An elementary particle detector using a special apparatus capable of
operating at high rates. The detector consists of an → array
of many closely spaced parallel wires, or → anodes,
in an enclosure filled with a carefully chosen gas. The wires, being placed between
two → cathode plates,
are under high voltage. Each wire acts as an independent
→ proportional counter.
The particle that passes through the chamber will ionize surrounding
gaseous atoms. The resulting ions and electrons are accelerated by the electric
field around the wire, causing a localized cascade of ionization which brings about
an electric current proportional to the energy
of the detected particle. Previous detectors, such as the
→ bubble chamber, could
record the tracks left by particles on photographic emulsions
at the rate of only one or two per second. In comparison, the multiwire chamber
records up to one million tracks per second in three dimensions with an accuracy of
a tenth of a millimeter and moreover sends the data directly to a
computer for analysis. The speed and precision of the multiwire chamber has
revolutionized high-energy physics. For instance it was crucial in finding the
predicted → W boson and → Z boson
of the → electroweak interaction theory.
Charpak’s chamber also has applications in medicine, biology, and industry.
Also called → multiwire proportional chamber.
See also: In honor of Georges Charpak (1924-2010), a French physicist,
who built the first detector of this type in 1968. He received
the Nobel Prize for physics in 1992; → detector.
