Parameter dependencies of the separatrix density in low triangularity L-mode and H-mode JET-ILW plasmas

The midplane electron separatrix density, n e,sep, in JET-ILW L-mode and H-mode low triangularity deuterium fuelled plasmas exhibits a strong explicit dependence on the averaged outer divertor target electron temperature, n e,sep ∼ T e,ot−1/2. This dependence is reproduced by analytic reversed two point model (rev-2PM), and arises from parallel pressure balance, as well as the ratio of the power and momentum volumetric loss factors, (1 − f cooling)/(1 − f mom-loss). Quantifying the influence of the (1 − f cooling) and (1 − f mom-loss) loss factors on n e,sep has been enabled by measurement estimates of these quantities from L-mode density (fueling) ramps in the outer horizontal, VH(C), and vertical target, VV, divertor configurations. Rev-2PM n e,sep estimates from the extended H-mode and more limited L-mode datasets are recovered to within ±25% of the measurements, with a scaling factor applied to account for use of T e,ot , an averaged quantity, rather than flux tube resolved target values. Both the (1 − f cooling) and (1 − f mom-loss) trends and recovery of n e,sep using the rev-2PM formatting are reproduced in EDGE2D-EIRENE L-mode-like and H-mode-like density scan simulations. The general lack of a divertor configuration effect in the JET-ILW n e,sep trends can be attributed to a significant influence of main chamber recycling, which has been shown in the EDGE2D-EIRENE results to moderate n e,sep with respect to changes in divertor neutral leakage imposed by changes in the divertor configuration. The unified n e,sep vs T e,ot trends can, however, be broken if large modifications to the divertor geometry (e.g. complete removal of the outer divertor baffle structure) are introduced in the model. The more pronounced high-field side high density region formation in the VH(C) configuration with reduced clearance to the separatrix does not appear to have a significant influence on the outer midplane separatrix and pedestal parameters when mapped to T e,ot , although conditions at the inner midplane could not be assessed.

Description

Funding Information: This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200—EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. This work was also supported by the US DOE under Contract No. DE-AC05-00OR22725 with UT-Battelle, LLC. This scientific paper has been published as part of the international project co-financed by the Polish Ministry of Science and Higher Education within the programme called ‘PMW’ for 2021. Publisher Copyright: © EURATOM 2023.

Keywords

divertor and main chamber recycling, separatrix density, SOL-pedestal-core integration, two point model

DOI

10.1088/1741-4326/aca9de

Citation

Lomanowski , B , Rubino , G , Uccello , A , Dunne , M , Vianello , N , Aleiferis , S , Canik , J , Carvalho , I , Corrigan , G , Frassinetti , L , Frigione , D , Garzotti , L , Groth , M , Meigs , A , Maslov , M , von Thun , C P , Rimini , F , Schneider , P A , Sergienko , G , Simpson , J , Van Eester , D & JET Contributors 2023 , ' Parameter dependencies of the separatrix density in low triangularity L-mode and H-mode JET-ILW plasmas ' , Nuclear Fusion , vol. 63 , no. 3 , 036019 , pp. 1-22 . https://doi.org/10.1088/1741-4326/aca9de

Permanent link to this item

https://urn.fi/URN:NBN:fi:aalto-202304262852

Collections

[article-cris] Perustieteiden korkeakoulu / SCI

Show all metadata