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The WASCOP (Water Saving for Concentrated Solar Power) project is an EU project dedicated to water saving in CSP power plants. Among the different technologies and aspects considered in the project, the concept of cold thermal energy storage (cTES) has been developed. cTES is considered in addition to the cooling system and used when ambient temperature is too high and may lead to turbine efficiency and electricity production reductions. In these conditions, heat from the condenser is partially stored in the cTES and evacuated trough the available cooler when ambient temperature is lower, typically during the night. A prototype of cTES has been built in the CEA site of Cadarache. Preliminary commissioning has been performed. Final commissioning is expected to be done before Spring 2019 and experimental tests will be made during Summer 2019. [ABSTRACT FROM AUTHOR]

Photovoltaic cells are devices that convert solar radiation directly into electricity. However, solar radiation increases the photovoltaic cells temperature [1] [2]. The temperature has an influence on the degradation of the cell efficiency and the lifetime of a PV cell. This work reports on a water cooling technique for photovoltaic panel, whereby the cooling system was placed at the front surface of the cells to dissipate excess heat away and to block unwanted radiation. By using water as a cooling medium for the photovoltaic solar cells, the overheating of closed panel is greatly reduced without prejudicing luminosity. The water also acts as a filter to remove a portion of solar spectrum in the infrared band but allows transmission of the visible spectrum most useful for the PV operation. To improve the cooling system efficiency and electrical efficiency, uniform flow rate among the cooling system is required to ensure uniform distribution of the operating temperature of the PV cells. The aims of this study are to develop a 3D thermal model to simulate the cooling and heat transfer in Photovoltaic panel and to recommend a cooling technique for the PV panel. The velocity, pressure and temperature distribution of the three-dimensional flow across the cooling block were determined using the commercial package, Fluent. The second objective of this work is to study the influence of the geometrical dimensions of the panel, water mass flow rate and water inlet temperature on the flow distribution and the solar panel temperature. The results obtained by the model are compared with experimental results from testing the prototype of the cooling device. [ABSTRACT FROM AUTHOR]

The 4K stage is a critical step for space missions. The Hershel mission is using a helium bath, which is consumed day by day (after depletion, the space mission is over) while the Plank mission is equipped with one He4 Joule-Thomson cooler. Cryogenic chain without helium bath is a challenge for space missions and 4.2K Pulse-Tube working at high frequency (around 30Hz) is one option to take it up. A low temperature Pulse-Tube would be suitable for the ESA space mission EChO (Exoplanet Characterisation Observatory, expected launch in 2022), which requires around 30mW cooling power at 6K; and for the ESA space mission ATHENA (Advanced Telescope for High ENergy Astrophysics), to pre-cool the sub-kelvin cooler (few hundreds of mW at 15K). The test bench described in this paper combines a Gifford-McMahon with a coaxial Pulse- Tube. A thermal link is joining the intercept of the Pulse-Tube and the second stage of the Gifford-McMahon. This intercept is a separator between the hot and the cold regenerators of the Pulse-Tube. The work has been focused on the cold part of this cold finger. Coupled with an active phase shifter, this Pulse-Tube has been tested and optimized and temperatures as low as 6K have been obtained at 30Hz with an intercept temperature at 20K. [ABSTRACT FROM AUTHOR]

Several Stirling-type pulse tube cryocoolers operating at liquid hydrogen temperatures for physical experiments have been designed, built and tested. For simplification and compactness, a single-stage configuration with a coaxial arrangement was employed. A multi-bypass configuration, together with a double-inlet and an inertance tube was adopted as the phase shifter, which resulted in the improved efficiencies. At present, typical cooling performance with a no-load temperature below 16 K and a cooling capacity over 1 W/30 K can be achieved with an input power less than 250 W. Some typical experimental results and considerations for achieving a better performance will be presented in this paper. [ABSTRACT FROM AUTHOR]

The High Capacity Raytheon Stirling/Pulse Tube Hybrid 2-Stage cryocooler (HC-RSP2) was originally developed to provide simultaneous cooling at temperatures of 85 K and 35 K. During testing performed in 2008 it was demonstrated that this stock-configuration cryocooler is capable of providing significant amounts of heat lift at 2nd stage temperatures as low as 12 K, and modeling indicated that minor changes to the 2nd stage inertance tube/surge volume setup could yield improved performance. These changes were implemented and the cooler was successfully retested, producing >350 mW of heat lift at 12 K. A comprehensive redesign of the system has been performed, the result of which is a robust 2-stage cryocooler system that is intended to efficiently produce relatively large amounts of cooling at 2nd stage temperatures <12 K. This cryocooler, called the Low Temperature RSP2 (LT-RSP2) will be fabricated and tested over the next 12 months. This paper reports on the recently-completed test activities, as well as details relating to the system redesign. Expected performance, mass and packaging volume are addressed. [ABSTRACT FROM AUTHOR]

The Micro-X Imaging X-ray Spectrometer is a sounding rocket payload slated for launch in 2011. An array of Transition Edge Sensors, which is operated at a bath temperature of 50 mK, will be used to obtain a high resolution spectrum of the Puppis-A supernova remnant. An Adiabatic Demagnetization Refrigerator (ADR) with a 75 gram Ferric Ammonium Alum (FAA) salt pill in the bore of a 4 T superconducting magnet provides a stable heat sink for the detector array only a few seconds after burnout of the rocket motors. This requires a cold stage design with very short thermal time constants. A suspension made from Kevlar strings holds the 255 gram cold stage in place. It is capable of withstanding loads in excess of 200 g. Stable operation of the TES array in proximity to the ADR magnet is ensured by a three-stage magnetic shielding system which consists of a superconducting can, a high-permeability shield and a bucking coil. The development and testing of the Micro-X payload is well underway. [ABSTRACT FROM AUTHOR]

