The isotope effect in ASDEX

Abstract

This paper describes the effect of the isotopic mass on plasma parameters as observed in the ASDEX tokamak. The paper comprises Ohmic as well as L-mode, H-mode and H"*-mode scenarios. The measurements reveal that the ion mass is a substantial and robust parameter which affects all confinement times (energy, particle and momentum) in the whole operational window. Both, core properties like the sawtooth repetition time and edge properties like the separatrix density change with the isotopic mass. Specific emphasis is given to the edge parameters and changes of the edge plasma due to different wall conditioning such as carbonization and boronization. The pronounced isotope dependence of edge and divertor parameters are explained by the secondary effect of different power fluxes into the scrape-off layer plasma and onto the divertor plates. Finally, the observations serve to test different transport theories. With respect to the ion temperature gradient driven turbulence, the isotope effect is also studied in pellet refuelled discharges with peaked density profiles. The results from ASDEX are compared with those from other experiments. (orig.)