time-projection chamber

time-projection chamber [′tīm prə¦jek·shən ‚chām·bər]

(nucleonics)

A particle detector consisting of a large cylinder filled with gas in which charged particles leave ionization trails, to which are applied strong, uniform electric and magnetic fields, both paralled to the cylinder axis.

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Time-projection chamber

An advanced particle detector for the study of ultra-high-energy collisions of positrons and electrons. The underlying physics of the scattering process can be studied through precise measurements of the momenta, directions, particle species, and correlations of the collision products. The time-projection chamber (TPC) provides a unique combination of capabilities for these studies and other problems in elementary particle physics by offering particle identification over a wide momentum range, and by offering high resolution of intrinsically three-dimensional spatial information for accurate event reconstruction.

The time-projection chamber concept is based on the maximum utilization of ionization information, which is deposited by high-energy charged particles traversing a gas. The ionization trail, a precise image of the particle trajectory, also contains information about the particle velocity. A strong, uniform magnetic field and a uniform electric field are generated within the time-projection chamber active volume in an exactly parallel orientation. The parallel configuration of the fields permits electrons, products of the ionization processes, to drift through the time-projection chamber gas over great distances without distortion; the parallel configuration offers a further advantage in that the diffusion of the electrons during drift can be greatly suppressed by the magnetic field, thus preserving the quality of track information. See Particle detector