publicationDate stringlengths 10 10 | abstract stringlengths 0 37.3k | title stringlengths 1 5.74k | doi stringlengths 11 47 ⌀ |
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1997-03-01 | A new generation of aircraft requires materials giving welded joints capable of operation under extreme conditions including the effect of various embrittling factors and active media in addition to static and cyclic loads. New steels have been developed and conventional steels have been modified with allowance for requirements on the base metal and the welded joints that would provide adaptability to different kinds of welding. The present work concerns the development of principles for alloying and optimizing the phase composition of added materials in welding high-strength steels for a new generation of aircraft. Corrosion-resistant steels and additives for parts operating under the effect of embrittling factors (cryogenic temperatures, temperature instability of the martensite matrix) and structural steels with elevated strength and reliability are considered. | Ways to increase the reliability of welded joints of high-strength steels in a new generation of aircraft | 10.1007/BF02466281 |
1997-01-01 | Electronic subsystems operating at temperatures significantly below room temperature offer a wide variety of opportunities for performance improvements at lower operational power and smaller size. Semiconducting materials operate at higher speeds with low power consumption; superconducting materials offer zero (low) resistance for interconnects, coils and filters as well as quantum properties for switching and logic elements, and electromagnetic detectors; and magnetic materials offer the possibility of spin-polarized devices. Key issues in the acceptance of cryo-electronics for commercial and military applications are: i) affordable, improved materials coupled with a viable materials integration technology, ii) total systems design which takes advantage of the improved material performance, and iii) affordable, reliable, efficient refrigerators coupled with systems integration. The first and second, (i) and (ii), focus on performance issues necessary to demonstrate the promise of cryo-electronics while the last, (iii), focuses on the challenge of acceptance by a community who does not want the “baggage” of the cryogenic environment to be noticeable. | Cryo-Electronics: The Promise and the Challenge | 10.1007/978-1-4757-9059-7_130 |
1997-01-01 | Development of new types of electrical machines with cryogenic cooling and superconducting windings is to be based on application of new materials and new technological processes. The superconducting field winding impregnation epoxies are to withstand a long-term operation with thermocycling, and the main coil insulation is to withstand overvoltages during the transitions and to provide adequate cooling at operating modes, including the excitation current variations. The slotless stator developments are being based on introduction of new stator winding geometries and technological processes. Development of superconducting and hyperconducting armature windings, operating at relatively high electrical voltages must be associated with the investigation of the problem of electrical insulation ageing. The results of practical experience with superconducting alternators and experimental investigation of the models are being presented. | Investigation of Electrical Insulation Applied in Cryoalternators | 10.1007/978-1-4757-9059-7_30 |
1997-01-01 | Polyimide films has been used as insulating component in superconducting machinery^1. A full understanding of the property at low temperatures and the radiation effect is very important for stabilization of superconducting coils. The tensile properties of polyimide films have been measured at 4.2 K ~ 473 K. Stress-Strain curve profiles vary as a function of temperature. At cryogenic temperature, the elongation is much lower but the tensile strength is higher than that at room temperature. Also, polyimide film degradation performances after exposure of to an electron beam at very high dose level are examined. The test device for irradiation has a cooling system for preventing polyimide film from heating by electron absorption. The tests are performed at room temperature in He gas. After 80 MGy absorption, the elongation maintains about 60 % level of the non irradiated film, and the tensile strength maintains about 85 %. | The Tensile Properties of Polyimide Film at Cryogenic Temperatures and Radiation Effects On Polyimide Films | 10.1007/978-1-4757-9059-7_4 |
1997-01-01 | Copolyesters of polyethylene terephthalate(PET) and polyethylene-2,6-naphthalene dicarboxylate(PEN) with composition of PET/PEN= 100/0, 95/5, 90/10, 85/15, 70/30, 50/50, 30/70, 10/90, 0/100 were prepared. The mechanical properties of uniaxial-drawn films were examined at 83 K and 296 K. PET/PEN=90/10 copolymer film possessed especially excellent cryogenic properties. It was found to withstand elongations in excess of 40 % at stress levels of about 400 MPa at 83 K for PET/PEN=90/10 film uniaxial-drawn 5 times. Differential scanning calorimetry(DSC) curves of samples before and after tensile test at 83 K were compared for PET/PEN=90/10 film uniaxial-drawn 5 times. After tensile test at 83 K, the peak position of cold-crystallization shifted and the peak area between the curve and a baseline decreased, indicating that crystallization is allowed to take place during tensile test at 83 K. Dielectric loss tangent was measured in the temperature range from 18 K to the glass transition temperature. The relaxation below 100 K of PET and its copolymers was observed to be dependent on the morphology of samples. On the basis of the results obtained, relationship between the structure of polymers and their cryogenic properties has been discussed. | Cryogenic Properties of Several Copolyesters | 10.1007/978-1-4757-9059-7_1 |
1997-01-01 | Two huge superconducting magnets are now under design for the future detectors of the Large Hadron Collider at CERN: the ATLAS toroidal system and the CMS solenoid. Both of them are designed to be wet impregnated with epoxy resin. Because of their large dimensions, and the indirect cooling of the superconductor, the strength of the resin and of the resin/conductor interface is of major importance. A new generation of epoxy resins for vacuum/pressure impregnation methods are now tested. Special care is taken to understand the influence of the macromolecular structure and of the cure cycle on the mechanical behaviour of the resin at cryogenic temperature. The paper will present preliminary results about the mechanical properties, the density and the chemical contraction occuring during the polymerisation for this new generation of epoxy resins. | Epoxy Resin Developments for the Atlas and CMS Superconducting Magnets Impregnation | 10.1007/978-1-4757-9059-7_6 |
1997-01-01 | The large coercivities (exceeding 2 kOe) obtained in Fe based ceramic granular films are found to be sensitive to the type of matrix material used, being higher in the SiO_2 matrix. In this study the hysteresis behavior of Fe_x(SiO_2)_1-x granular films was studied as a fiinction of the preparation technique and conditions. The films were prepared by dc and rf magnetron sputtering over the composition range of x _ v = 0.1–0.9 volume fraction of Fe. Tandem deposition method and deposition from a composite target both with and without titanium sublimation, were used to prepare the films. Magnetic properties showed that by varying the deposition method and some of the sputtering parameters (sputtering rate, argon flow, film thickness and substrate temperature), it is possible to switch from a relatively magnetically hard sample ( H _ c ~ 700 Oe) made by the tandem technique, to a soft sample ( H _ c ~ 20 Oe) made from a composite target. A dramatic increase in H _ c has been observed at cryogenic temperatures in the former samples. This result along with the Mössbauer data, which show the presence of an Fe-Si-O phase (Fe_2SiO_4), suggest a shell/core granule morphology with an Fe and/or (Fe-Si) core surrounded by Fe-Si-O. At high temperatures Fe-Si-O is paramagnetic and does not affect much the coercivity of core. However, below a critical temperature Fe_2SiO_4 orders antiferromagnetically and pins the interface spins through exchange anisotropy with the interface core spins leading to large increases of H _ c at cryogenic temperatures. | Effect of Preparation Conditions on the Structural and Magnetic Properties of Granular Fe-SiO_2
| 10.1007/978-94-011-5478-9_31 |
1997-01-01 | The critical module of all second generation thermal imaging systems is the Standard Advanced Dewar Assembly (SADA). To meet the requirements of advanced Infrared (IR) Imaging systems of the 1990s and beyond the Department of Defense (DOD) has established a family concept for the SADAs. The family concept for second generation systems consists of the SADA I, SADA II, and SADA III. The SADA family addresses the needs of high performance systems (Comanche), high/medium performance systems (Horizontal Technology Integration (HTI) Second Generation Imaging Systems and the Improved Target Acquisition System (ITAS)) and compact class systems (Javelin). A SADA consists of the Focal Plane Array (FPA), dewar, Command & Control Electronics (C&CE), and the cryogenic cooler. In support of the SADA family DOD has also defined a family of linear coolers. The purpose of this paper is to highlight the family of linear drive coolers that address the requirements of the SADA family and first generation applications. The linear drive cooler maintains the FPA at the desired operating temperature. The coolers are highly reliable, have low input power, a quick cooldown time, have low audible noise & vibration output, and are nuclear hardened. This paper will (1) outline the family of coolers that the Department of Defense has standardized on, (2) highlight the characteristics of each cooler, (3) present the status of the various developmental & qualification efforts, (4) discuss the various second generation users and first generation systems, and (5) cover application and integration. | The DOD Family of Linear Drive Coolers for Weapon Systems | 10.1007/978-1-4615-5869-9_3 |
1997-01-01 | Some aspects of data analysis are discussed in gravitational wave (g. w.) experiments obtained with the presently working cryogenic detectors, resonant bars of the type invented by Joe Weber. Until now the main scientific goal has been the burst detection. The improved performances, in terms of duty cycles, of the existing detectors and the expected sensitivities of bars and interferometers has lead us to consider also the search of other sources, such as pulsars and relic g. w. | Algorithms for the Detection of Monochromatic and Stochastic Gravitational Waves | 10.1007/978-1-4612-1968-2_22 |
1997-01-01 | The processes of defect formation in single crystals of gallium arsenide electron-irradiated at cryogenic temperatures (∼20 K) have been investigated by the luminescence method. It is shown that at such temperatures the primary radiation-induced defects, in particular, intrinsic interstitial atoms, can migrate in a crystal and form complexes with their participation. | Photoluminescence of gallium arsenide electron-irradiated at 20 K | 10.1007/BF02683502 |
