaway electron generation in TEXTOR disruptions

Zeng, Long; Koslowski, H. R.; Liang, Y.; Lvovskiy, A.; Lehnen, M.; Nicolai, D.; Pearson, James L.; Rack, M.; Denner, P.; Finken, K.H.; Wongrach, K.

doi:10.1017/s0022377815000380

Cited by 13 publications

(15 citation statements)

References 26 publications

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“…The presence of the H-T electrons leads to the significant increase of the REs. This effect has been discussed in several simulations [18,[21][22][23] and experiments [15,24,25].…”

Section: Introductionmentioning

confidence: 89%

Simulations of runaway electron generation including the hot-tail effect

Nuga¹,

Yagi²,

Fukuyama³

2017

Nucl. Fusion

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The hot-tail (H-T) effect in disruptions with impurity injection is considered. The contribution of H-T effect on runaway electron (RE) current, which arises from fast thermal quench, is studied using two-dimensional Fokker-Planck simulation. It is found that in a high density plasma, the total RE current is reduced owing to its high collisionality. We also found that if the thermal quench is fast enough to invoke the H-T effect, the effect produces more seed REs than that excluding H-T effect even in high density plasmas. In high density region (n e ∼ 10 21 m −3 ) with fast thermal quench, nevertheless the increment of the seed REs due to H-T effect is generally small (tens of mili amperes), the increment of the total RE current reached to 2 MA owing to the avalanche effect.

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“…The presence of the H-T electrons leads to the significant increase of the REs. This effect has been discussed in several simulations [18,[21][22][23] and experiments [15,24,25].…”

Section: Introductionmentioning

confidence: 89%

Simulations of runaway electron generation including the hot-tail effect

Nuga¹,

Yagi²,

Fukuyama³

2017

Nucl. Fusion

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“…Some qualitative trends in RE seed formation can be inferred from RE plateau current JT-60U, ASDEX-U, and JET have observed data supporting a B ∼ 2 T toroidal field threshold for RE seed formation [206,235,243], leading to speculation that excitation of whistler waves could prevent RE formation below B = 2 T [158]. However, later experiments in JET [244], KSTAR [245], TEXTOR [246], and J-TEXT [247] found that there is no clear toroidal field threshold, so that B = 2 T is not a prerequisite for RE formation. Nevertheless, a robust trend is observed across all machines that higher toroidal magnetic field does elevate the RE plateau levels.…”

Section: E Re Seed Formation During Tqmentioning

confidence: 99%

Physics of runaway electrons in tokamaks

et al. 2019

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Of all electrons, runaway electrons have long been recognized in the fusion community as a distinctive population. They now attract special attention as a part of ITER mission considerations. This review covers basic physics ingredients of the runaway phenomenon and the ongoing efforts (experimental and theoretical) aimed at runaway electron taming in the next generation tokamaks. We emphasize the prevailing physics themes of the last 20 years: the hot-tail mechanism of runaway production, runaway electron interaction with impurity ions, the role of synchrotron radiation in runaway kinetics, runaway electron transport in presence of magnetic fluctuations, micro-instabilities driven by runaway electrons in magnetized plasmas, and vertical stability of the plasma with runaway electrons. The review also discusses implications of the runaway phenomenon for ITER and the current strategy of runaway electron mitigation.

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“…Here, n e is the electron density and lnΛ is the Coulomb logarithm. Several mechanisms can cause electrons to run away, including the Dreicer generation, [9,10] hot tail RE generation, [11][12][13][14] RE avalanching, [15] tritium decay, [16] radio-frequency wave heating [15,17] and Compton scattering of γ-rays from the activated wall. During the flattop, the Dreicer generation is the dominant primary RE mechanism and creates adequate RE seed population which is further amplified by the secondary RE generation named avalanche mechanism.…”

Section: Introductionmentioning

confidence: 99%

Runaway electron dynamics in Experimental Advanced Superconducting Tokamak helium plasmas

et al. 2023

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The generation of runaway electrons (REs) is observed during the low-density helium ohmic plasma discharge in the Experimental Advanced Superconducting Tokamak (EAST). The growth rate of hard x-ray (HXR) is inversely proportional to the line-average density. Besides, the RE generation in helium plasma is higher than deuterium plasma at the same density, which is obtained by comparing the growth rate of HXR with the same discharge conditions. The potential reason is the higher electron temperature of helium plasma in the same current and electron density plateau. Furthermore, two Alfvén eigenmodes driven by REs have been observed. The frequency evolution of the mode is not fully satisfied with the Alfvén scaling and when extension of the Alfvén frequency is towards 0, the high frequency branch is ~50 kHz. The different spatial position of the two modes and the evolution of the helium concentration could be used to understand deviation between theoretical and experimental observation.

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Experimental observation of hot tail runaway electron generation in TEXTOR disruptions

Cited by 13 publications

References 26 publications

Simulations of runaway electron generation including the hot-tail effect

Simulations of runaway electron generation including the hot-tail effect

Physics of runaway electrons in tokamaks

Runaway electron dynamics in Experimental Advanced Superconducting Tokamak helium plasmas

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