A nearly monochromatic cavity for high current storage rings

A strong damping of the higher order mode (HOM) spectrum of an RF cavity can be obtained by coupling appropriate waveguides directly to the cavity. This type of HOM suppression has been investigated at S.T. After studies and tests on different shapes of cavities, particularly on bell-shaped cavities, it has been decided to design a pill-box cavity for the ELETTRA Storage Ring. A prototype of this cavity has been produced with two waveguide suppressors coupled to it. The suppression effect on the HOM spectrum is described along with discussions on the vacuum window design and on the shape and the material for the waveguide load. The effects on the accelerating mode are shown as well. (orig.)