High Vacuum Pump Research Articles

Study of the Effective Torus Exhaust High Vacuum Pumping System Performance in the Inner Tritium Plant Loop of EU-DEMO

The requirement for a reduction of the tritium inventory of the European demonstration fusion reactor (EU-DEMO) has led to the active research and development of a continuously working pumping process termed “KALPUREX.” This process foresees the direct recycling of a large fraction of the unburnt hydrogen isotopologues via superpermeation in metal foil pumps during the burn phase. The remaining exhaust gas mixture is pumped by continuously operating, mercury-driven linear diffusion pumps. Diffusion pumps are kinetic high vacuum pumps whose pumping principle is based on the momentum transfer from a supersonic mercury vapor jet to the pumped gas mixture. Like many high vacuum pumps, they feature species-dependent pumping speeds. In the present work, we develop a simplified hybrid model of the high vacuum pumping train in order to estimate the effective pumping speed of the integrated system. The results of this model and its implications on the further development of the vacuum system are discussed for the burn and dwell phases of EU-DEMO.

Design and Development of a New 0.5m Hypersonic Wind Tunnel Facility at Indian Institute of Science

This paper describes the realization of a 0.5m hypersonic wind tunnel, second largest of its kind in India, at the High Speed Wind Tunnel Complex at Indian Institute of Science (IISc), Bangalore. The project was fully funded by the Aerodynamics Panel of AR & DB. There were two major activities associated with the project. One of them pertains to the "Strengthening of the existing 0.3m Hypersonic Wind Tunnel "(originally built in 1985) by adding a new high pressure air compressor, a cascade of high pressure air storage tanks, vacuum pumps and vacuum tanks and another related to establishing "an Additional 0.5m Hypersonic Wind Tunnel Leg". Preliminary commissioning trials of the new facility at low stagnation pressures were conducted in October 2013. Subsequently several hypersonic blow downs were carried out on a variety of models at Mach 8.0. Pitot probe measurements performed in the test section confirmed that the flow Mach number was close to Mach 8.0. The total run time measured was around 10 seconds. Thus, a large 0.5m hypersonic wind tunnel was indigenously designed, developed and commissioned in about 30 months at a cost of Rs.6 Crores. The facility was inaugurated by Prof. R. Narasimha in the presence of a large gathering of leading aerospace scientists in the country, on 8th April 2014.

Simulation of Mercury-Driven Diffusion Pumps for Torus Exhaust Pumping

A new, continuous pumping train has been proposed for the European demonstration fusion power plant (DEMO). Mercury-driven linear diffusion pumps (LDPs) are suggested for use as high-vacuum pumps in this pumping train. In this work, we validate a 2-D simulation framework based on the direct simulation Monte Carlo (DSMC) method with experimental data of a two-stage mercury-driven LDP that was operated at the Lawrence Livermore National Laboratory (LLNL) in the 1950s. The simulation setup and assumed boundary conditions are described and their appropriateness discussed. Numerical results are compared to available experimental data for four different positions of the upper nozzle pipe. We find acceptable agreement between experimental and numerical results for the air pumping speed. This validation paves the way for using the simulation framework as a design and optimization tool in the further development process of the DEMO LDPs.

Safe Handling of Air-Sensitive Organometallic Reagents Using Schlenk Line Techniques: Negishi Cross-Couplings for Trainee Graduate Students

A laboratory experiment has been devised to train new graduate trainees in the safe and controlled handling of air-sensitive organometallic reagents using Schlenk lines, high vacuum pumps, liquid nitrogen traps, and cannula transfers. The reaction involves the formation of air-, moisture-, and thermally sensitive 2-pyridyllithium, generated in situ by the reaction of 2-bromopyridine with n-butyllithium in dry THF at −78 °C. Subsequent transmetalation with dried ZnCl2 and reaction with 4-bromo-6-methyl-2-pyrone in the presence of catalytic Pd(PPh3)4 afforded the heterobiaryl product, 4-(2′-pyridyl)-6-methyl-2-pyrone. The many sensitivities of this experiment serve to provide an excellent practical demonstration for new graduate trainees of what can go wrong when experimental procedures are not accurately followed.

