Initial Performance Of The Venus Transition Radiation Detector

The VENUS-TRD is a cylindrical transition radiation detector, extending from 127 cm to 157.7 cm radially and 296 cm axially. It is designed to improve the e/pi separation capability of the VENUS detector by a factor of 10 in order to complement the lead glass calorimeter. It covers an angular region of \cos theta\ < 0.68 and contains four layers of radiators and X-ray chambers. It has been working very stably since it started data-taking at the TRISTAN e+e-storage ring in June, 1991. The pion rejection power (R(pi) = 1/epsilon(pi)) at an electron efficiency of 90% is R(pi) = 10+/-1 and 15+/-2 for isolated tracks with a momentum range of 1 < P < 3 and 3 < P < 10 GeV/c, respectively. It decreases to R(pi) = 7+/-1 for tracks with P > 1 GeV/c in hadronic events due to overlap of the tracks in the chamber cells of the TRD. The VENUS-TRD is the largest TRD to perform in colliding beam experiments.