On the role of finite grid extent in SOLPS-ITER edge plasma simulations for JET H-mode discharges with metallic wall

Tutkimustuotos: Lehtiartikkeli

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On the role of finite grid extent in SOLPS-ITER edge plasma simulations for JET H-mode discharges with metallic wall. / JET contributors ; Groth, M.

julkaisussa: Nuclear Materials and Energy, Vuosikerta 17, 01.12.2018, s. 174-181.

Tutkimustuotos: Lehtiartikkeli

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Bibtex - Lataa

@article{cf859930e1c8478f89ed411518d19cfc,
title = "On the role of finite grid extent in SOLPS-ITER edge plasma simulations for JET H-mode discharges with metallic wall",
abstract = "The impact of the finite grid size in SOLPS-ITER edge plasma simulations is assessed for JET H-mode discharges with a metal wall. For a semi-horizontal divertor configuration it is shown that the separatrix density is at least 30{\%} higher when a narrow scrape-off layer (SOL) grid width is chosen in SOLPS-ITER compared to the case for which the SOL grid width is maximised. The density increase is caused by kinetic neutrals being not confined inside the divertor region because of the reduced extent of the plasma grid. In this case, an enhanced level of reflections of energetic neutrals at the low-field side (LFS) metal divertor wall is observed. This leads to a shift of the ionisation source further upstream which must be accounted for as a numerical artefact. An overestimate in the cooling at the divertor entrance is observed in this case, identified by a reduced heat flux decay parameters λq div. Otherwise and further upstream the mid-plane heat decay length λq parameter is not affected by any change in divertor dissipation. This confirms the assumptions made for the ITER divertor design studies, i.e. that λq upstream is essentially set by the assumptions for the ratio radial to parallel heat conductivity. It is also shown that even for attached conditions the decay length relations λne > λTe > λq hold in the near-SOL upstream. Thus for interpretative edge plasma simulations one must take the (experimental) value of λne into account, rather than λq, as the former actually defines the required minimum upstream SOL grid extent.",
keywords = "divertor, edge plasma, JET, modelling, SOLPS-ITER",
author = "{JET contributors} and S. Wiesen and S. Brezinsek and X. Bonnin and E. Delabie and L. Frassinetti and M. Groth and C. Guillemaut and J. Harrison and D. Harting and S. Henderson and A. Huber and U. Kruezi and Pitts, {R. A.} and M. Wischmeier",
note = "| openaire: EC/H2020/633053/EU//EUROfusion",
year = "2018",
month = "12",
day = "1",
doi = "10.1016/j.nme.2018.10.013",
language = "English",
volume = "17",
pages = "174--181",
journal = "Nuclear Materials and Energy",
issn = "2352-1791",
publisher = "Elsevier Science Publishers BV",

}

RIS - Lataa

TY - JOUR

T1 - On the role of finite grid extent in SOLPS-ITER edge plasma simulations for JET H-mode discharges with metallic wall

AU - JET contributors

AU - Wiesen, S.

AU - Brezinsek, S.

AU - Bonnin, X.

AU - Delabie, E.

AU - Frassinetti, L.

AU - Groth, M.

AU - Guillemaut, C.

AU - Harrison, J.

AU - Harting, D.

AU - Henderson, S.

AU - Huber, A.

AU - Kruezi, U.

AU - Pitts, R. A.

AU - Wischmeier, M.

N1 - | openaire: EC/H2020/633053/EU//EUROfusion

PY - 2018/12/1

Y1 - 2018/12/1

N2 - The impact of the finite grid size in SOLPS-ITER edge plasma simulations is assessed for JET H-mode discharges with a metal wall. For a semi-horizontal divertor configuration it is shown that the separatrix density is at least 30% higher when a narrow scrape-off layer (SOL) grid width is chosen in SOLPS-ITER compared to the case for which the SOL grid width is maximised. The density increase is caused by kinetic neutrals being not confined inside the divertor region because of the reduced extent of the plasma grid. In this case, an enhanced level of reflections of energetic neutrals at the low-field side (LFS) metal divertor wall is observed. This leads to a shift of the ionisation source further upstream which must be accounted for as a numerical artefact. An overestimate in the cooling at the divertor entrance is observed in this case, identified by a reduced heat flux decay parameters λq div. Otherwise and further upstream the mid-plane heat decay length λq parameter is not affected by any change in divertor dissipation. This confirms the assumptions made for the ITER divertor design studies, i.e. that λq upstream is essentially set by the assumptions for the ratio radial to parallel heat conductivity. It is also shown that even for attached conditions the decay length relations λne > λTe > λq hold in the near-SOL upstream. Thus for interpretative edge plasma simulations one must take the (experimental) value of λne into account, rather than λq, as the former actually defines the required minimum upstream SOL grid extent.

AB - The impact of the finite grid size in SOLPS-ITER edge plasma simulations is assessed for JET H-mode discharges with a metal wall. For a semi-horizontal divertor configuration it is shown that the separatrix density is at least 30% higher when a narrow scrape-off layer (SOL) grid width is chosen in SOLPS-ITER compared to the case for which the SOL grid width is maximised. The density increase is caused by kinetic neutrals being not confined inside the divertor region because of the reduced extent of the plasma grid. In this case, an enhanced level of reflections of energetic neutrals at the low-field side (LFS) metal divertor wall is observed. This leads to a shift of the ionisation source further upstream which must be accounted for as a numerical artefact. An overestimate in the cooling at the divertor entrance is observed in this case, identified by a reduced heat flux decay parameters λq div. Otherwise and further upstream the mid-plane heat decay length λq parameter is not affected by any change in divertor dissipation. This confirms the assumptions made for the ITER divertor design studies, i.e. that λq upstream is essentially set by the assumptions for the ratio radial to parallel heat conductivity. It is also shown that even for attached conditions the decay length relations λne > λTe > λq hold in the near-SOL upstream. Thus for interpretative edge plasma simulations one must take the (experimental) value of λne into account, rather than λq, as the former actually defines the required minimum upstream SOL grid extent.

KW - divertor

KW - edge plasma

KW - JET

KW - modelling

KW - SOLPS-ITER

UR - http://www.scopus.com/inward/record.url?scp=85056205845&partnerID=8YFLogxK

U2 - 10.1016/j.nme.2018.10.013

DO - 10.1016/j.nme.2018.10.013

M3 - Article

VL - 17

SP - 174

EP - 181

JO - Nuclear Materials and Energy

JF - Nuclear Materials and Energy

SN - 2352-1791

ER -

ID: 31444147