Large straw-tube tracking chambers for AGS experiment E864

We have built two very large planar straw tube detectors with 4 mm diameter tubes for AGS experiment E864. This is a Au+Pb collision experiment at 11.5 AGeV/c, designed to search for strangelets and other novel forms of matter. A central collision trigger requires tracking chambers to operate in a high multiplicity environment, with as many as 200 hits per event in the first data run, which represented an occupancy of 20%. Each detector consists of three planes of tubes, a vertical X plane as well as stereo U and V planes. Each plane has two close-packed layers of tubes. One detector is 40 cm×200 cm and contains 3×960 tubes, and the other is 80 cm×400 cm and has 3×1920 tubes. The function of the detector is to achieve high mass resolution in tracking charged particles, and it has been successfully used during three data runs at the AGS.