| 1. |
- Landreman, Matt, et al.
(författare)
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Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas
- 2014
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we examine the validity of several common simplifying assumptions used in numerical neoclassical calculations for nonaxisymmetric plasmas, both by using a new continuum drift-kinetic code and by considering analytic properties of the kinetic equation. First, neoclassical phenomena are computed for the LHD and W7-X stellarators using several versions of the drift-kinetic equation, including the commonly used incompressible-E × B-drift approximation and two other variants, corresponding to different effective particle trajectories. It is found that for electric fields below roughly one third of the resonant value, the different formulations give nearly identical results, demonstrating the incompressible E × B-drift approximation is quite accurate in this regime. However, near the electric field resonance, the models yield substantially different results. We also compare results for various collision operators, including the full linearized Fokker-Planck operator. At low collisionality, the radial transport driven by radial gradients is nearly identical for the different operators; while in other cases, it is found to be important that collisions conserve momentum.
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| 2. |
- Papp, Gergely, 1985, et al.
(författare)
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Runaway electron drift orbits in magnetostatic perturbed fields
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:4, s. 043004-
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Tidskriftsartikel (refereegranskat)abstract
- Disruptions in large tokamaks can lead to the generation of a relativistic runaway electron beam that may cause serious damage to the first wall. To mitigate the disruption and suppress the runaway beam the application of resonant magnetic perturbations has been suggested. In this work we investigate the effect of resonant magnetic perturbations on the confinement of runaway electrons by simulating their drift orbits in magnetostatic perturbed fields and calculating the orbit losses for various initial energies and magnetic perturbation magnitudes. In the simulations we use a TEXTOR-like configuration and solve the relativistic, gyro-averaged drift equations for the runaway electrons including synchrotron radiation and collisions. The results indicate that runaway electrons are well confined in the core of the device, but the onset time of runaway losses closer to the edge is dependent on the magnetic perturbation level and thereby can affect the maximum runaway current. However, the runaway current damping rate is not sensitive to the magnetic perturbation level, in agreement with experimental observations.
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| 3. |
- Papp, Gergely, 1985, et al.
(författare)
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Runaway electron drift orbits in magnetostatic perturbed fields
- 2010
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Ingår i: Proceedings of 23rd IAEA Fusion Energy Conference, Korea 2010.
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Konferensbidrag (refereegranskat)abstract
- Disruptions in large tokamaks can lead to the generation of a relativistic runaway electron beam that may cause serious damage to the first wall. To mitigate the disruption and suppress the runaway beam the application of resonant magnetic perturbations has been suggested. In this work we investigate the effect of resonant magnetic perturbations on the confinement of runaway electrons by simulating their drift orbits in magnetostatic perturbed fields and calculating the orbit losses for various initial energies and magnetic perturbation magnitudes. In the simulations we use a TEXTOR-like configuration and solve the relativistic, gyro-averaged drift equations for the runaway electrons including synchrotron radiation and collisions. The results indicate that runaway electrons are well confined in the core of the device, but the onset time of runaway losses closer to the edge is dependent on the magnetic perturbation level and thereby can affect the maximum runaway current. However, the runaway current damping rate is not sensitive to the magnetic perturbation level, in agreement with experimental observations.
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| 4. |
- Papp, Gergely, 1985, et al.
(författare)
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Runaway electron losses caused by resonant magnetic perturbations in ITER
- 2011
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 53:9, s. 095004-
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Tidskriftsartikel (refereegranskat)abstract
- Disruptions in large tokamaks can lead to the generation of a relativistic runaway electron beam that may cause serious damage to the first wall. To suppress the runaway beam the application of resonant magnetic perturbations (RMPs) has been suggested. In this work we investigate the effect of RMPs on the confinement of runaway electrons by simulating their drift orbits in magnetostatic perturbed fields and calculating the transport and orbit losses for various initial energies and different magnetic perturbation configurations. In the simulations we model the ITER RMP configuration and solve the relativistic, gyro-averaged drift equations for the runaway electrons including a time-dependent electric field, radiation losses and collisions. The results indicate that runaway electrons are rapidly lost from regions where the normalized perturbation amplitude δB/B is larger than 0.1% in a properly chosen perturbation geometry. This applies to the region outside the radius corresponding to the normalized toroidal flux ψ = 0.5.
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| 5. |
- Papp, Gergely, 1985, et al.
(författare)
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Runaway electron losses enhanced by resonant magnetic perturbations
- 2011
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Ingår i: Proceedings of 12th Technical Meeting on Energetic Particles in Magnetic Confinement Systems. ; , s. O.26-
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Konferensbidrag (refereegranskat)abstract
- Disruptions in large tokamaks can lead to the generation of a relativistic runaway electronbeam that may cause serious damage to the first wall. To suppress the runaway beam the applicationof resonant magnetic perturbations (RMP) has been suggested. In this work we investigate the effect ofresonant magnetic perturbations on the confinement of runaway electrons by simulating their drift orbitsin magnetostatic perturbed fields and calculating the transport and orbit losses for various initial energiesand different magnetic perturbation configurations. In the simulations we use model configurations withexisting (TEXTOR) and planned (ITER) RMP systems, and solve the relativistic, gyro-averaged driftequations for the runaway electrons including the electric field, radiation losses and collisions. The resultsindicate that runaway electrons are well confined in the core of the device, but the onset time of runawaylosses closer to the edge is dependent on the magnetic perturbation level, which can thereby affectthe maximum runaway current. Runaway electrons are rapidly lost from regions where the normalisedperturbation amplitude \delta B/B is larger than 0.1% in a properly chosen perturbation geometry. Thisapplies to the region outside the radius corresponding to the normalised flux \psi = 0.5 in ITER, when theELM mitigation coils are used at maximum current in their most favourable configuration.
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| 6. |
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