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• A two-stage adiabatic demagnetization refrigerator is built with GGG as the first stage and CPA as the second stage. • A 3D printed PEEK suspension system is used at the second stage. • A no-load lowest temperature of 66.1 mK is achieved at the second stage when starting from 1 K@4 T. • Simulations estimate each PEEK suspension has a 1.10 μW thermal leak between 4 K and 0.3 K and a further reduction with a 1 K heat sink in the middle. • Experiments validate the effectiveness of 1 K heat sink. The salt pill suspensions play a critical role in determining the performance of adiabatic demagnetization refrigerators (ADR). Kevlar suspensions are commonly used to hold the salt pill in place and to minimize the thermal leak. However, traditional solutions such as tensioning the Kevlar and fixing it on mechanical frame with the help of epoxy or running it around a pulley are quite challenging. This paper presents an innovative suspension using 3D printing technology and a polyether ether ketone (PEEK) multi-ring suspension has been designed and tested. Numerical analysis shows that a single piece of the suspension may contribute about 1.10 μW thermal leak between 4 K and 0.3 K. To test its performance, a two-stage ADR is built with Gadolinium Gallium Garnet (GGG) as the first stage and chromium potassium alum (CPA) salt pill as the second stage which is supported by the PEEK suspension. The GGG stage is mainly used to provide an initial temperature for CPA stage. Typically, starting from 1 K@4 T, a no-load lowest temperature of 66.1 mK is achieved at a demagnetization rate of 0.005 T/s in the experiments. The thermal leak of the PEEK suspension with and without 1 K heat sink has been analyzed and compared, with the former one showing a big reduction of the thermal leak. This paper confirms the feasibility of PEEK as an ADR suspension material and provides a potential 3D printing method for complex suspension designs. [ABSTRACT FROM AUTHOR]

• A low-cost copper-foam based salt pill is designed and manufactured. • A test from 4.3 K @ 4 T with a demagnetization rate of 0.0025 T/s leads to a no-load temperature of 176.5 mK. • Eddy current loss may be an issue with a high demagnetization rate. • Selection of the copper form parameters needs more investigation. Hydrated paramagnetic salt pills are important components in an adiabatic demagnetization refrigerator (ADR) for temperatures below 500 mK. To improve the heat transfer performance between salt crystals and external thermal links, thermal buses are commonly employed inside the salt pill. Common forms of thermal buses are either thin copper pillars made from electric discharge machining (EDM) or wire bundles, both of which generally involve considerable machining or labor. This paper introduces a novel design and fabrication of a simple foam copper-based paramagnetic salt pill. The foam copper has 30 pores per inch (PPI), a porosity of 98 %, 0.005 m2/g specific surface area, and an estimated pore diameter of 0.82 mm. The complete design, assembling process, and growth of the foam copper-based chromium potassium alum (CPA) salt pill (40 mm in length and 23 mm in diameter) are introduced. A single-stage ADR is built based on this salt pill to test its performance, while another salt pill with the wire thermal bus has also been tested for comparison. A typical cool-down from 4.3 K @ 4 T with a demagnetization rate of 0.0025 T/s led to a no-load temperature of 176.5 mK, slightly better than that using a wire thermal bus. In terms of cooling power per gram of salt, the cooling capacities at 600 mK of both salt pills have also been measured and both have shown similar performance. This preliminary study has shown the potential of the foam copper-based salt pill though more research is required to optimize its performance. [ABSTRACT FROM AUTHOR]

Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report some practical aspects concerning the application of La(Fe, Co)13−x Si x based materials in the magnetic cooling technology. For this purpose, two blocks of La(Fe, Co)13−x Si x with different Curie temperature were considered for this study. Before implementing the new refrigerants in the magnetic cooling machine, we have measured directly their magnetocaloric properties in practical conditions around room temperature. The obtained magnetocaloric effect values were corrected taking into account the demagnetization effect. The influence of the demagnetization field on the magnetocaloric performances of La(Fe, Co)13−x Si x is analyzed and discussed. A composite material based on La(Fe, Co)13−x Si x compounds was tested directly in our recently developed magnetic cooling system and a comparison with the gadolinium was made. Encouraging results were obtained showing the high potential of the studied materials in magnetic cooling application. In addition, the poor corrosion resistance of the intermetallics can compromise the potential of these materials. In this paper, we also present the corrosion tests performed on different samples of La(Fe, Co)13−x Si x using several heat transfer fluids. [Copyright &y& Elsevier]