Перспектива создания современных высоковакуумных механических насосов

High-vacuum mechanical pumps are widely used in various fields of science and technology for research and industrial applications. Modern high-vacuum mechanical pumps include molecular vacuum pumps, turbomolecular vacuum pumps and hybrid turbomolecular vacuum pumps, i.e., designs that represent a turbomolecular vacuum pump with one or more additional molecular stages. There are also a number of experimental and theoretical developments that propose combinations of different types of high-vacuum pumps in which, as a rule, on the suction side the main pumping is carried out by an axial turbomolecular stage. These schemes belong to the class of modern high-vacuum mechanical pumps. The paper examines the designs and analyzes scientific studies of modern high-vacuum mechanical pumps. Relying on this overview, we found the unsolved problems of designing and mathematical modeling of high-vacuum mechanical pumps working processes, which could give further prospects for vacuum technology development

Design features of a high-vacuum steam jet pump and some results of its tests

This paper presents an original design of a high-vacuum steam jet pump in which a heater made of a heating cable is immersed in a working fluid located in a stainless steel boiler. At the same time, the boiler itself is vacuum isolated from the pump housing. There is also a heater made of a heating cable in a stainless steel shell, made in the form of a spiral and immersed in a working fluid. Such an arrangement of the heater is possible only when a liquid with a homogeneous chemical composition and a low saturated vapor pressure is used as a working fluid in high-vacuum pumps.

Surface Engineering for Enhanced Triboelectric Nanogenerator

Triboelectric nanogenerator (TENG) is the new technique that can convert low-frequency mechanical energy into effective electricity. As an energy collector, the pursuit of high output characteristics is understandable. Although high charge density has been achieved by working in high vacuum or charge pumping techniques, it remains challenging to obtain the high output performance directly in the atmosphere. Herein, surface-engineering of the triboelectric layer for enhancing output performance has been reviewed carefully. By constructing surface morphology or developing surface modification, high performance of TENGs is finally presented in the review.

Airborne Fungi in Prison Indoor Environments of Nsukka and Enugu Metropolis, Nigeria

Air borne fungi are transmitted through the air which can cause respiratory infections in human leading to allergies, asthma and diseases of the respiratory tract. The study is to determine the prevalence of fungi isolates in Enugu and Nsukka indoor prison environments and the possible effects on the respiratory tracts of the prison inmates. Institutions that accommodate large number of people such as Prisons, schools and hospitals are prone to airborne diseases due to overcrowded and unhygienic environment. The study was carried out using convenience sampling method and health based questionnaires. One hundred and forty (140)samples were analyzed consisting prison offices(48),inmates cells (28),lavatory (16),furniture(8),nasal swabs(20) and hostels(20). AC single impactor with high vacuum pump was used for indoor air sample collection; thermometer was used in measuring the temperature of the room and hygrometer for measuring the humidity. Sterile swab was used in collection of nasal samples, walls, furniture, toilets and bathrooms. Sabouraund dextrose agar (0.05µg Chloramphenicol and 1µg of Streptomycin), Malt extract agar, Chromagar, Brain heart infusion agar, and Nutrient agar were used for culture media for isolation of fungi respectively. The data generated from this research was analyzed using SPSS statistical software version 23.The result obtained showed that the percentage distribution of fungi isolates in prison offices were 60.9%, 57.4% in Nsukka and Enugu respectively while the percentage distribution percentage distribution of fungi isolates in prison cells were 42.6% and 39.1% in Enugu and Nsukka respectively. There was a significant difference in the distribution of fungal isolates at P=0.042.The indoor temperature and humidity of Enugu and Nsukka were the same at P using ANOVA, when compared with the hostels that served as control. Considering the public health effects of these airborne fungi, appropriate measures should be put in place in prison indoor environment to prevent the growth of moulds and yeast and its dissemination.

EXPERIMENTS ON DESORPTION OF ATMOSPHERIC GASES FROM GRAPHITE ELEMENTS OF THE KTM TOKAMAK'S FIRST WALL

This article describes the preparation and conduct of experiments on atmospheric gas release from graphite elements (tiles) of the KTM tokamak during their heating to a temperature of 450-480 °С. The paper describes the design of the experimental device used for thermal desorption experiments with graphite tiles of the KTM. The method of conducting thermal desorption experiments is described. The time dependence of gas release from graphite tiles during their annealing at linear heating at a rate of 3.5 °C/min to a temperature of 450-480 °C in the constant pumping mode with a high-vacuum pump are given. A brief analysis of experimental data is presented. Recommendations on the technology of preparing graphite tiles before their mounting in the vacuum chamber of the KTM tokamak are proposed.

Study of partial pressures of gases in vacuum chamber using multifunctional high-vacuum plant

The article studies the mass spectrum of gases inside the vacuum chamber of a multifunctional high-vacuum plant during pumping by different types of high-vacuum pumps. The most effective method to provide the high vacuum inside the cryovacuum systems is to jointly use turbomolecular and cryoadsorption pumps with the ion pump operating periodically.

Multifunctional high-vacuum plant for cryovacuum systems in aerospace applications

The article describes a design and main features of a multifunctional high-vacuum plant. This installation provides high-vacuum pumping of cryovacuum systems for space applications during a long time with 100 liter volume, leak detection with 5-1013 m3Pa/s minimum registered helium flow and monitoring of the mass spectrum within 1…100 AMU range.

