hi, All I see some interesting slides for qweak collimator http://qweak.jlab.org/DocDB/0009/000932/002/Qweak_Slides%20Infrastructure%20Talk%20Mar%2009.pdf http://qweak.jlab.org/DocDB/0010/001025/001/As-Built%20Dimensions%20of%20the%20Defining%20Collimator.pdf We can learn something from their experience. Zhiwen