The Crystal Ball was a
hermetic
Hermetic or related forms may refer to:
* of or related to the ancient Greek Olympian god Hermes
* of or related to Hermes Trismegistus, a legendary Hellenistic figure based on the Greek god Hermes and the Egyptian god Thoth
** , the ancient and m ...
particle detector
In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing particles, such as those produced by ...
used initially with the
SPEAR
A spear is a pole weapon consisting of a shaft, usually of wood, with a pointed head. The head may be simply the sharpened end of the shaft itself, as is the case with fire hardened spears, or it may be made of a more durable material fasten ...
particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high speeds and energies, and to contain them in well-defined particle beam, beams.
Large accelerators are used for fun ...
at the
Stanford Linear Accelerator Center
SLAC National Accelerator Laboratory, originally named the Stanford Linear Accelerator Center,
is a United States Department of Energy National Laboratories, United States Department of Energy National Laboratory operated by Stanford Univers ...
beginning in 1979. It was designed to detect
neutral particle
In physics, a neutral particle is a particle with no electric charge, such as a neutron.
The term ''neutral particles'' should not be confused with ''truly neutral particles'', the subclass of neutral particles that are also identical to their ow ...
s and was used to discover the
ηc meson. Its central section was a
spark chamber {{short description, Charged particle detector
A spark chamber is a particle detector: a device used in particle physics for detecting electrically charged particles. They were most widely used as research tools from the 1930s to the 1960s and ha ...
surrounded by a nearly-complete sphere of
scintillating crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macr ...
s (
NaI(Tl)), for which it was named. With the addition of endcaps of similar construction, the detector covered 98% of the
solid angle
In geometry, a solid angle (symbol: ) is a measure of the amount of the field of view from some particular point that a given object covers. That is, it is a measure of how large the object appears to an observer looking from that point.
The po ...
around the
interaction point
In particle physics, an interaction point (IP) is the place where particles collide in an accelerator experiment. The ''nominal'' interaction point is the design position, which may differ from the ''real'' or ''physics'' interaction point, wher ...
.
After its decommissioning at SLAC, the detector was carried to
DESY
The Deutsches Elektronen-Synchrotron (English ''German Electron Synchrotron''), commonly referred to by the abbreviation DESY, is a national research center in Germany. It operates particle accelerators used to investigate the structure of matt ...
, where it was used for b-physics experiments.
In 1996, it was moved to the Alternating Gradient Synchrotron (AGS) at
Brookhaven National Laboratory
Brookhaven National Laboratory (BNL) is a United States Department of Energy national laboratory located in Upton, Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base and Japanese internment c ...
, where it was used in a series of pion- and kaon-induced experiments on the proton. Currently it is located at
Mainz Microtron
The Mainz Microtron (German name: ''Mainzer Mikrotron''), abbreviated MAMI,
is a microtron (particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel electric charge, charged particles to very high ...
facility, where it is being used by the
A2 Collaboration for a diverse program of measurements using energy tagged
Bremsstrahlung
''Bremsstrahlung'' (), from "to brake" and "radiation"; i.e., "braking radiation" or "deceleration radiation", is electromagnetic radiation produced by the deceleration of a charged particle when deflected by another charged particle, typicall ...
photons.
References
# (detector description)
# (η
c discovery)
A2 Collaboration website
External links
Crystal Ballexperiment record 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 ...
Particle experiments
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