This is the portion of the CESR vacuum chamber that passes through the CLEO detector. This segment of the beam pipe is a 2.0 cm radius beryllium tube. Beryllium was chosen to minimize the amount of material needed, reducing the chances that particles will interact with atoms in the beam pipe.
In the central region of the CLEO detector, the beam pipe is surrounded by central detector vertex chambers. At the ends of the detector, it is surrounded by the rare earth quadropole magnets, the endcap crystal calorimeter and normal solenoidal quadropole magnets.