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An AMR test apparatus has been developed for testing magnetic regenerators at temperatures ranging from room-temperature to 20 K. Near 300 K, no-load temperature spans over 80 K have been produced using regenerators composed of two and three different magnetocaloric materials. Modifications to the apparatus have been performed to allow testing at cryogenic temperatures. Initial tests near 80 K using magnetic fields of 5 T are presented using an AMR composed of Gd5Si0.33Ge3.67. A no-load temperature span of ∼8 K is achieved. The operating point is established using liquid nitrogen flow through the shell-side of the warm heat exchangers of the AMR. Design characteristics of the test apparatus, problems encountered, and modifications for improving experimental results are discussed.

Apart from specialized space requirements current development in applications of thermoelectric generation mainly relate to reducing harmful carbon emissions and decreasing costly fuel consumption through the recovery of exhaust heat from fossil fuel powered engines and emissions from industrial utilities. Focus on these applications is to the detriment of the wider exploitations of thermoelectrics with other sources of heat energy, and in particular natural occurring and waste low temperature heat, receiving little, if any, attention. In this presentation thermoelectric generation applications, both potential and real in harvesting low temperature waste/natural heat are reviewed. The use of thermoelectrics to harvest solar energy, ocean thermal energy, geothermal heat and waste heat are discussed and their credibility as future large-scale sources of electrical power assessed.

Use of a superconducting (SC) traveling‐wave accelerating (STWA) structure with a small phase advance per cell, rather than a standing‐wave structure, may provide a significant increase in the accelerating gradient in the ILC linac [1]. For the same surface electric and magnetic fields, the STWA achieves an accelerating gradient 1.2 larger than TESLA‐like standing‐wave cavities. In addition, the STWA allows longer acceleration cavities, reducing the number of gaps between them. However, the STWA structure requires a SC feedback waveguide to return the few hundreds of MW of circulating RF power from the structure output to the structure input. A test single‐cell cavity with feedback was designed and manufactured to demonstrate the possibility of proper processing to achieve a high accelerating gradient. The first results of high‐gradient tests of a prototype 1.3 GHz single‐cell cavity with feedback waveguide will be presented.

A tractable scheme for numerical diagonalization of the Bohr Hamiltonian, based on SU(1,1)×SO(5) algebraic methods, has recently been proposed. The direct product basis obtained from an optimally chosen set of SU(1,1) β wave functions and the SO(5) spherical harmonics ΨvαLM(γ,Ω) provides an exceedingly efficient basis for numerical solution, as compared to conventional diagonalization in a five‐dimensional oscillator basis. In this contribution, the status of the SU(1,1)×SO(5) algebraic collective model is summarized and applications are presented. In particular, the transition from axially symmetric to triaxial structure is explored.

The superconductive magnesium diboride (MgB2) sensor for detecting the level of liquid hydrogen has attracted attention as a new senor that has high resolution and good reproducibility. The MgB2 sensor utilizes the difference in the electric resistance between the liquid and vapor phases of hydrogen. In this study, external-heating-type MgB2 sensors are fabricated by the in situ method, and their level-detecting characteristics, e.g., the heater input dependence and the linearity of the detected level, are studied by comparison with the actual level of liquid hydrogen in a optical cryostat. It is shown that the MgB2 sensor demonstrates good reproducibility, a short response time of about one second, no hysteresis, and accurate operation even at low liquid levels.

The cryogenic and vacuum concepts for the electrostatic Cryogenic ion Storage Ring (CSR), under construction at the Max-Planck-Institut fur Kernphysik in Heidelberg, is presented. The ring will operate in a broad temperature range from 2 to 300 K and is required to be bakeable up to 600 K. Extremely high vacuum and low temperatures are necessary to achieve long lifetimes of the molecular ions stored in the ring so that the ions will have enough time to cool by radiation to their vibrational and rotational ground states. To test cryogenic and vacuum technological aspects of the CSR, a prototype is being built and will be connected to the commercial cryogenic refrigerator recently installed, including a specialized 2-K connection system. The first results and the status of current work with the prototype are also presented.

The cryogenic system [1] for the Large Hadron Collider accelerator is presently in its final phase of commissioning at nominal operating conditions. The refrigeration capacity for the LHC is produced using eight large cryogenic plants and eight 1.8 K refrigeration units installed on five cryogenic islands. Machine cryogenic equipment is installed in a 26.7-km circumference ring deep underground tunnel and are maintained at their nominal operating conditions via a distribution system consisting of transfer lines, cold interconnection boxes at each cryogenic island and a cryogenic distribution line. The functional analysis of the whole system during all operating conditions was established and validated during the first sector commissioning in order to maximize the system availability. Analysis, operating modes, main failure scenarios, results and performance of the cryogenic system are presented.

