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1995-01-01 | Geographical locations of major, wild relative diversity in members of Brassicaceae such as Brassica nigra , Sinapsis alba , Raphanus sativus , and Eruca sativa are centered in the Mediterranean, particularly Spain. Other regions of diversity include France and southern Britain, a few Brassica species exhibit xerophytic adaptations to the Saharan region (Tsunoda 1980). Relationships between agronomically important Brassica species are complex as they are based on interspecific hybridizations and the phylogenetic relationships between B. nigra , B. carinata , B. juncea , B. oleracea , B. napus , and B. campestris. Within this system, a scheme termed the U-triangle has been proposed (see Sjodin 1992), thus, B. napus is the amphidiploid derived from the hybridization of B. campestris and B. oleracea. To add further complexity, different wild forms of B. napus , including crosses with cultivated B. oleracea and B. campestris , have been found at various geographical locations. In addition, Tsunoda (1980) reports a wide range of wild Brassica diversity within different geographical centers, for example: B. fruticulosa (Mediterranean coast), B. oxyrrhina (S Spain and Portugal and Morocco), B. repanda (Algeria), and B. elongata (SE Europe, W Asia). Reports of endangered, wild, Brassica species include Coronopus navasii , from Spain (Iriondo and Perez 1990a,b), Lepidium hyssopifolium , an endangered watercress located in Victoria, Australia (Cropper 1987), and Braya humilis , a native of the alpine tundra of central Colorado, (Neely and Carpenter 1986). | Cryopreservation of Brassica Species | 10.1007/978-3-662-03096-7_21 |
1995-01-01 | The term “microfabrication” has been used to denote the technology for manufacturing integrated micro-circuits and microsystems. During the last 30 years the advanced micro-electronics could not maintain its place without microfabrication technology and this is also the case for the present and for the future. Integrated circuits whose fabrication consists of several processes that take place under conditions of higher temperature, vacuum film deposition, oxidation, and dopant implantation are all patterned into circuits by lithography and etching. Microfabrication requires three main ingredients: (i) a lithography tool capable of generating micro-patterns smaller than the minimum required structure dimensions; (ii) a recording medium (resist layer) into which the desired device pattern is written (the mask); and (iii) a pattern transfer-process of the structures created into the resist-relief mask. The aim of this work is to extend E lectron- B eam L ithography (EBL) and plasma R eactive I on E tching (RIE) technology into the manufacturing of M icro E lectro M echanical S ystems (MEMS) and sensors. In the first part of this paper the basic aspects of (i) drawing resist-relief mask structures onto the top of the wafers and (ii) pattern transfer of the resist-structures by plasma etching into the substrate will be presented. In later sections, the phenomenas studied will be discussed, which are necessary for the generation of structures with high aspect ratios from the nanometer scale up to the micron scale. Attention will be given to some promising applications and technological procedures for the realization of MEMS and microsensor manufacturing. | Lithography and Reactive Ion Etching in Microfabrication | 10.1007/978-94-011-0423-4_30 |
1995-01-01 | Developments are being carried out to extend the practical use of turbomachine-based reverse Brayton cycle cryocooler technology to lower capacity applications. These developments focus primarily on cooling loads in the range of 0.5 W to 2 W at temperatures from about 40 K to 70 K in a single stage cycle with neon. With some modification, the technology can also be applied to multi-stage helium cycles for cooling loads as low as 100 mW at temperatures as low as 5 K. The goal is to produce systems incorporating vibration-free turbomachines with performance characteristics comparable to those that have been demonstrated for larger cycles — i.e., the 5 W 65 K single stage reverse Brayton cycle cryocooler. These efforts, if successful, should result in turbomachine based cryocoolers with input powers of about 100 W or less. The critical components for a low capacity reverse Brayton cycle cryocooler include the expansion turbine and the turbo-compressor. This paper describes a novel turbine design that is currently under development and discusses developments associated with a high-performance miniature compressor. The expansion turbine drives an AC generator at cryogenic temperatures to extract shaft work with minimal parasitic heat leak to the cold end. Options for the compressor include magnetic bearings to reduce drag losses, and a new motor design using basic features of the expansion turbine’s AC generator. | Miniaturization of Components for Low Capacity Reverse Brayton Cryocoolers | 10.1007/978-1-4757-9888-3_52 |
