| 1. |
- Eriksson, Frida, 1986, et al.
(author)
-
Kinetic theory of phase space plateaux in a non-thermal energetic particle distribution
- 2015
-
In: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 22:9, s. art.no. 092126-
-
Journal article (peer-reviewed)abstract
- The transformation of kinetically unstable plasma eigenmodes into hole-clump pairs with temporally evolving carrier frequencies was recently attributed to the emergence of an intermediate stage in the mode evolution cycle, that of an unmodulated plateau in the phase space distribution of fast particles. The role of the plateau as the hole-clump breeding ground is further substantiated in this article via consideration of its linear and nonlinear stability in the presence of fast particle collisions and sources, which are known to affect the production rates and subsequent frequency sweeping of holes and clumps. In particular, collisional relaxation, as mediated by e.g. velocity space diffusion or even simple Krook-type collisions, is found to inhibit hole-clump generation and detachment from the plateau, as it should. On the other hand, slowing down of the fast particles turns out to have an asymmetrically destabilizing/stabilizing effect, which explains the well-known result that collisional drag enhances holes and their sweeping rates but suppresses clumps. It is further demonstrated that relaxation of the plateau edge gradients has only a minor quantitative effect and does not change the plateau stability qualitatively, unless the edge region extends far into the plateau shelf and the corresponding Landau pole needs to be taken into account.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Lilley, Matthew, 1983, et al.
(author)
-
Collective fast ion effects in tokamaks
- 2010
-
In: Meeting of the Swedish Research Unit, RUSA, November 10-11 2010, Stockholm.
-
Conference paper (other academic/artistic)
|
|
| 5. |
- Lilley, Matthew, 1983, et al.
(author)
-
Drag induced energetic particle modes
- 2011
-
In: International Sherwood Fusion Theory Conference, Austin, Texas, May 2 – 4, 2011.
-
Conference paper (peer-reviewed)
|
|
| 6. |
- Nyqvist, Robert, 1983, et al.
(author)
-
Adiabatic Description of Long Range Frequency Sweeping
- 2012
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 52:9
-
Journal article (peer-reviewed)abstract
- A theoretical framework is developed to describe long range frequency sweeping events in the 1D electrostatic bump-on-tail model with fast particle sources and collisions. The model includes three collision operators (Krook, drag (dynamical friction) and velocity space diffusion), and allows for a general shape of the fast particle distribution function. The behaviour of phase space holes and clumps is analysed in the absence of diffusion, and the effect of particle trapping due to separatrix expansion is discussed. With a fast particle distribution function whose slope decays above the resonant phase velocity, hooked frequency sweeping is found for holes in the presence of drag collisions alone.
|
|
| 7. |
|
|
| 8. |
- Nyqvist, Robert, 1983, et al.
(author)
-
Modeling of Long-Range Sweeping Phenomena
- 2011
-
In: Joint US-EU TTF Workshop, San Diego, California, April 6 – 9, 2011 (oral presentation).
-
Conference paper (peer-reviewed)
|
|
| 9. |
|
|
| 10. |
- Sharapov, S.E., et al.
(author)
-
Energetic particle instabilities in fusion plasmas
- 2013
-
In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104022-
-
Journal article (peer-reviewed)abstract
- Remarkable progress has been made in diagnosing energetic particle instabilities on present-day machines and in establishing a theoretical framework for describing them. This overview describes the much improved diagnostics of Alfvén instabilities and modelling tools developed world-wide, and discusses progress in interpreting the observed phenomena. A multi-machine comparison is presented giving information on the performance of both diagnostics and modelling tools for different plasma conditions outlining expectations for ITER based on our present knowledge.
|
|
