CONCEPTUAL DESIGN OF A 3RD HARMONIC CAVITY SYSTEM FOR THE LNLS ELECTRON STORAGE RING

The installation of a second RF cavity in the UVX electron storage ring at the Brazilian Synchrotron Light Laboratory (LNLS) at the end of 2003 brought about longitudinal instabilities driven by one of the HOMs of the new cavity. Even though the operational difficulties related to these unstable modes were successfully overcome by means of a combination of cavity tuning (using temperature and plunger adjustments) with phase modulation of the RF fields at the second harmonic of the synchrotron frequency, a more appropriate technique to avoid those problems is the use of higher harmonic cavities, which have the important advantage of providing damping of the longitudinal modes without increasing the energy spread. In this work we present the design of a passive higher harmonic cavity (HHC) system optimized for operation at the LNLS storage ring. The parameters for a set of cavities as well as the analysis of some of the effects that they may introduce in the beam dynamics are presented.