1995-01-01 | The Cryo System Experiment (CSE), a NASA In-Space Technology Experiments Program (INSTEP) Class D Flight Experiment, was developed by Hughes Aircraft Company to validate in zero-g space a 65 K cryogenic system for focal planes, optics, instruments, or other equipment (gamma-ray spectrometers and infrared and submillimeter imaging instruments) that require continuous cryogenic cooling. The system consists of a long-life, low-vibration Stirling-cycle, 65 K, Improved Standard Spacecraft Cryocooler (ISSC), and a diode oxygen heat pipe thermal switch that enables physical separation between the cooling source and the element to be cooled. A key value of this flight experiment has been the opportunity for Hughes and the Jet Propulsion Laboratory (JPL) to identify and resolve cooler and imaging-instrumentation integration issues that will be encountered when these enabling thermal management technologies are integrated in future space cryogenic cooling systems. Presented are generic lessons learned from the system integration of cryocoolers for a flight experiment including: launch-vibration restraints for the expander cold-tips, implementation of compressor and expander hysteresis test capability, the design and installation of a high-compliance thermal strap to minimize side loads on the expander, the inclusion of both the cooler as well as its heat rejection materials in the mass calculation, contamination/parasitics, system operations/software, electrical interface requirements, and the safety implications associated with the classification of mechanical components and the radiation environment. | Lessons Learned during the Integration Phase of the NASA IN-STEP Cryo System Experiment | 10.1007/978-1-4757-9888-3_85 |
1995-01-01 | Small amounts of carbon dioxide are usually present in natural gas mixtures. The relatively high triple-point temperature of this contaminant necessitates its removal from natural gas prior to cryogenic processing in order to avoid formation of solids in the process piping, valves, and the heat exchangers. It may also be necessary to remove carbon dioxide from the natural gas stream which passes through turbo- expanders in typical expander cycle liquefaction processes because, although commercial turboexpanders can operate into the region of partial condensation at the turbine outlet, present design practice requires that the gas expansion process be stopped short of the carbon dioxide frost point condition. It is therefore desirable to have information on the phase behavior of carbon dioxide in light hydrocarbon mixtures, especially in the range of carbon dioxide concentrations which are often encountered in the liquefied natural gas (LNG) applications. | Phase Behavior of the Methane-Carbon Dioxide System in the Solid-Vapor Region | 10.1007/978-1-4613-9847-9_40 |
1995-01-01 | A cryogenic liquid, after being introduced into a warm transfer line or apparatus, expands to many times its original volume. In some systems the liquid and vapor flow smoothly, while in others significant flow and pressure oscillations develop. Additional factors which often are not negligible in cooldown of an apparatus are the quantity of liquid evaporated and the time required before a stable flow is reached. | Cooldown Transients in Cryogenic Transfer Lines | 10.1007/978-1-4757-0513-3_43 |
1995-01-01 | Recent advances in liquefied natural gas technology, especially in the storage of liquefied natural gas, have created new demands for accurate prediction of the thermal behavior of the stored product. With LNG being a mixture of methane, heavier hydrocarbons, nitrogen, and some lighter gases, the composition of the liquid can be substantially different depending on the source, time in transit, and time in storage. With the importation of LNG from various locations about the world, it is important to more accurately predict LNG properties such as density, composition, heating value, etc. | Effect of Weathering of LNG in Storage Tanks | 10.1007/978-1-4613-9847-9_31 |
1995-01-01 | Superconducting-coil systems are usually contained in metal dewars so that the liquid helium level cannot be viewed directly. The liquid level can be monitored at fixed points by means of various level detectors [^1–4]. However, a simple detector which can give a continuous indication of liquid level is more desirable than fixedpoint detectors. A linear liquid helium level detector which uses a superconducting element of annealed Ta [^5] and another using a Pb-Sn [^6] alloy element fulfill the requirement of simplicity ; however, neither of them can be expected to work except in very low magnetic fields. Another linear detector which relies on the measurement of the small capacitance difference between liquid helium and gaseous helium [^7] should work in a magnetic field ; however, the associated electronics is complicated and the system must be constructed with great care. | A Superconducting (Nb-Ti) Liquid Helium Level Detector | 10.1007/978-1-4757-0513-3_18 |
