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A 1.1W/4.2K Gifford-McMahon (G-M) refrigerator has recently been developed by Advanced Research Systems, Inc. The typical cooling capacity of 40 W at 40K for the first stage and 1.1 W at 4.2 K for the second stage has been achieved. The cooling performance of this 4.2K G-M refrigerator was significantly improved by optimizing packing materials both inside 1st and 2nd stage regenerators, as well as operation conditions. The experimental results and improvements are presented and their optimal cases are also given in this paper. [ABSTRACT FROM AUTHOR]

Joule-Thomson (JT) sorption cryocooling is the most mature technology for cooling from a normal Room- Temperature (RT) down to temperatures below 100 K in the absence of moving parts. Therefore, high reliability and no vibrations are attainable, in comparison with other cryocoolers. Cooling to 80 - 100 K with JT cryocoolers is often implemented with pure nitrogen. Alternatively, mixed refrigerants have been suggested for reducing the operating pressures to enable closed cycle cryocooling. There is a variety of publications describing nitrogen sorption cryocoolers with different configurations of sorption compressors. In the present research we suggest a novel sorption JT cryocooler that operates with a mixed refrigerant. Merging of sorption cryocooling and a mixed refrigerant enables the use of a simple, single stage compressor for cooling to 80 - 100 K, lower operating temperatures of the sorption cycle, and thus - reduced power consumption. In previous studies we have analyzed sorption compressors for mixed gases and mixed refrigerants for JT cryocoolers, separately. In this paper the option of mixed refrigerant sorption JT cryocoolers is explored. The considerations for developing mixed refrigerants to be driven by sorption compressors and to be utilized with JT cryocoolers are provided. It appears that, unlike with pure nitrogen, mixed refrigerants can be suitable for JT cryocooling with a single stage sorption compressor. [ABSTRACT FROM AUTHOR]

This paper describes two kinds of optical cryostats designed and manufactured at Absolut System. The first one makes use of pressurized LN2 for temperature control of a sample holder in the 80 K - 470 K temperature range. An optical window is implemented above the sample holder to allow for rugosity and 3D distortion of heterogeneous semicon sample assemblies on a wafer. The second one makes use of CRYOMECH remote motor type pulse tube cryocoolers for temperature control of the sample holder in the 3 K - 300 K temperature range. In this type of cryostats, particular attention has been paid to reduce the vibrations exported by the cooler. These 4 K ultra low vibration cryostats are used for characterization of samples via optical windows. Both designs will be presented and the performance reported. [ABSTRACT FROM AUTHOR]

Solvay, Stirling and Gifford-McMahon types of cryocoolers employ an isentropic expander which is their elementary mechanism for temperature reduction (following the unified model of cryocoolers as described in a previous paper, Part A) . Solvay and Stirling cryocoolers are driven by a larger temperature reduction than that of the Gifford-McMahon cycle, for a similar compression ratio. These cryocoolers are compared from the view of the unified model, in terms of the lowest attainable temperature, compression ratio, the size of the interchanger and the applied heat load. [ABSTRACT FROM AUTHOR]

A liquid hydrogen target has been developed for the COMPASS experiment at CERN. The target has a diameter of 40 mm and a length of 2.5 meter, creating an active volume of about 3 liter of liquid hydrogen. The cylindrical part of the target wall is formed by a Kapton® foil strip, wound and glued to a thickness of 0.125 mm. The Kapton® foil is used to minimize the energy loss of the particles, scattered or created within the target volume, crossing the target boundary. The two end-caps enclosing the target volume have been fabricated from Mylar®. The system is cooled with a 30 W at 20 K cryocooler, delivering the cooling capacity for the cool-down as well as for the continuous operation of the system. [ABSTRACT FROM AUTHOR]

