Time Projection Chambers

The Time Projection Chamber (TPC) had originally been proposed to permit full reconstruction of events of up to 20 particles at an electron-positron collider. It was to provide 3-D information for tracking and momentum measurement together with particle identification by multiple ionization sampling, in a compact detector. This powerful combination soon found applications in other fields: at one end, for studies of rare events of simple structure; at the other extreme, for heavy ion collisions, handling ever higher particle densities, finally up to several thousand tracks in a single event, still providing information on a track-to-track basis. Basic physics, performance and limitations of drift chambers in general will be discussed first. Then the characteristics of TPCs will be introduced, as well as their practical realization and performance. The development from the first TPC, 30 years ago, to the present day will be covered and followed by a few final comments on the ongoing studies for future applications.