  In this bachelor's thesis, isotope effects for pedestal instabilities have
been studied based on an ASDEX Upgrade H-Mode scenario. This was done using the
JOREK code for extended MHD simulations, including the ion diamagnetic drift
and the establishment of ExB flows. Simulations with single toroidal harmonics
were performed for multiple times during the build-up of the pedestal, to
assess the evolution of the linear stability of modes occurring near the edge.
When changing the average ion masses from 2.0 to 2.5 and 3.0, the variations
were small, and MHD's momentum equation was shown to be the major cause for
them. As a second step, simulations with multiple toroidal harmonics were
performed to simulate an Edge Localized Mode (ELM) crash, again comparing
between the average ion masses of 2.0, 2.5, and 3.0. The resulting variations
of heat and particle losses were compared to JET results. The experimental
differences between ion masses could not be reproduced. Together with the fact
that the simulations' pedestal for an average ion mass of 2.5 and 3.0 was not
matched to the experiment, this indicates that other effects, such as
small-scale turbulences, must be included - for example, by adapting the
simulations' transport coefficients - to explain the experimental differences.
