TPC

From Detec-Rad.com

Time Projection Chamber

A Time Projection Chamber is a type of particle detector. It usually consists of a gas-filled cylindrical chamber with multiwire proportional chambers (MWPC) as endplates. The prototype shown on the picture incorporates a new type of avalanching structure consisting of a GEM (gas electron multiplier) or a Micromegas. This TPC was developped by Dr. M.S. Dixit (Carleton University, Ottawa) and co-workers and it is maintained with the assistance of DETEC.

In the middle section of the cylindrical chamber, a high voltage electrode disc creates an electric field with the endplates. A magnetic field along the z axis (parallel to the electric fields) is applied along the chamber, and helps minimizing the diffusion of 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 of the locus, is determined by measuring the drift time from the ionization event to the avalanching structure at the extremities of the chamber, as in a Drift Chamber. The GEM or Micromegas at the end have a pixel electron readout which provides information on the x-y coordinate.