Prototype results of a high resolution vertex drift chamber for the Mark II SLC upgrade detector

Test results from a full-length prototype of the drift chamber vertex detector for the Mark II SLC Upgrade detector are presented. The 22 cell jet chamber employs planes of grid wires above and below the sense wire plane to increase the electrostatic stability of the sense wires and to narrow the electron arrival time distribution. Two different grid designs have been investigated. The spatial resolution and pulse widths have been measured at a variety of operating points and for different timing schemes in a mixture of 92% CO2 and 8% isobutane. Typical results at 3 atmospheres pressure give an average resolution over a 2 cm drift distance of 30 μm for both designs. Efficient double track detection is achieved for tracks separated by 500 μm for one design and by 1000 μm for the other. (orig.)