Liquid helium offers a fascinating new way to make charged molecules
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Liquid helium offers a fascinating new way to make charged molecules
(Nanowerk News) A collaboration between researchers at the Universities of Leicester and Innsbruck has developed a completely new way of forming charged molecules which offers tremendous potential for new areas of chemical research ().
Professor Andrew Ellis from our Department of Chemistry has been working for several years with colleagues at the Institute of Ion Physics in Austria on exploring the chemistry of molecules inside liquid helium. The team?s latest and most startling discovery is that helium atoms can acquire an excess negative charge which enables them to become aggressive new chemical reagents.
Helium is a famously unreactive gas but when cooled to just above absolute zero it becomes a superfluid, a strange form of liquid. (Among other bizarre properties, liquid helium can flow upwards because it has zero viscosity and its capillary action is stronger than gravity.) The Anglo-Austrian team manufacture droplets of superfluid liquid helium by subjecting helium gas to a combination of high pressure and low temperature and then force it through a pinhole just 5 um in diameter into a vacuum chamber. These droplets provide a controlled environment into which molecules can be added to study chemistry.
The molecules in this case were fullerenes, a class of large carbon molecules, named after their geometrical similarity to the geodesic spheres developed by architect Buckminster Fuller in the 1950s. The droplets of helium were passed through a cell containing C60 or C70 fullerenes and the resultant mixture was hit by an electron beam of energy between 0 and 150 eV.
What Professor Ellis and his colleagues discovered was that clusters of five or more fullerene molecules became dianions (gained a double negative charge) when targeted by a beam of about 22 eV. Dianions are not uncommon in chemistry but they are normally very unstable and short-lived outside of common chemical solutions (such as water). The creation of relatively stable fullerene dianions in liquid helium opens up a whole new research area for chemists.
So how have these dianions come about? Adding two electrons sequentially to something is difficult because of Coulomb?s Law: the negative charge of the first electron will tend to repel the second electron. What has evidently happened is that two electrons have attached themselves to a fullerene molecule simultaneously. The key question is where do these two electrons come from and why don?t they repel each other?
The answer seems to lie with helium. Helium atoms have two electrons in their natural, neutral state, their negative charge being balanced by two positively charged protons. The first orbit or shell around an atomic nucleus can only hold two electrons, which is why helium is generally disinterested in reacting with anything.
However, in these new experiments an electron beam with the right energy excites one of these electrons, causing it jump up to the next orbit where it is joined by an electron from the beam, creating an anion of helium. There are now two electrons in large orbits around the helium nucleus which makes this helium anion very reactive. When a suitably sized target, such as a clump of fullerene molecules, presents itself the two outer electrons jump ship, ending up on the fullerene. This pairing of two electrons which would normally repel each other is most likely aided by the very low temperature (0.4 K) inside the helium droplets and has echoes of the behaviour of electron pairs in superconductors.
Professor Ellis said: ?Nothing like this has been observed before and the idea of helium as an electron donor is something completely new. This is really just the beginning of a new branch of chemistry and our research team is now exploring how other chemical processes might be influenced by this remarkable chemical reagent.?
Source: University of Leicester
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& , , Inc. or its affiliatesEUR 83 million contract signed for Liquid Helium Plant
EUR 83 million contract signed for Liquid Helium Plant-Sabina Griffith
The ITER Tokamak will rely on the largest cryoplant infrastructure ever built.The ITER Tokamak will rely on the largest cryogenic plant (cryoplant) infrastructure ever built. Three liquid helium plants, working in parallel, will provide a total average cooling capacity of 75 kW at 4.5 K and a maximum cumulated liquefaction rate of 12,300 litres/hour.
On&Tuesday, 11 December, ITER Director-General Osamu Motojima and the Managing Director of Air Liquide Advanced Technologies, Xavier Vigor, signed the contract for ITER's three identical liquid helium (LHe) plants. The contract comprises the design, manufacturing, installation and commissioning of the LHe plants, which are adapted to the long-term, uninterrupted operation of the ITER Tokamak. The contract is worth EUR 83 million.
ITER Director-General Osamu Motojima and the Managing Director from Air Liquide Advanced Technologies, Xavier Vigor, signing the contract. The cryoplant and cryo-distribution system will supply cooling for the ITER superconducting magnets to confine and stabilize the plasma. They will also provide the refrigeration for the cryosorption panels that are necessary to evacuate the helium ashes stemming from the fusion reaction and to assure the required vacuum for the cryostat and the vacuum vessel. All these users require helium cryogen at different temperature levels ranging from 4.5 K, to 50 K and up to 80 K.
The key design requirement is to cope with ITER's large dynamic heat loads ranging from 40 to 110 kW at 4.5 K mainly deposited in the magnets due to magnetic field variation and neutron production from deuterium-tritium fusion reactions. At the same time, the system must be able to cope with the regular regeneration of the cryopumps.
Manufacturing of the LHe plant main components will start after design finalization in 2014. The first compressor station will be delivered at the end of 2015 and the LHe plants will be ready for the cool-down of sub-systems in 2018.
This will be the place! The ITER Cryogenic Section together with the team on the site of the future liquid helium plants. "This is a major milestone not only for the cryogenic system but for the whole project," said the Head of the ITER Plant Engineering Division, Luigi Serio. "The contract covers the principal component that will drive the cool-down of the machine, seting the pace toward First Plasma."
"We are very happy and excited to participate in the great ITER adventure," Xavier Vigor said. "Be assured that we, the team from Air Liquide, are fully committed to making ITER a success."