High performance sensors are playing an increasingly important role in all aspects of all critical DoD missions. There is a family of sensors that operate with improved sensitivities if cooled to very low (cryogenic) temperatures. For these sensors, a healthy and reliable mechanical refrigeration system (cryocooler) is required. The ability to accurately predict the “health” or remaining useful life of the cryocooler has significant benefits from the viewpoint of ensuring that mission critical functions can be carried out with a high probability of success. The paper provides an overview and approaches used for the development of a Cryocooler Prognostic Health Management System (CPHMS) capable of assessing the cryocooler “health” from the viewpoint of the level of performance degradation and/or the potential for near term failure. Additionally, it quantifies the reliable remaining useful life of the cryocooler. While the proposed system is focused on the specific application to linear drive cryocoolers, e...

A luminosity upgrade of the CERN Large Hadron Collider (LHC) is planned to coincide with the expected end of life of the existing inner triplet quadrupole magnets. The upgraded inner triplet will have much larger heat loads to be removed from the magnets by the cryogenics system. A number of cryogenics design studies have been completed under the LHC Accelerator Research Program (LARP), including investigations of required heat exchanger characteristics to transfer this heat from the pressurized He II bath to the saturated He II system. This paper discusses heat exchangers both external to the magnet cold mass and internal to the magnet cold mass. A possible design for a heat exchanger external to the magnet cold mass is also presented.

An intense spallation neutron source (JSNS) driven by a 1-MW proton beam was constructed, as one of the main experimental facilities in J-PARC. In JSNS, supercritical hydrogen (1.5 MPa, 20 K) was selected as a moderator material. Three kinds of hydrogen moderator are installed (coupled, decoupled, and poisoned) to provide pulsed neutron beam with higher neutronic performance. The moderators contain cryogenic hydrogen transfer lines located in a radioactive area. Therefore, the transfer lines should be designed to have minimum pipe size and elbow-type bend sections to reduce the potential for radiation dose by radiation streaming. The design should also consider mechanical stress concentrations, deformation, and touching between the pipes due to the thermal shrinkage at the cryogenic hydrogen temperature. A FEM code analysis determined the appropriate locations of piping supporting spacers to keep the thermal stress below the allowable stress and to also avoid touching between the pipes.

A number of future European Space Agency (ESA), science missions may require detector cooling to sub-Kelvin temperatures. One such mission is the X-ray Evolving Universe Spectroscopy (XEUS), mission, which is a candidate for the ESA Cosmic Vision 2015-2025 plan, following XMM-Newton and Chandra. The Detector Spacecraft model payload comprises a passively cooled wide-field camera at 200K, and one of two narrow-field instruments at 300mK and 50mK. As with several other science missions, the required lifetime is at least 5 years, with a 10 year goal, necessitating the use of long-life closed cycle cooling systems. Under contract to ESA, Astrium has worked with the Mullard Space Science Laboratory (MSSL), Rutherford Appleton Laboratory (RAL), and CEA-SBT, to propose a payload accommodation design for XEUS capable of meeting the demanding requirements. Our baseline consists of a two stage Adiabatic Demagnetization Refrigerator (ADR), at 50mK, and a helium sorption cooler at 300mK. Each system will be pre-cooled by a closed cycle J-T system, similar to Planck, at 2.5K or 4K, which itself will be pre-cooled by a two-stage Stirling cycle cooler, at 17K or 18K. This paper describes the mission, and discusses the cryogenic architectures in depth.

A visualization study was carried out by applying shadowgraph method to investigate a number of phase transitions of superfluid helium (He II) in a two-dimensional narrow channel being composed of a transparent planar heater and a cover glass plate. A liquid-vapor, a He II-He I and a superheated He II (sHe II)—superheated He I (sHe I) interfaces were clearly observed with the aid of image processing technique to enhance the resolution. It was found that the characteristic features of onset of film boiling were distinguishable under the pressure condition atmospheric pressure and saturated vapor pressure. Furthermore, the interface of sHe II- sHe I was visualized in saturated He II at the temperature above 2.1 K.

An Energy Recovery Linac Prototype (ERLP) is currently being constructed at Daresbury Laboratory, (UK) to promote the necessary skills in science & technology, particularly in photocathode electron gun and Superconducting RF (SRF), to enable the construction of a fourth generation light source, based on energy recovery linacs-4GLS [1]. The ERLP uses two identical cryomodules, one as a booster Linac used to accelerate the beam to 8.5 MeV, the other as an Energy Recovery Linac (ERL) module with an energy gain of 26.5 MeV. Each module consists of two 9- cell cavities operating at a frequency of 1.3 GHz and a temperature of 2 K. As there is no energy recovery in the booster it requires a peak power of 53 kW; whereas the linac module only requires 8 kW. The RF power is supplied by Inductive Output Tube (IOT) amplifiers. The maximum heat load (or the cooling power) required in the SRF system is 180 W at 2 K and is achieved in two stages: a LN2 pre-cooled Linde TCF50 liquefier produces liquid helium at 4.5 K, fo...

