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Beijing
Spectrometer (BES) is a general-purpose detector located in the
interaction region at the southern end of the BEPC storage ring,
where the electron and positron beams collide. BES
is 6 meters long, 7 meters high and 7 meters wide, weighing more
than 500 tons. It is mainly composed of 4 kinds of detectors and
solenoids. |
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I.
Vertex chamber, main drift chamber and electronics system The
vertex chamber is a barrel detector that is composed of 640 drift
tubes with each being 84 cm long. By working together with the main
drift chamber, it measures the tracks of charged particles and the
momentum. It also works together with the time of flight counter (TOF)
for trigger. The main drift chamber is a cylindrical detector with
20 cm in length and 220 cm in diameter, containing 10 layers of
19,380 wires and 320 channels of 320 electronics circuits. |
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BES general layout |
MDC in stringing |
II.
Time of flight counter (TOF) and electronics system
TOF
contains the barrel part and the end part. The barrel part is composed of
48 plastic scintillators with each being 2.8 m long, optic fibers,
photo-multipliers and electronics circuits whereas the end part is
composed of 2×24
trapezoidal scintillators, optic fibers, photo-multipliers, electronics
circuits, etc. It operates to measure the speed of the charged particles.
