Overview of the SNS target system testing and initial beam operation experience

The Spallation Neutron Source (SNS) construction project has been completed including initial beam operation with the mercury target, moderators and associated systems. The project was initiated in 1999, with groundbreaking in December of 1999. Final integrated system testing for the mercury target, cryogenic moderators, shutter systems, water and other utility systems and all control and safety systems were completed in April 2006 and first beam on target was delivered April 28, 2006. This paper will give an overview of the system testing conducted in preparation for beam operation and initial operating experience with low power beams. One area of testing was extensive remote handling testing in the target service bay to demonstrate all key operations associated with the target and mercury loop. Many improvements were implemented as a result of this experience. Another set of tests involved bringing the supercritical cryogenic moderator systems on line. Again, lessons learned here resulted in system changes. Testing of the four water loops was very time consuming because of the complexity of the systems and many instrumentation issues had to be resolved. A temporary phosphor view-screen was installed on the front of the target which has been extremely useful in evaluating the beam profile on the target. Initial profile results will be presented. Target system performance for initial beam operation will be discussed. In general, all systems performed well with excellent availability. There were some unexpected findings. For example, xenon spallation gas products are believed to have deposited on a downstream gold amalgamation bed designed to remove mercury vapor and this disposition increased the local dose rate. A summary of findings and plans for ramping up in power will be given.