Low-mass Drift Chambers of the PHENIX central spectrometers at RHIC

Beginning of regular operation of Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory opened unique possibilities for the study of nuclear matter at unprecedentedly high energies. PHENIX is one of the two large-scale experiments at RHIC, which is intended for detection and study of new state of matter—the so called quark-gluon plasma. sic element of the PHENIX Central Tracking System is low-mass focusing Drift Chamber (DC). Distinctive features of ion–ion collisions at RHIC impose specific requirements on the DC which could not be satisfied by any structure developed earlier. DC should provide high efficiency of track reconstruction with use of “hot” gas mixture under conditions of high charged particle densities, high collision rates and large-scale of the detector (6 m3). Detailed description of the DC and its original wire structure characterized by the absence of left–right ambiguity and controlled charge collection geometry are given. Parameters of the DC during the first physical run of the RHIC are analyzed.