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On Self-Consistent ICRH Modelling
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
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(English)Article in journal (Other academic) Submitted
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-119996OAI: oai:DiVA.org:kth-119996DiVA: diva2:613172
Note

QS 2013

Available from: 2013-03-26 Created: 2013-03-26 Last updated: 2013-04-05Bibliographically approved
In thesis
1. Modelling Ion Cyclotron Resonance Heating and Fast Wave Current Drive in Tokamaks
Open this publication in new window or tab >>Modelling Ion Cyclotron Resonance Heating and Fast Wave Current Drive in Tokamaks
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fast magnetosonic waves in the ion cyclotron range of frequencies have the potential to heat plasma and drive current in a thermonuclear fusion reactor. A code, SELFO-light, has been developed to study the physics of ion cyclotron resonantheating and current drive in thermonuclear fusion reactors. It uses a global full wave solver LION and a new 1D Fokker-Planck solver for the self-consistent calculations of the wave field and the distribution function of ions.In present day tokamak experiments like DIII-D and JET, fast wave damping by ions at higher harmonic cyclotron frequencies is weak compared to future thermonuclear tokamak reactors like DEMO. The strong damping by deuterium, tritium and thermonuclear alpha-particles and the large Doppler width of fast alpha-particles in DEMO makes it difficult to drive the current when harmonic resonance layers of these ionspecies are located at low field side of the magnetic axis. At higher harmonic frequencies the possibility of fast wave current drive diminishes due to the overlapping of alpha-particle harmonic resonance layers. Narrow frequency bands suitable for the fast wave current drive in DEMO have been identified at lower harmonics of the alpha-particles. For these frequencies the effect of formation of high-energy tails in the distribution function of majority and minority ion species on the current drive have been studied. Some of these frequencies are found to provide efficient ion heating in the start up phase of DEMO. The spectrum where efficient current drive can be obtained is restricted due to weak electron damping at lower toroidal mode numbers and strong trapped electron damping at higher toroidal mode numbers. The width of toroidal mode spectra for which efficient current drive can be obtained have been identified, which has important implications for the antenna design.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xii, 53 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2013:013
Keyword
Thermonuclear fusion, Tokamak, DIII-D, JET, ITER, DEMO, ICRF, ICRH, Fast magnetosonic waves, TTMP, ELD, ICRH, Thermonuclear
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-119930 (URN)978-91-7501-692-4 (ISBN)
Public defence
2013-04-23, Sal F3, Lindstedsvägen 26, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20130327

Available from: 2013-03-27 Created: 2013-03-25 Last updated: 2014-08-29Bibliographically approved
2. Numerical solution of quasilinear kinetic diffusion equations in toroidal plasmas
Open this publication in new window or tab >>Numerical solution of quasilinear kinetic diffusion equations in toroidal plasmas
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the main challenges for the realization of a working fusion power plant is an increased detailed understanding of kinetic phenomena in toroidal plasmas. The tokamak is a toroidal, magnetically confined plasma device and is currently the main line towards a power plant. The spatial and temporal scales in a tokamak plasma are extreme and the only tractable path for quantitative studies is to rely on computer simulations. Present day simulation codes can resolve only some of these scales. Nevertheless they still require the largest high performance computing (HPC) resources available in the world. In combination with the increase of computational performance, it is therefore necessary to improve the numerical algorithms used in the simulations.

In this thesis we have developed new numerical methods designed for Monte Carlo simulation of plasma kinetic diffusion. Examples are simulation of fast-ion thermalization and radio-frequency heating. The aim has been to reduce the statistical random noise in particle codes, produced by a finite number of particles (or markers). Traditionally the statistical noise is improved by increasing the number of particles (N) or by simulating the perturbation of the distribution (with particles) from a known distribution function. This is the well known δf method. In this thesis we have developed a new type of δf method, which minimizes the number of particles used in a simulation. The computational speedup of the new method is substantial. In this thesis, we have further benchmarked quasi-Monte Carlo techniques that improve the convergence rate from N−1/2 to N−1 for some cases.

In Monte Carlo simulations, error appears also from the time step discretization. Based on the mathematics of operator splitting, a new scheme for the pitch-angle scattering diffusion process has been developed that outperforms the standard methods. Finally this thesis also presents a new code, SELFO-light, for self-consistent simulations of ion cyclotron resonance heating, suitable for routine calculations, which couples a one dimensional Fokker-Planck model with the finite element wave solver LION.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xiii, 54 p.
Series
Trita-EE, ISSN 1653-5146 ; 2013:012
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-120345 (URN)978-91-7501-697-9 (ISBN)
Public defence
2013-04-26, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20130405

Available from: 2013-04-05 Created: 2013-04-04 Last updated: 2013-04-05Bibliographically approved

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Johnson, Thomas

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