MD4147: 50 Hz harmonics perturbation

Since the beginning of the LHC commissioning, harmonics of 50 Hz have been observed in the beam spectrum. Several observations during the 2018 proton run show that these harmonics are the result of a real beam excitation, rather than an artifact of the instrumentation system. As many of these components reside in the vicinity of the betatron tune, their presence can complicate the tune measurement and tracking during operation and potentially lead to beam losses and emittance growth. This note summarizes the program of the first LHC Machine Development (MD) (Fills 7342 and 7343) dedicated to the investigation of this effect. The aim of this study is to reproduce some of the observations acquired during End-of-Fill experiments and parasitic observations, as well as to simulate the impact of dipolar noise on the beam with controlled ADT excitations.