Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas

Tuomas Korpilo

Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas

Julkaisun otsikon käännös: Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas

Tuomas Korpilo

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Fuusioplasman magneettiseen koossapitoon perustuvissa reaktoreissa, kuten tokamakeissa, plasman tehokas koossapito on välttämätöntä fuusioenergian tuottamiseksi. Plasmaturbulenssi ja sen aiheuttama hiukkasten ja lämmön kulkeutuminen ulos plasmasta kuitenkin heikentävät koossapitoa, mikä rajoittaa reaktoreiden suorituskykyä. Turbulenssin ymmärtäminen ja hillitseminen ovat täten tärkeitä tekijöitä reaktoreidentaloudellisuuden kannalta. Tokamak-plasmojen turbulenssia tutkitaan sekä kokeellisesti että laskennallisesti. Laskennallisen mallinnuksen tavoitteena on selvittää turbulentin kuljetuksen taustalla olevia fysikaalisia mekanismeja sekä ennustaa plasman koossapitoa tulevaisuuden reaktoreille. Tämä mallinnustyö perustuu nykyisin yhä enenevässä määrin tietokoneohjelmiin, jotka ratkaisevat gyrokineettiset Fokker-Planckin–Maxwellin yhtälöt plasman sisällä. ELMFIRE-koodi on yksi näistä gyrokineettisistä tietokoneohjelmista. Tässä väitöstyössä kuvataan ELMFIRE:n viimeaikaista kehitystyötä koodin numeerisen ja fysikaalisen tarkkuuden parantamiseksi. Ohjelman numeerista tarkkuutta on parannettu uudella kentänsuuntaisen epälineaarisuuden integrointimetodilla, joka vaikuttaa ratkaisevasti energian säilymiseen simulaatioissa. Fysikaalista tarkkuutta on puolestaan lisätty uudella laskentahilalla, joka mahdollistaa epähomogeenisen resoluution käytön simulointialueella. Simulointialue on lisäksi ulotettu kattamaan koko tokamak-plasman tilavuus plasman keskipisteestä aina seinän ja poloidaalisten rajoittimien muodostamalle materiaalirajapinnalle asti. ELMFIRE-simulaatioiden fysikaalista tarkkuutta tutkitaan testaamalla koodin kykyä toistaa plasman tasapainotila FT-2-tokamakille. Vertailu simulaatiotulosten ja FT-2-datan välillä osoittaa, että kokeellista tasapainoa ei saavuteta laskennallisesti. Tämän lisäksi ELMFIRE:n kykyä mallintaa kuorintakerrosplasmoja tutkitaan rajoitinkonfiguraatiossa. Saadut tulokset osoittavat kalvopotentiaalin ja plasmavirtausten muodostumisen sekä tiheys- ja lämpötilaprofiilien muutoksen reunaplasmassa. Kuorintakerroksessa havaitaan myös numeerinen plasmahäiriö, joka aiheutuu voimakkaasta E x B-virtauksesta rajoittimien ja plasman rajapinnalla. Lopuksi laskentahilalla ja reunaehdoilla näytetään olevan merkittävä vaikutus plasman kuljetustasoon.

Julkaisun otsikon käännös	Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Ohjaaja	Groth, Mathias, Vastuuprofessori Kiviniemi, Timo, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7561-7
Sähköinen ISBN	978-952-60-7560-0
Tila	Julkaistu - 2017
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

YK:n kestävän kehityksen tavoitteet

Tämä tuotos edistää seuraavia kestävän kehityksen tavoitteita:

SDG 7 – Edullinen ja puhdas energia

Tutkimusalat

ydinfuusio
tietokonesimulaatio
turbulentti plasman kuljetus

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7560-0Lisenssi: Määrittelemätön

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@phdthesis{ac786956b0f1482bb6ea762113bd682d,

title = "Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas",

abstract = "Magnetic confinement fusion reactors, such as tokamaks, rely on generating fusion power by confining the burning plasma effectively inside the device. Plasma turbulence and associated heat and particle transport out of the plasma, however, degrade the confinement in such devices, thus limiting their performance. Therefore, understanding and controlling of turbulence are of great importance for improving the economics of fusion reactors. The plasma turbulence in tokamaks is studied both experimentally and computationally. The role of computational studies is to elucidate the underlying physical mechanisms for turbulent transport and, eventually, predict and manipulate plasma confinement for future reactors. This modeling effort is increasingly based on numerical tools that solve gyrokinetic Fokker-Planck–Maxwell equations in the plasma. ELMFIRE is one of these gyrokinetic tools designed for first-principles transport simulations. In this thesis, the recent code development work to improve ELMFIRE{\textquoteright}s numerical and physical accuracy is presented. The numerical accuracy is improved by a new integration method for the parallel nonlinearity that significantly enhances the energy conservation in the simulation. The physical accuracy, in turn, is increased by a new computational grid that allows a non-uniform resolution. In addition, the simulation domain is extended to cover the entire tokamak plasma volume from the plasma center to the material boundary of a radial wall and poloidal limiter plates. The physical accuracy of ELMFIRE simulations is investigated by testing the code{\textquoteright}s ability to reproduce a FT-2 tokamak plasma. A direct comparison of the simulation results and FT-2 data shows that the experimental steady-state profiles are not obtained numerically. In addition to this, the ELMFIRE capability to simulate scrape-off layer plasmas is examined in a toroidal limiter-like configuration. The results of this study show a formation of sheath potential and plasma flows as well as a modification of density and temperature profiles in the scrape-off layer. A numerical plasma perturbation, induced by a large radial E x B flow at the limiter-plasma boundary, is also observed in the scrape-off layer. Finally, grid resolution and boundary conditions are shown to have a significant impact on transport levels.",

