Speaker
Description
The operation of ITER in high confinement mode hinges on the capability to mitigate or suppress edge localised modes (ELMs), in particular, in deuterium-tritium fuelled plasmas. A promising method to achieve this is the application of resonant magnetic perturbations (RMPs) to actively influence the plasma-edge transport keeping the pressure gradient below the ELM-triggering threshold. RMPs cause a resonant plasma response at flux surfaces where the safety factor is rational, by the formation of currents that screen the perturbation and negate the desirable impact on transport. Several necessary conditions for RMP ELM suppression have been established in deuterium plasmas (e.g. [1]). However, the corresponding conditions remain unclear for mixed-isotope plasmas [2]. To thoroughly understand the involved processes of field penetration, we study this problem with the linear kinetic plasma response codes KIM [3] and FLR2 [3, 4]. While the electrons are well described in the small Larmor radius limit, we demonstrate the need for an integral constitutive relation describing ions to all orders in the finite Larmor radius (FLR). Most notably, comparing the integral response of KIM with the FLR-expanded, differential response of FLR2, we find that the latter shows unphysical modes absent in the integral model. Despite KIM treating ions adequately, we observe no relevant isotope dependence which is necessary to understand the loss of ELM-suppression in deuterium-hydrogen mixed plasmas [2]. In that regard, the impact of turbulence may be an important missing ingredient that is susceptible to isotopes. Hence, we present progress on the development of an estimate for turbulent effects on the electron orbits. As the screening current is driven mostly by electrons, the turbulent electric field, having an isotope dependent radial correlation length of the order of or larger than the width of this current, introduces radial transport which affects (mostly reduces) this current. Possible isotope-dependence of this effect will be explored by the presented estimation scheme.
[1] W. Suttrop et al, Nucl. Fusion 58 096031, (2018)
[2] N. Leuthold et al, Nucl. Fusion 64 026017, (2024)
[3] M.J. Markl et al, in preparation
[4] P. Lainer et al, submitted to PPCF