螺旋轴流式多相泵外特性实验研究

本文在建立多相混输泵实验装置的基础上,以自行设计的螺旋轴流式多相泵原理机为实验研究对象,分别以纯水、空气—水为实验介质,系统地研究了多相泵的泵轴转速、进口压力、混合物特性等对多相输送性能的影响,为多相泵的进一步开发研制及完善设计提供了试验资料。     

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介绍了EAST真空室内巡视系统(IVVS)系统对EAST真空室第一壁进行巡检操作的工作原理,并基于系统部分材料出气率测试对其真空性能进行了分析.获得了在有效抽速为1064L·s–1的条件下,IVVS系统试验样机所采用的真空容器的极限真空度为3.37×10–3Pa.为优化IVVS真空性能,结合材料放气率试验,将部分材料更换为放气率低的材料,对系统进行烘烤处理,并对其中的相关结构提出了优化方案.优化后系统的真空性能有明显提高,在同等抽速条件下的极限真空度在1×10–4Pa范围内,能够满足EAST接受的真空环境要求.此外,抽气机组增添低温泵可以更进一步提高系统的真空性能.     

EAST真空室内巡视系统的真空性能研究分析

介绍了EAST真空室内巡视系统(IVVS)系统对EAST真空室第一壁进行巡检操作的工作原理,并基于系统部分材料出气率测试对其真空性能进行了分析。获得了在有效抽速为1064L•s^–1的条件下,IVVS系统试验样机所采用的真空容器的极限真空度为3.37×10^–3Pa。为优化IVVS真空性能,结合材料放气率试验,将部分材料更换为放气率低的材料,对系统进行烘烤处理,并对其中的相关结构提出了优化方案。优化后系统的真空性能有明显提高,在同等抽速条件下的极限真空度在1×10^–4Pa范围内,能够满足EAST接受的真空环境要求。此外,抽气机组增添低温泵可以更进一步提高系统的真空性能。     

Surface analysis of contamination layers in cold-cathode gauges

The influence of gas atmosphere on the long-term operation characteristics of a commercial cold-cathode gauge was studied. The changes of the electrode surfaces due to contamination effects of the so-called double-plasma gauge CF 2P by ALCATEL (double Penning system) were investigated by Auger-electron spectroscopy, X-ray photoelectron spectroscopy and scanning electron spectroscopy. Contrary to the widespread opinion that particular contamination is mainly caused by the polymerization of hydrocarbons in the discharge chamber of cold-cathode gauges, we found a contamination layer on the electrodes which consists only of sputtered cathode material. The distribution and thickness of the layer can give information about the preferred ion trajectories and convenient design features for a long life and stable operation of this type of gauge. Layer thickness seems to be a direct function of the pressure dose, independent of small changes in chemical composition of the layers and independent of the pressure itself. PACS 07.30.Dz; 07.30.Kf; 52.80.Vp; 68.47.-b; 81.15.Ef     

Investigations of the long-term measuring stability of cold-cathode gauges

Cold-cathode ionization gauges (CCGs) are used widely for pressure reading in vacuum systems due to large measuring range, robustness and relative low cost. Amongst the many advantages of CCGs, however, these instruments are restricted in use by decreasing measuring accuracy over operating time as internal electrodes become contaminated. Thus, to guarantee a consistently high measuring accuracy, this gauge type needs to be calibrated regularly after a fixed operating time period. With the aim of quantifying the useful lifetime of CCGs we investigated the measuring behavior of different commercial CCGs in several long-term-operation tests. After a first calibration, the gauges were operated in a vacuum atmosphere with a high fraction of hydrocarbons for several thousand hours at varying high-vacuum pressures. After use, the gauges were re-calibrated and changes in their characteristics analyzed. To compare the operating states of the used CCGs a new basic quantity was introduced: the so-called pressure dose. Using this quantity it should be possible to verify roughly the effective lifetime of CCGs until their pressure readings become erroneous due to contamination effects. It was found that the pressure reading of all tested CCGs become inaccurate after a pressure dose of about 1 mbarh. PACS 07.30.Dz; 84.47.+w     