1997-01-01 | CTI-Cryogenics is under contract with ARPA/NRL to develop a low cost, long life cryocooler to meet the cryogenic cooling needs of emerging applications for high temperature superconductive (HTS) microwave components. The design for this application was targeted to produce a minimum of 15 watts of refrigeration at 50K. Early prototype testing of this low cost design has shown performance to be > 25 watts at 50K. The selection of a cryogenic cooling system for this HTS application started with a comprehensive study to evaluate both Stirling and Gifford-McMahon refrigerator design approaches. After completing a trade-off analysis that assessed and ranked refrigeration capacity, reliability, size, efficiency and price, the Gifford-McMahon (G-M) cycle was selected as the preferred design approach. The design and manufacture of the cold head component represented the greatest potential for reducing the cost of the cryocooling system. Early in the design process, the development team members focused their efforts primarily on the cost drivers and design approaches that would reduce the total number of refrigerator parts. This effort led to the elimination of the traditional drive motor and a complete redesign of the associated mechanical linkages and valving. The subsequent redesign reduced our standard refrigerator part count by approximately 40%. Material selection and construction methods, such as the use of “near net shape” fabrication techniques, were the keys to reducing the cost of the refrigerator parts. To substantiate that our cost goals were achieved, we solicited and received quotations on over 90% of the component parts. Analysis shows that, for large volume procurements, the price of a new cryogenic system can be reduced significantly from what is currently available. | Low Cost Gifford-McMahon Cryocooler Development Program | 10.1007/978-1-4615-5869-9_69 |
1997-01-01 | The photosynthetic reaction center (RC) of purple bacteria is a large membrane protein which performs the primary steps of photo-induced electron transfer. After light excitation, a dimer of bacteriochlorophyll molecules (P) transfers an electron to an acceptor, and the oxidized species P^+ is then re-reduced by a secondary electron donor, a c -type cytochrome, in order to be reactivated. In some purple bacteria this secondary donor is a soluble c _2 cytochrome, but in most cases it is a RC-bound tetraheme cytochrome c . The best studied example is Rhodopseudomonas (Rps.) viridis , in which the tridimensional structure of the RC has been solved with a high atomic resolution (1). Some of the electron transfer reactions from c -type cytochromes to P^+ in the RC of purple bacteria occur even at cryogenic temperatures. Experimental observations of the effects of temperature on the rate and the yield of the cytochrome oxidation have contributed a lot to the development of current electron transfer theories (2). However, several of these observations, such as the extent of photooxidation of heme c 556 at cryogenic temperature in Rps. viridis are still controversial (for a review see (3)). In order to understand some of these effects we have investigated the effect of flash and continuous illumination at low temperature on cytochrome hemes in RC isolated from Rps. viridis . | Light-Induced Conformational Change at Low Temperature in the Protein Binding Site of Heme c556 in the Reaction Center of Rhodopseudomonas Viridis
| 10.1007/978-94-011-5622-6_48 |
1997-01-01 | This paper presents the current status of both continuous and periodic operation sorption cryocooler development for astrophysics missions requiring refrigeration to 10 K and below. These coolers are uniquely suited for cooling detectors in planned astrophysics missions such as the Exploration of Neighboring Planetary Systems, the Next Generation Space Telescope, and Darwin. The cooler requirements imposed by these missions include ten year life and the ability to scale designs to provide only a few milliwatts of refrigeration while consuming only a few watts of input power. In addition, the ExNPS and Darwin missions add stringent requirements for zero-vibration and zero EMI/EMC operation. Spaceflight test results are summarized for the Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment. This periodic operation sorption cooler is ideal for applications that require only intermittent operation at 10 K with quick cooldown capability (under 2 minutes). The experiment successfully provided flight characterization of all sorption cooler design parameters which might have shown sensitivity to microgravity effects. Full ground test performance was achieved with no indications of microgravity induced changes. Ground test results from a continuous 25 K cooler planned for use in a long duration airborne balloon experiment are also presented. This 25 K cooler, which is in final integration and test, can be used as an upper stage for a continuous 10 K sorption cooler. The potential benefits of using a 10 K sorption cooler as an upper stage for a 4 K cooler are additionally described. Finally, a NASA program to develop 30 K, 10 K and 4 K vibration-free coolers for astrophysics missions, which is planned to start in FY 1997, is outlined. | Continuous and Periodic Sorption Cryocoolers for 10 K and Below | 10.1007/978-1-4615-5869-9_66 |
1997-01-01 | Space cryogenics tries to solve the problems connected with cooling down components in space missions. Very low temperatures are required in particular to cool radiation detectors used in astrophysics. Up to now the cryogenic problems have been solved by using a reservoir containing a cryogen, say liquid helium, on board satellites. A new trend is now making progress, consisting in trying to “make the cold” on board: this could result in less weight and volume to put in orbit, and in longer time duration of the missions. The first step to cool on board can be performed by means of passive radiation, a subject that has been addressed in another paper in this Workshop. Next step is “active cooling”, which is the subject of this paper. Various techniques and associated problems are discussed, and the state of the art evaluated. | Active Cooling Systems | 10.1007/978-94-011-5468-0_35 |
1997-01-01 | A new test method was developed to determine shear/compression properties of composite insulation systems used in superconducting magnets. It was developed specifically to enable in-situ testing (without warm-up) of insulation systems in a high flux neutron radiation and cryogenic (4 K) temperature environment at the Munich Research Reactor (FRM — Forschungsreaktor München). The new shear/compression specimen consists of two sections of composite insulation bonded at a specific angle between three pieces of 316 stainless steel. During the test, the specimen is compressed between two loading platens. By varying the angle of the test specimen, different shear/compression ratios can be evaluated and a shear/compression envelope for various materials can be produced. This test method produces the same shear and compressive strengths found in other shear/compression tests, but the test fixture is smaller, and multiple test specimens are not required. The composite insulation systems were tested at 45° to demonstrate the feasibilty of the test. Specimens were produced from a vacuum pressure impregnation (VPI) resin system and a prepreg resin system. Design and fabrication of the test specimens and their shear and compressive properties are presented. | New Combined Shear and Compression Test Method | 10.1007/978-1-4757-9059-7_14 |
1997-01-01 | BEI is a manufacturer of Stirling-cycle cryocoolers based on the concept of clearance seal, pneumatically driven displacer and linear drive motors. Several cooler models are available covering refrigeration requirements ranging from 150 mW to 5.0 Watts of cooling at 78 K. This paper describes a computer simulation model, herein referred to as Hybrid Refrigeration Model (HRM), that was developed for the design of BEI coolers. The BEI computer model uses a novel technique that greatly reduces computation time without compromise in accuracy. The hybrid model is used at BEI for the design of both Stirling and Pulse-Tube refrigerators. The model is similar, to a third order model described in the literature as the Stirling Refrigerator Performance Model (SRPM), that has been extensively validated against various Stirling and Pulse Tube designs from different manufacturers. Although very accurate in its prediction, the SRPM suffers a major shortcoming in its long run time. The Hybrid Refrigeration Model, on the other hand, uses a third order approach in calculating mass flows and pressure drops within the refrigerator while the losses are imposed using the second order analysis. This approach has provided an accurate tool for performance prediction with fast turnaround. An example of the use of this computer model is provided in this paper with the parameters of the BEI Mini-linear cooler. The performance of the cooler is discussed, in particular, the effects of the regenerator material, configuration and operating conditions. | Experimental and Predicted Performance of the BEI Mini-Linear Cooler | 10.1007/978-1-4615-5869-9_15 |
1997-01-01 | The mechanical properties of several glass fiber reinforced plastics (FRPs) were investigated prior to and following neutron and gamma irradiation using the short beam shear (ASTM D2344) and the three point bending test (ASTM D790). The irradiations were carried out at room temperature and at low temperature (5 K) with different reactor spectra up to a fast neutron fluence of 5×10^22 m^-2 (E>0.1MeV). The samples were measured at 77 K, those subjected to low temperature irradiation were measured before and after an annealing cycle to room temperature. Special attention was paid to the influence of the boron (n, a)-reaction on the interlaminar shear strength, which occurs in E-glass, but not in boron free S- and T-glass reinforcements. | Interlaminar Shear and Flexural Strength of Fiber Reinforced Plastics at 77 K After Room and Low-Temperature Reactor Irradiation | 10.1007/978-1-4757-9059-7_15 |
1997-01-01 | Cryocooler thermal and vibrational performance is determined, fundamentally, by the dynamic interactions between the mechanical system and the working fluid. This paper explores the effect of working-fluid characteristics on the mechanical response of the cooler. Experimental data collected from two coolers characterized under the Jet Propulsion Laboratory’s extensive program of cryocooler testing and characterization show that a classical single-degree-of- freedom spring-mass-damper model does not capture the full frequency dependence of the mechanical response. The data from two modes of cooler operation (slosh and head-to-head) are used to motivate the explanation that working-fluid characteristics dominate at high frequencies, and mechanical system characteristics dominate at lower frequencies. Operating temperature is shown to be a significant factor in determining resonance behavior. Finally, the discussion provides a framework within which resonant parameters and cooler characteristics can extracted from the experimental data. | Investigation of Gas Effects on Cryocooler Resonance Characteristics | 10.1007/978-1-4615-5869-9_49 |
1997-01-01 | The improvement of the fracture toughness of epoxy resin has been tried to perform from the molecular level with an aim to improve the cryogenic properties of GFRP and/or the stability of superconducting magnets. The ceramic filler, which was formed by hydrolysis of alkoxide, was dispersed in the epoxy and cured. A coupling agent was also used to crosslink the filler and epoxy molecules. The positron annihilation lifetime was measured and the molecular state of the epoxies were evaluated. The thermal contraction and Vickers hardness were also measured. The thermal contraction and hardness were confirmed to reflect the molecular state as evaluated by positron annihilation lifetime. The fracture toughness was also measured down to cryogenic temperatures. It was found that the improvement of the fracture toughness at cryogenic temperatures is possible. | Improvement of Fracture Toughness of Epoxy Resins at Cryogenic Temperature | 10.1007/978-1-4757-9059-7_3 |
1997-01-01 | Nb_3Sn tape, manufactured by the General Electric Company for cryocooled, magnetic resonance imaging (MRI) magnets, was examined to determine the influence of strain on critical current, I_c, over a wide range of magnetic fields and temperatures. Copper stabilized Nb_3Sn tapes were strained by differential thermal contraction by waxing or epoxying the samples to 4.7 cm diameter short sample test bobbins made of brass, stainless steel, Inconel, nickel, niobium and molybdenum. These samples were measured for I_c in transverse fields ranging from 0 to 7 Tesla (T) and over a temperature range of 4 2 to 16 Kelvin (K). Additionally, Nb_3Sn tape, subjected to bend, twist and pressure stresses, was measured for I_c degradation to determine handling limits during manufacture and insulation of the tape, as well as magnet winding. Finally, unstabilized, reacted Nb_3Sn foil subjected to various tensile loads was tested for I_c degradation. Surface metallography was used to relate cracking of the Nb_3Sn layer to I_c degradation. | Strain Studies on Superconducting Nb_3Sn Tape Using Differential Thermal Contraction and Other Methods | 10.1007/978-1-4757-9059-7_188 |