An optimal control problem for a deterministic model of polymer crystallization processes is investigated. The applied cooling temperature and the duration of the cooling process are used as control parameters to minimize a cost functional which accounts for the two main industrial competitive interests: to avoid excessively low temperatures and to shorten the time spent in the total crystallization. We derive explicit expressions of the optimal controls by using an analytical approximation of the relation between the amount of polymer already crystallized at a given time and the total amount of cold injected into the sample until this instant of time. We present numerical simulations to illustrate the good agreement with the analytical expressions. It is surprising and remarkable that the explicit expressions of the optimal control values are obtained through the minimization of an elementary function in one real variable. [ABSTRACT FROM AUTHOR]

The model of localized adiabatic heating associated with release of a dislocation pile-up avalanche is described and re-evaluated. The model supplies a fundamental explanation of shear banding behavior in metal and non-metal systems. Now, a dislocation dynamics description is provided for more realistic assessment of the hot spot heating. Such localized heating effect was overestimated in the earlier work, in part, to show the dramatic enhancement of the work rate, and corresponding temperature build-up, potentially occurring in the initial pile-up release, say, at achievement of the critical dislocation mechanics-based stress intensity for cleavage. Proposed applications are to potentially brittle metal, ionic, and energetic material systems. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

FLARE (Fermilab Liquid ARgon Experiments) is an initiative to construct several liquid argon detectors to further exploit the two Fermilab neutrino beams, the operational Booster beam, and the recently completed NuMI beam. For optimum physics results, a liquid argon impurity level of less then 0.1 ppb oxygen equivalent is required. The necessary R&D program has been established and the experimental setup for the first stage is nearing completion. The purpose of the first stage is to gain experience in achieving, maintaining, and monitoring ultra pure liquid argon levels. An overview of the technology and methods utilized in the FLARE R&D program are discussed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have constructed a simple ortho-para hydrogen converter to generate para-hydrogen for our ongoing transport property measurement efforts. The apparatus utilizes hydrous ferric oxide as the catalyst. Conversion from normal hydrogen to para-hydrogen takes places at the boiling point of hydrogen. The heat due to condensation and conversion is removed by a liquid helium bath surrounding the vacuum jacketed apparatus. The temperature and the vapor pressure of the hydrogen inside the converter are used to determine the amount of the para content based on existing vapor pressure data. For verification purposes, we have also taken the more traditional approach to determine the para-hydrogen concentration by measuring the thermal conductivity of the converted gas in a flat plate calorimeter. The results from the thermal conductivity measurements have demonstrated that the composition of the gas can change significantly over the period of time needed to make the measurement. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Film boiling modes in both subcooled and saturated superfluid helium (He II) were experimentally investigated. The visual observation and the transient pressure and temperature measurements were performed to extract some characteristics of each boiling mode. The classification of all four film boiling modes, strongly subcooled and weakly subcooled modes in subcooled He II (He IIp) and noisy and silent film boiling modes in saturated He II (He IIs), was drawn on the boiling mode map. It was found from the heater temperature measurement that the boiling heat transfer is enhanced in the weakly subcooled mode compared with in the strongly subcooled mode. In the weakly subcooled mode, the vapor behavior is much activated by the instability in vapor-liquid interface. The boundary region between the strongly and the weakly subcooled modes becomes thick as the rise of He II temperature or the increase of the heat flux. The noisy film boiling does not occur at the pressure above 9 kPa, though it appears at the pressure above pλ. It is found that in the region adjacent to the lambda line He I film boiling mode occurs even in He II. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We proposed a normalized representation of the thermal conductivity function for heat transport in He II in the previous work. In order to check its validity, steady state heat transport characteristics of He II was investigated near Tλ. The temperature profiles along the channels were measured at various pressures of 0.1, 1.0 and 1.5 MPa. The measured temperature profiles were analyzed to get the thermal conductivity function near Tλ. The validity of the universal heat transport formula was confirmed up to T / Tλ = 0.99. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Steady state heat transport through He II was investigated. The exponent m in the Gorter-Mellink equation which gives heat flux dependence of the temperature gradient was measured in a wide range of heat flux. Our results indicate that there is no heat flux dependency of the exponent m in the heat flux region of our measurement. The exponent m is 3.4 at temperatures much lower than the lambda point and decreases down to 3.3 as the temperature approaches the lambda point. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The forced convection heat transfer coefficients were measured on a horizontal flat plate heater located on inner wall of a rectangular duct for pressures from 1 atm to 2.8 atm, flow velocities up to 2.1 m/s and for liquid temperatures from 1.8 to 6.5 K. Critical heat fluxes (CHFs) in He II under subcritical and supercritical pressures are higher for higher flow velocity and lower liquid temperature. In He I under supercritical pressures, there are two distinct ranges in heat transfer curves. The curve for lower heat flux range has a steeper gradient and the curve for higher heat flux has a lower gradient like film boiling regime. The peak heat fluxes of the former curves are treated as pseudo CHFs in this study and compared with the CHFs for He II. