The facility for ATLAS resistive plate chambers assembly

The dedicated facility built for the assembling of the nearly 1000 RPC units of the ATLAS μ-spectrometer is described in detail. The necessity of keeping the gravitational sagitta below 10 mm for the 5-m-long RPC units has driven the careful design of the extruded Al lateral profiles and suspension end-plates. A special assembly table allows to maintain the mechanical tolerances of each unit well below ±1 mm in all dimensions. Both gas gaps inside each unit are kept at a constant pressure of 103 Pa over the whole surface, in order to ensure the uniformity of the gap.