1997-01-01 | SCI’s advanced composite support structures are currently being utilized in numerous cryogenic systems. Advantages include low thermal conductivity, high strength and stiffness, lightweight, low outgassing, and integral fittings. Several types of fibers and resins are available to meet extreme structural and thermal requirements. Typical configurations including racetrack-shaped suspension bands, or straps, and tubular support posts with integral fittings, or struts. Design considerations for composite support straps for cryogenic systems are discussed. Common applications for composite support structures are dewar mounts for spacecraft, coolers for satellite instruments, and cryostat support such as superconducting magnets for medical imaging^1. | Composite Support Structures for Cryogenic Systems | 10.1007/978-1-4757-9059-7_34 |
1997-01-01 | One hundred and ninety five strains of fungi were observed during freezing and thawing using a cryogenic light microscope. There was no obvious link between taxonomic position and their morphological response to freezing and thawing. The viability of seven of these strains was examined following freezing and thawing in the presence or absence of the cryoprotectants glycerol and dimethyl sulphoxide. Intracellular ice and hyphal shrinkage were not necessarily lethal events, but in many cases they affected the rate and quality of growth. Both cryoprotectants reduced shrinkage, shifted the cooling rate where intracellular ice formed in many cases, and improved the recovery of strains. The results presented aid the development of successful cryopreservation protocols. | Cryogenic light microscopy and the development of cooling protocols for the cryopreservation of filamentous fungi | 10.1023/A:1008820432471 |
1997-01-01 | We consider the transient thermal-mechanical response of cracked G-10CR glass-cloth-reinforced epoxy laminates with temperature-dependent properties. The glass-cloth-reinforced epoxy laminates are suddenly cooled on the surfaces. A generalized plane strain finite element model is used to study the influence of warp angle and crack formation on the thermal shock behavior of two-layer woven laminates at low temperatures. Numerical calculations are carried out, and the transient temperature distribution and the thermal-mechanical stresses are shown graphically. | Transient Thermal-Mechanical Behavior of Cracked Glass-Cloth-Reinforced Epoxy Laminates at Low Temperatures | 10.1007/978-1-4757-9059-7_19 |
1997-01-01 | This paper considers rather usual methods for investigating the microstructure of the Nb_3Sn superconducting phase. These techniques deal with the quality and volume fraction of the Al 5 compound. Microhardness testing show very suitable in order to monotor a fabrication process. The metallurgical effects of each step of a conventional HT schedule are also studied with various designs of composites in an attempt of optimization. | Quantity and Quality of the Nb_3Sn Intermetallics Formed by the Internal Tin Process | 10.1007/978-1-4757-9059-7_178 |
1997-01-01 | A single stage orifice pulse tube cryocooler incorporating one compressor and regenerator, but two pulse tubes has been constructed and tested. This development is directed toward use as cooling for superconducting current leads where the voltage insulation between the two leads is critical. The purpose of the present study is to investigate the thermal stability of parallel oscillating flows and compare the performance of a specific pulse tube in a two-tube configuration with that of the same pulse tube working in the standard single tube configuration. Performance is characterized by the system cool-down speed and the minimum cold end temperature. Three pulse tube specimens named I, II, and III, have been assembled and tested individually and in various combinations. The experimental results reveal the absence of any thermal stability problem in the two pulse tube configuration. However, the performance of a specific pulse tube is degraded in the two-tube configuration as compared to its individual use. | An Experimental Investigation of a Single-Stage Two-Pulse-Tube Refrigerator | 10.1007/978-1-4615-5869-9_35 |
1997-01-01 | Future multi-TeV particle accelerators like the CERN Large Hadron Collider (LHC) will use superconducting magnets in which organic materials will be exposed to high radiation levels at temperatures as low as 2 K. A representative selection of organic materials comprising insulating films, cable insulations, epoxy resins and composites were exposed to neutron and gamma radiation of a nuclear reactor. Depending on the type of materials, the integrated radiation doses varied between 180 kGy and 155 MGy. During irradiation, the samples were kept close to the boiling temperature of liquid nitrogen, i.e. at 80 K, and thereafter stored in liquid nitrogen and transferred at the same temperature into the testing device for measurement of tensile and flexural strength. Tests were carried out on the same materials at similar dose rates at room temperature, and the results are compared with the ones obtained at cryogenic temperature. They show that within the selected dose range, a number of organic materials are suitable for use in radiation fields of the LHC at cryogenic temperature. | Radiation Tests at Cryogenic Temperature on Selected Organic Materials for LHC | 10.1007/978-1-4757-9059-7_29 |
1997-01-01 | A Technical Working Area 17, cryogenic structural materials, has been organized in the Versailles Project on Advanced Materials and Standards (VAMAS) to promote the prestandardization program on material properties tests of glass fiber reinforced polymer (GFRP) composite materials and alloys at liquid helium temperature. A series of international interlaboratory comparisons of both tensile and fracture toughness tests for aluminum alloy 2219 and compression and shear tests for composite material G-10CR were performed. Nine research institutes from seven nations have participated in this project. The results prove that there are few problems in cryogenic tensile tests for alloy materials. In compression and shear tests, the amount of data scatter was identified and further experiments are planned. This paper presents the program details and interim results of round robin tests. | VAMAS Tests of Structural Materials on Aluminum Alloy and Composite Material at Cryogenic Temperatures | 10.1007/978-1-4757-9059-7_37 |
1997-01-01 | Electric motors with high temperature superconducting (HTS) field windings have been under development for several years^1. Previous studies concluded that air-core synchronous motors with superconducting field windings offer the best motor topology. A cryocooler is required to provide refrigeration such that the salient-pole superconducting winding coils that reside in the rotor cryostat are kept at their nominal operating temperature of 30 K. Motor efficiency analysis indicates that the compressor input power of the cryocooler is limited to around 10 kW in order to make the motor economically viable. The delivery of refrigeration from the cryocooler in a stationary environment to a rotating frame with minimal loss appears to be the most challenging design issue. This work discusses pertinent issues concerning the integral design of the cryocooler and rotor cryostat of the HTS motor. Various schemes that could be potentially utilized to accomplish such an objective are also presented. | Cryocooler Integration with High Temperature Superconducting Motors | 10.1007/978-1-4615-5869-9_105 |
1997-01-01 | The replacement of the orifice and reservoir elements of a fixed orifice pulse tube cryogenic refrigerator with an expander piston results in a reversible cycle pulse tube machine. At the 7th International Cryocooler Conference, Ishizaki and Ishizaki presented the experimental performance of a machine where the phase relationship between the compressor and expander pistons was maintained by a kinematic drive. An alternate implementation can be based on flexure bearing supported reciprocating linear drive engines wherein the phase shift between the compressor and the expander pistons is maintained by either appropriate plumbing of several dual piston engines across a like number of regenerator/pulse tube elements, or by separate compressor and expander engines with appropriate phase control electronics. A generalized lumped parameter model of thermally regenerated engines has been developed and programmed to predict the comparative thermodynamic performance of Alpha type Stirling cycle, fixed and modulating orifice pulse tube, and piston-pulse tube machines. Subject to the modeling approximations, the analysis predicted the following: Alpha Stirling Cycle — 35%; Piston-Pulse Tube — 29%; Modulating Orifice Pulse Tube — 19.5%; Fixed Orifice Pulse Tube — 16.5% of Carnot for a 5 to 10 watt at 60K cryocooler with a 300K heat rejection temperature. The basis of the analytical model and computer program, the results of the computer analysis, a preliminary design of the flexure supported dual piston integrated compressor-displacer engine, and a schematic of the fluid circuit required for phase shift control will be presented. The prime cryocooler application of this technology is in multistage applications. A major attraction of piston-pulse tube machines is that all moving parts are operating at effectively the heat rejection temperature, which simplifies the design and fabrication of cryogenic refrigerators, and which allows increased temperature ratios (with resulting higher Carnot limits) for power producing integrated alternator-heat engines. | Reversible Cycle Piston Pulse Tube Cryocooler | 10.1007/978-1-4615-5869-9_37 |
1997-01-01 | The expansion bellows, used in the magnet interconnections of the Large Hadron Collider (LHC), are designed for severe service conditions (cryogenic temperatures, high internal pressure, large cyclic deflections). According to the results of the material research, a stainless steel of grade AISI 316 exhibits a high ductility at cryogenic temperatures. This results in the development of the plastic strain fields in the bellows wall, subjected to cyclic loadings, and to failure after a comparatively low number of cycles. In the present work the progressive deformation (ratchetting) of bellows subjected to a sustained load (internal pressure) and to a superimposed cyclic deflection programme at cryogenic temperatures is examined. In order to estimate the number of cycles to failure a generalized Manson-Coffin equation was developed. The model is based on two parameters: the ratchetting induced mean plastic strain and the plastic strain amplitude. The material model is based on the bilinear elastic-plastic response with kinematic hardening. The cyclic hardening and the evolution of the material model parameters (yield strength and hardening modulus) are accounted for. The finite element simulation of the initial 20 cycles leads to an estimation of the accumulated plastic strains and enables the calculation of the fatigue life of the bellows. An experimental stand for cryogenic fatigue tests is also presented and the first verification tests are reported. | Fatigue Life Prediction for Finite Ratchetting of Bellows at Cryogenic Temperatures | 10.1007/978-1-4757-9059-7_48 |
1997-01-01 | Despite the discovery of MACHO dark matter in our galactic halo, much of the inferred halo mass seems still to be missing [1]. If we assume that this missing mass is in the form of the weakly interacting massive particles (WIMPs) predicted by supersymmetry [2], then we expect to find a flux of 10^7/m_x cm^-2 in the solar neighborhood or 10^4-10^6 cm^-2 assuming the most likely mass range m_x ∽ 10 - 1000 GeV and standard models of the galactic halo. These WIMPs have a total cross section for scattering on a nucleon of no more than 10^-41cm^2, leading to total scattering rates below 0.1 kg^-1 day^-1 of target mass. | The Cryogenic Dark Matter Search (CDMS) | 10.1007/978-94-009-0053-0_25 |
