The GEM Detector projective alignment simulation system

Precision position knowledge (< 25 microns RMS) of the GEM Detector muonsystem at the Superconducting Super ColliderLaboratory (SSCL) is an important physics requirement necessary to minimize sagittaerror in detecting and tracking high energy muonsthat are deflected by the magnetic field within the GEM Detector. To validate the concept of the sagittacorrection function determinedby projective alignment of the muondetectors (Cathode Strip Chambers or CSCs), the basis of the proposed GEM alignment scheme, a facility, called the ``Alignment Test Stand`` (ATS), is being constructed. This system simulates the environment that the CSCs and chamber alignment systems are expected to experience in the GEM Detector, albeit without the 0.8 T magnetic field and radiation environment. The ATS experimental program will allow systematic study and characterization of the projective alignment approach, as well as general mechanical engineering of muonchamber mounting concepts, positioning systems and study of the mechanical behavior of the proposed 6 layer CSCs. The ATS will consist of a stable local coordinatesystem in which mock-ups of muonchambers (i.e., non-working mechanical analogs, representing the three superlayers of a selected barrel and endcapalignment tower) are implemented, together with a sufficient number of alignmentmore » monitors to overdeterminethe sagittacorrection function, providing a self-consistency check. This paper describes the approach to be used for the alignment of the GEM muonsystem, the design of the ATS, and the experiments to be conducted using the ATS.« less