Pitch angle scattering and synchrotron radiation of relativistic runaway electrons in tokamak stochastic magnetic fields

Martin-Solís, J.R.; Sánchez, Raúl

doi:10.1063/1.3013849

Cited by 8 publications

(7 citation statements)

References 22 publications

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“…In this case, FPAS of runaway electrons was most likely caused by the resonant interactions between runaway electrons and those MHD instabilities under proper conditions. It has been proposed that runaway electrons can experience a resonant interaction between their relativistic down-shifted cyclotron frequency and resonant modes satisfying the resonance condition [19] n ω ce = n eB 0 γ m e = k mn v (7) where n is an integer, v is the electron velocity parallel to the magnetic field and k mn is the parallel wave number associated with the resonant magnetic modes. This resonant mechanism will lead to a pitch angle scattering process, which can explain the experiment results reasonably and accurately based on the analysis above.…”

Section: Resonance Between Runaway Electrons and Mhd Modesmentioning

confidence: 99%

“…Many resonant interactions can cause FPAS processes, and have been proved effectively. For example, some possible resonant interactions of runaway electrons are the interaction with the magnetic field ripple [14][15][16], the interaction with lower hybrid waves [17,18] and the interaction with magnetohydrodynamic (MHD) modes in a stochastic magnetic field [19,20].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of ring-like runaway electron beams in the EAST tokamak

Zhou¹,

Hu²,

Li³

et al. 2013

Plasma Phys. Control. Fusion

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In the EAST tokamak, asymmetrical ring-like runaway electron beams with energy more than 30 MeV and pitch angle about 0.1 were investigated. Those runaway beams carried about 46% of the plasma current and located around the q = 2 rational surface when m/n = 1/1 and m/n = 2/1 MHD modes existed in the plasma. Those runaway beams changed from a hollow to a filled structure during the slow oscillations in the discharge about every 0.2 s, which correlated with a large step-like jump in electron cyclotron emission (ECE) signals, a big spike-like perturbation in Mirnov signals and a large decrease in runaway energy. Between those slow oscillations with large magnitude, fast oscillations with small magnitude also existed about every 0.02 s, which correlated with a small step-like jump in ECE signals, a small spike-like perturbation in Mirnov signals, but no clear decrease in runaway energy and changes in the runaway beam structure. Resonant interactions occurred between runaway electrons and magnetohydrodynamic instabilities, which gave rise to fast pitch angle scattering processes of those resonant runaway electrons, and hence increased the synchrotron radiation. Theoretical calculations of the resonant interaction were given based on a test particle description. Synchrotron radiation of those resonant runaway electrons was increased by about 60% until the end of the resonant interaction.

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Section: Resonance Between Runaway Electrons and Mhd Modesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of ring-like runaway electron beams in the EAST tokamak

Zhou¹,

Hu²,

Li³

et al. 2013

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…The evolution path of a runaway electron in momentum space due to these four physical effects has been studied in details [14,15]. The effects of stochastic magnetic field on the transport and energy limit of runaway electrons have also been studied [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Phase-space dynamics of runaway electrons in tokamaks

Guan¹,

Qin²,

Fisch³

2010

Physics of Plasmas

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The phase-space dynamics of runaway electrons is studied, including the influence of loop voltage, radiation damping, and collisions. A theoretical model and a numerical algorithm for the runaway dynamics in phase space are developed. Instead of standard integrators, such as the Runge-Kutta method, a variational symplectic integrator is applied to simulate the long-term dynamics of a runaway electron. The variational symplectic integrator is able to globally bound the numerical error for arbitrary number of time-steps, and thus accurately track the runaway trajectory in phase space. Simulation results show that the circulating orbits of runaway electrons drift outward toward the wall, which is consistent with experimental observations. The physics of the outward drift is analyzed. It is found that the outward drift is caused by the imbalance between the increase of mechanical angular momentum and the input of toroidal angular momentum due to the parallel acceleration. An analytical expression of the outward drift velocity is derived. The knowledge of trajectory of runaway electrons in configuration space sheds light on how the electrons hit the first wall, and thus provides clues for possible remedies.

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“…3(a) to 3(d), it can be seen that even with exactly the same vertical field and the same runaway electron current, the current center shows apparent displacement as the parallel momentum changes, in agreement with previous simplified model. [16] Such parallel momentum change could be caused by many mechanism, such as the collision with background species, [25] radiative drag, [26] kinetic instabilities [27] or toroidal electric field. In the small p ‖ limit, the deviation between the drift surface and the flux surface is small, while such deviation consistently grows as p ‖ increases.…”

Section: Numerical Results For Up-down Symmetric Boundary Conditionmentioning

confidence: 99%

Drift surface solver for runaway electron current dominant equilibria during the current quench

Yuan

2023

Chinese Phys. B

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Runaway electron current generated during the Current Quench phase of tokamak disruptions could result in severe damage to future high performance devices. To control and mitigate such runaway electron current, it is important to accurately describe the runaway electron current dominated equilibrium, based on which further stability analysis could be carried out. In this paper, we derive a Grad-Shafranov-like equation solving for the axisymmetric drift surfaces of the runaway electrons instead of the magnetic flux surfaces for the simple case that all runaway electron share the same parallel momentum. This new equilibrium equation is then numerically solved with simple rectangular wall with ITER-like and MAST-like geometry parameters. The deviation between the drift surfaces and the flux surfaces is readily obtained, and runaway electrons is found to be well confined even in regions with open field lines. The change of the runaway electron parallel momentum is found to result in a horizontal current center displacement without any changes in the total current or the external field. The runaway current density profile is found to affect the susceptibility of such displacement, with flatter profiles result in more displacement by the same momentum change. With up-down asymmetry in the external poloidal field, such displacement is accompanied by a vertical displacement of runaway electron current. It is found that this effect is more pronounced in smaller, compact device and weaker poloidal field cases. The above results demonstrate the dynamics of current center displacement caused by the momentum space change in the runaway electrons, and pave way for future, more sophisticated runaway current equilibrium theory with more realistic consideration on the runaway electron momentum distribution. This new equilibrium theory also provides foundation for future stability analysis of the runaway electron current.

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Pitch angle scattering and synchrotron radiation of relativistic runaway electrons in tokamak stochastic magnetic fields

Cited by 8 publications

References 22 publications

Investigation of ring-like runaway electron beams in the EAST tokamak

Investigation of ring-like runaway electron beams in the EAST tokamak

Phase-space dynamics of runaway electrons in tokamaks

Drift surface solver for runaway electron current dominant equilibria during the current quench

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