This study was inspired to investigate an alternative cooling system using a helium-based pulsating heat pipes (PHP), for low temperature superconducting magnets. In addition, the same approach can be used for exploring other low temperature applications. The advantages of PHP for transferring heat and smoothing temperature profiles in various room temperature applications have been explored for the past 20 years. An experimental apparatus has been designed, fabricated and operated and is primarily composed of an evaporator and a condenser; in which both are thermally connected by a closed loop capillary tubing. The main goal is to measure the heat transfer properties of this device using helium as the working fluid. The evaporator end of the PHP is comprised of a copper winding in which heat loads up to 10 watts are generated, while the condenser is isothermal and can reach 4.2 K via a two stage Sumitomo RDK408A2 GM cryocooler. Various experimental design features are highlighted. Additionally, performance results in the form of heat transfer and temperature characteristics are provided as a function of average condenser temperature, PHP fill ratio, and evaporator heat load. Results are summarized in the form of a dimensionless correlation and compared to room temperature systems. Implications for superconducting magnet stability are highlighted. [ABSTRACT FROM AUTHOR]

The natural circulation loop is designed for the cryogenic insert in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Sensitivity is the key parameter of a FTICR mass spectrometer and the cryo-cooling of the pre-amplifier can reduce the thermal noise level and thereby improve the signal-to-noise ratio. The pre-amplifier consisted of non-magnetic materials is thermally connected to the cooling loop which is passing through the flange maintaining ultra-high vacuum in the ion cell. The liquid nitrogen passes through inside of the loop to cool the preamplifier indirectly. At the end, a cryocooler is located to re-condense nitrogen vapor generated due to the heat from the pre-amplifier. The circulating fluid removes heat from the pre-amplifier and transports it to the cryocooler or heat sink. In this paper the natural circulation loop for cryogenic pre-amplifier is introduced for improving the sensitivity of cryodetector. In addition, the initial cool-down of the system by a cryocooler is presented and the temperature of the radiation shield is discussed with respect to the thickness of shield and the thermal radiation load. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for time trending space cryocooler technology (cold tip temperatures, cooling loads). This methodology analyzes historical trends starting from the 1960s across three dimensions (time, specific power, and temperature). It can be used as a basis to assess whether future industrial capability may satisfy future program technology needs. [ABSTRACT FROM AUTHOR]

Superconductor Technologies Inc. (STI) developed the Sapphire cryocooler specifically for the SuperLink® product; a high performance superconducting Radio Frequency (RF) front-end receiver used by wireless carriers such as Verizon Wireless and AT&T to improve network cell coverage and data speeds. STI has built and deployed over 6,000 systems operating 24 hours a day (24/7), 7 days a week in the field since 1999. Sapphire is an integrated free piston Stirling cycle cryocooler with a cooling capacity of 5 Watts at 77 Kelvin (K) with less than 100 Watts (W) input power. It has a field-proven Mean Time Between Failure (MTBF) of well over 1 million hours, requires zero maintenance and has logged over 250 million cumulative runtime hours. The Sapphire cooler is built on a scalable technology platform, enabling the design of machines with cooling capacities greater than 1 kilowatt (kW). This scalable platform also extends the same outstanding attributes as the Sapphire cooler, namely high reliability, zero maintenance, and compact size - all at a competitive cost. This paper will discuss emerging applications requiring higher heat loads and these attributes, describe Sapphire, and show a preliminary concept of a scaled machine with a 100 W cooling capacity. [ABSTRACT FROM AUTHOR]

As part of the vacuum system for the ITER fusion project, a cryogenic viscouscompressor (CVC) is being developed to collect hydrogenic exhaust gases from the toruscryopumps and compress them to a high enough pressure by regeneration for pumping tothe tritium reprocessing facility. Helium impurities that are a byproduct of the fusionreactions pass through the CVC and are pumped by conventional vacuum pumps andexhausted to the atmosphere. Before the development of a full-scale CVC, a representative,small-scale test prototype was designed, fabricated, and tested. With cooling provided bycold helium gas, hydrogen gas was introduced into the central column of the test prototypepump at flow rates between 0.001 g/s and 0.008 g/s. Based on the temperatures and flowrates of the cold helium gas, different percentages of hydrogen gas were frozen to the column surface wall as the hydrogen gas flow rate increased. Results from the measured temperatures and pressures will form a benchmark that will be used to judge future heattransfer enhancements to the prototype CVC and to develop a computational fluid dynamicmodel that will help develop design parameters for the full-scale CVC. [ABSTRACT FROM AUTHOR]