Highlights • The mechanism of multi-bypass was numerical studied. • Multi-bypass has the functions of orifice and double-inlet, making it like two-stage cryocooler. • A minimum no-load temperature 3.7 K was obtained, and the cooling power was 14 mW@4.2 K. • New mK cooling chain for HUBS satellite was proposed and analyzed. Abstract The Vuilleumier (VM) type pulse tube cryocooler (VPTC) is a new kind of 4 K cryocooler which had been experimentally verified. This paper presents the recent advances on a 4 K VPTC in our laboratory. First, the mechanism of multi-bypass was numerically studied using Sage software. The results showed that the function of the multi-bypass is not only similar to a double-inlet, but also to an orifice, which makes the VPTC work like a two-stage cryocooler. Based on the simulation results, the performance of VPTC was experimentally studied. Under its optimal operating conditions, a no-load temperature of 3.7 K has been obtained, which is the first demonstration of a single-stage VPTC obtaining temperatures below 4 K. It can supply about 14mW cooling power at 4.2 K and about 100 mW cooling power at 35 K simultaneously, which has potential application as the pre-cooler for an adiabatic demagnetization refrigerator (ADR). Finally, based on this VPTC, a new mK cooling chain for HUBS (Hot Universe Baryon Surveyor) satellite is proposed and its prospect has also been theoretically analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The noise-flatness-induced hypersensitive transport of overdamped Brownian particles in a tilted periodic sawtooth potential driven by a multiplicative nonequilibrium three-level noise and additive white noise is considered. The study is a follow-up of one of our earlier papers on trichotomous-noise-induced hypersensitive transport [Mankin et al., Phys. Rev. E 68 (2003) 011105]. In the current paper the exact formula for the stationary current is presented. All the physical results discussed are computed by means of the exact formula. It is demonstrated that (i) at low temperatures the enhancement of current is hypersensitive to the applied small static tilting force, (ii) the stationary macroscopic current has a bell-shaped dependence on the parameters, correlation time and flatness, of multiplicative noise which occurs even in the case of large (compared to the ultrasmall DC signal) additive thermal noise, and (iii) at low temperatures and small values of the switching rate, the differential mobility as a function of the tilting force has local minima in a finite range of the force. Implications of the case of multiplicative trichotomous noise are compared with the results of a deterministic square-wave stimulus. [Copyright &y& Elsevier]

ASTRO-H was an X-ray astronomy satellite that the Japan Aerospace Exploration Agency (JAXA) developed to study the evolution of the universe and physical phenomena yet to be discovered. The primary scientific instrument of ASTRO-H was the Soft X-ray Spectrometer (SXS). Its detectors were to be cooled to 50 m K using a complex cryogenic system with a multistage adiabatic demagnetization refrigerator (ADR) developed by the National Aeronautics and Space Administration (NASA), and a cryogenic system developed by Sumitomo Heavy Industries, Ltd. (SHI). SHI’s cryogenic system was required to cool the ADR’s heatsink to 1.3 K or less in orbit for three years or longer. To meet these requirements, SHI developed a hybrid cryogenic system consisting of a liquid helium tank, a 4 K Joule-Thomson cooler, and two two-stage Stirling coolers. ASTRO-H was launched from Tanegashima Space Center on February 17, 2016. The initial operation of the SXS cryogenic system in orbit was completed successfully. The cooling performance was as expected and could have exceeded the lifetime requirement of three years. This paper describes results of ground tests, results of top-off filling of superfluid liquid helium just before launch, and cooling performance in orbit. [ABSTRACT FROM AUTHOR]

A 3-stage adiabatic demagnetization refrigerator (ADR) (Shirron et al., 2012) is used on the Soft X-ray Spectrometer instrument (Mitsuda et al., 2010) on Astro-H (Takahashi et al., 2010) [3] to cool a 6 × 6 array of X-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system (Fujimoto et al., 2010) consisting of a superfluid helium tank, a 4.5 K Joule–Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes. [ABSTRACT FROM AUTHOR]

The performance of a fast thermal response miniature Adiabatic Demagnetisation Refrigerator (ADR) is presented. The miniature ADR is comprised of a fast thermal response Chromium Potassium Alum (CPA) salt pill, two superconducting magnets and unconventionally, a single crystal tungsten magnetoresistive (MR) heat switch. The development of this ADR is a result of the ongoing development of a continuously operating millikelvin cryocooler (mKCC), which will use only magnetoresistive heat switches. The design and performance of the MR heat switch developed for the mKCC and used in the miniature ADR is presented in this paper; the heat switch has a measured Residual Resistivity Ratio of 32,000 ± 3000 and an estimated switching ratio (on thermal conductivity divided by the off thermal conductivity) of 15,200 at 3.6 K and 38,800 at 0.2 K when using a 3 T magnetic field. The performance of the miniature ADR operating from a 3.6 K bath is presented, demonstrating that a complete cycle (magnetisation, cooling to the bath and demagnetisation) can be accomplished in 82 s. A magnet current step test, conducted when the ADR is cold and fully demagnetised, has shown the thermal response of the ADR to be sub-second. The measured hold times of the ADR with just parasitic heat load are given, ranging from 3 min at 0.2 K with 13.14 μW of parasitics, to 924 min at 3 K with 4.55 μW of parasitics. The cooling power has been measured for operating temperatures in the range 0.25–3 K by applying an additional heat load to the ADR via a heater, in order to reduce the hold time to 3 min (i.e. approximately double the recycle time); the maximum cooling power of the miniature ADR (in addition to parasitic load) when operating at 250 mK is 20 μW, which increases to 45 μW at 300 mK and continues to increase linearly to nearly 1.1 mW at 3 K. To conclude, the predicted performance of a tandem continuous ADR utilising two of the miniature ADRs is presented. [ABSTRACT FROM AUTHOR]

