UPGRADE OF INPUT POWER COUPLING SYSTEM FOR THE SNS RFQ

A RF input power coupler system has been developed and installed as an upgrade of input RF coupling to the RFQ in the SNS linac front-end. The design employs two coaxial loop couplers for 402.5 MHz operation. Two couplers are used in parallel to power the accelerating structure, with up to 800 kW total peak power at 8% duty cycle. Each coupler loop has a coaxial ceramic window that is connected to each output of a magic-T waveguide hybrid splitter through a coaxial-to-waveguide transition. The coaxial loop couplers have been designed, manufactured, and high-power processed. This paper presents the following: RF and mechanical designs of the couplers and system, procedure and result of high power RF conditioning, and test and operation results of the upgraded system.