During the past decade Kleemenko cycle coolers have been developed to operate at temperatures between 70 K and 180 K using throttle expansion of multi-component refrigerants. They have demonstrated remarkable reliability—continuous, maintenance-free operation now approaching 100,000 hrs, and the simplicity of their design and use of low cost components has kept their cost at a small fraction of that of any other cryocoolers. However, little attention has been focused on optimizing the efficiency of these coolers. The problem has been the lack of an adequate understanding of the heat transfer of such multi-component mixtures to the walls of the heat exchanger and to a lesser degree an understanding of the pressure drop along the exchangers. These factors have limited the ability to design more efficient, low cost exchangers needed for improved cryocooler performance. Recently we have made progress in this area allowing calculation of the heat transfer factors under the conditions of use of these exchangers in good agreement with experiment. We describe this work and identify some remaining issues.

The high cost of Pressure Wave Generators (PWGs) is a major barrier to the more widespread use of high-efficiency pulse tube and Stirling cryocoolers. This paper describes the development and testing of a low-cost industrial-style PWG which employs metal diaphragms. The use of diaphragms removes the need for rubbing or clearance seals, and eliminates contamination problems by hermetically separating the gas circuit and the lubricated driving mechanism. A conventional low-cost electric motor is used for power input, via a novel high-efficiency kinematic linkage. A first prototype of the diaphragm PWG produced 3.2 kW of PV power with a measured electro-acoustic efficiency of 72%. Accelerated testing predicts a diaphragm life time in excess of 40,000 hours. An additional advantage of the use of diaphragms is the ability to directly cool the gas in the compression space. This eliminates or significantly reduces the requirement for an after cooler, and further decreases the cost of the whole cryocooler system. A pulse tube cryocooler has been successfully run at Industrial Research Ltd to 59K with the diaphragm PWG and no aftercooler. Another pulse tube cryocooler with the diaphragm PWG is undergoing development at Cryomech, the results of which will be given in another presentation.

The United States Navy has a continued interest in the development of High Temperature Superconductivity (HTS) to provide power dense, efficient propulsion and electrical power generation. These machines have large HTS rotor coils that will undergo many thermal cycles during the life of the ship. Thermal fatigue tests for large coils are necessary to understand any degradation and life issues that could arise. The Naval Surface Warfare Center Carderock Division (NSWCCD) has sponsored Rowan University to design and build a device that will assist in the thermal fatigue testing of a superconducting coil. It was designed to be autonomous with programmable cool down and warm-up rates and varying temperature from ambient temperature (300K) down to 77K. A typical test would include thermally cycling a coil a specified number of times, then performing a critical current test on the coil and repeating the test cycle as many times as desired. This paper introduces the thermal cycling test setup and presents preliminary calibration data.

A dynamic measuring system is set up to measure the mass flow rates and pressure waves inside pulse tube coolers. An in-line orifice type pulse tube cooler is tested. Phase shift angles for different input powers are measured and compared. Difference of gas flow characteristics under small perturbation and larger pressure wave condition is discussed.

Gimbaled Forward Looking Infrared (FLIR) cameras are placing increasing demand for cryocoolers to deliver more performance without commensurate size and weight allowances. L-3 CE has re-optimized the design of its 0.6-Watt cooler to provide twice the refrigeration lift without significant changes to weight and size. This paper presents the performance characteristics of the re-optimized cooler model B610D2.

The NICMOS Cooling System consists of a closed-loop turbo-Brayton cryocooler coupled with a cryogenic circulator that provides refrigeration to the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST). The cryocooler heat is rejected to space through a capillary pumped loop connected to radiators mounted on the side of the telescope. The system was deployed and integrated with NICMOS by astronauts during STS–109 (Space Shuttle Columbia) in March 2002. It has operated nearly continuously without performance degradation since that time, maintaining NICMOS detectors at a constant temperature of 77 K. Miniature, high-speed turbomachines are used in the cryocooler and the circulator loop to provide vibration-free, long-life operation. A small centrifugal compressor and miniature turboalternator are key elements of the closed loop cryocooler. A miniature cryogenic centrifugal circulator in a separate pressurized neon loop transports heat from the NICMOS instrument to the cryocooler interface heat exchanger. This paper describes the development of the system, key operational features, ground and orbital tests prior to its deployment, and operational results during its five-year operational history on orbit.