Ti-Zr-V吸气剂薄膜在管道的制备与真空性能研究

利用直流磁控溅射方法在单晶硅片和内径为22 mm、长度分别为500 mm和1500 mm的银铜管道内壁镀制了Ti-Zr-V非蒸散型吸气剂薄膜,并对镀膜管道的极限真空进行了测量。结果显示:在180 ℃下激活24 h后,镀制了Ti-Zr-V薄膜真空管道的极限真空度可以达到9.2×10?10 Pa。在关闭测试系统和离子泵的阀门后,系统仅依靠Ti-Zr-V薄膜的吸气依然能够维持在9×10?9 Pa很长时间。利用测试粒子蒙特卡罗法对薄膜的抽速和容量进行了分析和测量,结果显示,Ti-Zr-V薄膜对CO的初始粘附系数最大可以达到0.3,容量可以达到1.2个分子层。     

Suitability of ion pump for evacuation of a closed He cycled Mössbauer cryostat

For Mössbauer studies at very low temperatures, the target holder kept at 11°K with the help of a closed He cycle Mössbauer shroud, has to be insulated by evacuating the outside enclosure surrounding the shroud. The target is kept in thermal contact with the cryostat cold finger through He gas at atmospheric pressure. This provides a vibrationless thermal contact between the two. The evacuation of the outside chamber has to be vibration free which can be accomplished by means of a suitable ion pump which is totally vibration free. However, use of Vac-ion pump here could not be made successful because the pump did not work at all after little pumping. To find out the cause of pump's failure, RGA was employed which showed the presence of He gas in the outside chamber at the time of purging of He gas in the internal chamber. The pump, however, worked efficiently again when the dry N₂ gas purged in place of Helium. This points out that totally vibration free Vac-ion pumps cannot be used for evacuation of such cryostats. Here, diffusion pump was used subsequantly taking extra precautions to minimise the vibrations.     

Velocity and ejector-jet assisted differential pumping: Novel design stages for environmental SEM

Velocity and ejection pumping are proposed as novel evacuation techniques to assist the static differential pumping already in use in the environmental scanning electron microscope. The gas velocity (or momentum) that accompanies the supersonic jet stream formed through the first pressure limiting aperture is used to initially force the gas out of the system by placing the second pressure limiting aperture at an optimum position in the gaseous jet. By this method, the gaseous particle thickness between the two apertures is minimised and the required pumping speed of the first evacuation stage is also reduced to an absolute minimum. A further improvement is achieved by inserting an appropriately shaped baffle between the two apertures, which shields the second aperture from the gas jet of the first and acts as an ejector-jet pump. The gas leak rate through the second aperture is maintained at an acceptable low level by both systems, even below the static leak rate level when the ejector-jet design is used, in particular. The result of either method has a double benefit, namely, the electron beam loss in the intermediate pumping stage is minimised together with a reduction of pump speed requirements. This translates to best instrument performance and minimal manufacturing costs.     

Manufacturing and qualification of UHV chambers

Vacuum chambers or vacuum components that are widespread in research and in industry must fulfill high degrees of cleanliness, especially if they are required for ultra-high-vacuum (UHV) applications. It is shown that common techniques that are used for manufacturing and testing of pressure containers and of related items are often not sufficient for UHV requirements. Outstanding vacuum chambers and components are described, which have been fabricated for actual research applications. The requirements for the design, manufacturing and performance of such systems will be displayed, providing support for adequate specification. PACS 07.30.Kf; 07.30.Hd     

Windowless transition between atmospheric pressure and high vacuum via differential pumping for synchrotron radiation applications

A differential pump assembly is introduced which can provide a windowless transition between the full atmospheric pressure of an in‐air sample environment and the high‐vacuum region of a synchrotron radiation beamline, while providing a clear aperture of approximately 1 mm to pass through the X‐ray beam from a modern third‐generation synchrotron radiation source. This novel pump assembly is meant to be used as a substitute for an exit vacuum window on synchrotron beamlines, where the existence of such a window would negatively impact the coherent nature of the X‐ray beam or would introduce parasitic scattering, distorting weak scattering signals from samples under study. It is found that the length of beam pipe necessary to reduce atmospheric pressure to below 10 mbar is only about 130 mm, making the expected photon transmission for hard X‐rays through this pipe competitive with that of a regular Be beamline window. This result is due to turbulent flow dominating the first pumping stage, providing a mechanism of strong gas conductance limitation, which is further enhanced by introducing artificial surface roughness in the pipe. Successive reduction of pressure through the transitional flow regime into the high‐vacuum region is accomplished over a length of several meters, using beam pipes of increasing diameter. While the pump assembly has not been tested with X‐rays, possible applications are discussed in the context of coherent and small‐angle scattering.     

