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AMS will be carried by the Space Shuttle "Discovery" on 21 May 1998 for its initial 10 day-flight. The purpose of the first flight is to test the performance of AMS detectors, and to take data of antiproton in space. Then it will be launched again and be installed in the Space Station in February, 2001 for three-year experimental run there.
The sensitivity of AMS to He and C will be 10^{-11}.
The AMS detector consists of a permanent magnet, a precision silicon tracker, time-of-flight counters and anti -coincident counters with the total weight of 3.1 tons. The key part of AMS is the permanent magnet made of 2 tons of NdFeB, the maximum energy product is 50 MGOe, the diameter 1.2 meter, the hight 0.8 meter and the magnetic field 1000 Guass. The NdFeB materials are produced spcecially for AMS by Baotou Research Institute of Rare Earth Material. The Chinese Academy of Launch Vehicle Technology (CALT) is in charge of installing the NdFeB blocks into the mechanical structure. IHEP group in AMS collaboration is responsible for organizing and coordinating the design, R£¦D, the production, the field -mapping and the space qualification of the magnet. The group also participates the design and the optimization of the magnet. The design and production of the prototype of the magnet is going smoothly.
IHEP group is also in charge of the design and R&D of the anti-coincident counters which are prepared to reject the cosmic-ray background from the direction of side walls of the magnet. These background may produce wrong timing in the time-of-flight counters. To reach the detection sensitivities of the antimatter to 10^{-11}, the inefficiency of the anti-coincident counters must be less than 10^{-5}. It has to be survived in the launching and landing conditions, and can work in space for a long period. It consists of 32 pieces of scintillation counters with length of 0.8 meter, thickness of 1 cm, width of 10 cm and interval of 14cm. The edges of the counters have step shapes for overlapping to minimize the inefficiency due to the gaps between counters. The readout of the counters is by WLS fibres coupled to Hamamatsu PMT R5600U.
The mechanical design of the counters has been finished and a test set-up was established. The counters with various patterns of WLS readout scheme were tested for studies of optimizing the WLS scheme. From the comparison with the single photon measurement, the light yield from the anti-coincident counters is shown to be enough to provide the necessary efficiency for AMS. The prototype of the anti-coincident counters will be installed in the prototype of the AMS magnet for the space qualification in 1996.
Another task for the IHEP group is to design, produce and test the prototype of the electronics crates and covers for AMS. There are 24 crates (two types) and 4 covers for AMS electronics. The design and the production of the prototype have been finished. They will be installed in the prototype of the AMS magnet for various space qualification.
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April 1996 BEPC News