Very sensitive high-temperature SQUID (Superconducting Quantum Interference Device) magnetometers are used for the detection of very small metal contaminants in food and other products. When the SQUIDs are cooled with liquid nitrogen, a detection sensitivity of 500 nA-m2 in a 150×150 mm2 orifice is obtained. However, when a commercial Joule-Thompson cryocooler was used, the sensitivity was reduced by a factor of 5 due to spurious magnetic signals.In this study the emphasis is on understanding noise that may be created due to mechanical vibrations in the cryocooler cold head. The natural frequencies of the cryocooler cold head are modelled and two mechanisms of noise generation are considered and analysed. Calculations show that the noise created by vibrating dipoles in the cold head may create noise of 1 pT up to 20 pT in the frequency range of 10 to 50 Hz.The vibration characteristics of several parts of the cryocooler cold head assembly were determined with a laser vibrometer, a fluxgate magnetometer and through finite element simulations. Two natural frequencies of approximately 21 and 49 Hz are particularly noticeable and are also observed in the SQUID noise.Anti-vibration measures are introduced to reduce external vibrations.

Fusion of Hydrogen to produce energy is one of the technologies under study to meet the mankind raising need in energy and as a substitute to fossil fuels for the future. This technology is under investigation for more than 30 years already, with, for example, the former construction of the experimental reactors Tore Supra, DIII-D and JET. With the construction of ITER to start, the next step to “fusion for energy” will be done. In these projects, an extensive use of cryogenic systems is requested. Air Liquide has been involved as cryogenic partner in most of former and presently constructed fusion reactors. In the present paper, a review of the cryogenic systems we delivered to Tore Supra, JET, IPR and KSTAR will be presented.

High-temperature superconducting (HTS) cable systems are expected to be a solution for improvement of the power grid and three demonstration projects in the real grid are under way in the United States. One of them is the Albany, NY Cable Project, involving the installation and operation of a 350 meter HTS cable system with a capacity of 34.5kV, 800A, connecting between two substations in National Grid's electric utility system. A 320 meter and a 30 meter cable are installed in underground conduit and connected together in a vault. The cables were fabricated with 70km of DI-BSCCO wire in a 3 core-in-one cryostat structure. The cable installation of a 320 meter and a 30 meter section was completed successfully using the same pulling method as a conventional underground cable. After the cable installation, the joint and two terminations were assembled at the Albany site. After the initial cooling of the system, the commissioning tests such as the critical current, heat loss measurement and DC withstand voltage test were conducted successfully. The in-grid operation began on July 20th, 2006 and operated successfully in unattended condition through May 1st, 2007. In the 2nd phase of the Albany project, the 30 meter section is to be replaced by a YBCO cable. The YBCO cable had been developed and a new 30 meter cable was manufactured by using SuperPower's YBCO coated conductors. This paper describes the latest status of the Albany cable project.

A switched reluctance motor has been operated in liquid nitrogen (LN2) with a power density as high as that reported for any motor or generator. The high performance stems from the low resistivity of Cu at LN2 temperature and from the geometry of the windings, the combination of which permits steady-state rms current density up to 7000 A/sq cm, about 10 times that possible in coils cooled by natural convection at room temperature. The Joule heating in the coils is conducted to the end turns for rejection to the LN2 bath. Minimal heat rejection occurs in the motor slots, preserving that region for conductor. In the end turns, the conductor layers are spaced to form a heat-exchanger-like structure that permits nucleate boiling over a large surface area. Although tests were performed in LN2 for convenience, this motor was designed as a prototype for use with liquid hydrogen (LH2) as the coolant. End-cooled coils would perform even better in LH2 because of further increases in copper electrical and thermal conductivities. Thermal analyses comparing LN2 and LH2 cooling are presented verifying that end-cooled coils in LH2 could be either much longer or could operate at higher current density without thermal runaway than in LN2.

We have measured the thermal conductivity of aerogel beads and glass microspheres at average temperatures ranging from 30 K to 180 K. The measuring device consists of two closed, concentric cylinders suspended inside of a vacuum insulated cryostat. The insulation being tested occupies the annular space between the cylinders. A single stage Gifford-McMahon cryocooler, thermally anchored to the outer cylinder, cools the apparatus to a desired temperature range. A heater mounted on the inner cylinder generates uniform heat flux through the insulating material between the two cylinders. During each measurement, a temperature difference of roughly 10 K across the insulation is maintained. Fourier's law of heat conduction is used to relate the temperature difference between the two cylinders and the applied heating power to a bulk effective thermal conductivity of the powder insulation. Data were collected for aerogel beads between 30 K and 80 K and for glass bubbles between 30 K and 180 K. Results are compared to data from the literature.

