Central Jet Chamber (CJ)

The job of the Central Jet chamber [17,18] is to improve the measurement of the trajectory of the charged particles. It also has an important role in helping in particle identification by measuring the specific energy loss, dE$/$dx. The curvature of the track of the charged particle in the magnetic field as it passes through CJ can be measured, thus making it possible to calculate the momentum of the tracked particle.

The chamber is 4 m long, with an inner radius of 0.245 m and an outer radius of 1.85 m. The chamber is divided around the $\phi$ direction into 24 segments of equal size. Each segment contains 159 anode sense wires running parallel with the beam direction along the $z$-axis. The wires are arranged in radial planes.

Between a polar angle of $43^{\circ}<\theta<137^{\circ}$, 159 points on the track are measured. For 98% of the $4\pi$ solid angle at least 20 points are measured on every track. The $r-\phi$ position of the hits is given by the radial position of the relevant wire and the drift time. A resolution of 135 $\mu$m is achieved. The $z$-position is given by the time difference between signals at either end of the wire, a resolution of 6 cm is possible in the $z$-direction.