MD3318 – Impedance Contribution of Secondary and Tertiary Collimators

This report summarises the results of MD3318 about impedance measurements of individual LHC secondary and tertiary collimators. The measurements took place during the MD block III of 2018, on the afternoon of the 27th of October. Individual collimators impedance can be esti- mated from the tune shift induced by the collimator gap variation. The transverse damper was set-up to coherently excite the beam, and its oscillations were recorded with the ADT ObsBox, as done in previous MD activities. The beam was excited in quick successions, while varying the collimator gap, to mitigate the effect of tune drift and tune jitter. This method allows to measure tune shifts in the order of a few 10−5.