14.Computer center   

   The purpose of building BEPC is mainly to carry out the research on charm and Tau lepton physics, the applied research on synchrotron radiation as well as mid-energy nuclear physics.

    Now the shaping of a National Laboratory which will be open to both home and abroad is on the pipeline.

   The Synchrotron Radiation Laboratory is flanking the east and west of the southern area of the storage ring. Seven beam lines are now extracted from the three synchrotron radiation front ends located at the outer flank of the storage ring. Nine experimental stations have been buite. Research in such fields as X-ray topography, X-fluorescence, EXAFS, diffuse scattering, small angle scattering, diffraction, photoemission spectroscopy, biology spectroscopy and lithography is being carried out.

   The central control room for BEPC consists of the colored monitor of the main frame computer, touch panels and program controlled knobs. All the parameters are connected with the main frame computer through various convertors and interfaces. It has rich software system which can transmit thousands of signals collected in real time to the data base at a rate of 2 to 3 times per second. Operators on duty in the central control room can readily get information on the changes of the parameters of the different components of the machine and exercise timely control.

  The injector is a linear accelerator which is composed of 56 disk loaded wave guide accelerating sections of 3.05 meters long each and some focusing cells with a total length of 202 meters and can accelerate electrons and positrons to 1.1-1.4 GeV. The emission current of the nanosecond electron gun is 5 amperes. The beam intensity of electrons from the injector is 600 milliamperes while that of positrons is 9 milliamperes.

    The positron source which is located between the 7th and the 8th accelerating sections has a target bombarding energy of 150 MeV and collects positrons with its magnetic compressor system.

    Here is the microwave power source for the injector which is composed of 16 sets of high power klystrons and pulse modulator and 13 sets of energy doublers.

    The transport line is composed of a shared section of 30 meters long and the eastern and western sections of 90 meters long each with the eastern section transporting electrons and the western section transporting positrons.

  The injection section ( about 22.8 meters ) of the transport line is a bending system on vertical direction. The altitude difference between the horizontal planes of the storage ring and the injector is about 3 meters.

  The injection system of the storage ring is composed of three in-one current kickers Lambertson magnet with a width of 7 mm septum being installed on the injection point.

  The circumference of the storage ring is 240.4 meters with four arcs. The linear sections on the eastern and western sides are injection sections while those on the north and south are interaction regions. Here installed are 44 bending magnets, 68 focusing magnets, 36 sextupole magnets, more than 30 other correction magnets and various of kinds of beam monitors and vacuum chambers and interfaces.

  There is a RF station on either side of the northern interaction region. The RF cavity which acts on the passing beams is the accelerating station of the electron and positron beams. Its working frequency is 200 megahertz.

  There are altogether 200 pieces of various kinds of magnets in the storage ring. The total power of the magnet power supply system is 2.5 MW with a current stability of 1*10^-4.

  The Beijing Spectrometer which is now being installed on the southern interaction point of the storage ring is more than 500 tons in weight, 6 meters in length, 7 meters in width and height. The central drift chamber, main drift chamber, shower counter and time of flight counter are installed in the solenoid magnetic field of 4000 Gauss. Surrounding the spectrometer is the muon detector.

   Both the length and the diameter of the cylinder of the main drift chamber are 2.3 meters. The cylinder which is used to give position parameters of the injecting particles contains more than 20,000 metal wires in 40 layers.

   The shower counter is divided into the barrel part and the end part. The barrel part of the shower counter is composed of 24 layers of wire chambers between which there are lead plates, and there altogether more than 20,000 wire chamber units. The purpose of the shower counter is to measure the energy of the charged or neutral particles.

   Outside the main drift chamber is the time of flight counter consisting of a large area of plastic scintillators which is used to record the charged particles and calculate their speed with the time difference of the scintillators.

   In April 1989, the Beijing Spectrometer was moved into the interaction region. In our design for the Beijing Spectrometer, we absorbed the characteristics of MARK III with improved performances such as the upgrading of the solid angle coverage, energy resolution and position resolution.

    This is the counter hall where the data on the secondary particles obtained through the detector enters the nanosecond electronic system consisting of dozens of thousand signal channels for event selection and processing.

   In the mt experiment of BES, the data taking, dated from November 1st of 1991 to January 20th of 1992, was done on the Beijing Spectrometer(BES). The measuring precision is 5 to 7 times as much as all the results ever obtained before.

   With white X-ray from beamline ( 4W1A ), experiments on defects in single crystals, phase transition in crystals under applied temperature and static electric field etc., have been performed at this station.

   The unfocused monochromatic X-ray from beamline 4W1B is applied to the study of Extended X-ray Absorption Fine Structure in the station.

   It is used for Huang scattering, the measurement of crystal character and phase structure and the study of phase transition.

    Beamline 4W1C is a time-shared branch with beamline 4W1B, it is designed for the Diffuse Scattering Station.

    The soft X-ray and VUV from the 4B9B beamline are applied to surface science studies in the station.

   There are two beamline here. Extracted from bending magnet 3B1, beamline 3B1A are used for the studies of lithography and biology spectroscopy.

   The scale of the computing center is equal to that of 15 VAX 11/780 computers. To cater for the physics research, it is used to analyze and process the data recorded in magnetic tapes. We have currently established communication networks with many high energy physics research institutions concerned.

   The Beijing Proton Linac and its application facilities consisted of the 35 MeV proton linac, research facilities for the treatment of cancer with fast neutrons, facilities for the production of short-life isotopes for medical applications and the experimental facilities for the positron emission tomography were completed and put into operation in 1998.

    To carry out the research and application of free electron laser, we started to do research on and fabricate the high performance electron linac in 1986. This is a 30 MeV electron linac which can be used to carry out research on the free electron laser in IR region and provide application.

   This facility has been used for treating patients since November 1991. The clinical treatment shows that the fast neutron radiotherapy is effective to certain cancers. With this facility, a lot of research works on several fields could be done, such as neutron radiation effect research etc.