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- Stahl, Adam, 1985, et al.
(författare)
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NORSE: A solver for the relativistic non-linear Fokker-Planck equation for electrons in a homogeneous plasma
- 2017
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655. ; 212, s. 269-279
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Tidskriftsartikel (refereegranskat)abstract
- Energetic electrons are of interest in many types of plasmas, howe ver previous modelling of their properties have been restricted to the use of linear Fokker-Planck collision ope rators or non-relativistic formulations. Here, we describe a fully non-linear kinetic-equation solver, capable of handling large electric-field strengths (compared to the Dreicer field) and relativistic temperatures. This tool allows modelling of the momentum- space dynamics of the electrons in cases where strong departure s from Maxwellian distributions may arise. As an example, we consider electron runaway in magnetic-confinement fusion plasmas and describe a transition to electron slide-away at field strengths significantly lower than pre viously predicted.
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| 2. |
- Stahl, Adam, 1985, et al.
(författare)
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Self-consistent nonlinear kinetic modeling of runaway-electron dynamics
- 2017
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Konferensbidrag (refereegranskat)abstract
- Runaway electrons represent the greatest threat to the plasma-facing components of atokamak when they are highly energetic and constitute a significant fraction of the electronpopulation, a regime which has not been previously accessible in modelling since it requiresa nonlinear relativistic treatment. To address this problem, we present an efficient numericaltool called NORSE for the study of runaway-electron momentum-space dynamics.The kinetic equation solved in NORSE includes a fully nonlinear relativistic collision operator, making it possible to consider scenarios where the electric field is comparableto the Dreicer field (or larger), or the electron distribution function is otherwise far froma Maxwellian (which can be the case already in present-day runaway experiments). Thiscapability makes NORSE unique in the field of runaway-electron studies.Using NORSE, we investigate the transition to a regime where the entire electronpopulation experiences continuous acceleration, so-called electron slide-away. Forthe first time, we apply a nonlinear kinetic-equation solver to study the evolution ofthe electron distribution in an ITER disruption. We use an electric field calculated self consistently,and show that the runaway-electron density becomes substantial, makingthe nonlinear treatment essential. In addition, we find that Ohmic heating and the rateof heat loss play an important role in determining the electron dynamics, with the latteraffecting the average energy reached by the runaways by several orders of magnitude.
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