Large CSC chamber for the PHENIX muon detector with ultra thin cathode foils

The muon tracking system for the PHENIX detector at RHIC uses cathode strip chambers (CSC) for the tracking detectors. These detectors must provide 100 /spl mu/m resolution per measurement plane to give satisfactory mass resolution of the vector mesons. The intermediate station (station 2) must have a very small radiation length, and large acceptance. We have prototyped a full scale CSC chamber to test the use of 25 micron metalized mylar foils for the cathode strips at station 2. The full scale prototype detector is a trapezoid 2.3 meters high and 2.3 meters wide. The foil and wire planes are mounted on thin 3,2 mm thick by 7.5 cm wide laminated frames and the tension of the planes is maintained by the two large 7.5 cm wide/spl times/3.0 cm thick aluminum support frames. The total radiation length of the active region is 8.5/spl times/10/sup 4/.