Long-term cryogenic propellant storage requires mechanical cryocoolers to maintainzero or very low cryogen boil-off rates. Very large cryogen tanks such as those proposedfor orbital fuel depots may require cryocoolers with very high cooling capacity. In-situresource generation and storage of oxygen and methane on Mars also requires highcapacity cryocoolers, and low mass is extremely desirable for planetary missions becauseof the cost associated with landing mass on the surface of another planet. LockheedMartin's Advanced Technology Center has developed a high capacity low mass aerospacecryocooler with very high power density. This 7 kg pulse tube cryocooler can provide20 W of cooling at 70 K while rejecting heat at 300 K. This large cooling capability couldalso be used to cool large optical structures or other devices with high heat loads. Testingof the cooler with a secondary heat exchanger attached to the pulse tube was alsoconducted, and results are discussed. [ABSTRACT FROM AUTHOR]

Applications in superconductivity have become widespread, enabled by advancements in cryogenic engineering. In this paper, the history of cryogenic refrigeration, its delivery, its preservation and the important scientific and engineering advancements in these areas in the last 100 years will be reviewed, beginning with small laboratory dewars to very large scale systems. The key technological advancements in these areas that enabled the development of superconducting applications at temperatures from 4 to 77 K are identified. Included are advancements in the components used up to the present state-of-the-art in refrigeration systems design. Viewpoints as both an equipment supplier and the end-user with regard to the equipment design and operations will be presented. Some of the present and future challenges in these areas will be outlined. Most of the materials in this paper are a collection of the historical materials applicable to these areas of interest. [ABSTRACT FROM AUTHOR]

Previously we demonstrated cryogenic cooling in a Joule-Thomson (JT) microcryocooler (MCC) with mixed refrigerants operating at pressure ratios of 16:1 that achieved stable temperatures of 140 K, with transient temperatures down to 76 K, with precooling of the refrigerant to 240 K. Pre-cooling improves the minimum enthalpy difference, (ΔhhT)min compared with that of pure fluids. Micro-scale compressors have been unavailable to meet 16:1 ratios. By reducing the ratio to 4:1, mini-compressors become viable in the near term. Utilizing mixed refrigerants optimized for 4:1 pressure ratios we compare the performance stability of this micro-JT employing a 25 mm long multichannel glass fiber heat exchanger (outer low-pressure capillary ID/OD=536 μm/617 μm, inner high-pressure channels ID/OD=75 μm/125 μm) with a scaled up (meso-scopic) version employing a 20 cm long single channel stainless steel heat exchanger (outer low pressure channel ID/OD=580 μm/760 μm, inner high pressure channel ID/OD=150 μm/266 μm). This easy to fabricate and modify meso-scale version was fabricated to investigate the temperature instabilities of mixed refrigerants for similar operating conditions but for proportionally higher flows of ~ 30 cm3/min compared with ~ 10 cm3/min. We compare measured pressures, flow rates, temperatures, and stabilities for both micro- and meso-JT cryocoolers to better understand the causes for the temperature instabilities within the micro-JT cryocooler. KEYWORDS: Cryocooler, Joule-Thomson, microcryocooler, micro-JT, mixed [ABSTRACT FROM AUTHOR]