Implementation of a conventional current lead with a pulse tube refrigerator has been validated to be working as an Integrated Current Lead (ICL) system for the Superconducting Magnetic Energy Storage (SMES). Realization of the system is primarily accounted for the flexibility of a pulse tube refrigerator, which does not posses any mechanical piston and/or displacer. As for an ultimate version of the ICL system, a High Temperature Superconducting (HTS) lead links a superconducting coil with a conventional copper lead. To ensure the minimization of heat loads to the superconducting coil, a pulse tube refrigerator has been upgraded to have a second cooling stage. This arrangement reduces not only the heat loads to the superconducting coil but also the operating cost for a SMES system. A prototype two-stage pulse tube refrigerator, series connected arrangement, was designed and fabricated to satisfy the requirements for the ICL system. Operation of the first stage refrigerator is a four-valve mode, while the second stage utilizes a double inlet configuration to ensure its confined geometry. The paper discusses the optimization of second stage cooling to validate the conceptual designImplementation of a conventional current lead with a pulse tube refrigerator has been validated to be working as an Integrated Current Lead (ICL) system for the Superconducting Magnetic Energy Storage (SMES). Realization of the system is primarily accounted for the flexibility of a pulse tube refrigerator, which does not posses any mechanical piston and/or displacer. As for an ultimate version of the ICL system, a High Temperature Superconducting (HTS) lead links a superconducting coil with a conventional copper lead. To ensure the minimization of heat loads to the superconducting coil, a pulse tube refrigerator has been upgraded to have a second cooling stage. This arrangement reduces not only the heat loads to the superconducting coil but also the operating cost for a SMES system. A prototype two-stage pulse tube refrigerator, series connected arrangement, was designed and fabricated to satisfy the requirements for the ICL system. Operation of the first stage refrigerator is a four-valve mode, while the...

One reason that heat transfer processes are not well understood is the difficulty of obtaining reliable temperature measurements when gas temperatures vary rapidly. In the work described here gas temperatures have been measured using a fine wire resistance thermometer with a 3.8 micron active sensor. The equipment represented the basic elements of a cryocooler: a clearance seal linear compressor and a wire mesh regenerator. Both were operated close to ambient temperature, with gas temperatures being measured close to the regenerator. The test rig was run at different volume ratios, frequencies (8-50 Hz), gases and filling pressures (1-26 bar). The waveforms of the gas temperature were found to vary dramatically for differing flow regimes. The results suggested that the thermometer was measuring the temperatures of two distinct volumes of gas, and that the gas must remain stratified in the compression space. A flow transition was identified from the cycle-by-cycle variations in temperature. The critical Reynolds number was determined to be 9.6-11. At the critical condition, the temperature was so unstable that fluctuations up to 250 Hz were observed. A series of validation tests have confirmed that the observed temperatures were not artifacts. © 2008 American Institute of Physics.

see also Advances in cryogenic engineering: Transactions of the Cryogenic Engineering Conference - CEC, Vol. 53 Conference 16–20 July 2007, Chattanooga (USA)ISBN: 978-0-7354-0504-2; International audience; Development on low temperature high frequency pulse tube cooler is underway at CEA/SBT. For space applications, it is possible to use passive cooling available on numerous science mission to decrease the no load temperature and enhance the cooling power. Based on previous experiments performed with in line configurations, an integrated coaxial configuration has been built and tested. Temperatures below 15 K without load and 20 K with 300 mW load has been achieved in inertance mode. The passive cooling is simulated by a GM cooler. The influence of the heat intercept temperature on the pulse tube performance is presented. The heat to be removed at the heat intercept as function of various parameters such as heat intercept temperature and input power is discussed. Finally, a second compressor has been used to perfectly control the phase shift in the pulse tube cold finger. Inertance limitation has been observed for ultimate temperature. A temperature as low as 10.1 K has been obtained with the phase shifter compressor

Lunar missions under consideration would benefit from incorporation of high specific impulse propellants such as LH2 and LO2, even with their accompanying boil-off losses necessary to maintain a steady tank pressure. This paper addresses a cryogenic propellant boil-off reduction system to minimize or eliminate boil-off. Concepts to do so were considered under the In-Space Cryogenic Propellant Depot Project. Specific to that was an investigation of cryocooler integration concepts for relatively large depot sized propellant tanks. One concept proved promising—it served to efficiently move heat to the cryocooler even over long distances via a compressed helium loop. The analyses and designs for this were incorporated into NASA Glenn Research Center's Cryogenic Analysis Tool. That design approach is explained and shown herein. Analysis shows that, when compared to passive only cryogenic storage, the boil-off reduction system begins to reduce system mass if durations are as low as 40 days for LH2, and 14 days ...

This paper is an update of papers written in 1991 and in 1997 by Rod Byrns and this author concerning estimating the cost of refrigeration for superconducting magnets and cavities. The actual costs of helium refrigerators and coolers (escalated to 2007 dollars) are plotted and compared to a correlation function. A correlation function between cost and refrigeration at 4.5 K is given. The capital cost of larger refrigerators (greater than 10 W at 4.5 K) is plotted as a function of 4.5-K cooling. The cost of small coolers is plotted as a function of refrigeration available at 4.2 K. A correlation function for estimating efficiency (percent of Carnot) of both types of refrigerators is also given.