1995-01-01 | As a lead-in to the use of 5083 for liquefied natural gas tanks [^1], a special series of fracture tests was ran to substantiate that the alloy has high tear resistance in the relatively thick sections in which it would be used in the structure. These tests were similar in nature to the tear tests which have been made for years [^2], but covered a much wider range of variables, viz. , (1) much thicker material., (2) specimens from the heat-affected zone as well as the parent metal and the welds, (3) welds made automatically, semiautomatically, and in different positions (flat, vertical, horizontal), and (4) welds in extruded shapes as well as plate. The purposes of this paper are to describe the test procedures, present the results, and discuss their meaning as an indication of the toughness of 5083 for engineering structures. | Tear Tests of 5083 Plate and of 5183 Welds in 5083 Plate and Extrusions | 10.1007/978-1-4757-0513-3_14 |
1995-01-01 | Reliable phase equilibrium data are essential for the design of effective and economical gas treatment processes such as natural gas liquefaction. Data on cryogenic mixtures involving relatively simple molecules are also of theoretical interest. An apparatus and the techniques developed to obtain solid–liquid phase equilibrium data for cryogenic systems are described here. Results are presented for the individual solubilities of solid benzene, toluene, n -hexane, and n -heptane in liquid methane. | Solubility of Solid Benzene, Toluene, n-Hexane, and n-Heptane in Liquid Methane | 10.1007/978-1-4613-9847-9_39 |
1994-08-01 | Tolerances for deviations of shape in welded cryogenic vessels and plant | 10.1007/BF01147981 | |
1994-07-01 | The room temperature application of sapphire as window material at higher frequencies is not feasible since its absorption coefficient increases almost linearly with increasing frequency in the millimeter wavelength region. At cryogenic temperature the absorption coefficient value decreases only by a few factors (factor of 2 to 3) in the 90 – 200 GHz region. The earlier reported temperature squared dependence (decrease) in the absorption coefficient or the loss tangent value is totally absent in our broad band continuous wave data we are reporting here (at 6.5 K, 35K, 77K and 300K) and one we reported at conferences earlier. Our results are verified by another technique. We utilize our precision millimeter wave dispersive Fourier transform spectroscopic techniques at room temperature and at cryogenic temperatures The extra high resistivity single crystal compensated silicon is no doubt the lowest loss material available at room temperature in the entire millimeter wavelength region At higher millimeter wave frequencies an extra high resistivity silicon window or an window made with extra high resistivity silicon coated with diamond film would certainly make a better candidate in the future. A single free standing synthetic diamond window seems to have higher absorption coefficient values at millimeter wavelength region at this time although it is claimed that it possesses good mechanical strength and higher thermal conductivity characteristics. It certainly does not rule out the use of diamond film on a single crystal high resistivity silicon to improve its mechanical strength and thermal conductivity | Window materials for high power gyrotron | 10.1007/BF02096072 |
1994-06-01 | Fracture toughness measurement at cryogenic temperatures using chevron notched specimens | 10.1007/BF00035032 | |
1994-06-01 | Cryogenic Technology in the Ukraine | 10.1007/BF01149981 | |
1994-06-01 | Calculation of the heat protection of cryogenic vessels | 10.1007/BF01149980 | |
1994-05-01 | On the basis of the results of acid hydrolysis, chromatographic analysis of the hydrolysates, and a study of IR spectra, it has been established that the suspended particles liberated under the action of electrohydraulic shocks on heterodisperse water—plant systems consist of small fragments of the lignocarbohydrate complex of the plant tissue. | Electrohydraulic effect in heterodisperse water-plant systems. II. Chemical nature of the suspended particles | 10.1007/BF00629985 |
1994-02-01 | A homemade cryogenic system derived from readily available material is described, illustrating its usage as an accessory for adsorption/thermal desorption chromatography. A small Chromsorb-W-HP packing (1 cm) was introduced into a deactivated precolumn as a cryofocussing, preconcentrating unit. This was able to retain the analyte which had been thermally desorpted from a Tenax TA sampling tube at a relatively higher temperature (−80°C∼−90°C), with the analyte also reinjected on the analytical column in a relatively narrow band. Average overall recoveries for 24 hydrocarbons tested were 97.5%. Cryofocussing enhanced sensitivity and improved resolution. Field studies at a petroleum industry site were carried out and the accessory proved to be useful for complex C_5−C_12 hydrocarbon analysis in ambient air. | Improved resolution and determination of ambient C_5−C_12 hydrocarbons by GC-coupled refocussing system | 10.1007/BF02290328 |
