Cryogenic refrigeration methods for low and ultra-low temperatures — a review

In this review, various cryogenic refrigeration methods to obtain temperatures extending down to the milliKelvin/microKelvin range are described after first explaining the concepts of a “thermodynamically ideal cycle” and the “figure of merit”. The various cycles are compared with each other. Data about some of the commercially available refrigerators/cryogenerators have also been included in this review.     

航天器上的氦制冷

综合介绍了氦制冷在航天器中的应用状况。氦制冷的温度低于４Ｋ。８０年代以来，氦制冷在红外天文卫星、空间实验室、空间站、航天飞机所进行的许多与液氦温区有关的实验中得到了成功的应用。介绍了应用状况、低温系统的特性。展望了９０年代航天器中氦制冷的应用前景。     

Analysis of helium II thermal links for instrument cooling in low gravity

The Low Temperature Microgravity Physics Facility (LTMPF) is a reusable, cryogenic facility that will accommodate a series of low temperature experiments to be conducted at the International Space Station. The facility will use a He II cryostat to cool the instruments. Some configurations of the science instruments in the cryostat will require an enhanced thermal link between the He II bath and parts of the instruments. Such an enhanced link can be made with plumbing filled with He II. This paper reports the results of analysis that was performed using the BATC proprietary helium flow software called SUPERFLO, on four different concepts for this link. The four concepts analyzed were: a simple tube with the heated end closed, a closed end tube with a porous plug at its entrance, a closed end tube filled with capillary tubes, and a porous plug driven flow loop. It was found that the concepts that used a porous plug were more robust since they were much less prone to boiling. This is due to the low gravity which causes all of the liquid in helium tank and plumbing to be very close to saturated conditions unless a porous plug is used to create a thermomechanical pressure. The effects of varying system parameters such as a acceleration, heat flux, pore size and tube size were also investigated and the results are reported.     

Working with non-cryogenic Hall sensors at 77 K

In this work we show the possibility of using non-cryogenic Hall sensors at cryogenic temperatures. To avoid the instabilities at cryogenic temperatures, 9 non-cryogenic Hall sensors are connected to the different channels of a multimeter and the average measurement is obtained as the truthful value. It is demonstrated that the average value is very close to the value obtained for a cryogenic sensor and opens the possibility of using these set of sensors instead of a cryogenic single one.     

ADR design for the Soft X-ray Spectrometer instrument on the Astro-H mission

In its instrument suite, the Japanese Astro-H mission will include the Soft X-ray Spectrometer (SXS), whose 36-pixel detector array of ultra-sensitive X-ray microcalorimeters will be cooled to 50 mK. This will be accomplished using a two-stage adiabatic demagnetization refrigerator (ADR). A complicating factor for its design is that the ADR will be integrated into a superfluid helium dewar at 1.3 K that will be coupled to a 1.8 K Joule-Thomson (JT) stage through a heat switch. When liquid helium is present, the coupling will be weak, and the JT stage will act primarily as a shield to reduce parasitic heat loads. When the liquid is depleted, the heat switch will couple more strongly so that the ADR can continue to operate using the JT stage as its heat sink. A two-stage ADR is the most mass efficient option and it has the operational flexibility to work well with a stored cryogen and a cryocooler. The ADR’s design and operating modes are discussed, with emphasis on how they reflect the capabilities and limitations of the hybrid cryogenic system.     

两用技术的发展动态

介绍了两用技术的发展状况。说明了９０年代美国国家航空航天局的最重要的两用技术。简要介绍了一些与真空、低温有关的两用技术。     

磁制冷器

磁制冷是一种以磁热效应为基础的制冷方法.最早是由德国物理学家于1880年发现。早期用于制取极低的温度。近年来,室温磁制冷取得了较大的突破,已经研制出适合家用的磁制冷冰箱,同时由于它的制冷系数高和对大气的全球气候变暖影响小等优点,将成为一种很有发展前途的制冷方式。本文论述磁制冷和磁制冷冰箱的基本原理。     

磁制冷技术研究现状

分析了磁制冷的热力学原理和常用的磁制冷循环过程，重点评述了室温磁制冷样机的研究进展及发展前景。     

A simple and efficient thermal link assembly for cryocoolers

The thermal connection between a cryocooler cold tip and any object to be cooled (the thermal load) is very often a technical challenge. The allowed mechanical load on the cooler cold finger is generally strongly restricted. It is therefore difficult to design a mechanically anchored thermal link with low induced mechanical load and high thermal conductance. The proposed heat link concept is based on an evaporation/condensation process between the cooler cold tip and the thermal load.     