The thermoacoustically driven two-stage pulse tube cooler has recently reached a lowest temperature of about 18.1K in our lab, and we are now developing a three-stage Stirling-type pulse tube cooler working at about 4K to match the thermoacoustic engine. In this paper, thermoacoustic theory is employed to simulate the three-stage pulse tube cooler. In order to decrease the cooling power losses of the second and third stage cold tips, two thermal bridges are introduced on the first and second stage cold tips to cool down the second and the third stage pulse tubes. Thus, the temperature gradients in the pulse tubes near the cold tips decrease, so do the cooling power losses through the thermal conductivity of the pulse tubes. After numerical optimization, the pulse tube cooler reaches a cooling temperature of 3.87K with 207 Watts of input acoustic power.

An instrument for the separation of particles by density (sorting) is being developed that uses the magneto-archimedes effect in liquid oxygen. With liquid oxygen strongly paramagnetic, the magneto-archimedes effect is an extension of diamagnetic levitation in the sense of increasing the effective buoyancy of a particle. The instrument will be able to separate ensembles of particles from 100 μm to 100 nm in size, and vertically map or mechanically deliver the separated particles. The instrument requires a column of liquid oxygen that is nearly isothermal, free of thermal convection, subcooled to prevent nucleate boiling, and supported against the strong magnetic field used. Thus, the unique cryostat design that meets these requirements is described in the present article. It consists in part of a column of liquid nitrogen below for cooling the liquid oxygen, with the liquid oxygen pressurized by helium gas to prevent nucleate boiling.

Superfluid turbulence (TSF) project uses liquid helium for the fundamental study of turbulent phenomena behind a passive grid and is able to work both in HeI and in HeII. The helium flow is generated by a cold Barber and Nichols circulating pump, whereas helium flow temperature is kept constant by means of a heat exchanger immersed in a saturated bath. This experiment takes profit of the CEA Grenoble refrigerator (nominal capacity of 400 Watt at 1.8 K) to remove the heat due to pressure losses in this high Reynolds number experiment. In order to resolve the Kolmogorov scale associated with high Re flow, local instrumentation (e.g. sub-micrometer anemometer) was developed. The difficulties encountered with this local and fragile instrumentation in a quasi industrial environment are discussed and the adopted solutions are also described. Finally, first results (permanent mass flow rate of a few hundreds g/s) obtained both in the two phases of helium are presented.

Two integrated models of coaxial miniature pulse tube coolers based on an experimental model are manufactured. Performance of the integrated models is compared to that of the experimental model. Reliability and stability of an integrated model are tested and improved.

Cryogenic thermosiphons are highly efficient heat transfer elements between a cryocooler and the thermal load that is to be cooled. This paper presents an idea of thermosiphon that peculiarly utilizes two evaporators to overcome spatial restriction. A so-called double-evaporator thermosiphon was designed, fabricated and tested using nitrogen under sub-atmospheric pressure condition. This thermosiphon is specifically aimed for cooling HTS bulk system. In this paper, the invisible interior condition of the double-evaporator themosiphon is described in detail during the cool-down process according to the internal thermal states. Although the double-evaporator thermosiphon worked successfully under sub-atmospheric pressure condition, there was a little temperature difference between two evaporators at steady-state operation. The cause of this problem is considered as the orientation effect of boiling heat transfer coefficient. An additional experiment was also conducted to examine the orientation effect of boiling heat transfer coefficient of nitrogen under sub-atmospheric pressure condition.

ITER is an international research and development project with the goal of demonstrating the feasibility of fusion power. The fuel for the ITER plasma is injected in the form of frozen deuterium pellets; the current injector design includes a batch extruder, cooled by liquid helium. A more advanced fuel system will produce deuterium pellets continuously using a twin-screw extruder, cooled by a cryocooler. One of the critical design parameters for the advanced system is the friction associated with the shearing planes of the frozen deuterium in the extruder; the friction determines the required screw torque as well as the cryocooler heat load.An experiment has been designed to measure the energy dissipation associated with shearing frozen deuterium. Deuterium gas is cooled to its freezing point in the gap between a stationary outer canister and a rotating inner cylinder. The dissipation is measured mechanically and through calorimetric means. The experiment has also been used to measure dissipation in othe...

In February 2006, Jefferson Laboratory in Newport News, VA, received “Critical Decision 1” (CD-1) approval to proceed with the engineering and design of the long anticipated upgrade to increase the beam energy of CEBAF, the Continuous Electron Beam Accelerator Facility, from 6 GeV to 12 GeV. This will require the installation of 10 new cryomodules, and additional 2.1-K refrigeration beyond the available 4600 W to handle the increased heat loads. Additionally, a new experimental hall, Hall D, is planned that will require the installation of a small, available refrigerator. This paper will present an overview of the integration of the new proposed refrigeration system into CEBAF, the installation of the available refrigerator for Hall D, and includes planned work scope, current schedule plans and project status.

