现代涡轮分子泵的技术现状与展望

本文介绍了涡轮分子泵的优点及普及的原因，讨论了泵轴承系统的改善，泵的工作寿命与可靠性的提高以及宽域型复合分子泵的开发，还给出了极高真空的获得方法和泵快速抽气的措施。     

分子泵的世纪回顾与展望

分子泵自1912年诞生以来,至今已快近一个世纪了,它在初期进展较缓慢,在1970年以前,分子泵的应用还仅限于核物理,电真空,表面科学等领域,但近20年来由于半导体产业的兴起和薄膜工业的发展,分子泵才被人们所重视,并得到了兴旺和发达,现代的分子泵已发展到实用和普及的阶段,本文回顾了分子泵分析近百年的发展历史,详细地介绍了分子泵在各个时期的发展状况,对初期的分子泵,涡轮分子泵,磁悬浮轴承和气体静压静轴式涡轮分子泵,复合式分子泵,低温型涡轮分子泵,新型牵引分子泵,陶瓷涡轮分子泵,轴反应生成物的涡轮分子泵和极高真空涡分子泵等做了重点的分析,最后指出分子泵的发展前景。     

短叶片涡轮分子泵—一种复合分子泵

本文分析了涡轮分子泵和拖动分子泵抽气机理的不同物理图象，并论证了短叶片涡轮分子泵的抽气作用是这二种分子泵抽气机理同时作用的结果，从而，这种泵具有涡轮分子泵和拖动分子泵的共同优点。     

涡轮分子泵的压缩比和泄漏

涡轮分子泵中存在着通过分子泵各级的泄漏现象，影响了分子泵实际的压缩比。如果在计算压缩比时不考虑这个影响，那么实际测得的压缩比大多远小于计算所得。对于从高压强级到低压强级的泄漏所产生的影响，本文作了一个理论估算。提出了一个简单模型亚计算泄漏引起的压缩比的降低。     

涡轮分子泵电源分析与研究

本文主要对一种F-150型涡轮分子泵电源设计要求和工作原理进行详细地分析和讨论。     

间隙对涡轮分子泵性能的影响

本文分析了涡轮分子泵内动叶片和定片间空隙所产生的影响，讨论了一个基于级间反流传导的简单模型。作者把单级的分析结果结合起来，用来评定多级泵的性能。计算结果表明间隙尺寸对抽速影响很小，而对压缩比的影响却是惊人的，尤其是对于高分子量的气体。最后，本文对不同间隙计算出来的压缩比和抽速与实验结果进行了比较。     

如何选择和使用涡轮分子泵

本文首先介绍了涡轮分子泵的工作原理,结构型式及其优缺点。为了利用涡轮分子泵,获得清洁真空,国外多利用干式机械泵作其前级泵,构成无油的真空系统。然而,目前国内涡轮分子泵多以油封机械泵为其前级泵,构成了有油真空系统,如果操作不当,很难避免油蒸汽返流,对真空系统的污染。利用有油系统获得清洁真空,国内外都有一些有效防止返流的措施和成功的操作经验。这些对用户正确选择和使用涡轮分子泵有油系统获得清洁真空,有一定的参考价值。     

Investigation of turbo-molecular pumps in strong magnetic fields

In modern particle and accelerator physics as well as in nuclear fusion experiments turbo-molecular pumps (TMP) are used in close proximity to super-conducting magnets. This can cause considerable heating of the fast moving rotor by eddy currents, which can ultimately lead to the destruction of the pump. Motivated by the KATRIN neutrino experiment, where TMPs are operated close to super-conducting magnets, a measurement programme has been elaborated to investigate the effect of magnetic fields on TMPs. An infra-red pyrometer has been used to measure the temperature of the revolving rotor. In addition the effect of different gas loads on the temperature was investigated. With these data a simplified model has been developed to predict the evolution of the rotor temperature over time, using easy to measure parameters. Here we introduce the new model and present first measurements and their application in predicting the rotor temperature in the pulsed field of a nuclear fusion experiment.     

Investigation of turbo-molecular pumps in strong magnetic fields

In modern particle and accelerator physics as well as in nuclear fusion experiments turbo-molecular pumps (TMP) are used in close proximity to super-conducting magnets. This can cause considerable heating of the fast moving rotor by eddy currents, which can ultimately lead to the destruction of the pump. Motivated by the KATRIN neutrino experiment, where TMPs are operated close to super-conducting magnets, a measurement programme has been elaborated to investigate the effect of magnetic fields on TMPs. An infra-red pyrometer has been used to measure the temperature of the revolving rotor. In addition the effect of different gas loads on the temperature was investigated. With these data a simplified model has been developed to predict the evolution of the rotor temperature over time, using easy to measure parameters. Here we introduce the new model and present first measurements and their application in predicting the rotor temperature in the pulsed field of a nuclear fusion experiment.     