1997-01-01 | A two-stage 8–12 GHz (X-band) cryogenically-cooled Low-Noise Amplifier (LNA) has been developed with a commercial pseudomorphic HEMT on AsGa substrate. In a first step, different commercial transistors have been fully characterized from 300 K to 20 K using a new method to measure the four noise parameters. Preliminary results have allowed the selection of the best device. This enabled the design of the two-stage LNA with the help of a microwave CAD software. In a second step, the LNA has been characterized at 300 K, 30 K and 4 K. As the physical temperature decreased from 300 K to 30 K, the LNA exhibited an average gain increase of 2 dB and as much as a fourfold reduction of noise temperature. A noise figure of 22.5 K and a gain of 23 dB have been achieved at 30 K around 10 GHz. The noise temperature has been furthermore reduced to 20 K by cooling the amplifier at the liquid helium temperature (4.2 K). Different methods to measure the noise characteristics of the amplifier are widely developed in this paper. | A low-noise cryogenically-cooled 8–12 GHz HEMT Amplifier for future space applications | 10.1007/BF02677898 |
1997-01-01 | In this paper we will describe recent advances in the development of optical systems for future space infrared telescope and interferometer applications which will operate at very low or cryogenic temperatures (T≤77K) with emphasis on beryllium and silicon carbide optics. New material formulations and advanced processing and manufacturing techniques are enabling the development of large, very low mass, high performance cryogenic optics. The design, manufacturing and cryogenic testing of several recently developed mirrors and optical assemblies will be discussed. | Recent Advances in Cryogenic Optics Technology for Space Infrared Telescope and Interferometer Systems | 10.1007/978-94-011-5468-0_24 |
1996-11-01 | A cryogenic radiometer with electrical substitution has been developed for precise photometric measurements. The radiometer design and specifications are described. The radiometer has an accuracy of 0.02%. Its main use is to calibrate the spectral response of reference radiometers. | Absolute cryogenic radiometer for high-current photometric measurements | 10.1007/BF02375386 |
1996-09-01 | Thermometry of cryogenic equipment produced by the Kriogenmash Company | 10.1007/BF02416580 | |
1996-06-01 | It is shown that cryogenic deformation (77 K) speeds up the kinetics of particle precipitation in the second phase, using the subsequent heat treatments in order to form the structure with increased volume contents of α-phase. Studied is the microstructural parametric influence upon J_c. | The effects of low temperature deformation on the microstructure and J_c of Nb-49Ti superconductor | 10.1007/BF02548157 |
1996-06-01 | AA 2219 aluminium alloy is the material proposed for the construction of tanks for liquid cryogenic fuels like liquid oxygen and liquid hydrogen, in Indian launch vehicle programmes. To meet the material requirement, ISRO has developed the alloy AA 2219 indigenously on an industrial scale. Process development and structure-property correlation of auto TIG weldments of AA 2219 Al alloy reported in this paper establishes that postweld reaging of AA 2219 weldments in T62 condition enhances both strength and ductility. | Structure-property correlation on AA 2219 aluminium alloy weldments | 10.1007/BF02744827 |
1996-05-01 | An avalanche effect has been observed in a cryogenic detector based on the planar array of superheated superconductors (PASS). The indium PASS, fabricated by photolithography on a mylar substrate, consisted of 40 well-separated lines each containing about 175 spheres of diameter 18 μm and separation 20 μm with those at the end being shielded by superconducting wire. The magnetic field was applied in the PASS plane parallel to the lines. Avalanche events in which several granules changed their state from superconducting to normal were triggered by the nucleation of the transition in a single grain by an α-particle. | Avalanche effect in the planar array of superheated superconductors | 10.1007/BF02570428 |
1996-05-01 | This report presents our results of both investigation of electrical condution mechanisms in Ge films on GaAs at low temperatures and designing thin-film Ge resistance thermometers. The electrical properties of Ge films on GaAs are determined by potential fluctuations caused by random inhomogeneous distribution of impurities. At low temperatures the conduction through the localized states in the vicinity of the Fermi level prevails. In this report we discuss the electrical conduction mechanisms of such films. Three types (TTR-1, TTR-2 and TTR-3) of thin-film Ge thermometers were fabricated. These temperature sensors may be used in the temperature ranges 1.5 to 350, 77 to 400 and 200 to 450 K, respectively. | Ge films on GaAs: low-temperature electrical properties and application to cryogenic resistance temperature sensors | 10.1007/BF02570414 |
1996-01-01 | Keeping the genetic integrity of Rhizoctonia spp. isolates is of great importance. When cultures are stored at inappropriate conditions and/or transferred many times on agar, they may undergo profound genetic changes and lose important characteristics such as: vigor, virulence (Butler, 1980), ability of certain non pathogenic isolates to increase plant growth or protect against pathogenic Rhizoctonia (Sneh, unpublished), cultural characteristics etc. Since the rates of mitotic recombination and mutation are likely to correspond to those of cell division and metabolic activity, an ideal system for germplasm preservation would be storage at a temperature where cultures remain viable, but are in a metabolic inactive state (Shannon et al. , 1975). This may be accomplished by storage below −139°C, at which there is no growth of ice crystals and the rates of other biophysical processes are too slow to affect cell survival. Rhizoctonia spp. isolates lose their viability when their cultures on PDA are kept in the refrigerator (4°C). Information on various preservation methods and data about the survival of isolates preserved by these methods that were kindly provided to us by Rhizoctonia researchers together with reports from the literature are assembled in this chapter. | Culture Preservation Methods for Maintaning the Genetic Integrity of Rhizoctonia SPP. Isolates | 10.1007/978-94-017-2901-7_12 |
1996-01-01 | All cryogens can present the hazard of unwanted condensation of substances that boil at higher temperatures. Table 6.1 shows the estimated vapor pressures of some of the substances that, if present, can be condensed, usually to a solid, at cryogenic temperatures.^1 From the magnitude of these vapor pressures it can be seen that, in some cases, even undetectable amounts of substances can be condensed, although probably only negligible quantities of solids could accumulate at such low concentrations. Table 6.1 indicates that any cryogen can almost totally condense water vapor and carbon dioxide. Air can be condensed to a liquid at liquid-nitrogen temperatures (possibly resulting in a condensate enriched in oxygen; see Section 6.1.2.). Argon, nitrogen, and oxygen are condensed to solids at the temperatures of liquid neon, liquid hydrogen, or liquid helium. Finally, all substances, other than helium, are solids at the temperature of liquid helium. | Condensation | 10.1007/978-1-4899-0307-5_6 |
1996-01-01 | Fermilab began operating a re-designed satellite refrigerator system in November 1993. Upgrades were installed to operate the Tevatron at a magnet temperature of 3.5K, approximately 1K lower than the original design. Refrigerator upgrades included new valve boxes, larger reciprocating expanders, the installation of cold vapor compressors, new sub atmospheric instrumentation and an entirely new distributed controls system. Cryogenic system reliability data for Colliding Physics Run 1B is presented emphasizing a failure analysis for each aspect of the upgrade. Comparison to data for Colliding Physics Run 1A (previous to the upgrade) is presented to show the impact of a major system overhaul. New operational problems and their solutions are presented in detail. | Initial Performance of Upgraded Tevatron Cryogenic Systems | 10.1007/978-1-4613-0373-2_90 |
1996-01-01 | Four sets of helium cryogenic systems for the mini-beta insertion quadrupole magnets were installed near the interaction points of the TRISTAN main ring in 1990. Each system consists of a helium compressor, a cold box, a subcooler, transfer lines, two magnet-cryostats, two helium gas tanks and a liquid nitrogen storage tank, and its nominal cooling capacity is 140 W at 4.2 K + 25 L/h. The four systems are controlled automatically by a process control computer system. The first operation started in 1991 and by the middle of 1995, the total operating time for each system reached about 28,000 hours. In this paper we report the experience gathered during 28,000 × 4 operating hours in running four cryogenic systems together with the control system. Maintenance experience and statistics of failures of different components are also described. | Operational Experience and Reliability of the Cryogenic Systems for the Tristan Insertion Quadrupole Magnets | 10.1007/978-1-4613-0373-2_93 |
1996-01-01 | CEBAF, The Continuous Electron Beam Accelerator Facility, is centered on a 4 GeV recirculating linac which has recently started routinely producing beam to the first of three experimental halls. Hall A, the second of three experimental halls, houses two high resolution spectrometers, HRS, and is due to become operational by the end of 1995. Each HRS consists of two nuclear physics detectors, with optics determined by a superconducting dipole and three superconducting quadrupoles cooled by the End Station Refrigerator, ESR. Minimization of the total heat load from Hall A to the refrigerator is essential since the capacity is fixed. The design, construction, and initial test of the cryogenic distribution system and how the overall heat load is controlled are discussed in this paper. | Thermal Performance of the CEBAF Hall a Cryogenic System | 10.1007/978-1-4613-0373-2_87 |
1996-01-01 | Collaborators on the design of a Tevatron Superconducting Linear Accelerator (TESLA) are working toward construction of a test cell consisting of four full length cryostats, 12 meters long, each consisting of eight, 9-cell superconducting RF cavities. The purpose of this facility is to test all aspects of the accelerator system design; vacuum, cryogenics, RF, and electron source, prior to initiating construction of the full linac. The design for these cryostats pose many interesting challenges to cryostat designers. The systems must be capable of supporting all eight cavity structures within tight alignment tolerances, impose very low thermal heat loads on the 1.8K cryogenic system, provide strength and stiffness to resist structural loads during fabrication, shipping, and installation, and be manufactured at low cost. Several design options are being explored, each of which attempt to address requirements imposed by the reference design guidelines. This paper describes the design and analysis of one design alternative. | Tesla Test Facility Alternate Cryostat Design | 10.1007/978-1-4613-0373-2_108 |
1996-01-01 | We describe the capture cavity cryostat, for the Tesla Test Facility at DESY in Hamburg, which was designed and is presently under assembly in France. We also discuss the construction of an ancillary feed box which is required for a preliminary cryogenic test prior to delivery. | Status Report of the TTF Capture Cavity Cryostat | 10.1007/978-1-4613-0373-2_111 |
1996-01-01 | Liquid breakthrough and choked flow are important phenomena in the operation of phase separators in space. Breakthrough results in loss of liquid which can reduce the life time of, and potentially terminate a mission. Choked flow limits the amount of liquid boiloff which passes through the phase separator and can result in the warming of the bath temperature. Since the capillary effect plays an important role in both the above phenomena, the distribution of pore sizes in the phase separator governs the critical limits of breakthrough and choked flow. In this paper, the pore size dependence of breakthrough and choked flow in vapor-liquid phase separators will be discussed in detail. The experimental data of various phase separators tested for the Relativity Mission will also be compared to present theory. | The Dependence of Choked Flow and Breakthrough on Pore Size Distribution in Vapor-Liquid Phase Separation of He II Using Porous Media | 10.1007/978-1-4613-0373-2_150 |