The adiabatic demagnetization refrigerator (ADR) system in this paper is composed of a conduction-cooled current cycling high-temperature superconducting (HTS) magnet system, a magnetic bed assembly, its heat exchange parts and an auxiliary precooling stage (a commercial GM cryocooler and a liquid nitrogen vessel). The whole magnetic refrigeration system including the conduction-cooled HTS magnet is cooled by the precooling stage to absorb the rejection heat of the ADR cycle. The packed bed type magnetic bed consists of tiny irregular powders of Dy 0.9 Gd 0.1 Ni 2 enclosed in a thin walled stainless steel container (22.2 mm in O.D., 0.3 mm in thickness and 40.0 mm in height). The precooled heat transfer fluid (helium) travels through the magnetic material when heat rejection is required; otherwise the helium stagnates within its pores (pseudo-adiabatic process). Flow of the heat transfer fluid substitutes for the function of a traditional heat switch, creating, essentially, a forced-convection type heat switch. The magnetic bed assembly is periodically magnetized and demagnetized at the center of the conduction-cooled HTS magnet which can stably generate both strong and alternating magnetic field from 0 T to 3.0 T (0–130 A) with an average ramp rate of 0.24 T s −1 . The cooling capacities of the ADR system at 20 K which is the normal boiling point (NBP) of hydrogen, are 11.1 J cycle −1 , 6.3 J cycle −1 and 1.9 J cycle −1 when the temperature spans are 1 K, 2 K and 3 K, respectively. We describe the detailed construction of the ADR system and discuss the test results with the operational parameters (the entrained helium pressure, the mass flow rate of helium and the operating temperature span) in the 20 K region. [ABSTRACT FROM AUTHOR]

The Soft X-ray Spectrometer (SXS) is one of four instruments on the Japanese Astro-H mission, which is currently planned for launch in late 2015. The SXS will perform imaging spectroscopy in the soft X-ray band (0.3–12 keV) using a 6 × 6 pixel array of microcalorimeters cooled to 50 mK. The detectors are cooled by a 3-stage adiabatic demagnetization refrigerator (ADR) that rejects heat to either a superfluid helium tank (at 1.2 K) or to a 4.5 K Joule–Thomson (JT) cryocooler. Four gas-gap heat switches are used in the assembly to manage heat flow between the ADR stages and the heat sinks. The engineering model (EM) ADR was assembled and performance tested at NASA/GSFC in November 2011, and subsequently installed in the EM dewar at Sumitomo Heavy Industries, Japan. During the first cooldown in July 2012, a failure of the heat switch that linked the two colder stages of the ADR to the helium tank was observed. Operation of the ADR requires some mechanism for thermally linking the salt pills to the heat sink, and then thermally isolating them. With the failed heat switch unable to perform this function, an alternate plan was devised which used carefully controlled amounts of exchange gas in the dewar’s guard vacuum to facilitate heat exchange. The process was successfully demonstrated in November 2012, allowing the ADR to cool the detectors to 50 mK for hold times in excess of 10 h. This paper describes the exchange-gas-assisted recycling process, and the strategies used to avoid helium contamination of the detectors at low temperature. [ABSTRACT FROM AUTHOR]

Adiabatic Demagnetization Refrigerator (ADR) is an efficient way to obtain sub-Kelvin temperatures in space environments. The SAFARI instrument for the Japanese spaceborne SPICA mission features detectors which will be cooled down to 50 mK. This cooling will be done by a hybrid cooler comprising a 300 mK sorption stage and a 50 mK ADR stage. For this cooler and ADR in general, the main contribution to the overall mass is in the magnetic system and particularly in the magnetic shielding required to keep the stray field within acceptable values. In order to reduce this mass, superconducting materials can be used as active magnetic shields thanks to un-attenuated eddy currents generated while ramping the magnet current. In this way they could reduce the need of heavy ferromagnetic material shields and increase the shielding efficiency to reach very low parasitic values. In the framework of SAFARI we have built a numerical model of a superconductor magnetic shield. The good results regarding the weight gain lead us to an experimental confirmation. In this paper we present an experimental study on MgB 2 and NbTi superconducting materials. 2 pairs of rings of typical diameter of 80 mm have been tested using a superconducting magnet matching closely the dimensions of the SAFARI ADR cooler. The magnetic shielding measurements have been compared to a numerical model. [ABSTRACT FROM AUTHOR]

This paper discusses the fabrication of a (RE)BCO solenoid magnet and its experimental results from the aspect of AC loss and thermal characteristics. A (RE)BCO coated conductor with polyimide tape insulation was utilized for a coil and wound by a standard layer-wound method. The (RE)BCO solenoid magnet consists of a stainless steel bore and a pair of OFHC copper supporting plates assembled at both ends. The coil winding has a novel thermal drain structure that can withstand high AC thermal loads generated externally and internally. The OFHC copper strips were installed between the interlayers in the perpendicular direction to the (RE)BCO conductor winding to mitigate both thermal resistance in the axial direction of the (RE)BCO coil and eddy current loss by an external magnetic field. Apiezon® N grease with hexane solution was applied on the entire (RE)BCO coil winding to minimize thermal contact resistance between the conductor and the OFHC copper strips. The (RE)BCO coil carried 150 A at 14.7 K and generated 3.5 T at the center of the coil. A sinusoidal current waveform (operating frequency from 0.1 Hz to 1.0 Hz) was applied with peaks of 25 A, 50 A, and 70 A (the corresponding magnetic field of 0.54 T, 1.08 T, and 1.54 T) and the corresponding AC losses were measured by both calorimetric and electrical methods. The AC losses measured by both methods were in good agreement. The experimental results were compared with theoretical and numerical solutions. [ABSTRACT FROM AUTHOR]

