Direct Impedance Measurement of the CERN PS Booster Finemet Cavities

Over CERN’s Long Shutdown 2, the conventional ferrite-loaded cavities of the PS Booster were replaced with wide-band Finemet-loaded cavities. The Finemet cavities bring many operational advantages, but also represent a significant broadband impedance source. The impedance is mitigated by servo loops, which suppress the induced voltage, reducing the impedance as seen by the beam. Accurately including the impedance of the cavity and the effect of the servoloops in longitudinal tracking simulations is essential to predict the performance with beam. This paper discusses the results of a measurement campaign, which is intended to give a direct measurement of the cavity impedance. Using the detected voltage and the measured beam profile, the cavity impedance can be inferred and used to improve beam dynamics modelling.