MD 3290: Instability threshold measurements in the presence of a controlled external excitation

During the MD 2722 an unexpected instability was observed at flat top energy during BTF measurements. Simulation studies have shown an decrease of the instability thresholds according to the impedance level when in the presence of a small external excitation amplitude. In this note we summarise the results of the MD 3290 devoted to measure the instability thresholds in the presence of a controlled external excitation introduced by the use of the BTF system. The MD procedure is described and the presented results will be used as a reference in order to avoid instabilities during future BTF measurements at flat top energy.