The performance of an adiabatic demagnetization refrigerator (ADR) is critically dependent on the design and construction of the salt pills that produce cooling. In most cases, the primary goal is to obtain the largest cooling capacity at the low temperature end of the operating range. The realizable cooling capacity depends on a number of factors, including refrigerant mass, and how efficiently it absorbs heat from the various instrument loads. The design and optimization of "salt pills" for ADR systems depend not only on the mechanical, chemical and thermal properties of the refrigerant, but also on the range of heat fluxes that the salt pill must accommodate. Despite the fairly wide variety of refrigerants available, those used at very low temperature tend to be hydrated salts that require a dedicated thermal bus and must be hermetically sealed, while those used at higher temperature - greater than about 0.5K - tend to be single- or poly-crystals that have much simpler requirements for thermal and mechanical packaging. This paper presents a summary of strategies and techniques for designing, optimizing and fabricating salt pills for both low- and mid-temperature applications. [ABSTRACT FROM AUTHOR]

Adiabatic demagnetization refrigerators (ADR), based on the magnetocaloric effect, are solid-state coolers that were the first to achieve cooling well into the sub-kelvin regime. Although supplanted by more powerful dilution refrigerators in the 1960s, ADRs have experienced a revival due to the needs of the space community for cooling astronomical instruments and detectors to temperatures below 100mK. The earliest of these were single-stage refrigerators using superfluid helium as a heat sink. Their modest cooling power (<1μW at 60mK [1]) was sufficient for the small (6×6) detector arrays [2], but recent advances in arraying and multiplexing technologies [3] are generating a need for higher cooling power (5-10μW), and lower temperature (<30mK). Single-stage ADRs have both practical and fundamental limits to their operating range, as mass grows very rapidly as the operating range is expanded. This has led to the development of new architectures that introduce multi-staging as a way to improve operating range, efficiency and cooling power. Multi-staging also enables ADRs to be configured for continuous operation, which greatly improves cooling power per unit mass. This paper reviews the current field of adiabatic demagnetization refrigeration, beginning with a description of the magnetocaloric effect and its application in single-stage systems, and then describing the challenges and capabilities of multi-stage and continuous ADRs. [ABSTRACT FROM AUTHOR]

Adiabatic Demagnetization Refrigerators (ADR) have many advantages that are prompting a resurgence in their use in spaceflight and laboratory applications. They are solid-state coolers capable of very high efficiency and very wide operating range. However, their low energy storage density translates to larger mass for a given cooling capacity than is possible with other refrigeration techniques. The interplay between refrigerant mass and other parameters such as magnetic field and heat transfer points in multi-stage ADRs gives rise to a wide parameter space for optimization. This paper first presents optimization strategies for single ADR stages, focusing primarily on obtaining the largest cooling capacity per stage mass, then discusses the optimization of multi-stage and continuous ADRs in the context of the coordinated heat transfer that must occur between stages. The goal for the latter is usually to obtain the largest cooling power per mass or volume, but there can also be many secondary objectives, such as limiting instantaneous heat rejection rates and producing intermediate temperatures for cooling of other instrument components. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a new type of reciprocating magnetic refrigerator working with high remanence permanent magnets as the source of the magnetic field is presented. The simulated and measured magnetic field at the machine air gap is about 1.45T. Initially, gadolinium metal (Gd) was used as the magnetocaloric refrigerant. Its magnetocaloric performances and its quality were checked experimentally in a developed test bench. To attain high values of temperature difference between the hot and the cold sources (temperature span), a new design of the Active Magnetic Refrigeration (AMR) cycle was implemented. However, in order to reduce the energy consumption and then increase the thermodynamic performances of the magnetic system, a special configuration of the magnetocaloric materials is developed. The numerical results of the applied magnetic forces on the new configuration are given and analysed. The developed machine is designed to produce a cooling power between 80 and 100W with a temperature span larger than 20K. The obtained results demonstrate that magnetic cooling is a promising alternative to replace traditional systems. [Copyright &y& Elsevier]

Abstract: The primary objective of this paper is to quantify the impact of the internal magnetic field and reversibility of the magnetocaloric effect on the numerical evaluation of the thermal performance of a parallel-plate active magnetic regenerator. To this end, direct measurements of the adiabatic temperature change of commercial-grade gadolinium samples were carried out for an applied field change of 1.65 ± 0.03 T (for both magnetization and demagnetization) and temperatures between 283 and 303 K. The tests were carried out in a specially constructed apparatus and the results were in good agreement with the literature. The data were incorporated into a mathematical model for solving the fluid flow and conjugated heat transfer in the parallel-plate regenerator. It was found that if demagnetization phenomena (i.e., the demagnetization factor and the reversibility of the magnetocaloric effect) are not take properly into account, the thermal performance of the regenerator can be severely over-predicted. [Copyright &y& Elsevier]