1994-02-01 | Some modern products operate under conditions of rapid loading at cryogenic temperatures. To evaluate the serviceability of structural materials under such conditions, it is important to know how their mechanical properties and the nature of fracture change. In the present work, we investigated the effect of the loading rate in the range 10^−4–10^−1 sec^−1 on the mechanical properties of the martensitic-austenitic steels 03Kh12N10MT (VNS-25), 07Kh16N6 (SN-2A), and 08Kh14N8M (VNL-6) at 4.2–293 K. | Effect of the loading rate on the plastic deformation of corrosion-resistant martensitic-austenitic steels at cryogenic temperatures | 10.1007/BF01390298 |
1994-01-01 | Fermilabs superconducting Tevatron accelerator has reached its tenth year of operation. This year, three significant upgrades to the cryogenic system will become operational; a second central helium liquefier, a Tevatron satellite refrigerator lower temperature upgrade, and a satellite refrigerator controls system upgrade. The decision to build a second central helium liquefier (CHL) was originally based on redundancy; protecting accelerator operation from a major CHL failure such as a heat exchanger. Higher capacity turbines were used in the second coldbox, which will result in an estimated 5400 liters per hour production rate. Preliminary commissioning of the coldbox took place in 1992. Full capacity testing will take place in 1993. To aid in the discovery of the top quark, it is desirable to increase the particle energy in the Tevatron accelerator. The machine is limited to an energy of 900 GeV due to magnet conductor short sample current at the existing operating temperature. An upgrade is underway to lower the temperature of the accelerator ~1K. The short term goal is 1000 GeV operation with a 1100 GeV long term goal. Cold vapor compressors will be used in each of the 24 satellite refrigerators to achieve the temperature reduction. An upgrade of the existing satellite refrigerator controls system is necessary to incorporate the added control devices, instrumentation, and controls algorithms required by the low temperature upgrade. The existing Z80 Multibus I based system will be replaced with a 386 Multibus II system. New features will be incorporated, including processor to processor communications, fast event driven circular buffer, hierarchical alarm system, higher level language support, and more elaborate controlling algorithms. | Upgrade of the Tevatron Cryogenic System | 10.1007/978-1-4615-2522-6_62 |
1994-01-01 | A significant upgrade to the Fermilab Central Helium Liquefier (CHL) facility’s 4000 liters/hour helium system has been made to support the Laboratory’s Tevatron superconducting accelerator. The upgrade includes a second helium liquefier with a rated capacity of 5400 liters/hour, a fourth reciprocating compressor rated at 750 grams/second, and an improved cryogenic distribution system including liquid helium dewars and pumps. The system design and operating experience to date are discussed. | Fermilab Central Helium Liquefier System Upgrade | 10.1007/978-1-4615-2522-6_63 |
1994-01-01 | The subcooler assembly installed in the MAGCOOL magnet test area at Brookhaven National Laboratory has been used for testing SSC dipoles, quadrupoles and a spool piece since 1989. A detailed description of the system, its steady state capacity and the performance after quenches of a 50 mm SSC dipole were given^1,2. Subsequent studies on low current quenches of the SSC dipoles^3 and quenches of the RHIC dipoles^4 were also carried out. In this paper, the performance of the subcooler after quenches of the SSC quadrupole QCC404 is presented. Pressures, temperatures and flow rates in the magnet cooling loop after magnet quenches are given as a function of time. The cooling rates and total energy removed by cooling during quench recovery have been calculated for quench currents between 2000 and 7952 amperes. Because the inductance of the quadrupole is about one tenth that of a SSC dipole, the stored energy released is small and the impact on the system is mild. The cooling loop pressure never exceeds 12 atmospheres and the cryogenic system recovers in less than 15 minutes. As in all past studies, the peak pressure and temperature in the magnet cooling loop are linearly proportional to the energy released during a quench and excellent agreement between the total cooling provided and the magnetic stored energy is found. | Performance of the Magcool-Subcooler Cryogenic System After SSC Quadrupole Quenches | 10.1007/978-1-4615-2439-7_22 |