1996-01-01 | The T-15 cryogenics system has been designed for cooling down, cryostatting, warming up of superconducting, cryoresistive and cryogenics T-15 objects. Maintenance of the cryogenics system has been on going since 1988. For the mentioned period, in the cryogenics T-15 system The capacity of screw compressor was increased from 0.181 kg/s to 0.236 kg/s (third stage compressors with increased capacity were developed and manufactured), their reliability was also enhanced. The capacity of liquefiers was increased from 0.0833 – 0.0972 L/s (300–350 L/h) to 0.222 L/s (800 L/h) due to replacement of turboexpanders by more effective ones and due to introduction of an end-stage turboexpander into maintenance. The heat influxes to the cryogenics pipelines were reduced by 50%. For the same period some technological regimes of cryogenics system have been developed to produce the maximal output of cold. The cooling down from 110 K to 15 K is done, when one or two liquefiers are in operation under refrigerating conditions with the reverse flow splitting. The further cooling is performed under joint operation of two liquefiers; one them operates in the liquefying mode, another, in the refrigerating one with excess reverse flow. A change in the operating conditions was necessary because of the impossibility of regulating the distribution of the reverse helium flow between two liquefiers at the temperature below 15K. The main regime at the level of 4,5 K is a two-loop operating diagram, when one Liquefier and a passive refrigerator with excessive reverse flow are in operation, the refrigerating capacity is about 3 kW. | Tokamak-15 Modernization and an Analysis of Cryogenic System Operation for the Period from 1988 to 1994 | 10.1007/978-1-4613-0373-2_96 |
1996-01-01 | One of the vital problems in developing high-speed cryogenically cooled electrical machines with a cryostat common to rotor and stator is availability of reliable shaft seals. Depending on the electric machine design, reliable rotary seals are required both for working media sealing and for maintaining vacuum in rotating cryostats. Newly designed rotary seals employ the principles of radial hydrodynamic sealing. Tentative experimental studies proved the advantages of the new design over the traditional radial hydrodynamic seals. Pressure difference withstood by the new seals with no obvious sealed media leaks is about 1.5 times greater than that provided by a conventional seal. | Development and Experimental Investigation of New Seals for Cryoalternators | 10.1007/978-1-4613-0373-2_130 |
1996-01-01 | An optical test Dewar has been constructed with the unique capability to test mirrors of diameter ≤ 1 m, f≤6, at temperatures from 300 to 5 K with a ZYGO Mark IV/V interferometer. The facility possesses extensive thermometry throughout for characterization of the test chamber thermal environment and Dewar performance. Optical access is controlled with cryogenically cooled shutters. The entire Dewar is vibration isolated by 40 dB where the fundamental resonances of the Dewar structure are highest. The facility has been brought on line for its first user, the Infrared Telescope Technology Testbed (ITTT) for the Space Infrared Telescope Facility (SIRTF) at JPL. The design requirements for this facility and the resultant design and implementation experiences and challenges will be presented. | Cryogenic Telescope Test Facility | 10.1007/978-1-4613-0373-2_146 |
1996-01-01 | The problem of construction of a space vehicle-borne 1 MVA cryogenic converter transformer, which provides serviceability of 12-pulse rectifying circuit has been studied. As a winding conductor pure aluminum foil is used, which is cooled by liquid hydrogen, which makes it possible to decrease the mass-to-power ratio several fold. Physical — technical problems, arising due to high current density in windings, for solution of which original approaches of windings and magnetic core design were suggested, have been described. Calculations of main parameters, demonstrating that hyperconducting transformers of medium power are promising devices, were made. | Physical Engineering Problems of Hyperconducting Transformer Construction | 10.1007/978-1-4613-0373-2_246 |
1996-01-01 | The cryogenic system for the 45-T Hybrid superconducting magnet employs an innovative design primarily driven by the requirement that it be a user-friendly, reliable facility. To achieve this requirement, the superconducting magnet is being built with highly stable cable-in-conduit conductors, operating at 1.8 K and internally cooled with static He II. Further, the magnet is housed in a separate cryostat connected to the refrigeration system through a services duct to the supply cryostat. This design allows the magnet cryostat to be free of penetrations that may interfere with the magnet user. The 45-T Hybrid cryostat was delivered to the NHMFL in March of 1995. The present paper reports on the design, development, fabrication, installation and preliminary testing of this unique system. | Design, Development and Testing of the Cryogenic System for the 45-T Hybrid | 10.1007/978-1-4613-0373-2_160 |
1996-01-01 | All oxygenic photosynthetic organisms contain a membrane protein complex, known as Photosystem I, that catalyzes a light-induced transfer of electrons from reduced plastocyanin to ferredoxin. This complex contains several bound electron carriers that are involved in the initial charge separation and stabilization. These carriers include the reaction center chlorophyll, P700, which undergoes oxidation in the light, and a number of compounds that serve as electron carriers in what is now believed to be a sequence of electron transfer events: a monomeric chlorophyll a molecule is the initial electron acceptor, a phylloquinone molecule is the second electron acceptor and a series of bound iron-sulfur clusters then function as terminal electron acceptors. The properties of these electron carriers and recent evidence supporting their proposed roles are described and an attempt is made to present a unified picture of our understanding of the role of these individual components. The kinetic sequence of the electron transfer events is then considered in detail. After the discussion of these bound electron carriers, the reduction of ferredoxin by the Photosystem I complex is described and the role of this soluble electron carrier in catalyzing a cyclic transfer of electrons around Photosystem I is considered. | Photosystem I Electron Transfer Reactions–Components and Kinetics | 10.1007/0-306-48127-8_16 |
1996-01-01 | A major milestone in the preparation of the Large Hadron Collider (LHC) project is the testing and operation of a 50-m long superconducting magnet string, representing a half-cell of the machine lattice. This also corresponds to the length of the elementary cooling loops providing refrigeration at the 1.9 K, 4.5-to-20 K, and 50-to-75 K levels to the LHC cryomagnets. Based on existing large-capacity cryogenic infrastructure, we have designed, built and are operating a dedicated cryogenic system feeding the LHC Test String, with installed capacities of 120 W @ 1.8 K and 10 g/s supercritical helium at 4.5 K. The system also includes 15 kA, 1.6 kA, 500 A, 250 A and 50 A current lead pairs for powering of main and auxiliary magnet circuits, as well as a 120 kW liquid nitrogen vaporizer for controlled cooldown of the 105 kg cold mass. The system is fully instrumented, controlled by dedicated industrial PLCs connected to an industrial supervision system. We report on performance in operation, including response of the system to transients such as current ramp and discharge, as well as magnet resistive transitions. | The Superfluid Helium Cryogenic System for the LHC Test String: Design, Construction and First Operation | 10.1007/978-1-4613-0373-2_100 |
1996-01-01 | Development of turbogenerators is associated with improvement of their cooling system, efficiency, size and weight parameters and operating characteristics. Application of cryogenic cooling and superconducting windings helps to achieve the best results, but there arises the problem of economical efficiency. Superconducting turbogenerator represents, on one hand, just a new type of turbogenerators, incorporating a number of serial units and technologies, and on the other it demands an introduction of new technological processes aimed at achievement of better parameters and higher reliability. Superconducting turbogenerators may be subdivided into two groups: alternators with slow-response excitation for the combined-cycle power plants with the unit rating of 200–250 MW; and, generators with unit ratings starting from 500–600 MW and with high response excitation intended mainly for the nuclear power plants. There exists a possibility to make the first ones relatively cheap while the second will be substantially more expensive. VNIIElectromash is now developing a design of a slow-response generator with the unit rating of 220 MW. Availability of a developed test facility for the generator investigation will help to decrease the investment in a prototype machine. | Superconducting Turbogenerators as a New Generation of High-Rated Electrical Machines | 10.1007/978-1-4613-0373-2_129 |
1996-01-01 | The X-Ray Spectrometer (XRS) instrument has gone through numerous iterations, first as an instrument on NASA’s Advanced X-Ray Astrophysics Facility (AXAF), then on AXAF-S, and now scheduled to fly on the Japanese Astro-E satellite. The Astro-E XRS is a high precision x-ray spectrometer with better than 20 eV resolution for x-ray energies from 0.3 to 10 keV. The requirement to obtain a lifetime greater than two years within the weight constraints of Astro-E has presented quite a challenge in the design of the cryogenic system. The design of the superfluid helium insert is described, with emphasis on innovative approaches taken to meet the requirements. | Design of the XRS Helium Insert | 10.1007/978-1-4613-0373-2_143 |
1996-01-01 | A superfluid Stirling refrigerator cooled to 168 mK using a 4.9% ^3He-^4He mixture and exhausting its waste heat at 383 mK. Cooling power versus temperature and speed is presented for 4.9%, 17%, and 36% mixtures. At the highest concentration, a dissipation mechanism of unknown origin is observed. | Measurements with a Recuperative Superfluid Stirling Refrigerator | 10.1007/978-1-4613-0373-2_192 |
1996-01-01 | The CEBAF End Station Helium Refrigerator (ESR) System ^1 provides refrigeration at 80 K, 20 K and 4.5 K to three End Station experimental halls. The facility consists of a two stage helium screw compressor system, 4.5 K refrigerator, cryogen distribution valve box, and transfer lines to the individual experimental halls. The 4.5 K cold box and compressors were originally part of the ESCAR 1500 W, 4 K refrigeration system at Lawrence Berkeley Laboratory which was first commissioned in 1977. The compressors, 4.5 K cold box, and control system design were modified to adapt the plant for the requirements of the CEBAF experimental halls. Additional subsystems of cryogen distribution, transfer lines ^2, warm gas management, and computer control interface were added. This paper describes the major plant subsystems, modifications, operational experiences and performance. | Commissioning and Operation of the CEBAF End Station Refrigeration System | 10.1007/978-1-4613-0373-2_82 |
1996-01-01 | Two models of small free piston cryocoolers with the potential for low cost and high reliability have been developed for emerging commercial applications. Model M223 has been designed for applications ranging from 173 K to 273 K lifting up to 40 W at 223 K. The other, model M77, has been designed for operation from 65 K to 150 K. This unit will lift up to 4 W at 77 K and more than 10 W at 150 K. Both passive and active balance units have been implemented to reduce vibration. Performance data for each model are presented over a wide temperature range for representative machines. A summary of the life and reliability information to date is also included. | Low Cost Small Cryocoolers for Commercial Applications | 10.1007/978-1-4613-0373-2_196 |