Abstract: The X-ray micro-calorimeter array in the Soft X-ray Spectrometer (SXS) instrument on Astro-H will be cooled by a 3-stage adiabatic demagnetization refrigerator (ADR). The ADR consists of two mechanically independent assemblies. When integrated with a mounting structure and the detector assembly, they form a self-contained unit that will be inserted into the top end of a liquid helium tank. The unique configuration requires many components and sub-assemblies to be thermally isolated from their structural mount. Normally in an ADR this is limited to suspending cold salt pills within their (much warmer) magnets, but in the case of SXS, it also involves one ADR stage being supported by, but thermally isolated from, the helium tank. This paper will describe the complex thermal and mechanical design of the SXS ADR, and summarize vibration and mechanical properties tests that have been performed to validate the design. [Copyright &y& Elsevier]

Abstract: The Japanese Astro-H mission will include the Soft X-ray Spectrometer (SXS) instrument provided by NASA/GSFC. The SXS will perform imaging spectroscopy in the soft X-ray band using a 6×6 array of silicon microcalorimeters operated at 50mK. The detectors will be cooled by a 3-stage adiabatic demagnetization refrigerator (ADR). The configuration allows the ADR to operate with both a 1.3K superfluid helium bath and a 4.5K cryocooler as its heat sink. Initially, when liquid helium is present, the two coldest stages of the ADR will operate in a single-shot mode to cool the detectors from 1.3K. During this phase of the mission, the 3rd stage may be used to reduce the net heat load on the liquid helium and extend its lifetime. When the liquid is depleted, the 2nd and 3rd stages will operate in a continuous mode to maintain the helium tank at about 1.3K, allowing continued operation of the 1st stage (in a single-shot mode) and hence the SXS instrument. This paper describes the design and operating modes of the ADR, as well as details of critical components. [Copyright &y& Elsevier]

Abstract: CEA/SBT is currently testing a 50mK cooler developed in the framework of a European Space Agency Technological Research Program targeted for the Advanced Telescope for High Energy Astrophysics space mission. This cooler is composed of a small demagnetization refrigerator pre cooled by a sorption cooler stage. This Engineering Model is able to produce 1μW of net heat lift at 50mK and an additional 10μW at 300mK provided by the sorption cooler stage. The autonomy of the cooler is 24h, and once the low temperature phase at 50mK is over, it can be recycled in about 8h with 10μW and 100μW available at respectively the 2.5 and 15K heat sinks. These performances are in agreement with the European Space Agency requirements. In this paper, we present the detailed thermal performances of the cooler in nominal conditions as well as sensitivity measurements of the variation of the heat sink and the cold end temperatures. [Copyright &y& Elsevier]

Abstract: The Primordial Inflation Explorer (PIXIE) is a proposed mission to densely map the polarization of the cosmic microwave background. It will operate in a scanning mode from a sun-synchronous orbit, using low temperature detectors (at 0.1K) and located inside a telescope that is cooled to approximately 2.73K – to match the background temperature. A mechanical cryocooler operating at 4.5K establishes a low base temperature from which two adiabatic demagnetization refrigerator (ADR) assemblies will cool the telescope and detectors. To achieve continuous scanning capability, the ADRs must operate continuously. Complicating the design are two factors: (1) the need to systematically vary the temperature of various telescope components in order to separate the small polarization signal variations from those that may arise from temperature drifts and changing gradients within the telescope, and (2) the orbital and monthly variations in lunar irradiance into the telescope barrels. These factors require the telescope ADR to reject quasi-continuous heat loads of 2–3mW, while maintaining a peak heat reject rate of less than 12mW. The detector heat load at 0.1K is comparatively small at 1–2μW. This paper will describe the 3-stage and 2-stage continuous ADRs that will be used to meet the cooling power and temperature stability requirements of the PIXIE detectors and telescope. [Copyright &y& Elsevier]

Abstract: In this paper, we have studied the magnetic and magnetocaloric properties of the perovskite manganite Pr0.55Sr0.45MnO3. It shows a sharp paramagnetic–ferromagnetic phase transition at 291K and possesses a moderate magnetic entropy change near room temperature. In addition, a large relative cooling power (143.64J/kg) and a wide temperature range (84K) have been found in this material. Compare with the Landau model, we find that the itinerant electrons mainly contribute the larger magnetic entropy change at paramagnetic region. [Copyright &y& Elsevier]

