Collimator systems for the SNS ring

The requirements and performance goals for the collimators are to reduce the uncontrolled beam loss by 2/spl times/10/sup -4/, absorb 2 kW of deposited heat, and minimize production and leakage of secondary radiation. In order to meet these requirements a self-shielding collimator configuration consisting of a layered structure was designed. The front layers (in the direction of the proton beam) are relatively transparent to the protons, and become progressively less transparent (blacker) with depth into the collimator. In addition, a high density (iron) shield is added around the outside. The protons will be stopped in the center of the collimator, and thus the bulk of the secondary particles are generated at this location. The conceptual design described, the method of analysis discussed, and preliminary performance parameters outlined.