1996-01-01 | In general, materials tend to increase in strength as their temperature is lowered. The deformation of metals occurs with the movement of crystal-lattice dislocations. As the temperature is raised, the thermal energy of the vibrating atoms assists this movement. Hence, as the temperature is lowered, the decreased thermal vibration of the metal lattice adds to the strength of the material.^1 However, in the design of cryogenic equipment it is usually best to use the ambient-temperature strength because of temperature gradients that might exist within the equipment and also because cryogenic equipment frequently must operate at warmer temperatures. | Embrittlement of Materials | 10.1007/978-1-4899-0307-5_3 |
1996-01-01 | A cryogenic hydrogen maser has been designed and constructed which operates at temperatures near 10 K with a surface of frozen neon in the atom storage region. Cryogenic operation is expected to improve masers performance by orders of magnitude over room-temperature masers in frequency standard applications. The maser has an atom storage region and microwave cavity made from three pieces of single crystal sapphire. The neon surface is expected to be isothermal and stable to within 1 mK during operation. The sapphire is contained within a copper enclosure which is surrounded by magnetic shields and cooled by conduction to a helium-cooled copper plate. The helium cooling to the plate is in the form of cold helium gas flowing through a tube attached to the plate. The internal vacuum of the maser is maintained by a helium-cooled cryopump located between the hydrogen atom source and the transition. Atomic hydrogen is supplied by an effusive discharge operated at liquid nitrogen temperatures. The maser has operated as a self-excited oscillator and most of the required cryogenic characteristics have been experimentally verified. At temperatures near 10 K a stability of 1 mK was achieved for periods exceeding ninety minutes. | A Cryogenic Hydrogen Maser Operating at 10K | 10.1007/978-1-4613-0373-2_222 |
1996-01-01 | A 5-kW/4.5-K helium refrigerator has been developed, which will be used for the test of ITER Central Solenoid Model Coil that is under fabrication by an international collaboration under the framework of the ITER Engineering Design Activity. Its acceptance test was recently finished and its specified refrigeration power of 5 kW with a surplus liquefaction rate of 114 l/h was demonstrated. A major feature of the refrigerator is that newly developed components, such as helium compressor and turbo-expander, are adopted in its simple refrigeration process in order that the results will be transferred to the ITER helium cryogenic system. | Cryogenic System for ITER CS Model Coil | 10.1007/978-1-4613-0373-2_92 |
1996-01-01 | As part of the TESLA-Collaboration, components of a 1.8 K cryogenic plant, designed for testing superconducting RF cavities at the DESY laboratory, have been designed and built at the CEN SACLAY, LAL ORSAY, FERMLAB, INFN FRASCATI and DESY. Some additional components are being fabricated at IHEP PROTVINO and industry. The general layout of a 1.8 K Test Facility for the test of superconducting RF cavities has been described earlier^1. The first stage of the cryogenic facility has been brought into operation. During tests of the prototype cavities, the cryogenic performance of the main components of the cryogenic plant was monitored and is presented. This includes vacuum compressors, vertical and horizontal test dewars, a collection box and a helium heater. For the second stage, required for the operation of the TTF-500 MeV-linac, the construction of the first module cryostat, the capture cavity cryostat, the 6-fold transfer line and the TTF-feedbox is almost finished. The construction of TTF-module transfer lines, TTF-module end caps and a large low pressure heat exchanger has begun. The design of these components and the present status of the installation at DESY is reported. | Status of the TTF Cryogenic System | 10.1007/978-1-4613-0373-2_109 |
1996-01-01 | For the production of the liquid helium and realization of technological operation modes of cooling down, steady state and warming up cryogenic objects at Tokamak T-15 facility liquefiers with the present flow rate, 0.222 L/s (800 L/h) each, are used. In 1988 the Liquefier was put into operation under conditions without implementation of the third turbine stage, at the liquid helium flow rate 0.0694 – 0.0972 L/s (250 – 350 L/h), for the time of continuous operation of 200 hours long. Since 1988, work has been done to enhance its reliability and capacity. This includes: Simplification pneumatic-hydraulic circuit-diagram of the liquefiers for increasing reliability. Start-up of the third turbine stages of the liquefiers. Piston expander and two variant of turbines were tested, only the last variant has demonstrated reliable and effective operation. Work out and realization of technological and circuit-diagram solution (usage of preliminary helium purification from neon, development and assembly of a neon adsorber) against freezing neon and hydrogen impurities — changing the mass flow ratio — in the valves and heat exchangers. Test of various prototype main turbines. Many prototype main turbines with various work pressure and various mass flow were tested. Turbines with optimal parameters have been selected. At present, the Liquefier has the flow rate equal 0.222 L/s (800 L/h), at the compressed helium flow rate — 0.222 kg/s (800 kg/h), and the inlet Liquefier pressure — 2.2 MPa. | An Experience in the Maintenance of a Liquefier from the T-15 Cryogenic System, Results of Its Reliability and Capacity Enhancement | 10.1007/978-1-4613-0373-2_95 |
1996-01-01 | There are several mechanisms by which contact of cryogenic fluids with a person can present a physiological hazard. The most obvious of these mechanisms is that the low temperature can cause freezing of living tissue. Also, in the case of cryogens other than oxygen, the large expansion that occurs upon evaporation and warming to ambient temperature can result in dilution of the oxygen in the surrounding atmosphere to the point where it cannot support life. In the case of a few cryogens, toxicity can also be a problem, but, fortunately, these are not frequently encountered. | Physiological Hazards | 10.1007/978-1-4899-0307-5_2 |
1996-01-01 | Fermilab’s superconducting Tevatron accelerator is cooled to liquid helium temperatures by 24 satellite refrigerators, each of which uses for normal operations a reciprocating “wet” expansion engine. These expanders are basically Process System (formerly Koch) Model 1400 expanders installed in standalone cryostats designed by Fermilab. This paper will summarize recent experience with operations and maintenance of these expansion engines. Some of the statistics presented will include total engine hours, mean time between major and minor maintenance, and frequent causes of major maintenance. | Operation and Maintenance of Fermilab’s Satellite Refrigerator Expansion Engines | 10.1007/978-1-4613-0373-2_123 |
1996-01-01 | Superconducting digital microelectronics require multi-gigahertz bandwidth performance of the signal I/O system, including multi-channel flat flexible I/O cables. The limited information on the thermal conductivity of modern engineering materials available to the designer of low temperature, high performance systems and devices, makes it difficult to optimize a design or even to know if it will perform as specified. This is particularly true of the newer dielectrics for which bulk thermal conductivity data do not exist. This paper presents the thermal conductivity measurements we have made of various metals and dielectrics commonly used for high performance, low loss flexible I/O cables and presents the design tradeoffs that these materials offer the designer. We also describe the relatively low cost procedure we are using to make thermal conductivity measurements of metals and dielectrics between 8 K and 100 K that satisfy design engineering requirements. A discussion of the value of thermal conductance vs. bulk thermal conductivity is also presented. | The Thermal Conductivity of Some Modern Engineering Materials Used in High Bandwidth I/O Systems at Cryogenic Temperatures | 10.1007/978-1-4613-0373-2_17 |
1996-01-01 | Many documents, both formal and informal, exist to advise on or specify methods for the design, construction, and operation of cryogenic systems. These documents are variously known as rules, guidelines, standards, codes, and regulations, and any of them can address any facet of the handling of a cryogenic fluid. A general goal of all of these documents is to minimize risk of injury to personnel and damage to facilities and to promote safety by informing all interested parties of required, accepted, and preferable methods of proceeding when working with a cryogenic fluid. | Guidelines, Standards, and Regulations | 10.1007/978-1-4899-0307-5_11 |
1996-01-01 | The detection of new physics signals at the highest luminosities available in proton-proton collisions at LHC requires identification and precise measurement of muons, photons and electrons. Toroidal and solenoidal fields were considered at the beginning of the design. For the CMS detector, the choice of a compact design led to the choice of a strong magnetic field. The most practical magnet that can generate a strong magnetic field is a solenoid. A long (about 13 m) superconducting solenoid of large radius generating a magnetic field of 4 T guarantees good momentum resolution. The magnetic flux is returned via a 1.8 m thick iron yoke of a weight of 12 000 tonnes. The magnetic stored energy is 2.52 GJ and the coil total weight is 500 tonnes. The coil main design features are indirect cooling, pure aluminium stabilisation and mechanically reinforced conductor. It is a four layer winding, composed of 4 axial sections bolted together. | Conceptual Design of the CMS 4 Tesla Solenoid | 10.1007/978-1-4613-0373-2_106 |
1996-01-01 | At 5:46 a.m. on 17 January 1995, a big earthquake with a magnitude of 7.2 on the Richter scale struck the Kansai area in western Japan. It was a shallow dislocation earthquake and resulted in huge damages in this area. Kobe, with a population of one million, was greatly affected by this disastrous earthquake. There are many hospitals, laboratories and universities in this area, and various kinds of cryogenic and superconducting equipment were about to go into operation. The Cryogenic Association of Japan immediately organized a special committee for damage investigation on this equipment purely from the technical point of view. This paper is presented as a quick report on what happened to MRI magnets, cold evaporators and other cryogenic and superconducting equipment in the universities affected by this earthquake. | What Happened to Cryogenic and Superconducting Equipment in the Great Hanshin Earthquake | 10.1007/978-1-4613-0373-2_238 |
1996-01-01 | Operation of most temperature sensors requires the dissipation of power in the sensor. The flow of the heat generated by the measurement creates a temperature difference and a potential temperature measurement error. The self-heating temperature difference is directly proportional to the thermal resistance. A procedure for measuring the thermal resistance of a mounted temperature sensor is described. Thermal resistances were measured at cryogenic temperatures (50 mK to 10 K) on several commercially available temperature sensors. The sensors were mounted to a copper block in either a vacuum, helium gas or helium liquid environment. The thermal resistance was found to depend on temperature, thermal environment and details of sensor mounting and packaging. Minimization of the temperature measurement uncertainty requires a balance between the uncertainties due to self-heating and measurement of the output signal. Equations are provided for calculating the operating point for minimum combined temperature measurement uncertainty. | Thermal Resistances of Mounted Cryogenic Temperature Sensors | 10.1007/978-1-4613-0373-2_213 |