新型涡旋多相泵原理及其工作过程研究

提出了一种新型涡旋式气液多相混输泵,通过构建变啮合间隙涡旋齿型线,使得所形成的压缩腔存在一条通向排出口的内泄漏卸压通道。构建了一种液相压缩卸荷的新方法,解决了容积式多相泵在混输较高含液率介质时易出现的压缩腔液击问题。介绍了新型涡旋多相泵的工作原理,得到了变啮合间隙涡旋齿型线的生成方法和型线方程,分析了工作腔容积和啮合间隙的变化规律。建立了涡旋多相泵工作过程中气液介质在伴有内泄漏时的增压过程热力模型,求解得到了工作过程中压力的变化规律。     

Effects of the pump-circuit acoustic coupling on the blade-passing frequency perturbations

Centrifugal pumps are a source of pressure and flow rate perturbations in hydraulic pumping systems. In particular, a significant excitation is usually induced at the blade-passing frequency and harmonics as a consequence of the fluid-dynamic interaction between the rotor and the stator. The magnitude of this excitation is very dependent on the internal geometry of the pump and on its point of operation, but it depends also on the acoustic response of the hydraulic network to the perturbations. The induced and transmitted perturbations can be either amplified or reduced depending on the pump-circuit acoustic coupling, and thus they can lead to excessive levels of noise and vibration under certain conditions. The purpose of the present investigation is the theoretical and experimental characterization of the perturbations induced in a laboratory pumping system, as a function of the acoustic impedance of the pipelines. For different points of operation, the blade-passing frequency impedance is changed by varying the speed of rotation and, additionally, by modifying a closed side branch of the hydraulic system (that is, in the absence of net flow through it). For the theoretical calculations an acoustic model, based on matrix formulation, is applied to obtain the influence of different acoustic impedances of the suction side on the pressure fluctuations at the pump. Test measurements with a fast-response piezoelectric pressure transducer situated at the tongue region of the pump under the same system configurations confirm the significant effect of the pump-circuit acoustic coupling on the pressure perturbations.     

磁绝缘线振荡器重复频率运行真空系统优化

为改善一种L波段磁绝缘线振荡器（MILO）重复频率运行时的真空环境,建立了器件在分子流下的抽气模型,采用Monte-Carlo方法对阴极脉冲放气后的瞬态抽气过程进行了模拟计算,获得了不同时刻气体分子在MILO内部的3维分布情况,并据此提出了一种分布式抽气方案,即在MILO靠近气源的微波传输区增加一抽气单元,以缩短脉冲间隔内的抽气时间。在Torch-01调制器上开展了MILO分布式抽气的实验验证,结果显示,分布式抽气时的气压下降特征时间为单泵的0.22倍,与模拟结果基本一致;初步的重复频率测试也表明分布式抽气能够缩短脉冲串间隔内的抽气时间以保持器件运行时的真空水平。在所给实验条件下,从真空的角度,分布式抽气能够使MILO有效运行的重复频率数提升至单泵抽气时的5倍。     

Characterization of a ferrofluid-based thermomagnetic pump for microfluidic applications

We experimentally characterize the performance of a miniature thermomagnetic pump, where suitably imposed temperature and magnetic field gradients are used to drive ferrofluid in a 2 mm diameter glass capillary tube, without application of any external pressure gradient. Such a pump can operate in a hermetically sealed micro electromechanical system configuration without any moving part, and is thus capable of handling microfluidic samples with little risk of contamination. In the experiment, the ferrofluid in the capillary is exposed to a magnetic field using a solenoid; a small resistive heater wrapped on the tube wall is used to create temperature gradient in such a way that the Kelvin body force in the medium produces a net unbalanced axial component. This causes a thermomagnetic pumping action, transporting the ferrofluid in the capillary tube from the colder end to the warmer end. Performance of the thermomagnetic pump is investigated experimentally to characterize the pump pressure head and discharge under different working conditions, namely, the magnetic field strength, heating power, and ferrofluid properties. A comparison with two other field actuation pumps at comparable length scales is also presented. The pump produces higher output at lower power supplies and magnetic field compared to the other two pumps.     

