Kinetics of relativistic runaway electrons

Breǐzman, B. N.; Aleynikov, P.

doi:10.1088/1741-4326/aa8c3f

Cited by 21 publications

(36 citation statements)

References 59 publications

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“…Equations (127), (129) correct the earlier inaccurate expressions for collisional frequency [160] and collisional damping [156][157][158]. The origin of those inaccuracies is explained in Section 3 of Ref.…”

Section: The Corresponding Wave Equation and Dispersion Relation Havementioning

confidence: 85%

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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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Section: The Corresponding Wave Equation and Dispersion Relation Havementioning

confidence: 85%

“…. The reason for such replacement is that the relativistic Coulomb logarithm used in Ref [127]. is problematic: it depends on background plasma temperature, whereas the collisional drag force is insensitive to the background temperature for relativistic electrons (see Section III B).…”

mentioning

confidence: 99%

Physics of runaway electrons in tokamaks

et al. 2019

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“…The minimum can be found analytically if A ≫ 1 (so that tanh A ≈ 1) and the critical momentum fulfills p c (E eff c ) ≫ 1, which are consistent with our final solution if partially ionized impurities dominate. Hence (6), (10) and (18) may be used, and (22) is approximately solved by (see Appendix C for more details): ‡…”

Section: Effective Critical Electric Fieldmentioning

confidence: 99%

“…These two assumptions are consistent with our final solution if partially ionized impurities dominate. Hence (6), (10) and (18) may be used in the expression for the effective critical field (22), and the requirement U (p) = 0 [with U given in (21)…”

Section: Appendix C Derivation Of the Effective Critical Fieldmentioning

confidence: 99%

Effect of partially ionized impurities and radiation on the effective critical electric field for runaway generation

Hesslow

Embréus

Wilkie

et al. 2018

Plasma Phys. Control. Fusion

108

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We derive a formula for the effective critical electric field for runaway generation and decay that accounts for the presence of partially ionized impurities in combination with synchrotron and bremsstrahlung radiation losses. We show that the effective critical field is drastically larger than the classical Connor-Hastie field, and even exceeds the value obtained by replacing the free electron density by the total electron density (including both free and bound electrons). Using a kinetic equation solver with an inductive electric field, we show that the runaway current decay after an impurity injection is expected to be linear in time and proportional to the effective critical electric field in highly inductive tokamak devices. This is relevant for the efficacy of mitigation strategies for runaway electrons since it reduces the required amount of injected impurities to achieve a certain current decay rate.

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“…As MGI is widely used in current devices, cases where runaways are formed in MGI-induced disruptions provide a valuable dataset to properly understand the physics of runaway electron formation and dissipation in such scenarios. To gain this understanding, theoretical models have been formulated and implemented in computational tools which can be used to model disruptions (Breizman & Aleynikov 2017). To be applicable for predictions for ITER and beyond, theoretical tools must first be validated against existing experimental data to ensure that they capture the relevant physics.…”

Section: Introductionmentioning

confidence: 99%

Kinetic modelling of runaway electron generation in argon-induced disruptions in ASDEX Upgrade

et al. 2020

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Massive material injection has been proposed as a way to mitigate the formation of a beam of relativistic runaway electrons that may result from a disruption in tokamak plasmas. In this paper we analyse runaway generation observed in eleven ASDEX Upgrade discharges where disruption was triggered using massive gas injection. We present numerical simulations in scenarios characteristic of on-axis plasma conditions, constrained by experimental observations, using a description of the runaway dynamics with a self-consistent electric field and temperature evolution in two-dimensional momentum space and zero-dimensional real space. We describe the evolution of the electron distribution function during the disruption, and show that the runaway seed generation is dominated by hot-tail in all of the simulated discharges. We reproduce the observed dependence of the current dissipation rate on the amount of injected argon during the runaway plateau phase. Our simulations also indicate that above a threshold amount of injected argon, the current density after the current quench depends strongly on the argon densities. This trend is not observed in the experiments, which suggests that effects not captured by zero-dimensional kinetic modelling – such as runaway seed transport – are also important.

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Kinetics of relativistic runaway electrons

Cited by 21 publications

References 59 publications

Physics of runaway electrons in tokamaks

Physics of runaway electrons in tokamaks

Effect of partially ionized impurities and radiation on the effective critical electric field for runaway generation

Kinetic modelling of runaway electron generation in argon-induced disruptions in ASDEX Upgrade

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