Abstract: This paper presents a numerical study of natural convection cooling of two heat sources vertically attached to horizontal walls of a cavity. The right opening boundary is subjected to the copper–water nanofluid at constant low temperature and pressure, while the other boundaries are assumed to be adiabatic. The governing equations have been solved using the finite volume approach, using SIMPLE algorithm on the collocated arrangement. The study has been carried out for the Rayleigh number in the range 104 ≤Ra≤107, and for solid volume fraction 0≤φ≤0.05. In order to investigate the effect of heat source location, three different placement configurations of heat sources are considered. The effects of both Rayleigh numbers and heat source locations on the streamlines, isotherms, Nusselt number are investigated. The results indicate that the flow field and temperature distributions inside the cavity are strongly dependent on the Rayleigh numbers and the position of the heat sources. The results also indicate that the Nusselt number is an increasing function of the Rayleigh number, the distance between two heat sources, and distance from the wall. In addition it is observed that the average Nusselt number increases linearly with the increase in the solid volume fraction of nanoparticles. [Copyright &y& Elsevier]

Abstract: This paper describes the design, development and performance of the engineering model double adiabatic demagnetization refrigerator (dADR) built and tested under contract to the European Space Agency for its former mission XEUS (now IXO). The dADR operates from a 4K bath and has a measured recycle and hold time (with a parasitic load of 2.34μW) at 50mK of 15h and 10h, respectively. It is shown that the performance can be significantly improved by operating from a lower bath temperature and replacing the current heat switches with tungsten magnetoresistive (MR) heat switches, which significantly reduce the parasitic heat load. Performing the latter gives an anticipated recycle and hold time of 2 and 29h (with a 1μW applied heat load in addition to the parasitic load), respectively. Such improved performance allows for a reduction in mass of the dADR from 32kg to 10kg by operating from a 2.5K bath (which could be reduced further by optimising the magnet design). Ultimately, continuous operation could be achieved by linking two dADRs to a common detector stage and operating them alternately. Based on this design the mass of the continuous ADR is estimated to be about 4.5kg. [ABSTRACT FROM AUTHOR]

Abstract: Cryocoolers’ vibrations prevent them from being used in some sensitive applications. Stopping the cryocooler even for a short period gives rise to a steep drift of temperature. Such a drift can be significantly attenuated by adding an enthalpy reservoir to the cryocooler, separated from its cold finger by a heat switch. The whole assembly for the enthalpy reservoirs and switch is here called ESU, the energy storage unit. Two units have been built and tested based on solid state materials. One unit was designed to work up to 20K, the other up to 6K. This paper presents the experimental results obtained for both ESUs. Lead was used for the 20K ESU while the ceramic GOS (Gd2O2S) was found adequate for the 6K ESU. After stopping the cryocooler, a fairly slow temperature drift was measured at each ESU (from 11 to 20K or from 3 to 6K, respectively) while applying 10mW for one hour, for instance. Otherwise, a temperature controlled platform experiment can use an ESU as a cold source allowing a constant temperature. Input power to the ESUs was monitored along with temperature and time. In the case of the 20K ESU, calculations match the stored amount of energy as well as the temperature drift of the energy reservoir. A study for a high enthalpy intercept at the middle of the switch is also presented here. This intercept shall allow the attenuated temperature drift to hold for longer times. A cryogenic experiment can then be carried on using a cryocooler in a completely silent environment. [ABSTRACT FROM AUTHOR]

Abstract: The Halbach cylinder is a construction of permanent magnets used in applications such as nuclear magnetic resonance apparatus, accelerator magnets and magnetic cooling devices. In this paper the analytical expression for the magnetic vector potential, magnetic flux density and magnetic field for a two dimensional Halbach cylinder are derived. The remanent flux density of a Halbach magnet is characterized by the integer p. For a number of applications the force and torque between two concentric Halbach cylinders are important. These quantities are calculated and the force is shown to be zero except for the case where p for the inner magnet is one minus p for the outer magnet. Also the force is shown never to be balancing. The torque is shown to be zero unless the inner magnet p is equal to minus the outer magnet p. Thus there can never be a force and a torque in the same system. [Copyright &y& Elsevier]

Abstract: Active magnetic regenerative refrigeration cycle is nowadays investigated in magnetic refrigeration prototypes in order to increase the temperature span between the Hot source and the Cold one. The AMRR model can give the magnetothermal behaviour of the regenerative refrigerant bed and the system cooling power considering the geometrical and the physical properties of the fluid and the material. In this paper an inverse approach is considered. Starting from the system performance required (cooling power, temperature profile, etc.); we go up by optimisation processes to the dimensions of the system. Let''s consider for example, a desired temperature profile. These curves are called the characteristics of the system. The dimensions of the system can be found out by using temperature characteristics for different geometrical configurations of the bed. In addition, the optimisation can be performed under external constraints, i.e. limited variation band of the parameters. When obtained, the results can be used to optimise the whole shape of the system. [Copyright &y& Elsevier]

Abstract: In the RACE (reactor–accelerator coupling experiments) project, a series of ADS (accelerator driven system) experiments are envisaged for the study of the coupling of a neutron source with sub-critical reactors. In these experiments, a continuous electron beam impacts on an actively cooled solid target where it is converted through photonuclear reactions in a neutron flux, able to feed the reactor. In a RACE foreseen ‘high power’ phase, where the beam power would be enhanced from 1 to about 30kW, the target would be submitted to very severe conditions both from the mechanical and the thermal points of view. In this paper, the development of a new concept of uranium target is described with detailed neutron production analyses, power deposition distributions, thermo-mechanical simulations and cooling schemes. Two possible solutions are envisaged in order to control the power deposition distribution. [Copyright &y& Elsevier]