keywords = "nuclear fusion, tokamak, computer simulation, turbulent plasma transport, ydinfuusio, tietokonesimulaatio, turbulentti plasman kuljetus, nuclear fusion, tokamak, computer simulation, turbulent plasma transport",

author = "Tuomas Korpilo",

year = "2017",

language = "English",

isbn = "978-952-60-7561-7",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "150",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas

AU - Korpilo, Tuomas

PY - 2017

Y1 - 2017

N2 - Magnetic confinement fusion reactors, such as tokamaks, rely on generating fusion power by confining the burning plasma effectively inside the device. Plasma turbulence and associated heat and particle transport out of the plasma, however, degrade the confinement in such devices, thus limiting their performance. Therefore, understanding and controlling of turbulence are of great importance for improving the economics of fusion reactors. The plasma turbulence in tokamaks is studied both experimentally and computationally. The role of computational studies is to elucidate the underlying physical mechanisms for turbulent transport and, eventually, predict and manipulate plasma confinement for future reactors. This modeling effort is increasingly based on numerical tools that solve gyrokinetic Fokker-Planck–Maxwell equations in the plasma. ELMFIRE is one of these gyrokinetic tools designed for first-principles transport simulations. In this thesis, the recent code development work to improve ELMFIRE’s numerical and physical accuracy is presented. The numerical accuracy is improved by a new integration method for the parallel nonlinearity that significantly enhances the energy conservation in the simulation. The physical accuracy, in turn, is increased by a new computational grid that allows a non-uniform resolution. In addition, the simulation domain is extended to cover the entire tokamak plasma volume from the plasma center to the material boundary of a radial wall and poloidal limiter plates. The physical accuracy of ELMFIRE simulations is investigated by testing the code’s ability to reproduce a FT-2 tokamak plasma. A direct comparison of the simulation results and FT-2 data shows that the experimental steady-state profiles are not obtained numerically. In addition to this, the ELMFIRE capability to simulate scrape-off layer plasmas is examined in a toroidal limiter-like configuration. The results of this study show a formation of sheath potential and plasma flows as well as a modification of density and temperature profiles in the scrape-off layer. A numerical plasma perturbation, induced by a large radial E x B flow at the limiter-plasma boundary, is also observed in the scrape-off layer. Finally, grid resolution and boundary conditions are shown to have a significant impact on transport levels.

AB - Magnetic confinement fusion reactors, such as tokamaks, rely on generating fusion power by confining the burning plasma effectively inside the device. Plasma turbulence and associated heat and particle transport out of the plasma, however, degrade the confinement in such devices, thus limiting their performance. Therefore, understanding and controlling of turbulence are of great importance for improving the economics of fusion reactors. The plasma turbulence in tokamaks is studied both experimentally and computationally. The role of computational studies is to elucidate the underlying physical mechanisms for turbulent transport and, eventually, predict and manipulate plasma confinement for future reactors. This modeling effort is increasingly based on numerical tools that solve gyrokinetic Fokker-Planck–Maxwell equations in the plasma. ELMFIRE is one of these gyrokinetic tools designed for first-principles transport simulations. In this thesis, the recent code development work to improve ELMFIRE’s numerical and physical accuracy is presented. The numerical accuracy is improved by a new integration method for the parallel nonlinearity that significantly enhances the energy conservation in the simulation. The physical accuracy, in turn, is increased by a new computational grid that allows a non-uniform resolution. In addition, the simulation domain is extended to cover the entire tokamak plasma volume from the plasma center to the material boundary of a radial wall and poloidal limiter plates. The physical accuracy of ELMFIRE simulations is investigated by testing the code’s ability to reproduce a FT-2 tokamak plasma. A direct comparison of the simulation results and FT-2 data shows that the experimental steady-state profiles are not obtained numerically. In addition to this, the ELMFIRE capability to simulate scrape-off layer plasmas is examined in a toroidal limiter-like configuration. The results of this study show a formation of sheath potential and plasma flows as well as a modification of density and temperature profiles in the scrape-off layer. A numerical plasma perturbation, induced by a large radial E x B flow at the limiter-plasma boundary, is also observed in the scrape-off layer. Finally, grid resolution and boundary conditions are shown to have a significant impact on transport levels.

KW - nuclear fusion

KW - tokamak

KW - computer simulation

KW - turbulent plasma transport

KW - ydinfuusio

KW - tietokonesimulaatio

KW - turbulentti plasman kuljetus

KW - nuclear fusion

KW - tokamak

KW - computer simulation

KW - turbulent plasma transport

M3 - Doctoral Thesis

SN - 978-952-60-7561-7

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Global Gyrokinetic Particle Simulations of Circular Limiter Tokamak Plasmas

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