The influence of drifts in the ITER divertor in nonlinear MHD JOREK simulations with fluid and kinetic neutrals

Funding

This work is part of the research programme of the Foundation for Nederlandse Wetenschappelijk Onderzoek Instituten (NWO-I), which is part of the NWO and has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2014-2018 and 2019-2020 under grant agreement No 633053 and from the ITER Organization under Implementing Agreement 43-2174 with the Eindhoven University of Technology. Computations were performed using the computer cluster Marconi-Fusion. The views and opinions expressed herein do not necessarily reflect those of the European Commission nor the ITER Organization. effective neutral diffusivitybased on the collision rates. The total heat load remains approximately the same across the whole domain. On the outer target shownin figure 4 the hoat load is reduced from 5.8 to 4.8 MW when switching to kinetic neutrals. The exact reason for the significant drop in heat loads just around the strike point in the simulation is not clear. However, the CX plays a dominant role for energy and momentum exchange. Conclusion Good quantitatvie agreement (< 15% difference) has been found between the SOLPS-ITER and JOREK solutions for the plasma heat load for a scan in neutral puffing.Heat flux profiles are sensitvi e to the plasma-neutral interactions. Ef- fective diffusivity is not a good description for the behavior of kinetic neutrals, resulting in narrow heat flux profiles. As a first application, the JOREK code is applied to study the effectsof ExB drifts on the divertor solutions. Applying the extended MHD model yields a strong asymmetry in the behaviour between low field and high field side. The inner Figure 4: Comparison JOREK (with ExB divertordetachesatasignificantlylowergaspuffratecom-flows)withfluidneutrals,andwithkinetic paredtotheouterdivertor,generallyconsistentwithresults neutralsalongthedivertorcontou.r of SOLPS-ITER [5]. The asymmetries arise from the opposite flow directions of the poloidal flows near the separatrix on the low and high field sides. These effectsare expected to be much lowerfor the ITER FPO phase, as PFPO-1 is an operating scenario with high temperature and low densities. Kinetic neutrals will be needed to obtain broadened profiles at the strike points. Although CX plays a dominant role in the momentum exchange with neutrals in the divertor region, we still clearly observe the influence of poloidal flows. The peak heat flux remains at the same location as for the JOREK simulations with neutral fluid including the poloidal flows. The next step is improving reflection physics on the wall and achievingpartially detached states with kinetic neutrals. AcknowledgementsandDisclaimer References This work is part of the research programme of the Foundation for[1] M. Hoelzl et al., Nuclear fusion 61, 065001 (2021) NederlandseWetenschappelijkOnderzoekInstituten(NWO-I),whichis[2] D.CvanVugt,PhDthesis,EindhovenUniversityof part of the NWO and has been carried out within the framework of the Technolog,y(2019) EUROfusionConsortium and has received funding from the Euratom[4]J.-S.Parketal,Nuclearfusion61, (2021)[3]WiesenS.etal,J. Nucl.Mater.463, (2015) research and training program 2014-2018 and 2019-2020 under grant[5] E. Kaveeva et al, Nuclear Fusion 60, (2020) agreementNo633053andfromtheITEROrganizationunderImple-[6] S.Carli,etal,Nucl.Fusion58(2018) menting Agreement 43-2174 with the Eindhoven University of Technol-[7] D. Reiter, The EIRENE Code User Manual. (2021) ogy. Computations were performed using the computer cluster Marconi-Fusion. The viewsand opinions expressed herein do not necessarily reflect those of the European Commission nor the ITER Organization.