1996-01-01 | The High-Temperature-Superconductivity (HTS) group of the RF Technology Branch, Space Electronics Division, is actively involved in the fabrication and cryogenic characterization of planar microwave components for space applications. This process requires fast, reliable, and accurate measurement techniques not readily available. A new calibration standard/test fixture that enhances the integrity and reliability of the component characterization process has been developed. The fixture consists of 50 Q thru, reflect, delay, and device under test gold lines etched onto a 254 urn (0.010″) thick alumina substrate. The Thru-Reflect-Line (TRL) fixture was tested at room temperature using a 30 Ω, 7.62 mm (300 mil) long, gold line as a known standard. Good agreement between the experimental data and the data modelled using Sonnet’s em ^© software was obtained for both the return (S_11) and insertion (S_21) losses. A gold two-pole bandpass filter with a 7.3 GHz center frequency was used as our device under test (DUT), and the results compared with those obtained using a Short-Open-Load-Thru (SOLT) calibration technique. Minimum insertion losses of 3.85 dB and 5.41 dB were measured with the TRL and SOLT calibration techniques, respectively. Room temperature return losses of 25.56 dB and 16.86 dB were measured using the TRL and SOLT calibration techniques, respectively. When used to perform calibrations and testing at cryogenic temperatures, the TRL fixture exhibited insertion and return loss data superior to its SOLT counterpart. A detailed description of the cryogenic components of the TRL fixture as well as results of their cryogenic characterization are presented. | A Single-Block TRL Test Fixture for the Cryogenic Characterization of Planar Microwave Components | 10.1007/978-1-4613-0373-2_217 |
1996-01-01 | Between 1990 and 1994 CERN procured, installed and commissioned six large-scale helium cryoplants for its programme of superconducting acceleration cavities in the electron-positron collider LEP. Two European suppliers were selected to each provide one plant of 6 kW and two plants of 12 kW equivalent cooling power at 4.5 K. All installations are now commissioned and operational, some have been running continuously for several years. The concepts applied to specification, tendering, sharing of responsibilities for infrastructure and controls, installation, and commissioning are presented. Conclusions are drawn from the experiences during the different phases of this project and applied to acquisition of plant upgrades and additional plants required for LHC, CERN’s new project for a proton-proton collider in the LEP tunnel using superconducting magnets. | Conclusions from Procuring, Installing and Commissioning Six Large-Scale Helium Refrigerators at CERN | 10.1007/978-1-4613-0373-2_98 |
1996-01-01 | The superconducting 2 x 250 GeV e^+e^- linear accelerator TESLA is composed of a series of high frequency resonators (cavities), fabricated of high purity niobium. It has to be operated at a temperature of ca. 2 K. A nominal refrigeration power of about 51 KW at 2 K, 37 KW at 4.5 K and 314 KW at 40/80 K is required. The cooling power has to be distributed over a distance of more than 30 km, Different aspects of the cryogenic system are discussed. | The TESLA 500 Cryogenic System Layout | 10.1007/978-1-4613-0373-2_117 |
1996-01-01 | As mentioned in Chapter 1, in order to have a safe operation, the system must be both designed and constructed to be safe, and it must also be operated in a safe manner. Safe operation requires excellent maintenance and housekeeping. Because new and different applications of cryogenics are frequently encountered, the possibility of inexperienced operators is always present. Furthermore, a new application might entail usage that does not have any precedent or existing applicable experience. Effective safety training is of the utmost importance, and the operators must not only be well versed in the basis of cryogenic safety but also have intimate knowledge of the system with which they are working. They must always be aware of the total inventory of cryogens and also know the location and amount of cryogen at every point in the system. Previous experiences, difficulties, failures, and accidents provide valuable knowledge that is important to anyone involved in the operation of a cryogenic system. | Accidents: Prevention and Examples | 10.1007/978-1-4899-0307-5_13 |
1996-01-01 | One of the most feared hazards in any system is that of unwanted combustion. The possibility of fire and explosion is a legitimate cause for concern and for additional attention to system safety. Although carbon monoxide, as well as oxygen and condensed air (see Chapter 9), can present a combustion hazard, here we will be concerned with liquid hydrogen and, to a lesser extent, with liquefied natural gas (LNG). | Combustion Hazards | 10.1007/978-1-4899-0307-5_7 |
1996-01-01 | The 29th Cryogenic Engineering Conference (CEC) was held as a joint conference with the International Cryogenic Materials Conference (ICMC) in Columbus, Ohio, during July of 1995. The CEC is the largest regularly held conference in the United States dedicated to all topics in cryogenic engineering. This paper briefly examines directions in cryogenic engineering by considering the CEC’s technical content as represented by submitted abstracts for the’95 and past conferences. Specific comments are made about the direction of large-scale refrigeration. It also remarks on the general health of the field in the U.S. by considering the origin of the abstracts. Finally, the demographics of the overall attendance, based on nationality, are presented. | Directions in Cryogenic Technology — 1995 | 10.1007/978-1-4613-0373-2_252 |
1996-01-01 | Although there are exceptions over limited temperature ranges, materials generally have positive thermal expansion coefficients. Usually, the temperature change from ambient to cryogenic temperature will amount to as much as 200 K (360 °F) or greater. This large temperature decrease will cause a significant thermal contraction in any material being cooled from ambient temperature to cryogenic temperature. However, the thermal expansion coefficient is also a function of temperature, decreasing as the temperature is lowered. Figure 4.1 shows the temperature dependence of the thermal expansion coefficient of copper.^1 Although there is still further contraction below the temperature of liquid nitrogen, usually over 90% of the total contraction from room temperature to any lower temperature will have already taken place at 77 K because of the decrease in the thermal expansion coefficient for many materials with temperature. Consequently, in cooling from ambient temperature to any cryogenic temperature, there will be a thermal contraction of about 0.3% in iron-based alloys, over 0.4% in aluminum, and well over 1% in many plastics. The first two of these figures give useful rule-of-thumb values for quick estimates. The more accurate values needed for system design can be obtained from published tables of integrated thermal contraction over the temperature range of interest. Tables 4.1 and 4.2 give some representative examples.^2 Figure 4.2 shows the total integrated thermal contraction from ambient temperature down to any cryogenic temperature for several materials.^3 | Stresses Caused by Thermal Contraction | 10.1007/978-1-4899-0307-5_4 |
1996-01-01 | We have developed a cryogenic NMR probe using HTS detection coils for high resolution chemical spectroscopy and have demonstrated a signal-to-noise improvement by more than a factor of four over conventional technology. The probe is cooled by a remotely located closed-cycle refrigeration system and coil temperatures below 20 K have been attained. The probe is designed to be inserted into a 37 mm diameter bore of a high homogeneity superconducting magnet with the coils located less than 2 mm from a room temperature NMR sample. The samples can be loaded using the standard pneumatic loading system, and sample temperatures can be regulated using the standard gas flow method. Standard sample spinning can also be performed. The closed-cycle refrigeration system consists of a closed loop of circulating helium gas cooled by a heat exchange network on a Gifford-McMahon refrigerator. A vacuum insulated transfer line is used to flow the helium from the cooling system to the probe. The probe has been optimized for minimal heat leak while maintaining RF performance for the NMR experiments. | Cryogenic System for a High Temperature Superconductor NMR Probe | 10.1007/978-1-4613-0373-2_235 |
1995-06-01 | The gyrotron system for ECH and burn control on ITER requires at least 50MW of RF power at frequencies near 170GHz operating in CW . To meet these requirements, high efficiency gyrotron tubes with ≥ 1MW power output capability are necessary, as well as simple coupling to either a quasi-optical or waveguide transmission line. The paper reports the feasibility study on the design of an ITER -relevant gyrotron oscillator at 170GHz , 1MW CW employing a diode electron gun, an advanced internal quasi-optical converter, a cryogenically cooled single disk sapphire window, and a depressed potential collector. The operating mode selection and the cavity design is a compromise between many design constraints. | Feasibility study of the eu home team on a 170GHz 1MW CW gyrotron for ECH on ITER | 10.1007/BF02068283 |
1995-04-01 | Critical conditions for the direct initiation of self-sustained detonation in cryogenic hydrogen-oxygen mixtures are examined experimentally. These initial conditions are expected to depend mainly on four parameters: the equivalence ratio of the mixture, the amount of the initial energy deposition, the initial temperature and pressure of the mixture. These critical conditions are determined by fixing alternatively three of these parameters and varying the fourth one from subcritical to supercritical detonation conditions. Results are presented for initial pressures P _o and equivalence ratios Φ ranging from 0.3 to 1 bar and from 1 to 2 respectively, for the two initial temperatures T _o, 123 K and 293 K. These results indicate that for the lowest values of the initial pressure, a decrease of initial temperature may favour the onset of detonation. Whatever the initial conditions, the measured detonation pressures and velocities are in reasonably good agreement with the corresponding Chapman-Jouguet values computed using the ideal-gas equation of state. | Direct initiation of detonation in cryogenic gaseous H_2-O_2 mixtures | 10.1007/BF01413875 |
1995-04-01 | The viability of 252 wood-inhabiting strains of Basidiomycetes was tested after storage under liquid nitrogen, using 10% glycerol as cryoprotectant. 164 strains survived the process: 103 Aphyllophorales (out of 138) and 60 Agaricales (out of 113). The results indicate that the process of freezing is rather complex and should be more precisely controlled to achieve higher survival. | Viability of wood-inhabitingBasidiomycetes following cryogenic preservation | 10.1007/BF02815422 |
1995-02-01 | Modern cryogenic helium systems. Development potentials | 10.1007/BF01147395 | |
1995-02-01 | The rates of recovery from cryogenic storage of suspension cultures of the Japonica rice cultivar Taipei 309, as determined by the reduction of triphenyl tetrazolium chloride and cell regrowth, were significantly influenced by the embryogenic potential of the non-frozen cultures. | The embryogenic potential of rice cell suspensions affects their recovery following cryogenic storage | 10.1007/BF00023966 |
1995-01-01 | With the increased use of cryogenics in both technical and theoretical applications, there is an increased requirement for reliable phase equilibrium and related thermodynamic data for cryogenic fluids and their mixtures. For this reason a new apparatus has been constructed which is capable of providing phase equilibrium data of sufficient accuracy for the derivation of meaningful, thermodynamic properties of fluid mixtures. | A Multipurpose Phase Equilibrium Apparatus to Study Mixtures of Cryogenic Fluids: Application to Argon-Methane | 10.1007/978-1-4757-0513-3_6 |
