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Author:Lindholm, Ville
Title:SOLPS simulations of a carbon injection experiment in the ASDEX Upgrade tokamak
SOLPS-simulationer av ett kolinjektionsexperiment i tokamaken ASDEX Upgrade
Publication type:Master's thesis
Publication year:2014
Pages:vi + 49 s. + liitt. 15      Language:   eng
Department/School:Perustieteiden korkeakoulu
Main subject:Ydin- ja energiatekniikka   (Tfy-56)
Supervisor:Groth, Mathias ; Salomaa, Rainer
Instructor:Groth, Mathias
Electronic version URL: http://urn.fi/URN:NBN:fi:aalto-201507013709
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  1162   | Archive
Keywords:SOL
SOLPS
EIRENE
impurity transport
carbon
AUG
orenhetstransport
kol
Abstract (eng): Global simulations of a C13 injection experiment have been performed to establish the impurity transport patterns of a L-mode plasma in ASDEX Upgrade.
Previously, simulations using a combination of the codes ASCOT, ERO and SOLPS have been used for the same purpose, but this work marks the first usage of SOLPS alone (coupled to the Monte Carlo neutral solver EIRENE).

Using experimental measurements obtained in the experiment (performed in 2011), a suitable base case was developed that minimized the error compared to outer mid-plane and outer target measurements.
Carbon neutrals were introduced into the computational domain, and their effect on the density and temperature profiles have been studied.
Likewise, the transport and deposition of carbon has been followed and compared to experimental measurements and ASCOT simulations.

It was found that the flow from the low-field side (LFS) to the high-field side (HFS) was insufficiently strong to reproduce the divertor a symmetry that was measured.
While roughly 5 % of the deposited carbon was found at the inner divertor and 1% at the outer divertor, SOLPS predicted corresponding values of 1 % and 10 %.
However, the majority of the simulated carbon promptly deposited close to the injection port at the OMP, which is supported by the previous work on this subject.

Overall, roughly 80 % of the carbon leaving the grid did so at the outer edges, i.e. towards the walls.
The density and temperature profiles at the inner divertor were overestimated compared to Langmuir probe measurements.
The inner divertor in SOLPS was in a transitional stage, where varying the outer mid-plane density parameter would change the HFS transport regime between sheath and conduction limited.
Stronger poloidal flows were created by increasing the ballooning effect of the perpendicular transport coefficients at the LFS, although typical values of (near) Mach 1 were not achieved.
Abstract (swe): En global simulation har gjorts av ett experiment som injicerade C13 in i en plasma i L-läge i tokamak-maskinen ASDEX Upgrade.
Syftet med simulationen var att fastställa rörelsemönstret och slutliga lagringen av kolatomerna i plasman.
Tidigare simulationer av samma fenomen har utförts med en kombination av kodpaketen ASCOT, ERO och SOLPS, men i detta arbete används för första gången enbart SOLPS (som även innefattar Monte Carlo-beräknaren Eirene från början till slut).
Utgående frän mätdata frän experimentet, kunde ett passligt "grundfall" utvecklas, med målet att passa in på mätdatan i grova drag.
Kolatomer introducerades sedan i beräkningarna, och deras påverkan på täthets och temperaturprofilerna analyserades.
Dessutom har rörelsen och den slutliga depositionen av kolatomerna studerats och jämförts med mätdata och ASCOT simulationer.

Det uppdagades att plasma ödet från lågfältssidan (LFS, från engelskans flow-field side) till högfältssidan (HFS) inte var tillräckligt starkt för att återskapa den asymmetrin som mättes vid divertorerna.
Runt 5 % av kolet som fastnat på väggarna återfanns vid den inre divertorn, samt 1 % vid den yttre.
SOLPS gav däremot värdena 1 % respektive 10 %.
Dock har majoriteten av det injicerade kolet lagrats nära injektionsporten enligt SOLPS, vilket tidigare forskning också har påvisat.
I allmänhet lämnade 80 % av kolet beräkningsområdet via de yttre kanterna, d.v.s. vid väggarna.
Täthets- och temperaturprofilerna vid den inre divertorn var högre vid simulationerna än i Langmuir-mätdatan.

Den inre divertorn var i SOLPS-simulationerna i en övergångsfas: varierade man täthetsparametern ändrade man transportmekanismen från mantelbegränsad till konduktionsbegränsad.
Ett försök att skapa större poloidala öden gjordes genom att höja på parametern för ballong-effekten som påverkar de vinkelräta transportkoefficienterna.
Detta gav en liten men lovande förbättring i ödesprofilen.
I framtidarbete bör även plasmans drivande tas med i simulationerna, för att skapa mer realistiska öden.
ED:2014-06-26
INSSI record number: 49343
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