The Beijing Electron Positron Collider (BEPC) consists of the injector, the storage ring, the transportation line, the Beijing Spectrometer (BES), the Beijing Synchrotron Radiation Facility (BSRF) and the computer center. Below t is the general layout of the BEPC.
1 The injector
It is an electron position linear accelerator that can accelerate the electrons and positrons to 1.3 GeV. It is composed of the following 6 systems:
1.1 The accelerating system
It is composed of 56 accelerating tubes of disk loaded waveguide with each being 3.05 m long, 42 sets of supports for the accelerating tubes, 45 quadruple magnets, 1ns electron gun and positron converter, totaling 202 m long. It was installed in the tunnel that is 6 meters from the ground.
1.2. The microwave power source
It consists of 16 high power klystrons and modulators, 13 sets of energy doublers, 1 power source, 1 phase control system and 1 microwave transmission line. It was installed in the 200 m long gallery on top of the tunnel.
1.3. The vacuum system
The vacuum required by the accelerating system and the microwave system is 10-8 torr. Both in the tunnel and the gallery, there is a 200 m long vacuum pipe connecting the vacuum system. In addition, there are also vacuum pumps, vacuum valves and vacuum protection system.
1.4. The automatic control system
It exercises remote control of the parameters of various electronic apparatuses from the local station of the injector.
1.5. The beam measuring system
80 beam measuring probes of 6 kinds were placed in the injector to monitor the beam behavior.
1.6. The constant temperature water system, the ventilation system, etc.
There are constant temperature water pipe lines, water pump stations and automatic adjustment lines to ensure that the accelerating tubes and the wave guide transmission lines work under constant temperature.
2 The beam transport line
The beam transportation line is connected with the injector and the storage ring. It encompasses a 30 m long common section and the east and west section with each being 90 m long. The beam transportation line is to transport the electron positron beams output from the injector respectively to the storage ring. In the transportation line, there are 33 bending magnets, 42 quadruple magnets and 26 correcting magnets, and 78 beam measuring probes of 9 kinds, high vacuum systems, etc.. All the magnets power supplies and the control system were installed in the ground hall with the required vacuum being 10-8 torr and the installation accuracy of each part being 0.2 mm. The beams pass the transportation line without any interruption and the transportation efficiency of the electron and positron beams being 80% and 90% respectively.
3 The storage ring
|the storage ring at BEPCII|
The storage ring is a sports track shaped accelerator with a circumference of 240.4 m. It comprises the following 6 systems:
3.1. Magnets and power supplies
There are 44 bending magnets, 60 quadruple magnets, 8 high precision insertion quadruple magnets, 36 sextuple correcting magnets and 175 high current power supplies of 17 kinds.
3.2. The RF accelerating system
It consists of 4 accelerating cavities, 8 RF transmitters and the accessories.
UHV & quardruple magnet
vacuum chambers in tunnel
3.3. The injector system
It contains 2 Lambertson magnets, 4 kicker magnets, 4 electrostatic separators and the power supplies.
3.4. The ultrahigh vacuum system
Its cross-section consists of 3 vacuum chambers. The circumference is 240.4 m long. There are 400 flanges. The aperture of the beam pipe is 58×120 mm.mm. The required vacuum is 3×10-10torr.
3.5. The beam measuring system
It is composed of 74 sets of beam measuring equipment of 9 kinds to monitor the beam behavior.
3.6. The automatic control system
The central control room of the collider contains one VAX 4500 computer, two work stations, 14 CAMAC crates, some series optic fibers, and etc. which exercises, through the local control stations, real time monitoring, display and control of the parameters of more than 900 equipment of various sub-systems and the performance parameters of the beams.
The luminosity of the BEPC at 1.55 GeV is 5×1030/cm-2.s-1，8 times that of SPEAR II. The beam energy spread reaches 0.64 MeV, half that of SPEAR II.
Synchrotron radiation is extracted from bending magnet and wiggler of the storage ring. The energy parameters of the synchrotron radiation light source when the storage ring works in a dedicated mode: beam emission at 2.2 GeV is 7.6×10-8m.rad and the current intensity is greater than 100mA. It is comparable with all the second-generation synchrotron radiation light sources running in the world.
Design goals of the BEPCII
|Beam energy range||1-2.1 GeV|
|Optimized beam energy region||1.89 GeV|
|Current of each beam in collision||0.93 A|
|Design luminosity||1 ′10 33 cm-2s-1 @189 GeV|
|Beam lifetime||2.7 hrs.|
|Injection from linac||Full energy injection: Einj = 1.55-1.89GeV
Positron injection rate >50 mA/min
|Dedicated SR operation||
250 mA @ 2.5 GeV