Research progress on analytical methods for the determination of hexachlorobutadiene

六氯丁二烯是一种持久性有机污染物,于2015年和2017年分别被列入《斯德哥尔摩公约》附件A和附件C的受控污染物名单中。六氯丁二烯的来源、环境赋存和影响等研究对控制该新增受控持久性有机污染物污染具有重要意义,而灵敏可靠的六氯丁二烯分析方法是开展相关研究的前提和基础。近年来已有不少学者将六氯丁二烯作为分析目标物之一进行了检测或方法学研究。基于这些研究成果,该文综述了六氯丁二烯分析方法的研究进展,其中重点介绍了空气、水体、土壤、污泥、生物组织等多种介质中六氯丁二烯的样品前处理方法,并比较了各方法的优缺点,以期为该领域的进一步研究提供参考。空气中六氯丁二烯主要由泵抽气通过吸附管而采集,再经热脱附后进行仪器分析,检出限在ng/m3水平。也有研究应用聚氨酯泡沫被动采样器和吸附剂填充聚氨酯泡沫被动采样器采集大气中六氯丁二烯及其他污染物。基于吸附剂填充聚氨酯泡沫被动采样器的分析方法灵敏度较高,其对六氯丁二烯的检出限低至0.03 pg/m3。然而目前被动采样体积仅根据六氯丁二烯的log KOA系数估算,未来仍需进一步实验校正。水体样品前处理通常也较简单,通过吹扫捕集、液-液萃取或固相萃取目标物后进行仪器分析。固相萃取法能够同步实现目标物的提取、净化和浓缩,在水样中六氯丁二烯分析方面具有明显优势。固相萃取柱类型以及干燥步骤中柱中残留水分去除率均会影响六氯丁二烯的回收率。灰尘、土壤、沉积物、污泥和生物组织等固体介质样品基质最为复杂,需联合多种方法进行前处理。固体样品中六氯丁二烯提取方法包括索氏提取,加速溶剂萃取和超声萃取,其中超声萃取法应用最为广泛。固体基质净化方面主要采用层析柱色谱法,多根净化柱联用或多层复合柱能够提升净化效果。仪器分析方面,六氯丁二烯主要采用气相色谱和质谱联用检测,高性能质谱检测器如串联质谱能够大大提高六氯丁二烯的检测灵敏度,具有较大的应用潜力。

Development Prospects of High-Vacuum Mechanical Pumps Using Magnetic Bearing Support

The analysis of existing high-vacuum mechanical pumps with magnetic suspensions is carried out. The schemes and algorithms used for calculations for permanent magnetic suspensions (PMS) and active magnetic suspensions (AMS) are presented. Based on the results of the analysis, the relevance of the use of magnetic suspensions in high-vacuum mechanical pumps was evaluated, the development prospects of high-vacuum mechanical pumps with magnetic suspensions were noted.

Design and fabrication of a differential pressure MEMS capacitance diaphragm gauge based on heavily boron-doping technique

In this paper, a differential pressure MEMS CDG with a full range of (5–4000) Pa has been developed, and its pressure-sensing diaphragm is manufactured by boron-doping technique. The design principle and manufacturing process of the MEMS CDG were demonstrated in detail. To test the working performance of the CDG, a differential pressure high vacuum pumping system and a precision LCR meter are adopted to obtain the capacitance value of the vacuum gauge varying with pressure. The test results show that the MEMS CDG can work normally in the pressure range of (5–4000) Pa, and the maximum sensitivity is 87.2 fF/Pa. In addition, boron-doped diaphragm can effectively improve the sensitivity of vacuum gauge and further extend its measurement upper limit.

Redox thermochemistry of Ca-Mn-based perovskites for oxygen atmosphere control in solar-thermochemical processes

Sustainable energy supply is a crucial issue in times of climate change and receding fossil energy reserves. The emerging field of solar-driven thermochemical H2O and CO2 splitting cycles is a very promising approach to address this challenge. Providing low oxygen partial pressures is crucial in these processes. This issue is tackled by either high vacuum pumping or inert-gas sweeping. Both techniques come with a rather high energy penalty, leading to lower efficiencies of the whole process. Thermochemical oxygen pumping offers great potential to efficiently reduce oxygen partial pressures in these splitting cycles. In this work a material investigation campaign focusing on earth-abundant, cheap and non-toxic perovskites is presented. The experimental results are complemented with an approach to correlate this performance to inherent material properties, and in particular to the tolerance factor. In this framework, Ca-Mn-based perovskite compositions were demonstrated to function effectively as combined thermochemical oxygen-pumping and energy storage materials. Not only an almost two-fold increase of the reduction extent of ceria as a water splitting material was achieved due to the operation of perovskites as oxygen pumping materials, but this increase was rendered three-fold by applying a suitable temperature swing operation strategy. In parallel, the perovskites’ energy storage density can be significantly increased by exploiting specific phase transitions that can be rationally explained via the Goldschmidt tolerance factor. Hence, the work offers a novel approach to reach low oxygen partial pressures with minimal energy penalties and a derived model to evaluate occurring phase transitions and their corresponding heat effects.

