Construction criteria and prototyping for the ISAC RFQ accelerator at TRIUMF

The ISAC RFQ consists of an 8 metre long 4-rod split ring structure resonating at 35 MHz. The rods are vaneshaped and are supported by 19 rings. The challenge of the mechanical design is the stringent, +/-0.08 mm, positioning tolerance on the four rod electrodes for 150 kW cw operation. A 1.2 metre long prototype with three full-scale modules, each comprising one ring and 40 cm of electrode, has already been built and successfully tested to fullpower. This enables us to complete the basic electrical and mechanical design for the final unit. The initial 7-ring portion of the final RFQ will be assembled first, together with an off-line source and a portion of the LEBT, so that RF parameters and beam dynamics behavior in the injection region can be tested as soon as possible. For the final RFQ the cross-section of the vacuum tank will be square, rather than circular. This will facilitate alignment of the modules and copper plating of the vacuum tank. The scope of the paper is to report the latest results from the full power tests on the prototype and to describe mechanical and RF design features including RF coupling, alignment philosophy and the copper plating technique