Abstract: In this paper, syngas (hydrogen and carbon monoxide) production was investigated by a numerical model of an adiabatic monolithic reformer (e.g. for a micro fuel cell system). The study includes the thermal and diffusive properties of a washcoat of finite thickness that is modeled as a porous layer composed of a ceramic support containing catalytic active rhodium sites. It was combined with a two-dimensional radially symmetric model of a single tubular mini-channel, considering both the thermal and the diffusive transport phenomena in all domains. It was found that both the methane conversion and the hydrogen yield depended markedly on the washcoat thickness. An interesting result was obtained by implementing the common experimental conditions into the numerical model: if the inlet volume flow and the amount of catalyst per washcoat volume are constant, an optimum washcoat thickness of was found, where the hydrogen yield is maximal. For a thinner washcoat, the smaller amount of catalyst is limiting, leading to a low methane conversion. For a thicker washcoat, the limiting effect is the reduced residence time, which stems inherently from the constraint of constant volume flow, rather than the increased diffusive resistance. The demonstration of the existence of an optimum washcoat thickness is important, because it can have economic effects due to saving of the precious catalyst rhodium. [Copyright &y& Elsevier]

Abstract: The capillary tube is often served as an expansion device in small refrigeration and air-conditioning systems. In this paper, a generalized correlation for predicting the refrigerant mass flow rate through the adiabatic capillary tube is developed with approximate analytic solutions based on the extensive data for R12, R22, R134a, R290, R600a, R410A, R407C, and R404A, in which a homogeneous equilibrium model for two-phase flow is employed, and there is a subcooled liquid or saturated two-phase mixture at the inlet of the capillary tubes. The collected database about capillary tubes covers the inner diameter from 0.5mm to 2mm, the tube length from 0.5m to 5m, the condensing temperature from 20°C to 60°C, the subcooling from 0°C to 20°C, and the quality from 0 to 0.3 at the inlet. Assessments for the correlation are made with some experimental data for R12, R22, R134a, R290, R407C, R410A, and R404A obtained from the open literature and some existing correlations based on the experimental database also. The present correlation yields an average deviation of −0.83% and a standard deviation of 9.02% from the database. [Copyright &y& Elsevier]

Abstract: The cooling system of an injection mould is very important to the productivity of the injection moulding process and the quality of the moulded part. Despite the various research efforts that have been directed towards the analysis, optimization, and fabrication of cooling systems, support for the layout design of the cooling system has not been well developed. In the layout design phase, a major concern is the feasibility of building the cooling system inside the mould insert without interfering with the other mould components. This paper reports a configuration space (C-space) method to address this important issue. While a high-dimensional C-space is generally required to deal with a complex system such as a cooling system, the special characteristics of cooling system design are exploited in the present study, and special techniques that allow C-space computation and storage in three-dimensional or lower dimension are developed. This new method is an improvement on the heuristic method developed previously by the authors, because the C-space representation enables an automatic layout design system to conduct a more systematic search among all of the feasible designs. A simple genetic algorithm is implemented and integrated with the C-space representation to automatically generate candidate layout designs. Design examples generated by the genetic algorithm are given to demonstrate the feasibility of the method. [Copyright &y& Elsevier]

Abstract: This paper presents an open air–vapor compression refrigeration system for air conditioning and hot water cooled by cool water and proves its feasibility through performance simulation. Pinch technology is used in analysis of heat exchange in the surface heat exchanger, and the temperature difference at the pinch point is selected as 6°C. Its refrigeration depends mainly on both air and vapor, more efficient than a conventional air cycle, and the use of turbo-machinery makes this possible. This system could use the cool in the cool water, which could not be used to cool air directly. Also, the heat rejected from this system could be used to heat cool water to 33–40°C. The sensitivity analysis of COP to η c and η t and the simulated results T 4, T 7, T 8, q 1, q 2 and W m of the cycle are given. The simulations show that the COP of this system depends mainly on T 7, η c and η t and varies with T 3 or T wet and that this cycle is feasible in some regions, although the COP is sensitive to the efficiencies of the axial compressor and turbine. The optimum pressure ratio in this system could be lower, and this results in a fewer number of stages of the axial compressor. Adjusting the rotation speed of the axial compressor can easily control the pressure ratio, mass flow rate and the refrigerating capacity. The adoption of this cycle will make the air conditioned room more comfortable and reduce the initial investment cost because of the obtained very low temperature air. Humid air is a perfect working fluid for central air conditioning and no cost to the user. The system is more efficient because of using cool water to cool the air before the turbine. In addition, pinch technology is a good method to analyze the wet air heat exchange with water. [Copyright &y& Elsevier]

