Gyrokinetic nonlinear isotope effects in tokamak plasmas

Previous observations of an isotope dependent energy confinement in magnetically confined plasmas are still largely unexplained and its interaction with apparently unrelated plasma conditions has become one of the main unsolved issues with great relevance for nuclear fusion. By means of numerical studies based on the gyrokinetic theory, we quantitatively show how the plasma microturbulence can depend on the isotope mass through nonlinear multiscale effects, involving the interplay and competition between zonal flow shearing, electromagnetic effects and the torque applied. This observation can help to disentangle some of the pieces that form the puzzle of the isotope effect and to provide useful guidelines for establishing priorities in future DT campaigns.