The RFQ prototype for the radioactive ion beams facility at TRIUMF

The ISAC radioactive ion beams facility being built at TRIUMF requires cw operation of a low frequency RFQ structure. This implies a large structure with adequate cooling while still maintaining mechanical alignment and stability. Our goal is to achieve a thermal stability alignment of +/-0.08 mm along the entire length of the RFQ structure and a dynamic stability of the operating assembled RFQ structure, taking into account deformation due to thermal drifts and vibrations induced by cooling and vacuum pumps, to within +/-0.025 mm. Cold model studies [1] have been carried out to confirm the RF characteristics of the RFQ design. To confirm the manufacturability of the design to maintain the above tolerances, a prototype section consisting of three RFQ rings is being fabricated and will be tested to full cw power (85 kV between electrodes). The basic design of the structure is different from other RFQ structures in that the RF surfaces have been de-coupled from the mechanical support structure for improved stability. The features of this mechanical design win be discussed and the first results of the RFQ prototype tests will be presented.