A new 50 MHz RF cavity for Aladdin

The 50.58 MHz RF system for the Aladdin synchrotron light source at the University of Wisconsin-Madison has been upgraded with the installation of a new aluminum RF cavity. The new cavity is a foreshortened quarter wave type designed to eliminate multipactoring under high field conditions by incorporating a toroidal shape for the short circuit end. Rigidity and ease of construction are enhanced by machining critical components from solid aluminum instead of using welded assemblies. A novel diaphragm tuner was incorporated to avoid the introduction of tuner modes. Drive power is coupled through a loop in air using a ceramic thimble for vacuum isolation. Coating of surfaces in the gap region with titanium made penetration of the first order multipactor region very easy and has eliminated all higher order multipactoring in the accelerating gap