Spallation neutron source 550 kW (805 MHz) klystron transmitter systems

The spallation neutron source (SNS) being built at the Oak Ridge National Lab (ORNL) in Tennessee includes a one GeV proton linac, which requires 3 distinct types of RF systems. The radio frequency quadrapole (RFQ) and the drift tube linac (DTL) have 2.5-MW peak, 402.5 MHz, klystron transmitters installed. The coupled-cavity linac (CCL) and the two energy corrector cavities utilize a 5-MW peak, 805 MHz klystron transmitter. The superconducting linac (SCL) has 550-kW peak, 805 MHz klystron transmitters. This paper describes the design, fabrication and testing of the 550-kW transmitters, which includes a klystron control console, two high voltage enclosures supporting three klystrons each, and a thirteen circuit klystron cooling metering cart. The 2.5-MW and 5-MW transmitters are described in an accompanying paper to be presented at this conference (D. Gapp, 2004). The hardware baseline design to accomplish the goals of a reliable RF transmitter system is presented. Features of the transmitters installed in the SNS at ORNL (14 production units), which allow component failures to be quickly diagnosed and repaired, are reviewed. Tailored features such as interlocks, PLC fault logging and the real-time interface to the linac's data archive system are described. A novel concept to accurately monitor klystron filament voltage and current with high accuracy based on ground level voltage and current measurements is described. Factory acceptance tests used to facilitate reduced installation and commissioning time of the klystron transmitters are summarized. Transmitter operating experience during klystron conditioning at LANL and linac commissioning at ORNL is reviewed to demonstrate transmitter reliability and availability for meeting the SNS linac goals.