Professor Felix Parra Diaz

Abstract:

The heating power to access the high confinement mode (H-mode), PLH, scales approximately inversely with the isotope mass of the main ion plasma species as found in (protonic) hydrogen, deuterium and tritium plasmas in many fusion facilities over the last decades. In first dedicated L–H transition experiments at the Joint European Torus (JET) tokamak facility with the ITER-like wall (ILW), the power threshold, PLH, was studied systematically in plasmas of pure tritium and hydrogen–tritium mixtures at a magnetic field of 1.8 T and a plasma current of 1.7 MA in order to assess whether this scaling still holds in a metallic wall device. The measured power thresholds, PLH, in Ohmically heated tritium plasmas agree well with the expected isotope scaling for metallic walls and the lowest power threshold was found in Ohmic phases at low density. The measured power thresholds in ion cyclotron heated plasmas of pure tritium or hydrogen–tritium mixtures are significantly higher than the expected isotope mass scaling due to higher radiation levels. However, when the radiated power is taken into account, the ion cyclotron heated plasmas exhibit similar power thresholds as a neutral beam heated plasma, and are close to the scaling. The tritium plasmas in this study tended to higher electron heating fractions and, when heated with ion cyclotron waves, to relatively higher radiation fractions compared to other isotopes potentially impeding access to sustained H-modes.The authors thank P.A. Schneider, F. Ryter, A. Nielsen, and A. Kappatou for fruitful discussions and for help with data analysis tools. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom Research and Training Programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. G. Birkenmeier received funding from the Helmholtz Association under Grant No. VH-NG-1350.Peer Reviewed"Article signat per 27 autors/es: G. Birkenmeier, E.R. Solano, E. Lerche, D. Taylor, D. Gallart, M.J. Mantsinen, E. Delabie, I.S. Carvalho, P. Carvalho, E. Pawelec, J.C. Hillesheim, F. Parra Diaz, C. Silva, S. Aleiferis, J. Bernardo, A. Boboc, D. Douai, E. Litherland-Smith, R. Henriques, K.K. Kirov, C.F. Maggi, J. Mailloux, M. Maslov, F.G. Rimini, S.A. Silburn, P. Sirén, H. Weisen and JET Contributors"Postprint (published version

Abstract:

Supplementary data for the article "Extended electron tails in electrostatic microinstabilities and the nonadiabatic response of passing electrons": arXiv 2108.02822. The dataset includes a readme, GS2 FORTRAN namelist input files necessary to reproduce the simulations presented in the article, as well as scripts (using a mixture of Mathematica, MATLAB, and Python) for the calculation of collisional transport coefficients that appear in the collisional theory of the studied microinstabilities.

Abstract:

In this work, we compare gyrokinetic simulations in stellarators using different computational domains, namely, flux tube (FT), full-flux-surface (FFS), and radially global (RG) domains. Two problems are studied: the linear relaxation of zonal flows (ZFs) and the linear stability of ion temperature gradient (ITG) modes. Simulations are carried out with the codes EUTERPE, GENE, GENE-3D, and stella in magnetic configurations of LHD and W7-X using adiabatic electrons. The ZF relaxation properties obtained in different FTs are found to differ with each other and with the RG result, except for sufficiently long FTs, in general. The FT length required for convergence is configuration-dependent. Similarly, for ITG instabilities, different FTs provide different results, but the discrepancy between them diminishes with increasing FT length. FFS and FT simulations show good agreement in the calculation of the growth rate and frequency of the most unstable modes in LHD, while for W7-X differences in the growth rates are found between the FT and the FFS domains. RG simulations provide results close to the FFS ones. The radial scale of unstable ITG modes is studied in global and FT simulations finding that in W7-X, the radial scale of the most unstable modes depends on the binormal wavenumber, while in LHD no clear dependency is found.