The Time Projection Chamber (TPC), shown with inventor David Nygren (left), was designated by LBL physicists for use at PEP, the positron-electron colliding beam ring at Stanford, 1981. In physics, a time projection chamber (or TPC) is a particle detector. A time projection chamber consists of a gas-filled detection volume in an electric field with a position-sensitive electron collection system. The original design is a cylindrical chamber with multi-wire proportional chambers (MWPC) as endplates. Its first major application was in the PEP-4 detector, which studied 29 GeV electron-positron collisions at the PEP storage ring at SLAC. David Robert Nygren (born December 30, 1938) is a particle physicist who has worked at Lawrence Berkeley National Laboratory since 1973. He has been called "the most distinguished developer of particle detection instruments in the country".