Test of a small prototype of the COMET cylindrical drift chamber

The performance of a small prototype cylindrical drift chamber (CDC) used in the COMET Phase-I experiment was studied by using an electron beam. constructed with alternating all-stereo wire configuration and operated He-iC$_{4}$H$_{10}$ (90/10) gas mixture without magnetic field. space-time relation, velocity, d$E$/d$x$ resolution, hit efficiency, spatial resolution as function distance from were investigated. average 150 $\mu$m efficiency 99% obtained at applied voltages higher than 1800 V. We have demonstrated that design match operation CDC.