The target is surrounded by an enclosure similar to a scattering chamber. The enclosure serves three purposes: First, it provides a containment volume in case of explosion of the target cell and so limits the potential hazard working area. Second, it holds the RF coils in a stable position and provides a strong frame for the support assembly. Third, it allows the region around the target to be filled with helium gas, minimizing ionization and energy loss of the electron beam crossing the target area.
The enclosure is made of high density polyvinyl (HDPV) material and has several removable windows. The windows are of three types: The incident electron beam entrance and exit windows are 0.127 mm thick aluminum. The windows on the side of the chamber through which the scattered particles pass are 2.54 mm thick aluminum. Five-mm thick optical-perfect windows allow the laser beam to enter the enclosure.
If any windows are open, people working anywhere on the target platform must wear ear protection and a face shield. This region is designated as the ``target area''. Signs will be posted indicating that the windows are open and that work is in progress. If the windows are closed the target area is no longer restricted except for possible reasons of radiation safety.
The electron beam crosses two windows before reaching the target, the electron beam pipe window and the target enclosure beam inlet window. Similarly, it crosses two similar windows as it leaves the target area. The electron beam line is under vacuum and separate from the target enclosure for both upstream and down-stream of the target enclosure. The gap between the upstream beam line and the enclosure inlet window is very narrow. Both upstream and downstream beam lines are terminated with a 0.254mm thick beryllium window. The beam inlet and outlet windows of the target enclosure are made of 0.127mm thick aluminum and are strong enough to stop any flying glass shreds in case of a target cell explosion.