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A set of commercial paints was studied to assess its applicability to cryogenic thermography system. In the proposed system, the object is lit by a black light or UV-LEDs and the image of the fluorescence is observed by a CCD camera. In case of the studied set of paints, the efficiency of the fluorescence of a longer wavelength increases with the temperature rise and the one of the shorter wavelength has an opposite dependence. As the result, the color of the observed fluorescence changes from red/yellow to green when it is cooled down to liquid nitrogen temperature. As the present system uses the color instead of the intensity of the light, it is basically immune to the light absorption along the light path. As the fluorescent image can have a luminous intensity high enough for the commercial CCD camera, one can observe the thermal diffusion phenomena as a development of the change in the color. The spectrum and its dependence on the temperature will be reported. To assess the applicability of the present system for the temperature distribution in the magnetic field, the magnetic field effect was also studied up to 15T. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In the cryogenic range, temperature standards are based on the measurement of phase transitions of substances that are gaseous at room temperature. For total uncertainty budgets today approaching, for the most accurate realizations, 50 μK, the effect of different isotopic compositions in the samples measured can become so large as to be the leading component of the total uncertainty budget. The variability of the isotopic composition is a well-known issue and is regularly monitored and reviewed by bodies such as the IUPAC. However, these data cover the whole spectrum of the variability observed on the earth. The actual variability that can be observed when buying commercial substances could be smaller to such an extent to alleviate or eliminate the practical problem, or could instead remain relevant. Only recently attention has been paid to the latter problem and the results were partially unexpected. This paper briefly reviews the modern analytical and thermal techniques, the resulting present knowledge and problems, and some recent solutions. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Following Siemens (1857), we explore the formulation of a fundamental and common principle behind the operation of all cryocoolers. This conceptual model requires any cryocooler to include two essential elements: (a) a generator of an elementary and relatively small temperature-reduction and (b) a device that magnifies this reduction to produce a large cryocooling span. The magnification (b) is sustained by two thermally interacting counter flowing streams so arranged that the cold inlet temperature is permanently maintained below the warm outlet by (a), the elementary temperature-reducing mechanism. High magnification ratios are obtained when the two streams are balanced and even higher when the capacity rate of the high temperature stream is lower than that of the low temperature stream. When the elementary temperature-reduction is produced via a continuous (DC) flow, the associated magnification device is a recuperative heat exchanger. When an oscillatory (AC) flow device is used to produce the temperature reduction, then the magnification device is a regenerative heat exchanger. The various cryocoolers known as Joule-Thomson (JT) with a pure or mixed coolant, reverse-Brayton, Stirling, dilution refrigerator, active magnetic regenerative refrigeration (AMRR) and single shot adiabatic demagnetization refrigerators (ADR) are all discussed and reviewed in terms of this model. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The objective of the present work was to develop a precise instrument for measuring the thermal conductivity of powder insulating materials over a temperature range from 20 K to near room temperature. The instrument consists of two concentric copper cylinders with the annular space filled with the insulating material. The outer cylinder is thermally anchored to the coldhead of a single stage Gifford-McMahon cryocooler, while the inner copper cylinder is used for generating uniform heat flux through the insulating material. The temperature of both cylinders is measured at several locations to ensure uniform boundary conditions. The entire apparatus is wrapped in multi-layer insulation and suspended in a vacuum cryostat that provides an insulating environment. For a supplied heat flux, the temperature difference between the two cylinders is measured in steady state, from which the thermal conductivity of powder insulation is calculated and compared with published results. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The proposed international “Facility for Antiprotons and Ions Research project” — FAIR will consist of a large double-ring synchrotron, a radioactive secondary beam fragment separator, several heavy ion and antiproton storage rings and a number of beam transfer lines for connection between the individual facilities. Superconducting magnet technology will be extensively employed in the whole facility. The beam transfer system will be equipped with two types of synchrotron magnets which work in AC operation mode. The super-FRS fragment separator and the CR collector storage ring will be equipped with a number of superconducting dipole, quadrupole and hexapole magnets which work in DC operation mode. The preliminary layout of the cryogenic distribution and the control scheme of feedbox are discussed for the individual sections of the beam transfer line as well as for the super-FRS and CR ring. Special requirements are addressed for the beam transfer lines which have inclinations up to 13.2 degrees. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In the framework of the cryogenic cooling system design of the 4T CMS magnet, heat and mass transfer has been experimentally studied at CEA-Saclay on a 9-m high helium two-phase convection loop under atmospheric pressure. The loop includes a 5-m high heated section surmounted by a 4.5-m high collector and is connected to the final CMS phase separator. The heated section of the loop is composed of seven aluminum tubes placed in parallel and heated on one side to reproduce the heating configuration of the magnet cooling system. We focused in this paper on the hydraulic characteristics of the two-phase convection loop. Evolutions of mass flow rate and vapor quality are presented and analyzed as a function of the heat flux with an equations system based on the homogeneous model. