Time projection chamber

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In physics, a time projection chamber is a particle detector consisting of a gas-filled cylindrical chamber with multiwire proportional chambers (MWPC) as endplates. Along its length, the chamber is divided into halves by means of a central high voltage electrode disc, which establishes an electric field between the center and the endplates. Furthermore, a magnetic field is applied along the length of the cylinder, parallel to the electric field, in order to minimize the diffusion of the electrons coming from the ionization of the gas. On passing through the detector gas a particle will produce primary ionization along its track. The $z$ -coordinate, the coordinate along the cylinder axis, is determined by measuring the drift time from the ionization event to the MWPC at the end. This is done using the usual technique of a drift chamber. The MWPC at the end is arranged with the anode wires in the azimuthal direction, $θ$ , which provides information on the radial coordinate, $r$ . To obtain the azimuthal direction, each cathode plane is divided into strips along the radial direction.