Improved gain for the Ar 2 * excimer laser at 126 nm

Argon was excited by intense electron beam pumping. The optical gain obtainable in Ar ₂ ^2* at 126 nm was investigated as a function of gas pressure and pumping density. The gas pressure necessary to achieve a gain of 10%/cm is reduced from 3.2 to 1.0 MPa if the gas is cooled at 170 K. The effect is partly due to reduced absorption by the removal of impurities. The results allow one a new approach to construct high-power lasers in the vacuum ultraviolet below 150 nm.     

清洁、大流量真空差分系统的研制

本研究是为了设计一套大流量、清洁的真空差分系统. 计算了超重反冲核实验装置终端真空差分系统各级的真空度; 介绍了差分系统的设计和真空泵、测量设备选择; 选择能在高压强下连续运行的新型分子/增压泵作为过渡流范围内的主排气泵, 对分子增压泵进行了性能测试并对差分系统进行了模拟靶室实验, 最后对实验结果进行了分析.     

激光干涉技术在超声速气体喷嘴特性研究中的应用

在激光与物质相互作用的实验中,气体靶通常由超声速喷嘴在高背压下向真空中高速喷射气体产生。激光与气体靶相互作用时确定打靶条件对整个实验有着十分重要的意义。为了得到不同实验条件下气体靶密度的分布特性，采用马赫-曾德尔干涉法测量了气体靶密度分布，获取了干涉图样。使用基于傅里叶变换的条纹处理方法测得的干涉图样，得到不同实验条件下气体分子密度的全空间分布。实验表明：用M-Z干涉仪测量超声速气体喷嘴产生的气体靶密度分布十分有效。基于傅里叶变换的条纹处理方法具有精度高、实时性好的优点，为打靶时气体靶密度的实时测量提供了可能。     

Hagena团簇尺度定律中锥形喷嘴的等效孔径

本文首先详细重演了锥形喷嘴的等效孔径d_eq, 并根据d_eq的定义给出了它与气体团簇喷流的径向宽度之间的依赖关系. 然后以高背压氩气团簇喷流为例, 通过成像喷流的Rayleigh 散射光的空间分布研究了不同背压下喷流的径向宽度, 并与Hagena 团簇尺度定律中直线流模型假设的喷流径向宽度进行了比较. 结果表明, Hagena 直线流模型假设的喷流径向宽度小于实际的径向宽度, 且实际宽度与气体背压有关. 进一步的研究表明, 直线流模型对喷流宽度的估计偏差导致对锥形喷嘴等效孔径的估计偏差, 这为Hagena 尺度定律估计团簇平均尺寸的偏差给出了一种可能的解释. 关键词： 气体团簇 Hagena尺寸定律 锥形喷嘴的等效孔径     

Automatic regulation of hydrogen partial pressure using a proton conducting ceramic based on SrCeO3

Electrochemical regulation of hydrogen partial pressure in flowing gas was examined using a proton-conducting ceramic tube made of Yb-doped SrCeO₃. Hydrogen partial pressure in the test gas was controlled by electrochemical hydrogen pump. When pumping current was controlled based on the Faraday's law, hydrogen content in the test gas with a constant flow-rate was well regulated, while change in flow-rate of the gas caused some deviation of hydrogen partial pressure from that desired. The pumping current could be determined in a self-correcting manner, which was efficient to regulate gas even with changes in flow-rate and/or initial hydrogen content in the gas.     

载气密闭循环氧碘化学激光技术模拟实验研究

载气密闭循环氧碘化学激光器技术是一种有望大幅减小氧碘化学激光器体积和降低运行成本的技术,然而至今鲜见相关实验报道。采用超音速喷管加双螺杆真空泵建成了模拟实验装置,并通过测量超音速喷管前后和双螺杆真空泵出入口处的气动参数的方法开展了载气密闭循环氧碘化学激光器的可行性研究和工作稳定性模拟实验研究。模拟实验研究结果证明了该技术的可行性,发现并分析了其光腔压力随双螺杆真空泵转速提高而出现压力拐点的现象,确定了其稳定运行工作条件,为实现载气密闭循环氧碘化学激光器的真正运行和小型化奠定了良好的基础。