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Self-consistent study of fast particle redistribution by Alfvén eigenmodes during Ion cyclotron resonance heating
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.ORCID iD: 0000-0002-7142-7103
2005 (English)In: Proceedings of the 9th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems, 2005, 14-20 p.Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
2005. 14-20 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6936OAI: oai:DiVA.org:kth-6936DiVA: diva2:11789
Conference
The 9th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems, November 9-11 (2005), Takayama, Japan
Note
QC 20100628Available from: 2007-03-29 Created: 2007-03-29 Last updated: 2012-03-20Bibliographically approved
In thesis
1. Non-linear dynamics of Alfvén eigenmodes excited by fast ions in tokamaks
Open this publication in new window or tab >>Non-linear dynamics of Alfvén eigenmodes excited by fast ions in tokamaks
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The tokamak is so far the most promising magnetic configuration for achieving a net production of fusion energy. The D-T fusion reactions result in 3.5 MeV alpha-particles, which may destabilize Alfvén eigenmodes through wave-particle interaction. These instabilities redistribute the alpha-particles from the central region of the plasma towards the edge, where they are thermalized, and hence result in a reduced heating efficiency. The high-energy alpha-particles may even be thrown out of the plasma and may damage the wall.

To investigate the destabilization of Alfvén eigenmodes by high-energy ions, ion cyclotron resonance heating (ICRH) and neutral beam injection (NBI) are often used to create a high-energy tail on the distribution function. The ICRH does not only produce high-energy anisotropic tails, it also decorrelates the wave-particle interaction with the Alfvén eigenmodes. Without decorrelation of the wave-particle interaction an ion will undergo a superadiabatic oscillation in phase space and there will be no net transfer of energy to the mode. For the thermal ions the decorrelation from collisions dominates while for the high-energy ions the decorrelation from ICRH dominates. As the unstable modes grow up, the gradients in phase space, which drive the mode, are reduced, resulting in a weaker drive. The dynamics of the system becomes non-linear due to a continuous restoration of the gradients by D-T reactions and ICRH.

In this thesis the non-linear dynamics of toroidal Alfvén eigenmodes (TAEs) during ICRH has been investigated using the SELFO code. The SELFO code, which calculates the distribution function during ICRH self-consistently using a Monte-Carlo metod, has been upgraded to include interactions with TAEs. The fast decay of the mode amplitude as the ICRH is switched off, which is seen in experiments, as well as the oscillation of the mode amplitude as the distribution function is repetetively built up by the ICRH and flattened by the TAE has been reproduced using numerical simulations. In the presence of several unstable modes the dynamics become more complicated. The redistribution of an alpha-particle slowing down distribution function as well as the reduced heating efficiency in the presence of several modes has also been investigated.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xiv, 61 p.
Series
Trita-EE, ISSN 1653-5146 ; 2007:001
Keyword
fusion plasma, tokamak, MHD, toroidal Alfvén eigenmodes, thermonuclear alpha particles, ion cyclotron resonance heating
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-4320 (URN)978-91-7178-564-0 (ISBN)
Public defence
2007-04-23, Sal F3, KTH, Lindstedtsvägen 23, Stockholm, 10:15
Opponent
Supervisors
Note
QC 20100628Available from: 2007-03-29 Created: 2007-03-29 Last updated: 2010-06-28Bibliographically approved

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