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The Beijing Electron–Positron Collider II (BEPC II) is a Chinese electron–positron collider, a type of
BEPC-BES II
experiment on
The Beijing Electron–Positron Collider II (BEPC II) is a Chinese electron–positron collider, a type of particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for fundamental research in particle ...
, located in Shijingshan District
Shijingshan District () is an urban district of the municipality of Beijing. It lies to the west of the urban core of Beijing, and is part of the Western Hills area, bordering the districts of Haidian to the northeast and east, Fengtai to the so ...
, Beijing
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Beijing ( ; ; ), alternatively romanized as Peking ( ), is the capital of the People's Republic of China. It is the center of power and development of the country. Beijing is the world's most populous national capital city, with over 21 ...
, People's Republic of China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
. It has been in operation since 2008 and has a circumference of 240.4 m.
It was intended as a charm factory and continues the role of CLEO Cleo may refer to:
Entertainment
* ''Cleo'' (magazine), an Australian magazine established in 1972, now active in Indonesia, Malaysia, Singapore, and Thailand
* Cleo (group), a South Korean girl group formed in 1999
* ''Cleo'' (play), by Lawrenc ...
-c detector. The center of mass energy can go up to 4.6 GeV with a design luminosity of 1033 cm−2·s−1. Operations began in summer 2008 and the machine has run at multiple energies.
History
The construction of the original Beijing Electron Positron Collider was approved in 1983, as China was emerging from theCultural Revolution
The Cultural Revolution, formally known as the Great Proletarian Cultural Revolution, was a sociopolitical movement in the People's Republic of China (PRC) launched by Mao Zedong in 1966, and lasting until his death in 1976. Its stated goal ...
, based on a proposal developed by Xie Jialin, who went on to oversee the construction of the machine. The construction of this collider was considered so important that then vice-premier Deng Xiaoping
Deng Xiaoping (22 August 1904 – 19 February 1997) was a Chinese revolutionary leader, military commander and statesman who served as the paramount leader of the People's Republic of China (PRC) from December 1978 to November 1989. After CC ...
attended the groundbreaking in 1984 and returned in 1988 as the machine neared operation.
The original Beijing Electron Positron Collider was commissioned in 1989 and decommissioning began in 2000 as plans were developed for BEPC II, although operation continued until 2004. The shape of the BEPC has been described as a tennis racquet, with a linac
A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear beam ...
with a beam energy of from 1.5 to 2.8 GeV serving as the handle, injecting counter-rotating beams of particles into a storage ring
A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating typically for many hours. Storage of a particular particle depends upon the mass, momentum and usually the charge of th ...
at the head, giving collision energies in the range from 3.0 to 5.6 GeV. The BEPC was built to investigate tau
Tau (uppercase Τ, lowercase τ, or \boldsymbol\tau; el, ταυ ) is the 19th letter of the Greek alphabet, representing the voiceless dental or alveolar plosive . In the system of Greek numerals, it has a value of 300.
The name in English ...
-charm
Charm may refer to:
Social science
* Charisma, a person or thing's pronounced ability to attract others
* Superficial charm, flattery, telling people what they want to hear
Science and technology
* Charm quark, a type of elementary particle
* Ch ...
physics, using the Beijing Spectrometer. Major accomplishments of the original BEPC included precision measurement of the Tau mass.
BES III
The BES III (''Beijing Spectrometer III'') is the main detector for the upgraded BEPC II. BES III uses a large superconductingsolenoid
upright=1.20, An illustration of a solenoid
upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines
A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
to provide a 1-tesla magnetic field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
, and also features a helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
gas-based tracking chamber and an electromagnetic calorimeter
A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimete ...
using 6240 caesium iodide
Caesium iodide or cesium iodide (chemical formula CsI) is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are hi ...
crystals.
See also
*Large Electron–Positron Collider
The Large Electron–Positron Collider (LEP) was one of the largest particle accelerators ever constructed. It was built at CERN, a multi-national centre for research in nuclear and particle physics near Geneva, Switzerland.
LEP collided electr ...
* Super Charm-Tau factory
Super Charm-Tau factory (SCT) is an electron–positron collider being designed and built by Budker Institute of Nuclear Physics in Novosibirsk. Its main goal is to study the CP-violation in the processes involving charmed hadrons, to investiga ...
* Electron–positron annihilation
Electron–positron annihilation occurs when an electron () and a positron (, the electron's antiparticle) collide. At low energies, the result of the collision is the annihilation of the electron and positron, and the creation of energetic photo ...
References
2008 establishments in China Projects established in 2008 Particle physics facilities Particle experiments Science and technology in the People's Republic of China Buildings and structures in BeijingExternal Links
Record foBEPC-BES II
experiment on
INSPIRE-HEP INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1970 ...
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