1995-01-01 | Experimentation in the temperature range 1 to 4°K in liquid helium requires very little skill or sophistication. An experimentalist of very modest dexterity can learn to conduct experiments in liquid helium in a very short time. Considering the ease of this first step into this temperature range, it is only natural that the experimentalist is appalled at the great difficulty of the next step, that of applying continuous reliable refrigeration for the same temperatures. The complexity and cost of even the simplest systems are surprisingly large. | Simon Helium Liquefaction Method Using a Refrigerator and Thermal Valve | 10.1007/978-1-4757-0513-3_52 |
1995-01-01 | Cryogenic coolers for small satellites require low power and minimum weight. In this paper we report on the status of both our miniature flight-qualified pulse tube cooler as well as our miniature flight-qualified Stirling cooler. Both integral linear coolers are small, efficient, low-power, and vibrationally balanced, and incorporate Oxford-type single flexure-bearing compressors. Vibrational balance is achieved with a motor-driven balancer. The Stirling cooler cold head incorporates a colinear flexure-bearing suspended displacer/regenerator with a motor drive used for phase control. The larger capacity pulse tube cooler uses a completely passive cold head which contains no cold moving parts. Nonwearing clearance seals in both coolers advance the long 10-year life projections. The vibrationally balanced, miniature pulse tube cooler weighs 2.0 kg and delivers a maximum cooling power at 80 K of 800 mW for an input power to the compressor of 30 watts. The unit is suitable for cooling sensors and optics between 60 and 200 K, with cooling powers up to 3.5 watts at 200 K. Self-induced measurements indicate that the cooler can be balanced to reduce vibration forces below 0.1 newtons (N) from 0 to 1000 Hz in all three axes. Using adaptive vibration cancellation, vibration has been reduced below 0.02 N along the cooler axis. The cooler has passed launch vibration tests and is now in life test. The miniature integral Stirling cooler weighs 1.4 kg. It was developed for cooling infrared sensors to temperatures as low as 50 K on lightsats. A number of the vibrationally balanced nonwearing Stirling coolers have been built and tested. Typical cooling performance is 0.25 watt at 65 K for an input power to the compressor of <12 watts. Cooler vibration forces have been balanced below 0.1 N in all three axes from 0 to 1000 Hz. The cooler recently passed launch vibration tests prior to its entry into an extended life-test and its first scheduled flight in 1995. | Miniature Long-Life Space-Qualified Pulse Tube and Stirling Cryocoolers | 10.1007/978-1-4757-9888-3_33 |
1995-01-01 | The first industrial application of superconducting materials appears to be their use as the field windings of rotating electrical machines. Research is being carried on throughout the world on this application, and many reports have appeared in the literature on the testing of ac and dc machines. A research group at the Massachusetts Institute of Technology, supported by the Edison Electric Institute, has been studying the application of superconductors to the rotating field windings of alternators since early in 1967. Two machines have been constructed by this group. The first machine, which is rated at 45 kVA, has been discussed in the literature ^[1-3]. Details of the design and construction of the second machine are also in the literature ^[4-5]. Initial tests have been performed on the second superconducting alternator constructed. This presentation describes the operation of the machine during these tests, and outlines their results. | Superconducting Alternator Test Results | 10.1007/978-1-4613-9847-9_7 |
1995-01-01 | During the course of an earlier investigation to determine the. minimum insulation that would prevent the formation of liquid air on bare cryogenic transfer lines carrying liquid hydrogen and liquid nitrogen, it was evident that ambient conditions were extremely important and that frost had some insulating value. | Frost Formation on a Cylinder at Cryogenic Temperatures | 10.1007/978-1-4757-0513-3_58 |
1995-01-01 | Vuilleumier was granted a patent in 1918 on a refrigeration method which produces cold directly from heat. For many years this method was completely ignored and only very recently efforts were begun [^1,2] to explore the practical possibilities of the cycle. The present paper describes a further contribution to the study of this “hot gas refrigerator” in view of its potential advantages, namely the absence of acoustical noise and the minimal wear of the moving parts due to the small forces in the drive mechanism. | Miniature Vuilleumier-Cycle Refrigerator | 10.1007/978-1-4757-0513-3_56 |
1995-01-01 | Thermal-acoustic oscillations are thermally driven oscillations in low rate and fluid pressure and temperature which sometimes occur in forced convection. The oscillations are sustained and occur at frequencies which can be related to acoustic frequencies. A possible cause of these oscillations are perturbations during heat transfer. Following the perturbation, the flow relaxes toward steady conditions as the disturbance is propagated throughout the system by a pressure wave, traveling at the velocity of sound, and by a slower density wave, traveling at the velocity of the fluid. If there is a controlling downstream restriction, such as an orifice or a valve, the arrival of the slower density perturbation there will again perturb the flow rate, and hence heat transfer. The net effect is a delayed feedback of the perturbation to its source, which can sustain oscillations if the feedback is sufficiently strong. The mechanical analog for this system, which can generate oscillations having the characteristics of Helmholtz resonance, is a damped spring-mass system with the addition of a term that is proportional to displacement at an earlier time. The time delay corresponds to the time required to feed the perturbation back to its source. It will be shown that this analog can account for the qualitative differences in stability limits reported by Hendricks et al. [^1] and by Thurston et al. [^2]. It also quantitatively accounts for the departure from acoustic Helmholtz frequencies which the latter authors experimentally observed. | A Time-Delay Analog for Thermal-Acoustic Oscillations | 10.1007/978-1-4757-0513-3_44 |
1995-01-01 | Recent research in this laboratory has led to the identification of a group of ferritic alloys from the iron-nickel-titanium system which show an unusual combination of strength and ductility at cryogenic temperatures. The details of this research are reported elsewhere [^1]. This presentation provides some of the best results obtained to date with an Fe—12 Ni—0.25 Ti alloy and compares these to the best available properties of two commonly used cryogenic steels: type 304 stainless steel and Fe—9 Ni—1 Mn—0.1 C (9% nickel steel). | An Iron-Nickel-Titanium Alloy with Outstanding Toughness at Cryogenic Temperature | 10.1007/978-1-4613-9847-9_46 |
1995-01-01 | A differential thermal analysis (DTA) apparatus for use in the temperature range from 20 to 300 K has been constructed and put into operation. This apparatus has multiple sample cells for simultaneous testing of up to twelve samples. Both temperature control and data sampling are handled by a minicomputer using a modified version of an interpretive language. | A Differential Thermal Analysis Apparatus for Use at Cryogenic Temperatures | 10.1007/978-1-4613-9847-9_49 |
1995-01-01 | Knowledge of mechanical properties of industrial materials at cryogenic temperatures is essential for designing cryogenic equipment such as superconducting magnets. To augment available data [^1,2] an apparatus for tensile tests was designed and constructed to perform in the temperature range from room temperature to 4°K. The apparatus consisted of a universal testing machine, a cryostat which cools the specimens., an automatic temperature controller, and an automatic recovery system for the helium gas. Liquid helium was used as a coolant and Au(Co 2 %)-Cu thermocouples were used as temperature-sensing elements. | Tensile Properties of Various Materials at Cryogenic Temperatures | 10.1007/978-1-4757-0513-3_15 |
1995-01-01 | The largest LNG project, the El Paso project, was finally approved by the Federal Power Commission (FPC) in October 1972, some fifteen months after the hearings were held; but it took El Paso Natural Gas until March 1973 to finalize the liquefaction plant financing and an additional three months to order the three ships it requires. There are now in front of the FPC three major applications to import Algerian LNG: the Easco project for an estimated 600 million ft^3/day, the Phase II El Paso project for 1.0 billion ft^3/day, and the Distrigas project for 120 million ft^3/day. As of August 1973, no hearing date has been set for any of these projects. Substantial delays in obtaining any FPC order may place all three projects in jeopardy of cancellation[^1]. However, if an optimistic viewpoint is maintained, Tables I and II summarize the LNG ship construction potential and the LNG ship requirements. | Status Report on LNG Tanker Designs | 10.1007/978-1-4613-9847-9_35 |
1995-01-01 | Efficient tensile cryostats for some years have been used at temperatures as low as boiling liquid helium [^1]. It seems appropriate, however to extend the low-temperature capabilities, since millidegree equipment design, potential space applications, and fundamental deformation studies all may profit from tensile data obtained at temperatures nearer absolute zero. | Cryostat and Strain Measurement for Tensile Tests to 1.5°K | 10.1007/978-1-4757-0513-3_16 |
1995-01-01 | A research and development program has been conducted since 1962 to develop new electrical machines using high-purity metals as conductors. This program is principally aimed at the development of high-rating and consequently high-voltage electrical machines. In support of this program it was decided to undertake high-voltage tests of cryogenic fluids and of solid insulators at cryogenic temperatures. The possibility of tests in liquid helium was also considered since the use of fastdischarge superconducting coils induces a high voltage in such equipment. | The Dielectric Strength of Cryogenic Fluids and Solid Insulators | 10.1007/978-1-4757-0513-3_12 |
1995-01-01 | The goal of controlled fusion research is to eventually produce electric power; after some twenty years of worldwide research effort, there has been much progress toward this goal. We can now outline a reasonable timetable for the U. S. fusion program which leads to the possibility of commercial power in about thirty years [^1]; this assumes that a scientific feasibility demonstration will be successful within the next ten years, and serious design studies are now underway on several scientific feasibility demonstration experiments. | Cryogenic Engineering and Fusion Power | 10.1007/978-1-4613-9847-9_4 |
1995-01-01 | Citrus rank second after grapes as the major fruit crop. Commercial citrus are grown in tropical and subtropical climates, mainly in a uniform belt from 35°N to 35°S. Under mild environmental conditions such as those found in the Mediterranean regions, citrus may be grown as far as 44°N. About 90 countries produce citrus, most of which are grown for local consumption. Only eight countries produce 50% of the total world production with five accounting for most of the exported citrus as fresh fruit and processed juices (FAO 1992). | Cryoconservation of Germplasm of Citrus | 10.1007/978-3-662-03096-7_4 |
1995-01-01 | The general methods for obtaining low-temperature refrigeration under laboratory conditions are: boil-off of a bath of liquefied gas such as helium, closed-cycle refrigeration employing expansion engines alone, and closed-cycle refrigeration employing a Joule-Thomson expansion loop tied thermally to an expansion engine cycle for precooling. | Operation and Application of a Three-Stage Closed-Cycle Regenerative Refrigerator in the 6.5°K Region | 10.1007/978-1-4757-0513-3_53 |
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