Due to their relatively smaller volume and available cooling power, miniature cryocoolers are likely to be more sensitive to hydrodynamic losses than their full scale counterparts. Abrupt changes in diameter between cryocooler components are a possible source of such losses as flow separation and recirculation may occur at these points. Underutilization of regions of the regenerator and heat exchanger porous matrices may also occur due to jetting of fluid into these components. Eliminating such abrupt diameter changes by tapering transitions between cryocooler components may therefore improve system performance. The effects of various tapers applied at component interfaces on the performance of miniature pulse tube cryocoolers were investigated using system-level CFD models. A miniature scale pulse tube cryocooler design whose suitability for cryocooling under ideal conditions has been theoretically demonstrated was used as the basis for these models. Transitions between different combinations of open and porous regions were considered; tapers or chamfers were applied to these component junctions and the performance predictions for the resulting systems were compared to those for a model with sharp component transitions. Visualizations of the predicted flow patterns were also used to determine the effects of the applied tapers on the flow within the pulse tube. [ABSTRACT FROM AUTHOR]

Helium-3,4 dilution refrigeration is indispensable for low temperature science and engineering as it is the only method which provides temperatures between 0.3 K and 0.005 K for unlimited working periods. Cryogen-free dilution refrigerators are about to replace traditional cryostats with liquid helium precooling. The dilution circuit is always precooled by a two-stage pulse tube cryocooler; therefore, refrigeration capacities are available to the experimentalist at the temperatures of the two stages of the pulse tube cooler, and furthermore at three temperatures of the dilution circuit (~ 0.7 K - still, 0.1 K - heat exchanger, ~ 0.01 K - mixing chamber). However, there are quite a few applications (e.g. quantum information processing or astro-physics) where the cooling power of the still near ~ 1K is not sufficient to cool amplifiers and electric lines. In our work we present a dilution refrigerator where a He-4 cooling circuit has been added in the cryostat to the dilution circuit. This He-4 circuit provides up to 60 mW of refrigeration capacity in addition to the cooling capacity of ~ 30 mW of the still. The dilution circuit and the 1Kcircuit can be operated together or separately. [ABSTRACT FROM AUTHOR]

Second-law of thermodynamics (2nd law) and exergy analyses and optimization offour Reverse Brayton Refrigeration (RBR) cryogenic cycle configurations: Conventional 1-stage compression cycle; Conventional 2-stage compression cycle; 1-stage compressionModified cycle with intermediate cooling of the recuperator using an auxiliary cooler; andan Integrated 2-stage expansion RBR cycle are performed. The conventional RBR cyclesare analyzed for low and high pressure ratio applications using multistage compressorswith intercooling. Analytical solutions for the conventional cycles are developed includingthermal and fluid flow irreversibilities of the recuperators and all heat exchangers inaddition to the compression and expansion processes. Analytical solutions are used to findthe thermodynamic bounds for the performance of the cycles. Exergy irreversibilitydiagrams of the cycles are developed and the effects of important system parameters onRBR cycle performance are investigated. 2nd law/exergy analyses, and optimization of thecycles with intermediate cooling of the recuperator, considering the cooling temperatureand the recuperator effectiveness and pressure drop, are included. The effect of the 2ndlaw/exergy efficiency of the auxiliary cooler on the total system efficiencies is presented. [ABSTRACT FROM AUTHOR]

New efforts are underway to develop thermoelectric materials for cooling of infrared detectors at cryogenic temperatures. In this study, a control thermodynamic model of multistage Thermoelectric (TE) cryocoolers is developed that includes the effect of heat transfer between the cryocooler and the thermal reservoirs as well as thermal resistance between the stages. It is assumed that a reservoir at 80 K is available and a cooling load at about 35 K, typical of the second stage of conventional cryocoolers, is desired. It is shown that under the assumption of availability of TE materials with a reasonably high figure of merit, a multistage TE cryocooler is required. As an example, a control thermodynamic model of a four-stage TE cryogenic refrigerator is developed. The effect of thermal conductance of the heat exchangers at the hot and cold sides of the refrigerator, the thermal resistance between the stages and the effect of the figure of merit of the TE material on the cooling capacity and efficiency of the multistage TE cryocooler is presented. The thermal design challenges of the development of multistage TE cryocoolers with high efficiency for cryogenic applications including the effect of heat leak are discussed. [ABSTRACT FROM AUTHOR]