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Helium sub-cooling heat exchangers of the counter-flow type are used to minimize the vapor fraction produced in the final expansion of the 1.9 K distributed cooling loops used for cooling the superconducting magnets of the Large Hadron Collider (LHC). These components are of compact design, featuring low-pressure drop and handling very low pressure vapor at low temperature. Following a qualification phase of prototypes, a contract has been placed in European industry for the supply of 239 heat exchanger units. Different levels of extracted heat load require three different variants of heat exchangers. This paper will describe the manufacturing phase with emphasis on the main difficulties encountered to keep the production quality after a brief recall of the prototype phase. Finally, the acceptance tests performed at room temperature and at the nominal cryogenic condition at the factory and at CEA-Grenoble will be presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A helium cryogenic plant with a maximum cooling power of 450 W at 4.5K was installed at the end of the year 2003. This plant has provide the cooling power for the test of one superconducting cavity and the commission of one superconducting magnet for nine months. In November 2004, we installed one helium transfer system in NSRRC’s storage ring to fulfill the cooling requirement for the operation of one superconducting cavity and two superconducting magnets. This helium transfer system consists of a switch valve box and the nitrogen-shielding multi-channel transfer lines. The averaged heat leak to the helium process line (including the straight section, the joint, the elbow, the coupling) at liquid helium temperature is specified to be less than 0.1 W/m at 4.2K; the total heat leak of the switching valve box to helium process lines is less than 16 W at 4.2K. In this paper we present the function, design parameters and test result of the helium transfer system. Commissioning results of both the cavity and the magnets using this helium transfer system will be shown as well. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In a conventional vacuum-jacketed cryogen transfer line, the major heat transfer is dominated by two modes: i) radiation between the warm outer pipe and the cold inner pipe and ii) thermal conduction through support members and penetrations. Magnetic levitation makes it possible to eliminate the conduction portion by use of non-contact support, consisting of high temperature superconductor (HTS) and permanent magnet (PM). Several transfer line prototypes (including a 6-meter prototype) have been designed and constructed to optimized the levitation and thermal performance. This paper reviews the key design/fabrication issues, such as levitation configuration, levitation force measurement, warm-support design using smart materials, fabrication process, and technical milestones throughout a 3-year period. This novel transfer line offers the potential of significant savings of cryogens and hence reduces the cost of crygon use. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Low temperature medicine is becoming a widely appreciated method in surgery, dermatology, gynecology and rheumatology. The cryomedical equipment is usually supplied with liquid nitrogen LN2 stored in a dewar and transferred to a tip, where it is evaporated providing a cooling power. LN2 in quantities sufficient for cryo-surgical and cryo-therapeutical applications can be first separated from air and then liquefied using a system combining polymer membrane gas separation technology and a Joule-Thomson closed-cycle refrigerator filled with a nitrogen-hydrocarbons gas mixture. Nitrogen is separated from the compressed air, then liquefied and throttled to atmospheric pressure. The paper analyzes the demanded cooling capacity of the system resulting from cryomedical treatment requirements. Thermal design and flow scheme of the apparatus are given. The system is thermodynamically optimized. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A 6-meter prototype cryogenic transfer line with magnetic suspension was tested for its mechanical and thermal performance at the Cryogenics Test Laboratory of NASA Kennedy Space Center (KSC). A test facility with two cryogenic end-boxes was designed and commissioned for the testing. Suspension mechanisms were verified through a series of tests with liquid nitrogen. The thermal performance of the prototype was determined using the new test apparatus. The tested prototype has incorporated temperature and vacuum pressure data acquisition ports, customized interfaces to cryogenic end-boxes, and instrumentation. All tests were conducted under simulated onsite transfer line working conditions. A static (boiloff rate measurement) testing method was employed to demonstrate the gross heat leak in the tested article. The real-time temperature distribution, vacuum level, levitation distance, and mass flow rate were measured. The main purpose of this paper is to summarize the testing facility design and preparation, test procedure, and primary test results. Special arrangements (such as turning on/off mechanical support units, observing levitation gap, and setting up the flowmeter) in testing of such a magnetically levitated transfer line are also discussed. Preliminary results show that the heat leak reduction of approximately one-third to one-half is achievable through such transfer lines with a magnetic suspension system. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The final cool-down of a 107-m standard cell of LHC, which consists of the helium filling operation at 4.5 K and the further cool-down from 4.5 K to 1.9 K, has been previously simulated and analyzed numerically. To model and analyze the final cool-down process of a whole 3.3-km sector of the LHC, additional boundary conditions must be introduced. In this paper, the slope of the sector, the efficiency of the sub-cooling heat exchanger, the pressure drops and heat loads in different headers of the cryogenic distribution line as well as the fact that both the filling flow of the cold mass and the vaporized flow in the 1.8 K heat exchanger are concurrently supplied have been taken into account. The simulation results, such as the temperature evolution in the LHC magnet cold mass and the pressure profiles in cryogenic line headers during the filling and cool-down from 4.5 K to 1.9 K of a LHC sector are presented. Taking into account the required distribution of the total flow to each cell, all the cells can be filled up to 67% of the volume and further cooled down to 1.9 K simultaneously in 15 to 20 hours. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nuclear fusion reactors of the Tokamak type will be operated in a pulsed mode requiring the helium refrigerator to remove periodically large heat loads in time steps of approximately one hour. What are the necessary steps for a refrigerator to cope with such load variations? A series of numerical simulations has been performed indicating the possibility of an active refrigerator control with low exergetic losses. A basic comparison is made between the largest existing refrigerator sizes and the size required to service for example the ITER requirements. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The goal of the overall program is to develop a dynamic numerical model of helium refrigerators and the associated cooling systems based on commercial simulation software. The aim is to give system designers a tool to search for optimum control strategies during the construction phase of the refrigerator with the help of a plant “simulator”. In a first step, a simple Brayton refrigerator has been investigated, which consists of a compressor, an after-cooler, a counter-current heat exchanger, a turboexpander and a heat source. Operating modes are “refrigeration” and “liquefaction”. Whereas for the steady state design only component efficiencies are needed and mass and energy balances have to be calculated, for the dynamic calculation one needs also the thermal masses and the helium inventory. Transient mass and energy balances have to be formulated for many small elements and then solved simultaneously for all elements. Starting point of the simulation of the Brayton cycle is the steady state operation at design conditions. The response of the system to step and cyclic changes of the refrigeration or liquefaction rate are calculated and characterized. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have manufactured and tested a cryocooled superconducting magnet designed for 10 T with a room temperature bore of 360 mm for a hybrid magnet designed for 29 T. The cryocooled superconducting magnet generated so far a magnetic field of 9.5 T. Furthermore, in combination with a water-cooled resistive magnet it generated a magnetic field of 27.5 T. As we succeeded in the magnetic levitation test of InSb using this hybrid magnet, we confirmed the usefulness of the newly developed magnet system for a novel process development of diamagnetic materials in the minute gravity environment. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Conversion into Hydrogen Energy Society is advanced focusing on the application to a fuel cell electric vehicle. As volume and weight density of liquid hydrogen are large, it is the method which was most excellent as the storage method of hydrogen. However, in order to store liquid hydrogen stably over a long period of time, decreasing the loss of energy, development of an efficient small cryocooler becomes important. This paper reports the research about improvement in the refrigeration efficiency of a two-stage GM cryocooler. In order that the GM cryocooler may operate by the Simon expansion, it carries out asymptotic of the COP of the GM cryocooler to the Carnot COP as a compression ratio is lowered. When experimented based on this view, it was checked that refrigeration efficiency rises with reduction in a compression ratio. Furthermore, if the compression ratio is lowered, refrigeration efficiency will fall rapidly. The peak value of the refrigeration efficiency in 20K level attained 28%Carnot. It was verified by optimization of the compression ratio of the GM cryocooler that refrigeration efficiency can be improved significantly. Therefore, sharp reduction of the energy consumption of a liquid hydrogen system will be attained by applying the result of this research. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A dynamic simulation of a large scale cryogenic plant has been conducted, using the Cryogenic Process REal-time SimulaTor (C-PREST) developed as a platform to study cryogenic plant processes. The target plant, Large Helical Device (LHD), consists of a 10 kW class helium refrigerator/liquefier and superconducting coil systems with their supporting structure. Since the development of helium refrigerator/liquefier had been completed, the simulation model was focused on the superconducting coil systems. As the preliminary step for the entire cryogenic plant, the coils are simplified and modeled to have certain temperature efficiencies. Cooldown of the coil systems were conducted from the room temperature to close to 4.4 K, utilizing automatic cooldown sequence programs for the actual cryogenic plant. The paper discusses the computational speed just before establishing the two-phase flow condition and the validity of the simulations compared with the real plant operation. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper describes the cryogenic thermal management advances made during the AFRL-sponsored CRYOTOOL program. Advances occurred as a result of conducting four technology development tasks: (1) development of a differential thermal expansion cryogenic thermal switch (DTE-CTSW) made with high purity Al end-pieces and an Ultem support rod; (2) carrying out of a dual DTE-CTSW/dual cryocooler performance test to quantify CTSW benefits in a redundant cryocooler system; (3) development of a miniaturized cryogenic loop heat pipe (mini-CLHP) that combines flex link, conduction bar, and CTSW functionalities; and (4) development of an across-gimbal cryogenic thermal transport system (GCTTS) with large diameter transport line coils for optics cooling. The results are as follows. The DTE-CTSW achieved an ON conductance of 2–3.6 W/K (from 35–90 K) and an OFF resistance of 1100–2300 K/W (300–230 K warm end). The redundant cryocooler test showed modest parasitic heat leak savings when dual DTE-CTSWs were used versus when they were not used. The mini-CLHP, using neon as the working fluid, transported 2.5 W at 35 K, achieved an OFF resistance of 1555 K/W, and had cross/axial flexibilities of 100–450 N/m. Lastly, GCTTS, using nitrogen as the working fluid, transported 20 W at 100 K in a flat configuration. Additional work is needed to verify GCTTS operation in an elevated orientation. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Air Liquide’s Advanced Technology Division is a manufacturer of cryogenic expanders. More than 450 units are now working around the world, mainly dedicated to liquefiers, refrigerators and H2-CO purification units. In order to cope with the power increase of these units, a new expander called “TC7” has been developed and tested. This expander permits turbine wheel diameters up to 110 mm, while the other units of the range (from TC3 to TC6, by increasing wheel diameter) are limited to 78 mm. The maximum flow rate is therefore doubled. The main technical features of the existing range have been kept, and adapted in size: static radial and thrust bearings, low loss casing, variety of wheel shapes (radial-radial shrouded or un-shrouded, radial-axial). This paper describes the main design characteristics of this new expander, together with manufacturing aspects and test results. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Up to now He piston pumps were used in the TOSKA facility of the Forschungszentrum Karlsruhe for circulating supercritical He in a secondary cooling loop. The performance of these pumps was a mass flow rate up to 150 g/s each, a pressure head of up to 0.3 MPa and an operation in the temperature range between 1.8 K and 5 K. For redundancy reasons, a centrifugal pump, developed by industry, was installed in an extension of the control cryostat, integrated into the existing cooling system, and tested in 2004. During the first tests, large oscillations and a huge heat input to the cooling circuit prevented operation of the pump. After some modifications by the supplying company, the pump was tested again with very promising test results. The results are in very good agreement with the predictions of the supplier. Details of the installation, the integration into the cooling system as well as the operational experience and test results will be outlined. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Thermal acoustic oscillations (TAOs) were recently observed and eliminated in two vacuum-housing cryogenic pumps. This paper documents the results of research performed to identify the critical parameters that affect thermal acoustic oscillations in a vacuum-housing cryogenic pump. Techniques for simplifying this complex oscillation system were developed so that an existing mathematical model for a straight tube with uniform radius could be applied. Based on the simplified model, criteria were defined. These criteria provide design guidelines to prevent thermal acoustic oscillations from occurring inside vacuum-housing cryogenic pumps. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Turbomachine-based Brayton (turbo-Brayton) cryocoolers are an ideal option for long-duration space missions. Key attributes inherent to the technology are high reliability, extremely low vibration emittance, and flexible packaging and integration with instruments and spacecraft systems. The first space implementation of the technology was the NICMOS Cryocooler, which is a single-stage unit that was installed on the Hubble Space Telescope in March 2002. This cryocooler provides 7 W of cooling at 70 K and has been operating for 3.3 years (July 2005) without degradation in performance. New developments at Creare are focused on two-stage configurations with load temperatures as low as 6 K. The lower temperatures and loads have required advances in component technologies to meet aggressive targets for cryocooler mass, size and performance. The development of the electronics, compressors and intermediate turboalternator for a 6–10 K cryocooler are complete. This paper summarizes our accomplishments on the completed components, and reviews our progress towards the development of the remaining critical components, a lightweight recuperator and a high performance low temperature turboalternator. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A multi-stage 10K cryocooler is under development that achieves compactness and reliability by using modern microelectronics to enable complex valve timing in a mechanically simple yet efficient cold head design. The cryocooler is based upon a novel modification of the Collins cycle, a cycle commonly used in many large-scale high-efficiency terrestrial cryogenic machines. This cycle is particularly well suited for cryocoolers operating from 4 K up to about 30 K. The modular nature of this design enables the configuration of application specific two stage (30 K), three stage (10 K), and four stage (4 K) cryocoolers. Innovations of the design include floating piston expanders and electromagnetic smart valves, which eliminate the need for mechanical linkages and thereby reduce the input power, size, and weight of the cryocooler in an affordable modular design. A sophisticated LabView based control algorithm enables electronic control of the expansion cycle. Software based control enables variable valve timing and adaptive control logic. An engineering prototype has been built that integrates the floating piston expander and recuperative heat exchanger as a functional cryocooler. The engineering prototype is currently undergoing development testing. This paper will present the design of the engineering prototype, the results of initial engineering prototype development testing, and the direction of future development. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Under contract with the Air Force Research Lab (AFRL), Lockheed Martin has built and tested a 3-stage pulse tube cryocooler which provides cooling at 10K and 75K. The cooler was designed for 200mW cooling at 10K and 8W cooling at 75K. The pulse tube is a simple 3-stage coldhead with no moving parts, driven by a long-life linear flexure-bearing clearance-seal compressor. The coldhead is a robust U-tube arrangement, with all metal seals for long life. Performance data will be presented. Future Air Force and Department of Defense (DoD) satellites will require efficient, low temperature cryocoolers to support space surveillance, missile defense, and other mission applications. The use of Very Long Wave Infrared (VLWIR) focal planes using arsenic doped silicon detectors operating at 10K which can detect to 25 micron wavelength has long been sought as the solution to the mid course missile defense mission. The immaturity of 10K cryocooler technology has impeded the use of VLWIR focal planes in current space payloads. A viable, efficient 10K cryocooler could provide further benefits through the use of on-focal plane readout and signal processing using low temperature superconducting electronics. The resultant smaller apertures produce cheaper, lighter sensors, much easier to host in a space-based system. An efficient, compact 10K cryocooler would provide significant capability improvements to future DoD systems. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Advances in the field of microfabrication have resulted in the ability to fabricate advanced geometries in various materials for use as regenerators in cryocoolers. Microchannels have been produced in nickel, stainless steel, lead and erbium, and these microfabrication techniques can also be applied to other rare-earth materials. Regenerators produced by this method will greatly benefit the cryocooler industry due to the fact that the power efficiency and the attainable cold end temperature are strongly influenced by the geometry of the regenerator. These new fabrication techniques allow the designer to reduce the pressure drop across the regenerator and optimize the regenerator performance by varying the porosity, channel shape, and channel size. The resulting regenerators support lower NPH/NTU values over the screens and powders currently in use. Models that have been developed for microchannel regenerator designs indicate that cryocooler efficiencies can be significantly improved relative to packed powder and screen regenerators. Both DC and oscillating testing systems are being developed to experimentally determine the performance of microchannel regenerators. The current fabrication and testing results will be presented as well as the future development strategy. Improvements in the thermal performance of regenerators will result in an overall improvement in cryocoolers, especially at the lower temperature ranges. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The ceramics oxide magnetic materials have shown excellent properties for use as regenerator materials used in 4 K crycoolers. Currently four kinds of oxide magnetic materials GdVO4, GAP=GdAlO3, GOS=Gd2O2S and Tb2O2S are available for applications for regenerators or thermal anchors from 2 K to 8 K. This paper focused on controlling the heat capacity of the (GdxTb1-x)2O2S system to cover the refrigeration temperatures between 6 K and 8 K. A concept of multilayer regenerator material consisting of multicomponent magnetic materials has been proposed and investigated. Two-layer ceramic material including two kinds of magnetic materials (Gd0.1Tb0.9)2O2S+Tb2O2S was successfully fabricated in the form of regenerator particles with an average diameter of 0.25 mm. Measured heat capacity data showed that it had twin peaks relating to those of (Gd0.1Tb0.9)2O2S and Tb2O2S, and the entire curve became broader and wider. The mechanical properties of strength and hardness of the two-layer ceramic material were the same as other ceramic regenerator materials like GOS. Thus, it is concluded that the multilayer ceramic material is very useful to control the heat capacity of the regenerator particles. The cooling tests using the two-layer ceramic material with HoCu2 and GOS have been done to investigate the 2nd stage regenerator configuration. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Pulse tube refrigeration (PTR) systems are often modeled as one-dimensional flow fields. However, recent computational fluid dynamics (CFD) — based investigations have shown that multi-dimensional flow effects can be significant in the regenerator of a PTR, especially when the aspect ratio of the regenerator is small. Anisotropic hydrodynamic parameters of regenerators are therefore needed for the realistic simulation of their multi-dimensional flow phenomena. In this paper we report on measurements of the lateral or radial permeability and Forchheimer’s inertial coefficient of a widely used PTR regenerator filler. Using helium as the working fluid, steady-state pressure drops were measured over a wide range of flow rates in annular test sections that contained regenerator fillers. The aforementioned hydrodynamic parameters were then obtained by comparing the data with the results of CFD calculations that simulated the test sections and their vicinity. CFD simulations of the experiments were performed iteratively, whereby permeability and Forchheimer coefficient that brought about agreement between data and simulation results were calculated. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The size of Stirling and Stirling-type pulse tube cryocoolers is dominated by the size of the pressure oscillator. Such cryocoolers typically operate at frequencies up to about 60 Hz for cold-end temperatures above about 60 K. Higher operating frequencies would allow the size and mass of the pressure oscillator to be reduced for a given power input. However, simply increasing the operating frequency leads to large losses in the regenerator. The simple analytical equations derived here show how the right combination of frequency and pressure, along with optimized regenerator geometry, can lead to successful regenerator operation at frequencies up to 1 kHz. Efficient regenerator operation at such high frequencies is possible only with pressures of about 5 to 8 MPa and with very small hydraulic diameters and lengths. Other geometrical parameters must also be optimized for such conditions. The analytical equations are used to provide guidance to the right combination of parameters. We give example numerical calculations with REGEN3.2 in the paper for 60 Hz, 400 Hz, and 1000 Hz operation of optimized screen regenerators and show that the coefficient of performance at 400 Hz and 1000 Hz is about 78 % and 68 %, respectively, of that for 60 Hz when an average pressure of 7 MPa is used with the higher frequency, compared with 2.5 MPa for 60 Hz operation. The 1000 Hz coefficient of performance for parallel tubes is about the same as that of the screen geometry at 60 Hz. The compressor and cold-end swept volumes are reduced by a factor of 47 at 1000 Hz, compared with the 60 Hz case for the same input acoustic power, which can enable the development of microcryocoolers for MEMS applications. