Abstract
The Spallation Neutron Source (SNS) continues a ramp up in proton beam power toward the design goal of 1.4 MW on target. At Megawatt levels, US and Japanese studies have shown that cavitation in the Mercury target could lead to dramatically shortened target lifetime. Therefore, it will be critical to measure and control the proton beam distribution on the target, in a region of extremely high radiation and limited accessibility. Several sources of photons have been considered for imaging the beam on or near the target. These include a freestanding temporary screen, a scintillating coating, Helium gas scintillation, optical transition radiation, and a beam- heated wire mesh. This paper will outline the selection process that led to the current emphasis on coating development. In this harsh environment, the optics design presented significant challenges. The optical system has been constructed and characterized in preparation for installation. Optical test results will be described along with predictions of overall system performance.