A new cryogenic system is under construction at the National High Magnetic Field Laboratory (NHMFL) for the cooling of the Series-Connected Hybrid (SCH) magnet as well as the existing 45 T hybrid system. The SCH is a vertical bore, 36 T magnet under development at the NHMFL and it will be installed at the NHMFL in 2013. The 45 T hybrid magnet system producing a 45 T steady field has been operating successfully as a user facility since 1999. The existing cryogenic system at the NHMFL has been in service since 1994 and it is used for supplying Liquid Helium (LHe) to the users and also cooling the 45 T hybrid magnet. The new system has a specified refrigeration capacity of 750 W at 4.5 K and will replace the current refrigerators after its construction due to the increasing maintenance in current refrigerators and the increasing LHe demand by the users at the NHMFL. The design of the new cryogenic system, consisting of a main refrigerator, a distribution system and a gas management and purification system, and its status are presented in this paper. [ABSTRACT FROM AUTHOR]

The Advanced Photon Source (APS) upgrade project at Argonne National Laboratory includes the implementation of superconducting undulator insertion devices. A development program is under way to build, test, and operate a prototype device in the storage ring. We present the overall design concept including superconducting magnet structure, cryocooler-based cooling system, and cryostat as well as a status report on the R&D program. Results of cryocooler performance characterization using a model magnet in a test cryostat are described. [ABSTRACT FROM AUTHOR]

Single and two-stage Pulse Tube Cryocoolers (PTC) have been designed, fabricated and experimentally studied. The single stage PTC reaches a no-load temperature of ~ 29 K at its cold end, the two-stage PTC reaches ~ 2.9 K in its second stage cold end and ~ 60 K in its first stage cold end. The two-stage Pulse Tube Cryocooler provides a cooling power of ~ 250 mW at 4.2 K. The single stage system uses stainless steel meshes along with Pb granules as its regenerator materials, while the two-stage PTC uses combinations of Pb along with Er3Ni / HoCu2 as the second stage regenerator materials. Normally, the above systems are insulated by thermal radiation shields and mounted inside a vacuum chamber which is maintained at high vacuum. To evaluate the performance of these systems in the possible conditions of loss of vacuum with and without radiation shields, experimental studies have been performed. The heat-in-leak under such severe conditions has been estimated from the heat load characteristics of the respective stages. The experimental results are analyzed to obtain surface emissivities and effective thermal conductivities as a function of interspace pressure. [ABSTRACT FROM AUTHOR]

Joule-Thomson (JT) sorption cryocooling is the most mature technology for cooling from a normal Room-Temperature (RT) down to temperatures below 100 K in the absence of moving parts. Therefore, high reliability and no vibrations are attainable, in comparison with other cryocoolers. Nitrogen is usually used as the working fluid for cooling to temperatures between 80 and 100 K and activated carbons are the best adsorbent for this purpose. In this paper we present the development of a sorption compressor for nitrogen with a commercial Chemviron pelleted activated carbon. The development consists of sorption measurements that we performed for characterizing the adsorption of nitrogen on the selected adsorbent, and the compressor experimental results are compared with equilibrium condition analysis and numerical heat transfer analysis predictions [ABSTRACT FROM AUTHOR]

Liquid gases distribution system is an unavoidable element of practically each high capacity cryogenic installation. It comprises transfer lines, which in spite of their first view simplicity, are complex parts of the system, relevant both for its thermodynamic efficiency and its reliability. The presently constructed transfer lines may comprise several process pipes filled with different fluids at different thermodynamic parameters. The heat that inflows to cold process pipes influences significantly the thermal budget of the cryogenic system and consequently the required supply power of the refrigerator. Transfer lines are multi-dimensional, thermo-mechanical objects that can be thermodynamically optimized with entropy generation minimization, based on the Second Law of thermodynamics. The paper presents two practical examples of a simple and complex transfer line optimization. The lines are split into a number of constructional nodes which enables one to calculate the entropy generated in elementary heat transfer and fluid flow processes. The presented examples show that the Second Law analysis can help in identifying the constructional nodes which are responsible for high rate of entropy generation and the method enables constructional and engineering decisions. [ABSTRACT FROM AUTHOR]

