1000L卧式液氦供气杜瓦的研制

低温液体储运具有效率高，供气质量好，压力稳定，供气简便及使用安全的特点，液氦供气杜瓦不仅具有常规杜瓦的要求，而且气压可控，本文主要论述了1000L液氦供气杜瓦的工作原理和结构设计，及主要研制工艺和试验情况，介绍了液氦供气系统的特点，产品于1997年9月投入正常使用，全部性能指标达到设计要求，液氦日蒸发率为0．9％。     

GM制冷机在磁共振成像低温恒温器中的应用

旨在降低氦蒸发率的双级ＧＭ制冷机在磁共振成像低温恒温器中应用已有１０多年的历史。本文介绍了美国ＡＰＤ低温公司应用ＧＭ制冷机冷却磁共振成像恒温器冷屏的经验。实践表明，应用这种制冷机，低温恒温器加注液氦的间隔期及维修期延长了，操作可靠性提高，使用成本降低了。     

The problem of current leads in superconducting devices

A method is described for determining the heat flux along electrical leads to a cryostat with liquid helium. Formulas are obtained which enable the heat flux to the liquid helium to be calculated.     

Measurement of the transient heat transfer to liquid helium from a thin metal film

A method to measure transient heat transfer to liquid helium from a thin metal film heater under the condition of pulsed heating during τ ≤ 400 ns is proposed. The experimental equipment used for the measurements is described. The method is based on the comparison of heat pulses transfered from the heater into a monocrystal substrate which is surrounded either by vacuum or by liquid helium. The method can also be used to investigate the heat flux density transmitted into liquid helium over a wide region of thermal loads. Experimental results showing the heat flux density radiated from a Cu heater into liquid helium at 3.8 K as a function of the electric power fed into the heater by pulses of 200–400 ns duration are demonstrated.     

Application of gas oscillation in a tube to pressurization in a liquid helium storage vessel

A novel application of gas oscillation in a tube connected between room and liquid helium temperatures is described. The apparatus is designed to increase the internal pressure in a liquid helium storage vessel, in order to transfer the liquid from the storage vessel to an individual cryostat. The apparatus includes a liquid level meter which can be used even under pressure.     

A cryostat enabling thermal conductivity measurements of specimens deformed plastically at liquid helium temperatures

A new type of cryostat is described which enables tensile plastic deformation of copper alloys at liquid helium temperatures and measurements of thermal conductivity to be made without allowing the samples to age at temperatures above the liquid helium range. The cryostat has also been adapted for residual electricity resistivity measurements.     

AMS-02超导磁体中超流氦加注过程研究

论述了AMS-02超导磁体中超流氦的加注过程,进行了各个环节压降和温降的计算分析,并用图表表示了在不同质量流量加注超流氦工况下管路系统中氦工质的速度、压力、温度和含气量的变化情况.计算结果表明,氦工质从液氦主杜瓦加注到磁体杜瓦的过程中,其压力和温度不断降低,而含气量不断增加.同时也表明在节流阀VVP9中实现了常流氦向超流氦的转变和质量流量的控制.     

A proposed new and quick method for measuring surface tension of liquid helium

Experimental difficulties in measuring the surface tension of liquid helium by the existing methods are discussed. A new, fast and reliable experimental technique for measuring the surface tension of liquid helium is described. The instrument is simple, compact and sensitive for such investigations. The principle of this method is to balance the downward pull due to surface tension on the edges of a glass-slide against the upthrust of liquid helium. The instrumental technique is flexible for modification, to facilitate the measurements of surface tension of other liquified gases and chemicals subjected to various physical conditions     

Liquid pool helium cryopump

A liquid pool helium cryopump, without liquid nitrogen bath, is described. The details of its construction and experimental results are presented.     

Helium cryostats for physical studies in space

The design of liquid helium cryostats intended to operate on-board space apparatus is described. The distinctive features of such cryostats are the presence of a phase separator preventing the ejection of liquid from the helium space, and a special neck support to reduce gas convection in it when the cryostat alters its position in space. Results are given of tests of the designs developed, both under laboratory conditions and in earth satellites.     