In the framework of the ITER Broader Approach, CEA is carrying out the procurement of the Cryogenic System to the JA-EU Satellite Tokamak JT-60SA, which should be operated in Japan at JAEA, Naka in 2014. According to the Conceptual Design Report, JT-60SA is to operate for periods of at least 6 months per year, with major shutdown periods in between for maintenance and further installation upgrades. For this operation scenario, the cryoplant and the cryodistribution have to cope with different heat loads which depend on the different JT-60SA operating states. The cryoplant consists of one 4.5 K refrigerator and one 80 K helium loop, each pre-cooled by LN2. These cryogenic subsystems have to operate simultaneously in order to remove the heat loads from the superconducting magnets, 80 K shields and the divertor cryopumps.The first part of this study is based on the Process Flow Diagram (PFD) and presents the current design status of the JT-60SA cryogenic system. The second part is dedicated to the analysis of the cryoplant normal operation modes including the regeneration mode of the divertor cryopumps.Thanks to this analysis, the architecture of the present PFD is proposed in order to match the technical specifications of the cryoplant with the JT-60SA operation requirements.

Thanks to important internal development efforts completed and partial ESA funding, AL/DTA is now in position to propose two Pulse Tube cooler systems in the 40-80K temperature range for coming Earth Observation missions such as MTG, Sentinel 3, etc… The two pulse tube coolers thermo-mechanical units have been qualified against thermal and mechanical environment constraints.To complete these two Pulse Tube coolers, a Cooler Drive Electronic has been developed for active damping and vibration cancellation.The paper presents the current status of these products and associated Cooler Drive Electronics.

The oil injected screw compressors have practically replaced all other types of compressors in modern helium refrigeration systems due to their large displacement capacity, minimal vibration, reliability and capability of handling helium's high heat of compression.At the present state of compressor system designs for helium systems, typically two-thirds of the lost input power is due to the compression system. Therefore it is important to understand the isothermal and volumetric efficiencies of these machines to help properly design these compression systems to match the refrigeration process. This presentation summarizes separate tests that have been conducted on Sullair compressors at the Superconducting Super-Collider Laboratory (SSCL) in 1993, Howden compressors at Jefferson Lab (JLab) in 2006 and Howden compressors at the Spallation Neutron Source (SNS) in 2006. This work is part of an ongoing study at JLab to understand the theoretical basis for these efficiencies and their loss mechanisms, as well ...

A 3 stage Engineering Model pulse tube cooler was built and tested for low temperature operations. The staged cooler uses the same compressor and parallel staging configuration for the 1st and 2nd stages previously employed in the High Capacity Cryocooler Qualification (HCCQ). Addition of the third stage extends the performance of this cooler to operating temperatures below 10K. The EM cooler was fabricated and assembled to meet typical space dynamic and thermal performance requirements. The cooler performance at 10K has been characterized and test data are presented.

This paper describes the experimental study of the dynamic behavior of a linear compressor in a Stirling-type pulse tube refrigerator (PTR). The dynamic behavior of the piston is closely coupled with the hydraulic force of gas and, therefore, directly influenced by the specific load condition of the pulse tube refrigerator. In the experiment, the frequency response of the pressure at each component, the cooling performance and the piston displacement are measured while an alternate current with fixed magnitude is supplied to the linear motor. The linear compressor in this study was originally designed for a Stirling cryocooler and its maximum input power is approximately 200 W. The pulse tube refrigerator is configured as an in-line type and an inertance tube is incorporated as the phase control device in the pulse tube refrigerator. The pressure difference between both ends of the piston imposes additional stiffness and the PV power in the compression space can be considered a damping effect in the vibration system of the piston. From the experimental results, the effect of the gas force on the dynamic behavior of the piston is discussed. The dynamic relation among the input current, the displacement of the piston, the pulsating pressure and the cooling performance is also studied.

Two-temperature regimes have been envisaged for the SST-1 machine, 80 K on the thermal shield and 4.5 K on the superconducting magnet system. The aim of temperature measurement is two folds (i) to monitor the temperature distribution as well as process parameters (ii) to achieve controlled cool down from 300 K to 4.5 K and 80 K. Temperature sensors have been mounted on cold surfaces at required locations to ease the operation during cool down and steady state. Techniques employed for temperature measurement and controls are based on continuous resistance measurement. Cernox™ sensors (Lakeshore made) and PT-102 have been used for the temperature measurement at 4.5 K and 80 K surfaces respectively. The data acquisition system (DAS) has been indigenously developed using 4-20 mA current loop temperature transmitter, which provided better functioning in terms of flexibility. The control functioning has been designed and developed using programmable logic controller with direct interfacing of the transmitter. T...