The cryogenic infrastructure at CERN was originated in the 1960s with the era of bubble chambers and the associated superconducting solenoids. Since then and especially with the construction of the LHC accelerator and its detectors, large and complex cryogenics plants have been installed to provide cooling power from 800 W to 18 kW at different temperatures down to 1.9 K, demanding high and distributed technical capabilities from the control systems. The size and the complexity of the dedicated cryogenics has required the adoption of the CERN standard control framework UNICOS in order to enhance ease of operation and maintenance, and to provide long-term availability. After the completion of the LHC construction, exploiting the gained experience, CERN has started the upgrade of several obsolete cryogenic control systems. This paper describes (i) the overall project challenges, (ii) the technical procedure used in order to meet the technological operational requirements in terms of installation constraints, reduced manpower and minimal financial impact, (iii) an advanced methodology for the virtual commissioning of the new control systems, and (iv) three case studies as examples of the application of the aforementioned strategy. [ABSTRACT FROM AUTHOR]

Ball Aerospace and Redstone Aerospace are developing a space cryocooler for cooling complex optical systems whose loads are intermittent. An example of such a system would be an Earth observation satellite that images for only a fraction of its orbit. If a cooler can store refrigeration during the lull and provide it when the system is active, the cooler can be considerably smaller than one sized to provide the full load continuously. Our cooler provides two stages of refrigeration, a stage of intermittent cooling at 35 K for a focal plane assembly and a stage of continuous cooling at 85 K for the surrounding thermal shields. The cooler provides the intermittent cooling by collecting liquid neon in a unique internal thermal storage tank and forwarding it to the focal plane when the heat loads are high. Our paper presents extensive performance data for neon at 35 K. It carries 2 W at 35 K for 30 minutes plus the 8.5 W of continuous cooling at 85 K for less than 300 W DC power. It is ready to cool again in an hour. For contrast, the same hardware was filled with nitrogen and tested at 82 K. It carries 5 W for 25 minutes plus 15 W of continuous cooling at 130 K for less than 220 W DC power. It is ready to cool again in a little over an hour. The system has many features for space system compatibility. Because the storage is located within an active control loop, the cooler can maintain the 35 K interface temperature to better than ± 0.1 K. Because it circulates liquid it can be located remotely, which solves many compatibility issues. And with careful liquid management, it can work in any orientation and in 0-g. In this paper our flight like equipment will be described, and its continuing evolution to flight will be discussed. [ABSTRACT FROM AUTHOR]

Miniature pulse tube coolers operating at 100Hz have been designed and manufactured. The regenerator is designed by REGEN 3.2, and the inertance tube is simulated by DeltaE. An in-line prototype is manufactured according to the theoretical design parameters initially. On that basis, a coaxial cooler is developed and with double inlet it gains higher cooling performance. [ABSTRACT FROM AUTHOR]

A methane cryogenic heat pipe with a liquid trap for on-off actuation was developed by ATK for use on Jet Propulsion Laboratory's Space Interferometer Mission Lite (SIM Lite) pre-Phase A hardware technology demonstration tests. The cryogenic heat pipe coupled to a cold radiator at 160K provides cooling to the Charged Coupled Device camera focal planes. The heat pipe was designed for a transport capacity of 15 W across a 1.5 m span through a near room-temperature spacecraft environment. A key and driving requirement for the heat pipe was the need for switching the heat pipe on and off needed to support low power decontamination cycles to near room temperature of the cryogenic focal planes. The cryogenic heat pipe is turned off by removing the methane working fluid from the heat pipe and storing in the liquid trap. The heat pipe is turned-on by simply reintroducing the working fluid from the liquid trap. This on-off switching capability is a key requirement for cryogenic heat pipes used with passive or active cryocoolers for cooling focal planes or optics. This switching capability provides a means to decouple a cold focal plane or optics from a redundant stand-by cryocooler or a passive cooler when in need for a decontamination cycle. [ABSTRACT FROM AUTHOR]

