Design and measurements of a deflecting mode cavity for an RF separator

Abstract

The Fermilab Main Injector can produce intense 120 GeV/c proton beams for fixed target experimentation. Two deflecting mode RF systems can be used to separate charged kaons from a momentum selected secondary beam, consisting of pions, kaons and protons, using a time of flight method. We present the RF design of a 3.9 GHz superconducting cavity which operates in the deflecting (TM110) pi-mode and the dependence of the RF parameters on the cavity shape, as determined with finite difference calculations. End cell compensation has been treated, providing cell-to-cell field flatness. First results from measurements on a prototype cavity are shown. We demonstrated that it is possible to tune the deflecting mode of a five cell cavity with bead pull measurements. Effects relating to the polarization of the modes are discussed.