Shielding solutions at the SNS target/accelerator interface

At the Spallation Neutron Source (SNS), a 1.4 MW proton beam at 1 GeV energy intercepts the liquid mercury target and sets free neutrons and a range of other particles. A fraction of the particles is scattered back into the last section of the accelerator tunnel, upstream from the target, and increases the already present radiation field caused by proton beam losses. The accelerator structures are exposed to high radiation fields limiting their lifetime and causing activation. Much higher activation is expected in the target and surrounding structural materials. These components become highly intense decay gamma sources and shine back into the accelerator tunnel even after beam termination. All these issues were investigated to support material selection, shielding design and maintenance planning.