The IPNS RCS RF-system third cavity upgrade

The IPNS RCS is a rapid cycling synchrotron used to accelerate protons from 50 MeV to 450 MeV, 30 times per second. Currently, two single-gap, ferrite-loaded coaxial cavities, located 180/spl deg/ apart, provide a total peak accelerating voltage of approximately 21 kV over the 2.2 MHz to 5.1 MHz revolution frequency band. An amplifier chain, which includes a 2 kW predriver, a 20 kW driver and a 100 kW final, drives each cavity. A third RF system, consisting of a cavity, cavity bias supply, and amplifier chain, is currently under construction. When complete, this upgrade will provide flexibility in operation that is expected to enhance reliability (i.e., three cavity operation at higher total accelerating voltage, three cavity operation at lower voltage per cavity, or two cavity operation with an on-line spare). In addition, the third cavity will provide an experimental station for second harmonic RF cavity studies. We report progress to date.