Influence of magnetic fields on turbo-molecular pumps

Recently, turbo-molecular pumps (TMPs) have been widely used in nuclear fusion devices and sometimes used in particle accelerators. In order to use them in the quasi-static magnetic field often employed in these devices, the influence of these fields on TMPs was investigated in detail.First of all, the influence of two special magnetic fields was examined, a magnetic field orthogonal to the TMP, and one which was parallel. The parallel magnetic field had no influence on the operation of the TMP. On the other hand, the driving power and the rotor temperature were greatly affected by the vertical magnetic field. The eddy current loss in the vertical field increased rapidly with the field strength, proportionally to the square of the field strength. The eddy current loss also increased with the rotation frequency; however, it was roughly proportional to the square root of the frequency at higher frequencies. These dependences are well explained by the skin depth, which indicates the region beneath the surface of the rotor where a localized magnetic field and current flow exist.Then, we successfully calculated the influence of a magnetic field in an arbitrary direction by adding the contributions from the above two magnetic components. Furthermore, experiment revealed that a magnetic field with symmetry around the rotor axis does not affect the operation of the TMP.     

Some improvements of the performance of turbo-molecular pumps

To improve the performance of a vacuum pump means are required to increase the pumping speed and to reduce the final pressure the pump can attain.     

Characterisation of a turbo-molecular pumps by a minimum of parameters

The design of complex vacuum systems including turbo-molecular pumps requires knowledge of the characteristics of the turbo-molecular pumps. Normally, such characteristics for commercially available turbo-molecular pumps are presented as graphs of pumping speed, compression ratio and so on as a function of inlet or outlet pressure. It is difficult to incorporate such information into a model for designing complex vacuum systems, especially when optimising the number of pumps, their pumping speed and choice of backing pump.Voss [Characteristics of the turbomolecular pumps. Vakuum in Forschung ung Praxis 2002;14(4)] has published fitting formulae for specific pumps as a way of describing pressure, pumping speed and compression at the inlet, by means of a number of parameters which are described in a table for each gas and throughput. These fitting formulae can be used in modelling, but the fitting parameters for an arbitrary pump are not in general available.A new approach is proposed based on ‘true zero-throughput’, which has been defined as the ratio of the probability of a gas molecule travelling from the pump inlet to the outlet to that of its travelling from the outlet to the inlet. This is different from the usually reported ‘zero-throughput’ data which are measured with zero gas injection, but not ‘zero gas load’ at the inlet (due to thermal outgassing of a measuring dome and the pump itself). Parameters in the formulae developed here are no longer simply fitting parameters, but have clear physical meaning. The dependence of the parameters for different gases may be included as a function of mass. The new formulae presented, allow us to model the performance of cascaded turbo-molecular pumps. As an example, the formalism is applied to the differential pumping stages of the KATRIN experiment [KATRIN Collaboration. KATRIN design report 2004. Forschungszentrum Karlsruhe Scientific Report # FZKA 7090, 2005].     

Model of the rotor temperature of turbo-molecular pumps in magnetic fields

The KATRIN neutrino experiment operates about 20 turbo-molecular pumps (TMP) in the vicinity of super-conducting magnets, pumping out tritium gas from the electron beam-line of the experiment. In a dedicated test setup with Helmholtz coils systematic studies have been conducted, investigating the rotor temperature and stability of operation of TMPs at full speed as a function of gas load, magnetic field strength and direction of the field. The temperature of the magnetically levitated spinning rotor was measured in vacuum with an infra-red pyrometer. A simple model has been developed, which describes quantitatively the temporal progression of the rotor temperature as a function of gas flow and field strength of an external static magnetic field. The model requires 5 pump-specific parameters, characterising the heating effects of eddy currents and gas friction and cooling by radiation loss and convection. When designing a vacuum system with TMPs in a critical environment (e.g. magnetic beam-line, fusion reactor), the model can be used to predict the maximum temperature of the rotor, to ensure a safe operation of the pump.     

干式螺杆真空泵研究现状与展望

介绍目前螺杆式真空泵现状,分析了螺杆端面型线研究情况和整机冷却中存在的问题,并对下一步的研究方向进行了展望.