Study of a liquid helium jet pump for circulating refrigeration systems

A basic diagram of the refrigeration system, in which liquid helium is circulated by means of a jet pump, is described. The equations have been derived to design jet devices which operate with liquid helium.In the experimental setup with a jet pump the flow rate of liquid was 5 to 10 times larger than that of compressed gas in a direct stream of the refrigerator. After pumping the pressure was equal to (0.15–0.40) × 10⁵Nm^?2. A circulating stream of liquid helium at supercritical pressure, due to the heat load corresponding to the refrigerator capacity, was heated to 0.15–0.25 K.The results of our studies permit one to determine circulation loop parameters and main geometric dimensions of the jet pump.     

Visualisation of Convective Flow Patterns in Liquid Helium

The advantages of using liquid helium as the investigative fluid in Rayleigh-Bénard experiments are reviewed. A low temperature shadowgraphy apparatus is described that permits convective flow pattern visualisation in liquid helium, thus overcoming the main disadvantage until now of using quantum fluids. The factors involved in maximising the optical resolution for both the shadowgraph and schlieren methods are examined for several fluids and this discussion is applied to the low temperature apparatus in assessing its performance. Some preliminary results on pattern formation in liquid helium are presented.     

An apparatus for visualizing continuous flow boiling in liquid helium I

An apparatus is described which is currently being used to observe flow boiling of subcooled and saturated liquid helium in vertical channels.     

Gas-liquid chromatography with a volatile "stationary" liquid phase

A unique type of gas-liquid chromatography is described in which both mobile and "stationary" phases are composed of synthetic mixtures of helium and carbon dioxide. At temperatures below the critical point of the binary mixture and pressures above the vapor pressure of pure liquid carbon dioxide, helium and carbon dioxide can form two immiscible phases over extended composition ranges. A binary vapor phase enriched in helium can act as the mobile phase for chromatographic separations, whereas a CO2-rich liquid in equilibrium with the vapor phase, but condensed on the column wall, can act as a pseudostationary phase. Several examples of chromatographic separations obtained in "empty" capillary columns with no ordinary stationary liquid phase illustrate the range of conditions that produce such separations. In addition, several experiments are reported that confirm the proposed two-phase hypothesis. The possible consequences of the observed chromatographic phenomenon in the field of supercritical fluid chromatography with helium headspace carbon dioxide are discussed.     

An inexpensive liquid helium level sensing unit

Two units to measure the level of liquid helium in a superconducting magnet and in a storage dewar are described.     

A novel cryopump configuration

Liquid helium cooled cryopumps are normally optically opaque to prevent thermal radiation reaching the liquid helium panels whatever the position of the source. A new type of design with either spherical or cylindrical symmetry is described and results obtained with different designs of LN₂ radiation shields are discussed.     

低温贮运设备选型中有关问题的探讨

以一台 15m3 、设计压力为 1 0MPa、粉末真空绝热低温液体贮罐为例 ,分析了用户选型时进行经济性分析的重要性及设计人员对日蒸发率的误解 ;推荐了计算贮运设备单位漏热量的一种反算方法。     

300kW超导单极电机低温技术及试验研究

简述了３００ｋＷ超导单极电机试验的低温系统，介绍了超导单极电机的磁体低温系统及液氦、液氮冷却，输液及运行情况，分析比较了多次试验研究的结果。     

A portable self-contained refrigerants transfer system for use with superconductive magnet dewars

A system which automatically supplies quantities of liquid helium and nitrogen to a portable 16.5 T superconductive magnet facility is described. The problems involved in making the system mobile and dependent only on mains electricity are discussed. Details are presented on how the operation of the system extends the use of a facility which is in heavy demand.     

Design and performance of a liquid helium scintillation polarimeter

A new and improved liquid helium polarimeter has been built and tested. A uniform pulse height response has been achieved over the entire volume of the scintillator. This response depends on the uniformity of the wavelength shifter and the geometry of light collection. An experimental energy resolution of 13% for liquid helium with a ²¹⁰Po alpha source has been achieved. Details of construction and operation are described.