The U.S. Department of Energy is designing and building the world's premier accelerator-based pulsed-neutron source, called the Spallation Neutron Source (SNS). The $1.3 billion facility, which is being built in Oak Ridge, Tennessee, will provide nearly a factor of ten more neutrons than any other source in the world for the purpose of studying material structures and properties of such materials as complex fluids, polymers, semiconductors, thin films, and biological materials.
The SNS project is a collaboration of six DOE national laboratories, including Oak Ridge, Lawrence Berkeley in California, Los Alamos in New Mexico, Argonne in Illinois, Brookhaven in New York, and Thomas Jefferson in Virginia. The most advanced computational tools and methods are being used for the SNS design, especially for the target, which must endure the extreme power loads deposited by the incident high-energy protons, and the surrounding moderator components, which must shape and redirect the intense shower of neutrons produced in the target to the large array of scientific instruments.
The upper panel in the display shows a simulation of the highly turbulent flows that are produced in the circulating mercury target material. Sophisticated analyses of the mercury flow profiles and temperature distributions are required to ensure that the proton beam power is adequately removed and that a sufficient lifetime is achieved for the target assembly.
The lower panel in the display shows specific power densities produced in the target by the bombarding protons. A total of 2 MW of power must be be absorbed and removed. Complex particle production and transport simulations are used to predict the power distributions in the target and the space-, energy-, and angle-dependent neutron distributions produced from the spallation process.