A drift chamber is an apparatus for measuring the space coordinates of
the trajectory of a charged particle. This is achieved by detecting the
ionization electrons produced by the charged particle in the gas of the
chamber and by measuring their drift times and arrival positions on
sensitive electrodes. When the multiwire proportional chamber, or
'Charpak chamber' as we used to call it, was introduced in 1968, its
authors had already noted that the time of a signal could be useful for
a coordinate determination, and rst studies with a drift ch- ber were
made by Bressani, Charpak, Rahm and Zupanci c in 1969. When the rst
operational drift-chamber system with electric circuitry and readout was
built by Walenta, Heintze and Schurlein ] in 1971, a new instrument for
particle experiments had appeared. A broad study of the behaviour of
drifting electrons in gases began in laboratories where there was
interest in the detection of particles.