EFFECT OF LONGITUDINAL BEAM-COUPLING IMPEDANCE ON THE SCHOTTKY SPECTRUM OF BUNCHED BEAMS

Schottky spectra can be strongly affected by collective effects, in particular those arising from beam-coupling impedance when a large number of bunch charges are involved. In such conditions, the direct interpretation of the measured spectra becomes difficult, which prevents the extraction of beam and machine parameters in the same way as is usually done for lower bunch charges. Since no theory is yet directly applicable to predict the impact of impedance on such spectra, we use here time-domain, macro-particle simulations and apply a semi-analytical method to compute the Schottky spectrum for various machine and beam conditions, such as the ones found at the Large Hadron Collider. A simple longitudinal resonator-like impedance model is introduced in the simulations and its effect studied in different configurations, allowing preliminary interpretations of the impact of longitudinal impedance on Schottky spectra.