中性束注入器低温冷凝泵抽气性能测试平台的研制

Development of pumping performance test platform for NBI cryocondensation pump

中性束注入器用液氦低温冷凝泵抽气性能的主要影响因素是低温冷凝抽气面温度,单位时间进气量和被冷凝的气体总量。本文采用流量计法抽速测试装置;同时依据液氦温度与其饱和蒸汽压之间的变化规律,系统中采用了氦气出气压力控制单元,通过调节液氦杜瓦内压力改变液氦的温度从而实现控制液氦低温冷凝面温度;且采用压电晶体阀对单位时间进气量以及被冷凝气体总量进行精确控制;使用ZJ-12型B-A规测量测试装置内真空度。设计了仿真中性束注入器用的低温冷凝泵的测试泵,对其进行ANSYS热力学分析,从而计算出该泵的低温冷凝面积。加工组装了测试平台,并在中性束注入器的工作条件下进行实验,得到测试泵的对氢抽速为940 L/s,表明该系统能够满足测试要求,为中性束注入器低温冷凝泵设计提供实验和理论依据。

The pumping performance of cryocondensation pumps used for neutral beam injector （NBI） is mainly determined by the temperature of cryopanel, intake flowrate and the gas quantity to be condensed. A single-dome flow-meter was introduced to measure the pumping speed on the test platform we developed. A pressure control unit was designed to readjust the system helium outgassing pressure in accordance to the change of liquid He temperature in relation to its vapor pressure, thus controlling the temperature of cryopanel by changing the liquid He temperature through readjusting the liquid He pressure in Dewar flask. Furthermore, the precision control was availabe to intake flowrate and total quantity of gsa to be condensed by introducing a MV-112 piezocrystal valve, with a ZJ-12, B-A gauge used to measure the air pressure in testing setup. A testing pump was also designed to simulate the cryocondensation pump used for NBI, and an ANSYS thermodynamic analysis was made to it so as to compute its cryocondensation area. The test platform after machining and assembling was used to test it on NBI operating conditions, and the result showed that its pumping speed is 940 L/sec for hydrogen, which means that the system is able to meet testing requirement. A theoretical and experimental reference is thus provided for the design of cryocondensation pumps for NBI.