SIRTF cryostat requirements and development

The Space Infrared Telescope Facility (SIRTF) is the last of NASA’s four great observatories, scheduled for launch in 2001. At the heart of the SIRTF observatory is a 363 l, superfluid helium cryostat, designed and built by Ball Aerospace & Technologies, Inc. The cryostat houses provides the direct cooling of the three scientific instruments which will observe the infrared universe. One major innovation of the SIRTF observatory is that the instrument optics are launched warm, and cooled down on orbit to the final operating temperature of 5 K by radiation to space and direct vapor cooling by the effluent helium. To accomplish this the cryostat system design includes two cryogenic mechanisms, and must meet stringent cold alignment requirements, in addition to the thermal and mechanical performance requirements typical for space flight cryostats. Currently the cryostat is completing the fabrication and assembly process, and will go into performance testing as a system in the second half of 1999. We present here the design requirements, production development of the SIRTF cryostat, and the predicted ground and on-orbit performance.     

A magnet system design for reduced gravity environment

Simulating a reduced gravity environment experienced in spaceships in a laboratory setting for studying different technical aspects (fluid transfer or propellant behavior, for example) is a primordial step prior to extraterrestrial explorations. We first present some results on boiling heat transfer in helium under reduced gravity using a commercial magnet and point out the limitations in volume and magnetic force homogeneity to perform reduced gravity experiments with such a non ad hoc magnet. Then, we present a new magnetic design to create a reduced gravity environment in large volume suitable for boiling test experiments in oxygen. Based on a modified design we present the magnetic configurations that allow compensating gravity for different elements such as hydrogen, water or helium but in smaller volumes. We detail the different aspects of winding techniques to achieve the requirements on magnetic force.     

Magnetocaloric Effect in MnCo_(1-x)Al_xGe Compounds

The effects of substitution of Al for Co on magnetic and magnetocaloric properties of MnCo1-xAlxGe (x=0.00, 0.03, 0.05, 0.08, 0.10, 0.13, 0.15, and 0.20) compounds have been investigated by X-ray diffraction (XRD) and magnetization measurements. XRD exhibits that MnCo1-xAlxGe compounds crystallize in the orthorhombic TiNiSi-type structure for x≤0.03 and in the hexagonal Ni2In-type crystal structure for x>0.03. Magnetic measurements show that the Curie temperature can be tuned between 286 and 347 K by changi...     

磁制冷技术商品化开发的可行性探索

本文利用最新的国外资料 ,对新型的磁制冷技术商品化开发中存在的一些问题进行了探讨 ,指出磁制冷材料和热交换技术是磁制冷技术商品化开发的主要难关并提出了解决这两个难关的探索性方案。     

The fast alternative cryogenic experiment testbed

Subsystems for a “proof of concept” cryogenic payload have been developed to demonstrate the ability to accommodate low temperature science investigations within the constraints of the Hitchhiker siderail (HH-S) carrier on the Space Shuttle. These subsystems include: a hybrid solid neon – superfluid helium cryostat, a multi-channel Versa Modular European (VME) architecture Germanium Resistance Thermometer (GRT) readout and heater control servo system, and a multiple thermal isolation stage “probe” for thermal control of helium samples. The analysis and tests of these subsystems have proven the feasibility of a cryogenic HH-S carrier payload.     

磁制冷循环分析

磁制冷循环是磁制冷技术中的重要环节,为磁制冷机的高效运行提供了理论基础.本文结合磁制冷循环的理论研究,详细介绍了磁制冷基本循环和活性蓄冷器(Active Magnetic Regenerator,AMR)循环,重点分析了影响循环的不可逆因素,并对磁制冷循环的发展进行了展望.     

Numerical analysis of active magnetic regenerators for hydrogen magnetic refrigeration between 20 and 77 K

A model active magnetic regenerator refrigerator (AMR) with the Brayton-like operation cycle was analyzed by numerical cycle simulation in the temperature range between 20 and 77 K. In order to study the performance using magnetic material with various transition temperatures T_c, entropy of magnetic material with second order phase transition was calculated using mean field theory and Debye approximation. The cooling performance is shown to be high when the heat exhaust temperature is close to the transition temperature. It is shown that the optimized operation condition depends on both T_c and operation temperatures. Multi-layered AMR beds were shown to improve the performance of AMR. Multi-stage AMR was also discussed.