In order to achieve and maintain the proper cryogenic conditions for fusion experiments, the ITER Cryogenic System has to cope with various operation modes as per the requirements of the superconducting (SC) magnets and the 4 K Cryopumps (CPs). The refrigerators, source of the cooling power, should operate as much as possible in a quasisteady- state manner for efficiency and reliability reasons, and also to optimize their cooling capacity. The cryogen-related transients generated or required by the magnets and CPs therefore have to be managed and smoothed inside the primary helium loops of the Cryodistribution (CD) cold boxes which distribute and recover the cooling flows. In this proceeding we will propose the internal-component layouts of the ITER CD cold boxes and demonstrate in terms of operation modes how they fulfill the duties of the Cryogenic System with respect to the ITER Tokamak. The methods foreseen for the smoothing of the cryogenic loads and optimization of the cooling power requirements will also be introduced. [ABSTRACT FROM AUTHOR]

The needs of thermal links in cryogenic applications are increasing, especially because of the use of cryocoolers which offer a reduced size cold finger. The Pulsating Heat Pipe (PHP) is a passive two-phase high performance thermal link. Like the conventional heat pipe, it features a closed tube filled with a two-phase fluid able to transfer heat from its hot part (evaporator) to the cold part (condenser). A general problem for any two-phase cryogenic thermal link is the pre-cooling of the evaporator to ensure the presence of liquid inside the evaporator to start the flow motion. In conventional heat pipes, this problem is by passed by the wick but in the case of PHPs it has to be specially addressed. We have designed, manufactured and tested a helium PHP associated to a novel pre-cooling system. The cool down time of the PHP evaporator is reduced significantly. The maximum transferred power of the PHP is 145 mW with a cold source at 4.2 K. [ABSTRACT FROM AUTHOR]

Future lunar and planetary explorations will require the storage of cryogenic propellants, particularly liquid oxygen (LOX) and liquid hydrogen (LH2), in low earth orbit (LEO) for periods of time ranging from days to months, and possibly longer. Without careful thermal management, significant quantities of stored liquid cryogens can be lost due to boil-off. Boil-off can be minimized by a variety of passive means including insulation, sun shades and passive radiational cooling. However, it has been shown that active cooling using space cryocoolers has the potential to result in Zero Boil-Off (ZBO) and the launch-mass savings using active cooling exceeds that of passive cooling of LOX for mission durations in LEO of less than 1 week, and for LH2 after about 2 months in LEO. Large-scale DC-flow cryogenic refrigeration systems operate at a fraction of the specific power levels required by small-scale AC-flow cryocoolers. The efficiency advantage of DC-flow cryogenic cycles motivates the current development of a cryocooler based on a modification of the Collins Cycle. The modified Collins cycle design employs piston type expanders that support high operating pressure ratios, electromagnetic valves that enable "floating pistons", and recuperative heat transfer. This paper will describe the design of a prototype Modified-Collins cryocooler for ZBO storage of cryogenic fuels in space. [ABSTRACT FROM AUTHOR]

