MD1875 – Impedance Contribution of Single IR7 Secondary Collimators

This report summarises the results of MD1875 about impedance measurements of single LHCsecondary collimators in IR7. The activity was carried out during MD block 5 of 2016, on 28th October. The impedance of each collimator was measured from the tune–shift induced by cycling its gap. As done in previous measurements of the same kind, the tune was reconstructed from the damped oscillations of the beam when coherently kicked with the MKQA, in order to have a clearer signal. The same methodology was applied to crystals, measured during this MD activity for the first time since the LHC start-up. Due to the high level of losses while kicking and the consequent cut of tails, tune signals are not clean; therefore, measurements do not agree with expectations by a factor 2–3.