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Theory and models for Monte Carlo simulations of minority particle populations in tokamak plasmas

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en
dc.contributor.advisor Kurki-Suonio,Taina, Prof., Aalto University, Department of Applied Physics, Finland
dc.contributor.author Hirvijoki, Eero
dc.date.accessioned 2014-02-18T10:02:11Z
dc.date.available 2014-02-18T10:02:11Z
dc.date.issued 2014
dc.identifier.isbn 978-952-60-5560-2 (electronic)
dc.identifier.isbn 978-952-60-5559-6 (printed)
dc.identifier.issn 1799-4942 (electronic)
dc.identifier.issn 1799-4934 (printed)
dc.identifier.issn 1799-4934 (ISSN-L)
dc.identifier.uri https://aaltodoc.aalto.fi/handle/123456789/12614
dc.description.abstract This thesis presents the essential parts of the first principles theory that is used to describe the evolution of minority particle populations in tokamak plasmas. Also, numerical models specific for Monte Carlo studies of fast ion transport are introduced, and the transport of alpha particles due to magnetohydrodynamical (MHD) activity is investigated in ITER scenarios. The thesis starts by introducing the very idea behind Monte Carlo simulations: an explicit proof of the connection between a Fokker-Planck equation and stochastic processes is given. This connection is then used to provide the stochastic differential equation for a charged particle that describes both the Hamiltonian and collisional motion of the particle in a plasma. Although following stochastic trajectories of charged particles and constructing the distribution functions a statistical average allows first principle solutions of the corresponding kinetic equation, the method is computationally very expensive. To offer numerically more attractive approach, the theoretical part is continued by introducing the guiding center transformation of the particle kinetic equation. The transformation is discussed in detail, and derivation of the guiding center motion is given explicitly. The theoretical work and the fast ion specific models are then implemented to construct a revieved version of the numerical Monte Carlo tool called ASCOT. As an application, the code is used to study MHD induced alpha particle transport in ITER. The results for the transport studies confirm that the neoclassical tearing modes would not endanger the integrity of the plasma facing components. However, it is noticed that the transport due to toroidal Alfvén eigenmodes could significantly change the power deposition from the alphas to the bulk plasma. en
dc.description.abstract Tämä väitöstyö kattaa perusteorian, joka kuvaa vähemmistöhiukkasia tokamak plasmoissa. Lisäksi työssä esitetään Monte Carlo malleja nopeiden hiukkasten mallintamiseen ja tuloksia nopeiden alfa hiukkasten simuloinnista ITER tokamakissa. Jotta Monte Carlo menetelmien käyttö olisi perusteltua, yhteys vähemmistöhiukkasten distribuutiofunktiota kuvaavan Fokker-Planck yhtälön ja stokastisen prosessin välillä todistetaan heti työn aluksi. Yhteyttä hyödyntämällä työssä esitetään stokastinen differentiaaliyhtälö varatulle hiukkaselle huomioiden sekä Hamiltoniaaninen että törmäyksellinen liike. Käytännössä distribuutiofunktion suora ratkaiseminen on kuitenkin numeerisesti erittäin kallista. Tämän vuoksi distribuutiofunkiota kuvaavalle Fokker-Planck yhtälölle suoritetaan muunnos, joka antaa paremmat valmiudet numeeriseen ratkaisuun. Muunnoksen perustana oleva johtokeskusteoria esitään tarkasti välivaiheet sisältäen. Teoriaa ja laadittuja malleja on myös sovellettu rakentamalla ASCOT-niminen ohjelmakoodi. Koodin avulla nopeiden alfa-hiukkasten kulkeutumista on voitu tutkia ITER tokamakissa aiempaa tarkemmin. Ensimmäistä kertaa tutkimus on voitu tehdä huomioiden sekä plasman aiheuttemat magneettiset epästabiiliudet, että itse tokamak laitteen tuottamat epähomogeeniset muodostumat magneettikentässä. fi
dc.format.extent 83 + app. 53
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Aalto University en
dc.publisher Aalto-yliopisto fi
dc.relation.ispartofseries Aalto University publication series DOCTORAL DISSERTATIONS en
dc.relation.ispartofseries 16/2014
dc.relation.haspart [Publication 1]: E. Hirvijoki and T. Kurki-Suonio. Monte Carlo diffusion operator for anomalous radial transport in tokamaks. Europhysics Letters, 97, 5, 55002, March 2012.
dc.relation.haspart [Publication 2]: E. Hirvijoki, A. Snicker, T. Korpilo, P. Lauber, E. Poli, M. Schneller, and T. Kurki-Suonio. Alfvén Eigenmodes and Neoclassical tearing modes for orbit-following implementations. Computer Physics Communications, 183, 2589-2593, July 2012.
dc.relation.haspart [Publication 3]: E. Hirvijoki, A. Brizard, A. Snicker, and T. Kurki-Suonio. Monte Carlo implementation of a guiding-center Fokker-Planck kinetic equation. Physics of Plasmas, 20, 9, 092505, September 2013.
dc.relation.haspart [Publication 4]: E. Hirvijoki, O. Asunta, T. Koskela, T. Kurki-Suonio, J. Miettunen, S. Sipilä, A. Snicker, and S. Äkäslompolo. ASCOT: solving the kinetic equation of minority particle species in tokamak plasmas. Accepted for publication in Computer Physics Communications, January 2014.
dc.relation.haspart [Publication 5]: A. Snicker, E. Hirvijoki, and T. Kurki-Suonio. Power loads to ITER first wall structures due to fusion alphas in a non-axisymmetric magnetic field including the presence of MHD modes. Nuclear Fusion, 53, 9, 093028, July 2013.
dc.subject.other Physics en
dc.subject.other Energy
dc.title Theory and models for Monte Carlo simulations of minority particle populations in tokamak plasmas en
dc.title Teoria ja mallit vähemmistöhiukkasten Monte Carlo simulointiin tokamak plasmoissa fi
dc.type G5 Artikkeliväitöskirja fi
dc.contributor.school Perustieteiden korkeakoulu fi
dc.contributor.school School of Science en
dc.contributor.department Teknillisen fysiikan laitos fi
dc.contributor.department Department of Applied Physics en
dc.subject.keyword Monte Carlo-method en
dc.subject.keyword tokamak en
dc.subject.keyword plasma en
dc.subject.keyword ITER tokamak
dc.subject.keyword ASCOT code
dc.subject.keyword fast ion transport
dc.subject.keyword stochastic differential equations
dc.subject.keyword alpha particles
dc.identifier.urn URN:ISBN:978-952-60-5560-2
dc.type.dcmitype text en
dc.type.ontasot Doctoral dissertation (article-based) en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.contributor.supervisor Salomaa, Rainer, Prof., Aalto University, Department of Applied Physics, Finland
dc.opn Helander, Per, Prof., Max Planck Institute for Plasma Physics, Stellarator Theory Division, Germany
dc.contributor.lab Fusion en
dc.rev Lackner, Karl, Prof., Max Planck Institute for Plasma Physics, Germany
dc.rev Peysson, Yves, Prof., National Institute of Nuclear Science and Technology, France
dc.date.defence 2014-03-20
local.aalto.digifolder Aalto_64772
local.aalto.digiauth ask


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