A curved rotating heat pipe for use in superconducting motor and generator applications is introduced here. The heat pipe shown here is built so that both the condenser and evaporator sections are parallel to the axis of rotation. The condenser section is concentric with the axis of rotation while the evaporator section can be placed in contact with off-axis heat sources in the rotating machine. The geometry is achieved by incorporating an S-shaped curve between the on-axis rotating condenser section and the off-axis revolving evaporator section. We show that because the heat pipe is a sealed, passive heat transfer device with nearly isothermal operation, the heat pipe concept may be advantageous when considering the overall refrigeration system used with the superconducting machine. High-speed, room temperature test data with this heat pipe geometry indicate that the working fluid in the heat pipe continued to circulate, resulting in heat transfer with a high effective thermal conductivity, with the heat pipe operating under the influence of centrifugal accelerations approaching 400 g.

A cooling system for a 3-phase 100-m HTS power cable with 22.9kV/1.25kA was installed and tested at the KEPCO's Gochang power testing center in Korea. The system consists of a liquid nitrogen decompression cooing system with a cooling capacity of 3kW at 66K and a closed circulation system of subcooled liquid nitrogen. Several cooling performance tests of the cable system such as cooling capacity, heat load, AC loss and temperature stability, were performed at operating temperature of 66.4K. Thermal cycle test which is cool-down to liquid nitrogen temperature and warm-up to room temperature, was also performed to investigate thermal cycle influences. This paper describes the installed cooling system, temperature stability and heat load test results.

Distributed thermal loads are frequently encountered in large deployable structures used in space applications such as optical mirrors and focal plane electronics. An innovative mechanism for providing distributed cooling is an oscillatory pulse-tube cryocooler that is integrated with a fluid rectification system consisting of check-valves and buffer volumes in order to extract a small amount of continuous flow. This continuous flow allows relatively large loads to be accepted over a long distance.An additional advantage of the rectified system is the ability to provide rapid and precise temperature control via modulation of the flow rate in the flow loop. This paper presents an experimental demonstration of this temperature control method. A rectified interface is integrated with a thermal load and subjected to various thermal disturbances. Temperature regulation is enabled using temperature feedback control of a valve placed in the distribution loop. The control parameters are selected to meet temperatu...

ALUHEAT project aims to build a cryogen-free superconducting induction heater. In this paper, the cryogenic design, which includes heat loss calculations, mechanical analysis, optimization of current leads and description of cooling conditions, is presented in detail. The induction heater consists of two magnets in separate cryostats and the billet to be heated is rotated between the cryostats. Short distance between the magnet and cryostat wall, large forces between the magnets, and the need to rotate the billet create application specific requirements that must be taken into account. Finite element analysis is used to design the cryostat to withstand the forces created by the vacuum and magnetic field. Finally, thermal interface, radiation shield, magnet support and apparatus to rotate the billet are designed and all components assembled into the complete system.

The Cooler Subsystem for the Mid InfRared Instrument (MIRI) of the James Webb Space Telescope (JWST) features a 6 Kelvin Joule-Thomson (JT) cooler pre-cooled by a three-stage Pulse Tube (PT) cryocooler to provide 65 mW of cooling at the instrument. MIRI's 6 Kelvin cooling load, directly behind the primary mirror of JWST, is remote from the location of the compressors and pre-cooler. This distance, and the parasitic heat load on the refrigerant lines spanning it, is accommodated by the design. The effort during 2006 and the first part of 2007 has focused on the demonstration of a MIRI Cooler prototype in the relevant environment, required to achieve Technology Readiness Level 6 (TRL 6) as defined by NASA[1]. The tests that have been used to successfully demonstrate TRL 6: launch vibration and cooler performance in the relevant thermal-vacuum environment, will be discussed.

Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately 1 kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. Subsequent testing may also be performed in-flight on an Air Force transport aircraft.Creare has developed a turbo-Brayton cryocooler for the Air Force that is designed to produce approximately 1 kW of refrigeration at 95 K. The cryocooler is intended to provide cryogenic cooling for an air separation system being developed to produce and store liquid oxygen and liquid nitrogen onboard large aircraft. The oxygen will be used for high-altitude breathing and medical evacuation operations, while the nitrogen will be used to inert the ullage space inside the fuel tanks. The cryocooler utilizes gas bearings in the turbomachines for long life without maintenance, which is a critical requirement for this application. The mass of a flight version of this cryocooler is expected to be around 270 kg, while the input power is expected to be 21 to 25 kW. This paper describes the design and testing of the technology demonstration cryocooler that was constructed to establish the feasibility of the approach. In the future, the cryocooler will be integrated and tested with a distillation column subsystem. ...