Drift Chamber Tracker

Since the cosmic ray is a charged particle, it gets deflected by the magnetic field. The amount of curvature in the path is related to the rigidity which is measured by our multiwire Drift Chamber Tracker (DCT). The DCT tracks particles by recording the ionization trail the cosmic ray creates in the gas-filled volume. There are 3 planes of 'sense' wires that the cosmic ray-induced ionization drifts to and these wires measure the resultant voltage pulse. Analyzing the pulses on many wires and knowing the gas properties in the DCT precisely gives HELIX a method to reconstruct the track and hence measure the rigidity. The expected spatial resolution for particles of charge more than 3 is about 150 μm when the drift field is 1kV/cm. The DCT uses 10% Argon and 90% CO₂ gas mixture, is kept at atmospheric pressure and constant temperature.