Observation and Modelling of the Onset of Parametric Decay Instabilities during Gyrotron Operation at ASDEX UpgradeS.K. Hansen, S.K. Nielsen, J. Stober, J. Rasmussen, M. Stejner and ASDEX Upgrade TeamEPJ Web Conf., 203 (2019) 02007DOI: https://doi.org/10.1051/epjconf/201920302007