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Research for a clean and large throughput differential pumping system
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Yang, Xiaotian; Meng, Jun; Chu, Jiguo; Zhang, Suping; You, Zhiming; Zhao, Yugang; Hu, Zhenjun; Yang, Weishun; Guo, Dizhou; Yang, Xiaotian; Meng, Jun; Zhang, Suping; You, Zhiming; Hu, Zhenjun; Yang, Weishun; Guo, Dizhou
China |
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The Gas-filled Recoil Separator built in one terminal of Heavy Ion Research Facility in Lanzhou (HIRFL) needs to be sent He of 100Pa as a support medium. The working pressure in the beam line connected with the device is 10-5~10-6Pa. In the other hand, the device is near the vacuum system of Cooler Storage Ring (CSR) which has a working pressure of less than 10-9Pa and must be protected from the contamination of any oil vapour. Our research is not only to design a differential pumping system to achieve the pressure transition with a large throughput, but to achieve a clean system without oil vapour contamination. The working pressure of this differential pumping system covers whole pressure ranges. In the ranges of viscous flow and molecular flow, dry pump and trubo-molecular pump (TMP) can be used respectively to keep the system clean. However, they can not work well in the intermediate flow range (102~10-1Pa). Pumping speed and compression ratio of TMP will be reduced sharply in the range. Further more, TMP would be damaged by the high temperature caused by internal viscosity. Dry pump(s) can work in the pressure range continuancely, but the price is very high and pumping speed is much small which can not be used to establish a differential pumping ratio, especially in a large throughput differential pumping system. Therefore, Roots pump is being used in the intermediate flow range for almost all differential pumping systems. However, Roots pump has a big problem of back-streaming of pump oil. To reduce the contamination, the cold trap or other device has to be adopted. Not only the cost is higher and the operation is more complex. In our research, a special kind of molecular-drag pump, which is developed by ourselves, is adopted to replace the Roots pump. The new pump can operate continuously in the intermediate flow range with large pumping throughput as that of Roots pump, and low contamination as that as of normal TMP. As a result, a clean and large throughput differential pumping system has been set up in our institute. In the paper, the design, equipment and performances of the differential pumping system for Gas-filled Recoil Separator is described. |