Air Liquide is the world leader in gases for industry, health and the environment, and is present in 80 countries with 46,200 employees. Oxygen, nitrogen, hydrogen and rare gases have been at the core of Air Liquide's activities since its creation in 1902. In 2011, the Group's revenues amounted to EUR 14.5 billion, of which more than 80% were generated outside France.液氦杜瓦,liquid helium Dewar英语短句,例句大全
词句:液氦杜瓦,liquid helium Dewar1)liquid helium Dewar液氦杜瓦英文短句/例句1.After liquid-helium test we find that helium permeability is an important factor for FRP liquid-helium dewar.液氦试验发现:氦气渗透是影响玻璃钢液氦杜瓦性能的重要因素,应予以重视。2.This paper describes tile design of the liquid helium dewar for the superconducting heteropolar d· c· machine of 17 kW prototype.本文介绍超导异极直流电动机17千瓦模型样机液氦杜瓦的设计。3.The control system for the pressure control in the helium dewar is designed and simulated.最后,设计了制冷机停机工况下液氦杜瓦的压力控制系统并进行了动态仿真。4.Development Of Metal Liquid Helium Open Dewar For Superconducting Magnets超导磁体用金属液氦广口杜瓦的研制5.In this article, a dewar for this superconducting magnet system is mainly described and experimental results about boil-off rate of the LHe under the condition of rotation and vibration is presented.本文将主要描述该系统的杜瓦部分,并且给出在旋转和振动条件下的液氦挥发实验结果。6.The structure feature and fabrication technology of a special-shaped LHe dewar for superconducting unipolar motor are described.本文叙述了超导单极电机液氦异型杜瓦容器的结构特点和制造工艺。7.In this paper we reported the experimental results on electro-magnetic shielding properties of a kind of small metal dewar.本文介绍了一种小型金属氦杜瓦瓶电磁屏蔽性能的初步实验结果。8.THEORETICAL AND EXPERIMENTAL INVESTIGATION OF EVAPORATION RATE IN VEHICLE LIQUID HYDROGEN DEWAR车载液氢杜瓦蒸发率理论与试验研究9.The types of containers in use include the dewar, cryogenic liquid cylinder, and cryogenic storage tank.使用中的容器类型包括杜瓦瓶、低温液体钢瓶和低温储存罐。10.INTERNALLY-THROTTLING LIQUID NITROGEN DEWAR OF COOLING FINGER TYPE AND ITS APPLICATION IN FLUORESCENCE STUDY OF MULTIPLE QUANTUM WELLS内节流式冷指型液氮杜瓦瓶及其在多量子阱荧光研究中的应用11.Study of 50 mW high power helium-cadmium white light laser50毫瓦大功率氦-镉白光激光器的研究12.Phase equilibrium diagram of the liquid helium isotopes mixtures at extremely low temperatures低温下氦-3/氦-4液态混合物相平衡关系13.Regional Centre for Remote Sensing at Ouagadougou瓦加杜古区域遥感中心14.OPTIMAL THERMAL DESIGN OF HELIUM DEWAR WITH LIQUID NITROGEN AND BOIL-OFF HELIUM COOLED SHIELDS具有液氮和蒸发氦气冷却屏的液氦容器的最佳热设计—能量优化法15.Calculation and Analysis of Van der Waals Volume Modifying Value氦的范德瓦尔斯体积修正项的计算与分析16.holds liquid air or helium for scientific experiments.放液体空气或氦气的用于科学试验。17.However, materials must be suitable for use at the extremely low temperatures of liquid helium.材料必须适用于液态氦的极低的温度。18.Experimental Study of the Two Stage Pulse Tube Crycooler which Maintenance Below Liquid Helium T液氦温区两级脉冲管制冷机实验研究相关短句/例句zero evaporation rate dewar零蒸发率液氦杜瓦3)Dewar杜瓦1.Experimental Study on Residual Gas Analysis of Exhausting from Infrared FPA Dewar;红外焦平面杜瓦排气残余气体分析实验研究2.The Thermal and Heat Leak Analyses of Dewar;液氮杜瓦瓶热力与漏热分析4)Liquid helium液氦1.Theoretical research on shock compression properties of liquid helium at high tem高温高密度液氦冲击压缩特性理论研究2.Influence factors on separate two-stage pulse tube cooler working at liqui液氦温区分离型脉管制冷机性能影响因素<parison of calculation methods of limit of superheat temperat液氦极限过热度计算方法比较5)Non-magnetic liquid nitrogen GFRP dewar无磁液氮玻璃钢杜瓦6)Dewar bottle杜瓦瓶，真空瓶(储液氮用)延伸阅读奥杜瓦伊峡谷现代人类最早的直系祖先是“能人”，或称“巧手人”。他们是被称做“南方古猿”的早期人类人猿的后裔，但与之有显著的区别。“能人”的颅骨是圆的，面孔看上去很像人类，脑部体积稍大一些，能直立行走以及用手制造工具。“能人”这一名称是由英国考古学家路易斯·利基创定的，是他首次在坦桑尼亚的奥杜瓦伊峡谷发现了“能人”的遗迹。他发现的只是遗骸的碎片，但他设法鉴定出了这些碎片所属的物种，并根据他们能够制造工具这一特征为之定名为“能手”。1972年，利基的儿子理查德在肯尼亚的特卡那湖附近发现了与“能人”同一类型的遗骸。在那里，利基还发现了一些简单的石制工具，这是迄今为止发现的最古老的石制工具。奥杜瓦伊峡谷的景致。在近50万年中，一条溪流穿过堆积在古遗址上的地层，将古人类骨骼和古代工具的遗迹暴露了出来。在奥杜瓦伊峡谷发现的一个南方古猿化石。其额头低低的，面孔似类人猿。奥杜瓦伊峡谷位于一个古湖遗址上。因峡谷形成于数千年前，遗骸和工具被埋在地层中间，使它成为一个对研究人类最早的祖先有重大价值的遗址。}