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The need for improved regenerative cryocooler efficiency may require the replacement of conventional matrices with ducts. The ducts can not be continuous in the direction of temperature gradient when using conventional materials to prevent unacceptable conduction losses. However, this discontinuity creates a complex geometry to model and determine conduction losses. Chesapeake Cryogenics, Inc. has designed, fabricated and tested an apparatus for measuring the heat conduction through regenerative heat exchangers implementing different matrices. Data is presented for stainless steel photo etched disk, phophorus-bronze embossed ribbon coils and screens made of both stainless steel and phosphorus-bronze. The heat conduction was measured with the regenerators evacuated and pressurized with helium gas. In this test apparatus, helium gas presence increased the heat leak significantly. A description of the test apparatus, instrumentation, experimental methods and data analysis are presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Launched on NASA’s Aura spacecraft on July 15, 2004, JPL’s Tropospheric Emission Spectrometer (TES) instrument has completed a successful first year in space and captured a number of important lessons. The instrument contains four focal plane arrays in two separate housings cooled to 65 K by a pair of NGST pulse tube cryocoolers. The instrument includes a two-stage passive cooler to cool the optical bench to 180 K. The cryocooler system design is tightly coupled with the overall thermal control design to maximize performance. Soon after cooling the optical bench and focal planes to their operating temperatures on August 20, 2004, ice contamination of the focal planes led to the need of a decontamination cycle. Ice buildup of cryogenic surfaces led to increased cryocooler heat loads. After six months of successful science operations, plans were developed to increase the optics temperature to 187 K to improve the interferometer optical alignment and obtain higher quality science data. The plan is in place and will be implemented in the near future. This paper provides a general overview of the cryogenic system design and reviews the instrument cryogenic performance over the past year. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper describes the HIRDLS (High Resolution Dynamic Limb Sounder) Cryocooler Subsystem (CSS) and its on-orbit flight performance. The HIRDLS Instrument was launched on July 15, 2004 as part of the NASA GSFC EOS Aura platform. Ball Aerospace provided the CSS, which includes the long life Stirling cryocooler (cooling at 59 K), cold plumbing to connect the cooler to the instrument Detector Subsystem, an ambient radiator to reject the cooler dissipation, and a vacuum enclosure system that enabled bench top ground testing. As of August 20, 2005, the cryocooler has over 9,000 hours of continuous operation with performance that exceeds requirements. Of note is that the CSS has experienced virtually no change in performance, including no indication of external contamination related degradation that has been evident on several other cryocooler systems in space flights. This steady performance can be attributed to the multi-layer insulation (MLI) based insulation design, which will be described in the paper. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

A Large heat lift 40 to 80 K Pulse Tube Cooler (LPTC) is currently under development in partnership between AL/DTA, CEA/SBT and THALES Cryogenics. The Engineering Model (EM) foreseen is aiming to provide 2 W of cooling capacity at 50 K for 10°C rejection temperature and for 125 watts input power to the compressor’s motors. Cold finger development models (DM) have been manufactured with an in-line architecture and connected to an off-the-shelf compressor from Thales Cryogenics. In parallel, the compressor motor has been optimized and prototyped. The various trade-offs, performed both on the cold finger and compressor side, during the development phase are presented. This work is funded by the European Space Agency (ESA/ESTEC Contract N°18433/04/NL/AR) in the frame of future Earth Observation instruments development. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Under contract with the Space Dynamics Laboratory, Lockheed Martin’s Advanced Technology Center (LM-ATC) has built and tested the two-stage Engineering Model of a space flight pulse tube cryocooler, which provides simultaneous cooling at 75 K and 130 K. The cryocooler is robust and simple, consisting of a two-stage coldhead with no moving parts, driven by a linear flexure-bearing compressor and powered by a high-efficiency electronic controller that includes ripple suppression and vibration cancellation. A distance of up to one meter separates the coldhead and compressor. The cryocooler was designed to simultaneously provide 0.75 W of cooling at 75 K and 6 W cooling at 130 K while conductively rejecting heat at 313 K. Total system power is 125 W. Performance data is presented, showing excellent cryocooler performance. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Lockheed Martin’s Advanced Technology Center has developed a compact coaxial pulse tube cryocooler for avionics applications. The cooler was designed to deliver in excess of 1W cooling at 77K with a heat rejection temperature of 70°C, and to cool down from ambient temperature in a very short period of time. The cryocooler utilizes our MINI compressor, developed for NASA-GSFC, coupled with a newly-designed coaxial pulse tube designed to approximate the Standard Advanced Dewar Assembly (SADA II) packaging envelope. The cryocooler mass is 1.25 kg. Test data show excellent performance, with cooldown times of less than 6 minutes (coldhead only, with no additional thermal mass attached to the coldhead). Performance data will be shown for a variety of operating conditions. A discussion of low cost pulse tube cryocoolers will also be presented. This cryocooler was developed and tested with Lockheed Martin IRAD funding. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

An analysis of the Claude form of an idealized helium liquefier for the minimum input work reveals the ‘Carnot Step’ for helium refrigerator cycles. As the ‘Carnot Step’ for a multi-stage polytropic compression process consists of equal pressure ratio stages; similarly for an idealized helium liquefier the ‘Carnot Step’ consists of equal temperature ratio stages for a given number of expansion stages. This paper presents the analytical basis and some useful equations for the preliminary examination of existing and new Claude helium refrigeration cycles. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We present an overview of our recent measurements on the crossover from a Bose-Einstein condensate of molecules to a Bardeen-Cooper-Schrieffer superfluid. The experiments are performed on a two-component spin-mixture of 6Li atoms, where a Feshbach resonance serves as the experimental key to tune the s-wave scattering length and thus to explore the various interaction regimes. In the BEC-BCS crossover, we have characterized the interaction energy by measuring the size of the trapped gas, we have studied collective excitation modes, and we have observed the pairing gap. Our observations provide strong evidence for superfluidity in the strongly interacting Fermi gas. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]