Charpak multiwire proportional chamber
date: label: Date made
content: 1968
name: label: maker
content: Charpak, G.
notes: label: Description
content: This object consists of an aluminum housing with two planes of stainless steel wires, rotated by 90 degrees, in a single window with four preamp units attached, one on each side. The wires are stretched between two planes of stainless steel mesh. See G. Charpak, et. al., Nucl. Instr. Meth. 62, 262 (1968) for details.
label: Description
content: Basic Principles and History
label: Description
content: A multiwire proportional chamber (MWPC) is constructed with alternating planes of high voltage wires (cathode) and sense wires (anode), which are at ground. All the wires are placed in a special gas environment. Spacing between planes is usually on the order of millimeters and voltage differences are typically in the kilovolt range. When a charged particle passes through the gas in the chamber, it will ionize gas molecules. The freed electrons are accelerated towards the sense wire (anode) by the electric field, ionizing more of the gas. In this way a cascade of charge develops and is deposited on the sense wires. The smaller the diameter of the sense wires, the higher the field gradient near the wire becomes. This in turn causes a larger cascade, increasing the efficiency of the chamber.
label: Description
content: Georges Charpak built the first MWPC in 1968. Unlike earlier particle detectors, such as the bubble chamber and the first generation of spark chambers, which can record the tracks left by particles at the rate of only one or two per second, the multiwire chamber records up to one million tracks per second and sends the data directly to a computer for analysis. The price was that each wire, accumulating ions in its immediate neighborhood, must have its own electronic amplifier to record the signal; this was only practical due to the development during the previous decade of compact and inexpensive solid-state amplifiers.
label: Description
content: In 1992 Charpak received the Nobel Prize for Physics in acknowledgment of his invention of the MWPC, an electronic particle detector that revolutionized high-energy physics experiments and has had applications in medical physics.
label: Description
content: With the invention of the MWPC, high-energy physics entered a new era. The speed and precision of the MWPC and its subsequent generations of detectors – the drift chamber (see Charpak drift chamber, object ID no. 1977.0708.01) and the time-projection chamber – revolutionized the field of experimental particle physics. The MPWC allowed experiments to collect data at much higher collision rates and to test theories predicting the production of rare events and new massive particles. Notable examples include the discoveries of the charm quark at SLAC and Brookhaven in 1974 (Nobel Prize awarded in 1976), the W and Z bosons at CERN in 1983 (Nobel Prize awarded in 1984), and the top quark at Fermilab in 1995. For additional technical information see:
label: Description
content: http://www.nobelprize.org/nobel_prizes/physics/laureates/1992/charpak-lecture.pdf and,
label: Description
content: http://cds.cern.ch/record/117989/files/CERN-77-09.pdf?bcsi_scan_2687365ababd2c82=b3SiuvtOAg0NfXwMHl9pO/npSm4KAAAArlNvLw==&bcsi_scan_filename=CERN-77-09.pdf
label: Description
content: The Modern Physics Collection also contains one of the MPWCs used in the discovery of the charm quark at Brookhaven; see Multiwire proportional chamber from J-particle experiment of S.C.C. Ting at BNL; object ID no. 1989.0050.01.1.
label: Location
content: Currently not on view
topic: label: general subject association
content: Science & Scientific Instruments
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content: Medicine and Science: Modern Physics
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content: Energy & Power
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content: Science & Mathematics
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content: Modern Physics
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content: Measuring & Mapping
creditLine: label: Credit Line
content: CERN, European Organization for Nuclear Research
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1977.0708.02
label: catalog number
content: 1977.0708.02
label: accession number
content: 1977.0708
objectType: label: Object Name
content: chamber, multiwire proportional
physicalDescription: label: Physical Description
content: copper; stainless steel; other metal (overall material)
label: Measurements
content: overall: 48 cm x 48 cm x 10 cm; 18 29/32 in x 18 29/32 in x 3 15/16 in