Runaway Electrons in a Plasma

Kulsrud, Russell M.; Sun, Yung-Chiun; Winsor, N. K.; Fallon, Henry A.

doi:10.1103/physrevlett.31.690

Cited by 134 publications

(95 citation statements)

References 3 publications

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“…The collisional effects for runaway electrons are modeled by the Monte-Carlo method, where each collision induces changes in momentum space according to [2,4,11] ∆p = − n e e 4 ln Λm…”

Section: Theoretical Model and Numerical Algorithmmentioning

confidence: 99%

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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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“…The collisional effects for runaway electrons are modeled by the Monte-Carlo method, where each collision induces changes in momentum space according to [2,4,11] ∆p = − n e e 4 ln Λm…”

Section: Theoretical Model and Numerical Algorithmmentioning

confidence: 99%

“…In tokamaks, relativistic runaway electrons are often observed during and after a plasma disruption or during a fast plasma shutdown [1][2][3][4]. The growth-rate of avalanche runaway electron induced by knock-on process, synchrotron radiation and magnetic fluctuations has been studied extensively [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Phase-space dynamics of runaway electrons in tokamaks

Guan¹,

Qin²,

Fisch³

2010

Physics of Plasmas

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“…where A = z/v, and the collisional flux is taken in the approximation of Maxwellian field ions and electrons with T = T. In the 2-D code 4 we use the most general expressions for the coefficients A(v) and B(v) 5 , but otherwise we work with their simpler high-energy limits Az~1+Z, B=~1…”

Section: The Distribution Function From 2-d Numerical Integrationmentioning

confidence: 99%

A one-dimensional model for lower-hybrid current drive including perpendicular dynamics

Fuchs

Cairns

Shoucri

et al. 1985

The Physics of Fluids

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“…Recent researches indicate that tokamak, a magnetic confinement fusion energy device, may be the largest artificial positron factory in the world [4,5]. In large tokamaks like JET and JT-60U, above 10 14 positrons are generated in a post-disruption plasma by runaway electrons [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The dynamics of these positrons after birth in tokamaks is a noteworthy question that may yield valuable information about the runaway dynamics and disruption process in tokamaks.…”

mentioning

confidence: 99%

What is the fate of runaway positrons in tokamaks?

et al. 2014

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Massive runaway positrons are generated by runaway electrons in tokamaks. The fate of these positrons encodes valuable information about the runaway dynamics. The phase space dynamics of a runaway position is investigated using a Lagrangian that incorporates the tokamak geometry, loop voltage, radiation and collisional effects. It is found numerically that runaway positrons will drift out of the plasma to annihilate on the first wall, with an in-plasma annihilation possibility less than 0.1%. The dynamics of runaway positrons provides signatures that can be observed as diagnostic tools.

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Runaway Electrons in a Plasma

Cited by 134 publications

References 3 publications

Phase-space dynamics of runaway electrons in tokamaks

Phase-space dynamics of runaway electrons in tokamaks

A one-dimensional model for lower-hybrid current drive including perpendicular dynamics

What is the fate of runaway positrons in tokamaks?

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