Surface charge density of triboelectric nanogenerators: Theoretical boundary and optimization methodology

Although high charge densities of triboelectric nanogenerators (TENG) were achieved by working in high vacuum or charge pumping techniques in atmosphere, owing to their complex structure and/or stability issues, it still remains a great challenge and necessity to directly obtain the high charge density directly through triboelectrification effect in atmosphere. Here, a basic theory about the limitation factors of surface charge density is comprehensively rebuilt through analytical mathematical derivation of the limitation equation. As a result, high surface charge density can be obtained directly by a new optimization methodology, i.e. using thin dielectric layer, which is demonstrated by the designed contact-separation model TENG and sliding model TENG. In addition, the theoretical models of charge decay and charge accumulation during triboelectrification process were built. This work provides not only a new facile and universal optimization methodology for TENG, but also a new insight in the triboelectrification process, both of which will prompt the applications of TENG ranging from powering electronic devices to harvesting large-scale blue energy.

High-vacuum Pump of Orbitron Type: Electrophysical Principles of Work and Design Features

High-vacuum Pump of Orbitron Type: Electrophysical Principles of Work and Design Features

Cryopump development of the 5 MW neutral beam injector system on HL-2M tokamak.

In order to carry out the long pulse and high power neutral beam injector (NBI) heating experiment on the HL-2M tokamak and satisfy its high vacuum pumping speed in the NBI, two built-in cryopumps with large area and based on a three-stage adsorption structure have been developed. The design idea and size of the three stage structure, the manufacturing technique, and the test experiment for cryopumps have been described in this paper. The experimental result shows that the cooldown time of liquid nitrogen pipes and liquid helium pipes are 1.5 h and 10 min, respectively. With activated charcoal bonded on the condensation plates, the pumping speed reaches 1.13 × 106 l/s, and the consumption of liquid helium is 2.53 g/s and 3.11 g/s for the 4-component pump and the 5-component pump, respectively. The conductance probability of the pump inlet is 0.25 for hydrogen.

Effects of cryopump on vacuum helium leak detection system

A molecular pump is always used as the main pump of the vacuum leak detection system because of its strong ability for pumping helium. But the pumping speed of a molecular pump is not enough for large vacuum chamber. A cryopump is a clean, oil-free and high pumping-speed vacuum pump. If a cryopump is used as the main pump of the vacuum leak detection system, the number of the pumps will decrease. This paper describes the experiments on vacuum leak detection system with cryopump as a main pump, and analyses the phenomena in the experiments. The results show that the cryopump decreased the vacuum pressure of the system significantly, but it had nearly no influence to the system sensitivity. The response time and the clean-up time of the leak detection system with only molecular pump were both 3 min. But the response time of the leak detection system with both molecular pump and cryopump was 10 min–20 min, and the clean-up time of the system was longer than an hour.

Condensable Supersonic Jet Facility for Analyses of Transient Low-Temperature Gas Kinetics and Plasma Chemistry of Hydrocarbons

LEMPUS-2 facility is designed and built to study processes of cluster formation and plasma-chemical reactions that include atoms, molecules, and clusters, in supersonic jets. The facility is equipped with modern diagnostics tools and molecular-beam, electron-beam, mass-spectrometer, spectrometer, and laser systems for testing and fine-tuning technological processes in a laboratory environment. One of the key advantages of the discussed facility is that in a single system and a single experiment, it combines the tools for the activation of transient and steady-state supersonic flow with self-sustaining or nonself-sustaining discharge, and flow analysis using electron-beam spectroscopy and molecular-beam mass spectroscopy. Dry roughing and high-vacuum pumps enable accurate diagnostics of chemically reacting processes in virtually any gas mixture, including hydrocarbons. A pulsed flow regime controlled by developed in-house fast valves provides an efficient way to examine quasi-stationary flows at fairly high flow rates, with significant material and energy savings. The facility serves a number of purposes, from cluster-surface interaction studies with thin film and surface structure formation, to high-pressure jet expansions that emulate spacecraft nozzles at high altitudes, to technological process development, primarily focused on hydrocarbons. Details of key applications of the facility are presented that include the gas dynamics of cluster jets, the formation of heterogeneous clusters, the study of plasma-chemistry of hydrocarbons, and the thin film deposition.