大口径低温泵抽速性能研究

Pumping Speed Evaluation of Cryopumpwith Diameter of 1250 mm

针对大口径大抽速低温泵的抽速性能进行了研究。由于我国对小于400 mm的低温泵的抽速测试有规范,但是对1250 mm大口径的低温泵还没有规范,因此类比电子行业标准低温泵总规范SJ/T11259-2001中规定的抽速测试方法,提出了一种在真空系统中实际测量低温泵抽速的方法;采用流量标定法获得低温泵在不同氮气流量下的压强和抽速,最后将抽速的理论值和试验值进行了比较分析。结果表明,低温泵在1-10 m L/min小进气条件下的抽速为44441-53280 L/s,在大进气条件200-800 m L/min时抽速为51393-59132 L/s,均小于低温泵的理论抽速60891 L/s。小流量进气条件下的实际抽速低于大流量下的实际抽速。并给出影响抽速的因素不仅与被抽气体物性参数、低温泵流导参数及冷凝板面积等自身参数有关还受到真空舱的体积、实际材料放气等因素的影响。

The pumping speed of the large-sized cryopump, 1250 mm in diameter, was evaluated in the plume effects experimental system by gas flow calibration method, a conventional technique widely used in electronic industry. The influence of the pumping conditions, including but not limited to the nitrogen flow rate, pressure, volume, gas properties, surface area of cold-plate, and surface desorption rates of different materials, on the pumping speed was experimentally investigated. The preliminary results show that the pressure and gas flow rate all have a major impact on the pumping speed. At a fixed pressure, the smaller the N2 flow rate, the higher the pumping speed. For example, the pumping speeds, at a N2 flow-rate in both.1 - 100 mL/min and 200- 800 mL/min ranges,were found to be n.n.n.n. 1 -53280 L/s, and 51393 - 59132 L/s, respectively, being much lower than the theoretically calculated 60891 L,/s. Possible mechanisms responsible for the discrepancy between theory and experiment were tentatively discussed in a thought provoking way.