Performance of a cylindrical drift chamber for multi-GeV photo-induced experiments

A 50 cm high cylindrical drift chamber CDC) has been constructed with the z -coordinate determination by the charge division. The active volume extends from 9 to 25 cm in radius, which is divided into 12 jet-type sectors. The performance of the CDC has been investigated using cosmic ray muons in the absence of magnetic field. The CDC was operated with a 70/30 gas mixture of argon and isobutane at atmospheric pressure. A drift velocity of v = 52.1 +/- 0.7 mum/ns was found to be nearly constant at drift distance larger tha n 0.5 mm. The left-right discrimination of the track was achieved with an a ccuracy of 98% due to a sense wire staggering. The spatial resolution in r- phi plane was found to be 100-190 mum, which depends on the drift distance. The z-coordinate resolution was 2.5-3.5 mm. Observing the direct signal fr om the sense wire, the difference of the rise times between two wire ends w as found to be negligible irrespective of the different pulse height due to different hit positions of the muons. (C) 2000 Elsevier Science B.V. All r ights reserved.