This paper theoretically studied a traveling-wave thermoacoustic cryocooler (TWTAC), simultaneously comparing with an inertance-tube pulse tube cryocooler operating in liquid nitrogen temperature range. The same core thermodynamic components are fixed and used in the both cryocoolers. First, thermodynamic design and optimization mainly on their phase shifting devices are made. For 77 K operation, the theoretical results show that the TWTAC has an increase of efficiency by about 10% compared with the inertance pulse tube cryocooler. Then, preliminary experiments on the TWTAC driven by a linear compressor were conducted. So far, the traveling-wave thermoacoustic cryocooler has achieved a no-load refrigeration temperature of 135 K with a pressure ratio of 1.15, and the reasons for huge different between the theoretical and experimental results are being indentified. [ABSTRACT FROM AUTHOR]

Ball Aerospace has completed qualification testing of its flight Stirling-cycle mechanical cryocooler for the Thermal Infrared Sensor (TIRS), an instrument slated to fly on the Landsat Data Continuity Mission (LDCM) platform. The TIRS cooler, developed under subcontract to NASA Goddard Space Flight Center, consists of a sophisticated and highly reliable, two-stage, fixed regenerator Stirling cryocooler and its drive electronics. The TIRS cooler provides 2 W of 38 K cooling to the TIRS detectors and 9.8 W shield cooling to 85 K for less than 225 W total input power. Performance test results are reported. [ABSTRACT FROM AUTHOR]

This paper reviews recent advances in high frequency pulse tube cryocoolers developed in SITP/CAS to provide high reliability, low-noise and long life cooling for potential space applications. The advances in understanding the cooler mechanism and minimizing irreversible losses in various components are described, which have made a great contribution to the improved efficiencies. At present, the operating temperatures cover from 30 K to 200 K and the cooling capacities vary from hundreds of milliwatts to over 20 W to meet a variety of requirements. Some typical cryocooler development programs are introduced and a brief overview of the updated data package is presented. The proposed applications, design approaches, research advances, the major problems and the efforts to overcome them are described. [ABSTRACT FROM AUTHOR]

For coupling between the thermoacoustic engine and pulse tube cooler, an acoustic transmission line model is built and simulated based on linear thermoacoustic theory. The simulations shows that with the acoustic transmission line, the input pressure amplitude of the cooling system can be amplified and more acoustic power can be transmitted from the thermoacoustic engine to the cooler, which can improve the performance of the pulse tube cooler. The computational results also reveal that the performance of the thermoacoustic engine can be improved by acoustic transmission line with appropriate length and diameter. In experiments, a linear pulse tube cooler driven by a miniature thermoacoustic engine is constructed and tested. Good agreements are obtained between the theoretical analysis and experimental results. This research is instructive for comprehensively understanding the coupling mechanism in the thermoacoustically driven pulse tube coolers. [ABSTRACT FROM AUTHOR]

Over the past year, Air Force Research Labs (AFRL), Space Vehicles Directorate, has significantly defined the science and technology (S&T) path forward for cryocoolers in support of Air Force space missions. There are two trends that are emerging for cryocooler S&T: the first is missile warning and the second is responsive space. Missile warning is moving towards larger Focal Plane Arrays (FPAs), which generate large heat loads. Responsive space is moving towards a cheap, fast alternative to augment, or reconstitute space capabilities. At first glance, these two trends require completely different approaches to cryocooler S&T. However, decreasing the size, weight, and power of cryocoolers supports both trends. This paper will discuss the technology path chosen by AFRL to meet the Air Force (AF) mission needs for cryocoolers to include AFRL's research path, and potential Broad Agency Announcement (BAA) opportunities to help support the research goals. [ABSTRACT FROM AUTHOR]

We have developed and installed a cryogenic sample chamber system to the soft x-ray microscope BL-12 at SR Center of Ritsumeikan University. The temperature of the specimens can be regulated continuously from 273 K up to 173 K. The cryogenic images of biospecimens have been taken. However, the resolution of the image was lower than that of the microscope. Therefore, the control method of LN2 and the sample chamber have been improved. The new chamber is compact, and LN2 flow is controlled with the LabVIEW program strictly. The compact chamber succeeded in high cooling efficiency, and the LN2 controlling system succeeded in high temperature stability. [ABSTRACT FROM AUTHOR]