RF Test Facility has been completed in the SNS project at ORNL to support test and conditioning operation of RF subsystems and components. The system consists of two transmitters for two klystrons powered by a common high voltage pulsed converter modulator that can provide power to two independent RF systems. The waveguides are configured with WR2100 and WR1150 sizes for presently used frequencies: 402.5 MHz and 805 MHz. Both 402.5 MHz and 805 MHz systems have circulator protected klystrons that can be powered by the modulator capable of delivering 11 MW peak and 1 MW average power. The facility has been equipped with computer control for various RF processing and complete dual frequency operation. More than forty 805 MHz fundamental power couplers for the SNS superconducting linac (SCL) cavities have been RF conditioned in this facility. The facility provides more than 1000 ft2 floor area for various test setups. The facility also has a shielded cave area that can support high power tests of normal conducting and superconducting accelerating cavities and components.

The Spallation Neutron Source (SNS) is an accelerator-based neutron source being built in Tennessee by a partnership of six national laboratories. The control system components for the SNS were produced by personnel at the collaborating laboratories, by vendors of the equipment, and by commercial contractors. A number of different approaches were used to provide the programming for both the programmable logic controllers (PLCs) and the input-output controllers (IOCs) which were all based on the Experimental Physics and Industrial Control System (EPICS). For conventional facilities, both the PLCs and the IOCs were programmed under a commercial contract. The PLCs for the high power radio frequency system (HPRF) were programmed by the vendors of the equipment, while the IOCs were programmed by the collaborating laboratory. Finally, while the IOCs for the cryogenic systems were programmed at Oak Ridge, three different approaches were used to produce the PLC programming: some were programmed at Oak Ridge, some at TJNAF, and some at vendor sites. This paper discusses the status of the PLCs in the control system and the integration challenges encountered in the various approaches.

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is nearing completion. The cold section of the Linac consists of 81 superconducting radio frequency cavities cooled to 2.1K by a 2400 watt cryogenic refrigeration system. The 2.1K cold box consists of four stages of centrifugal compressors with LN2-cooled variable speed electric motors and magnetic bearings. The cryogenic system successfully supported the Linac beam commissioning at both 4.2K and 2.1K and has been fully operational since June 2005. This paper describes the control principles utilized and the experimental results obtained for the SNS cold compressors turn-down capability to about 30% of the design flow, and possible limitation of the frequency dependent power factor of the cold compressor electric motors, which was measured for the first time during commissioning. These results helped to support the operation of the Linac over a very broad and stable cold compressor operating flow range (refrigeration capacity) and pressure. This in turn helped to optimize the cryogenic system operating parameters, minimizing the utilities and improving the system reliability and availability.