基于Monte Carlo方法的CFETR低温泵设计与关键参数分析

中国聚变工程实验堆—CFETR(China Fusion Engineering Experimental Reactor)的运行离不开稳定的真空环境。针对CFETR装置聚变等离子体运行环境和真空要求,设计了一种聚变堆堆芯专用的4.5 K大抽速低温泵。采用蒙特·卡罗方法研究低温泵泵送概率和低温泵连接过渡管道流导,发现内开阀门结构满足CFETR抽速要求;采用正交实验,模拟了不同百叶窗障板结构对泵送概率的影响,确定了百叶窗障板的最佳倾斜角度为45°;探究了低温板气体吸附均匀性,阵列的各层低温板吸附均匀性良好。研究方法和结果不仅为CFETR堆芯大抽速低温泵的设计提供了依据,并且为同类型大型低温泵的设计提供了有益的参考。     

制冷机工况变化对低温泵抽气特性的影响

低温泵的冷源是小型气体制冷机。制冷系统在长期运行中可能发生种种故障，使制冷工况发生变化。制冷机制冷工况的变化，对制冷机一，二级冷头的制冷量和制冷温度有明显影响，从而对低温泵抽气特性产生重大影响。     

用于中性束注入器的4.2 K液氦低温冷凝泵的设计

在中性束注入器的研制中 ,大抽速低温泵的设计是其中非常重要的一部分。本文结合中性束注入器对真空系统的要求 ,介绍了中性束注入器真空系统的构成 ,并以布置于中性化室部位的低温泵为例 ,详细阐述了用于中性束注入系统的低温泵的结构设计以及抽速确定、冷凝面积确定等关键问题 ,成功设计了一套完全满足中性束注入系统对动态真空度要求的低温泵。     

The vacuum systems of ITER

ITER is a large vacuum facility which comprises many service, diagnostic and monitoring vacuum sub-systems as well as three large cryogenic pumping systems for evacuation and maintenance of the requested pressure levels. The presence of hydrogen (including the radioactive isotope tritium) and exclusion of other gases defines the parameters of fusion vacuum systems. This paper will focus on the areas of the ITER vacuum systems which require customized developments and cannot rely on commercial solutions. The complex pumps have been tailored for the very specific applications and requirements at ITER, characterized by high magnetic and radiation fields, excellent availability and maintainability and, especially, the need to be tritium-compatible. An outline of the development path which was needed to come up with a sound design for the ITER cryopumps is given and the status of the programme in view of the imminent manufacturing phase is described in this paper.     

低温,低压下吸附等温线实验参数的处理

介绍了低温、低压下活性碳对Ｈ２的吸附等温线实验参数的处理和误差分析。     

低温泵缸套柱塞防磨损和提高密封性的措施

介绍在KL 15A型制氧制氮车研制过程中 ,解决与之配套的往复式低温柱塞泵缸套柱塞使用寿命短、磨损严重、泄漏量大的方法 ,提高设备运行的可靠性 ,取得一定的经济效益     

Compound cryopump for fusion reactors

We reconsider an old idea: a three-stage compound cryopump for use in fusion reactors such as DEMO. The helium “ash” is adsorbed on a 4.5 K charcoal-coated surface, while deuterium and tritium are adsorbed at 15–22 K on a second charcoal-coated surface. The helium is released by raising the first surface to ～30 K. In a separate regeneration step, deuterium and tritium are released at ～110 K. In this way, the helium can be pre-separated from other species. In the simplest design, all three stages are in the same vessel, with a single valve to close the pump off from the tokamak during regeneration. In an alternative design, the three stages are in separate vessels, connected by valves, allowing the stages to regenerate without interfering with each other. The inclusion of the intermediate stage would not affect the overall pumping speed significantly.The downstream exhaust processing system could be scaled down, as much of the deuterium and tritium could be returned directly to the reactor. This could reduce the required tritium reserve by almost 90%.We used a well-established free Direct Simulation Monte Carlo (DSMC) code, DS2V. At very high upstream densities (～10²⁰ molecules/m³ and above) the flow into the pump is choked. Enlarging the aperture is the only way to increase the pumping speed at high densities. Ninety percent of the deuterium and tritium is successfully trapped at 15 K (assuming that the sticking coefficient is 80–100% on the 15–22 K surface). On the other hand, the remaining 10% still exceeds the small amount of helium in the gas input.     

Economical helium bath cryopump: design and testing

A small UHV helium bath cryopump with low cryoliquid consumption has been designed, manufactured and tested. The cryopump is designed to keep UHV in electron optical devices without generation of disturbing electromagnetic fields or vibrations. The outer volume of its shell is 15 l, the filling volumes of liquid helium (LHe) and liquid nitrogen (LN₂) are 3.0 l and 3.4 l, respectively. Operating times between cryoliquid fillings are 35 days for LHe and 6 days for LN₂. A pump speed of 25 l/s was measured for the He gas. A lowest pressure of 1.5×10⁻⁷ Pa was achieved in a test chamber and the pumping tests indicated that an even lower pressure would be achieved in a well-degassed chamber. Good agreement between the calculated and measured values both of the pump speed and the cryoliquid evaporation has been found. The system of chevron-type baffles was designed and checked by Monte Carlo simulations of molecular flow and radiative heat transfer. The pump prototype was successfully used to evacuate an operating cryostat of a NMR spectrometer.