Abstract: In the US scenario for a Neutrino Factory presented in “A feasibility study of a neutrino source based on a muon storage ring”, N. Holtkamp (Ed.), D. Finley (Ed.), Fermilab, April 15th, 2000), a large percentage of the cost is related to an induction linac for phase-energy rotation and bunching of the muon beam collected after the production target and decay channel. A more cost-effective adiabatic buncher and phase-energy rotator has been proposed to replace the induction linac system (D. Neuffer, A. Van Ginneken, High-frequency bunching and rotation for a muon source, Proceedings of the 2001 Particle Accelerators Conference, Chicago, 2001, p. 2029). The new method uses consecutive RF cavities with differing frequencies. The frequencies are changed to enable bunching and phase-energy rotation. In this paper, the theoretical concept is developed and demonstrated with simulation results obtained with the map code COSY Infinity (http://cosy.pa.msu.edu). An optimization strategy is also explored. [Copyright &y& Elsevier]

Abstract: Adiabatic demagnetization refrigerators (ADRs) using superconducting magnets are under development for cooling many NASA instruments. Due to higher efficiency of cryocoolers at 10K, Nb3Sn magnets operating at 10K are favored for space ADRs. Further, magnets need to be as light as possible and have low operating currents. This paper discusses technologies for the manufacture of lightweight, low-current Nb3Sn magnets and reports on testing of a 35mm bore by 60mm long magnet. This magnet weighed less than 1kg and successfully produced 3T at 11.5K with an operating current of 8A. [Copyright &y& Elsevier]

Constellation-X is a multi-satellite X-ray astronomy mission presently being planned for launch in the 2010 time frame. Each of four identical satellites will contain a telescope and instruments for imaging and spectroscopic analysis of hard and soft X-rays. The X-ray Microcalorimeter Spectrometer (XMS) instrument will use arrays of microcalorimeters to detect X-rays with energies from 0.2 to 6 keV. To achieve the desired energy resolution of 2 eV, the detectors will be cooled to 50 mK. The projected cooling power requirement is approximately 5 μW. In order to meet the mission lifetime requirement of 6 years (with a goal of 10 years), a mechanical cryocooler will be used to provide a heat sink for the low temperature cooler. In this paper we discuss the development of a continuous adiabatic demagnetization refrigerator (CADR) that meets the cooling requirements of the XMS instrument. The four-stage CADR presently being tested can operate continuously at 50 mK using a 4.2 K helium bath as a heat sink. Its cooling power of 6 μW at 50 mK exceeds the XMS requirement, and its peak heat rejection rate is less than 7 mW. Details of the CADR''s design and operation, as well as the development program leading up to a flight-qualified instrument, are discussed. [Copyright &y& Elsevier]

• We designed the cooling system from room temperature to about 1 K for XRISM Resolve. • Based on ASTRO-H (Hitomi) SXS lessons learned, changes on the design are adopted and new tests are planned. • The major design changes include an aperture baffle, an eddy current damper and a new vibration isolation system. The X-ray Imaging and Spectroscopy Mission (XRISM) is a recovery mission of ASTRO-H (Hitomi) launched in 2016. The Resolve instrument on the XRISM is an 6 × 6 array of silicon-thermistor microcalorimeters cooled down to 50 mK combined with a 5.6 m focal length X-ray telescope. Its design inherits that of the Soft X-ray Spectrometer (SXS) onboard ASTRO-H that demonstrated high resolution spectroscopy of the X-ray microcalorimeters by observing astronomical objects and providing superb resolution spectra. The cooling chain of the Resolve consists of a 3-stage adiabatic demagnetization refrigerator (ADR), a Joule-Thomson cooler, ~ 30 L superfluid helium, four Stirling coolers and a vacuum vessel or a dewar. Design of the Resolve cooling system is basically the same as that in the SXS but several changes are adopted based on lessons learned. This paper describes mainly the cooling system from room temperature to about 1 K providing the ADR heat sink. Major changes include an aperture baffle for micrometeoroid and orbital debris protection and optical light reduction, an eddy current damper to slow a gate valve opening, a new vibration isolation system with launch-locks. [ABSTRACT FROM AUTHOR]

Abstract: The X-ray Spectrometer (XRS-2) instrument on the Japanese Space Agency (JAXA) Astro-E2 spacecraft will measure faint X-ray emissions in the energy range of 0.2–10keV. A square array of 32 X-ray microcalorimeters used will be able to distinguish individual photons to better than 10eV at 6keV, with a quantum efficiency near 100%. The detectors are cooled to 60mK by means of an adiabatic demagnetization refrigerator (ADR). The ADR rejects heat to a 1.3K superfluid helium tank, which is surrounded by a 17K solid neon tank. A Stirling cycle cryocooler precools an outer shield around the neon tank. This system will provide an estimated 3 years of on-orbit lifetime. This paper describes the helium insert, the ADR, the high temperature superconducting leads, and early on-orbit performance. [Copyright &y& Elsevier]

Provides information on the `separation formula,' a method for computing the adiabatic inter-hemispheric meridional transport, and its application to the Pacific Ocean. Derivation of the formula; Application of the formula to an adiabatic continuously stratified upper layer on a spherical earth; Adiabatic wind-driven throughflow; Upwelling in the Pacific; Relation to the baroclinic island rule calculations.