1994-01-01 | The Accelerator System String Test (ASST) was a congressionally mandated milestone for the Superconducting Super Collider Laboratory (SSCL) to demonstrate powered operation of a half-cell of industrially-fabricated collider magnets before mass production could begin. In this paper I describe the installation of the string components and the results from the full-powered tests of the magnet string, consisting of five dipole magnets having an aperture of 50 mm and a single quadrupole having an aperture of 40 mm. Power and cryogenic connections were made to the string through spool pieces that were prototypes for SSC operations. The string was cooled to cryogenic temperatures in early July, 1992 and power tests were performed at progressively higher currents up to the nominal SSC operating point near 6500 Amperes. | The Accelerator Systems String Test: Objectives, Problems, Results, Anecdotes, and Reflections | 10.1007/978-1-4615-2439-7_15 |
1994-01-01 | Fermilab has tested a modified helium oil injected two-stage Mycom screw compressor for possible use in the Tevatron. The tests are part of a joint venture with Mycom. Modifications to the compressor include a new modified rotor profile and new generation lubricant which resulted in increased performance and efficiency. The effects of the modifications on shaft-power and isothermal efficiency are included. The results of these tests will determine the practicality of incorporating these modifications to the thirty-four existing screw compressors of the Tevatron. | Test of an Improved Oil Injected Helium Screw Compressor at Fermilab | 10.1007/978-1-4615-2522-6_107 |
1994-01-01 | Application of stable austenitic steels as structural materials in the temperature range 293 to 4.2 K requires development of welding technologies that provide structure and properties of welds close to those of the base metal. The main problem in welding stable austenitic steels is hot cracking. One the most common procedures to eliminate hot cracking is to form a two-phase welding structure, where the second phase is ferrite, its content being 5 to 10%. However, the addition of delta-ferrite leads to marked embrittlement of welds at 77 to 4.2 K. | Effect of Delta-Ferrite on the Properties of Welds in Austenitic Steels at Cryogenic Temperatures | 10.1007/978-1-4757-9053-5_160 |
1994-01-01 | Electron emissions from synthetic quartz during and after the fracture process were observed at room and cryogenic temperatures. Fracture at room temperature caused a larger number of emitted electrons with a longer decay time than at cryogenic temperature. Specimens quarried perpendicular to the Z-axis of the quartz emitted more electrons for a longer time than ones to the X-axis. With microscope observation of the fracture surface, these results are supposed to be caused by the difference in the crack propagation velocity during fracture. Electron emissions from defect rich samples irradiated by high energy electrons, were also observed and compared with pure samples. The obtained results had some difference from other insulating materials (ceramics, glasses) reported previously.^1–3 | Fracto-Emission from Single Crystals of Quartz at a Cryogenic Temperature | 10.1007/978-1-4757-9053-5_179 |
1994-01-01 | The Accelerator Systems String Test (ASST) was a major milestone in SSCL R&D. Phase I demonstrated that the smallest repetitive sequence of bending magnets (a half cell) could be installed, leak checked, cooled to liquid helium temperatures, energized, and safely quenched. To support this activity, a control system had to be developed to operate and monitor cryogenic systems in the string, along with LCW and vacuum systems. Also, since this is a test facility, the magnet systems were heavily instrumented to provide sufficient data to confirm that design requirements were met, that the system was operating safely and as expected, and allow further design studies necessary for the construction of the SSC. This required the design and implementation of an acquisition system capable of collecting relatively large amounts of data, at various data rates, and presenting this data both to operations personnel and to a database for off-line analysis. In this paper, we describe the design, implementation, and operation of the data acquisition system and controls employed on the ASST. | Data Acquisition and Controls for the SSCL Accelerator Systems String Test Phase I | 10.1007/978-1-4615-2439-7_19 |
1994-01-01 | An analytical model has been developed for the performance of a double inlet pulse tube cryocooler employing a stepped piston compressor. Numerical results are presented as a function of the area ratio of the stepped piston. In some cases, the double inlet pulse tube cryocooler is shown to have more refrigeration power than the corresponding single inlet device. However, the increased refrigeration power is achieved at the cost of reduced thermal efficiency. | Double Inlet Pulse Tube Cryocooler with Stepped Piston Compressor | 10.1007/978-1-4615-2522-6_175 |
1994-01-01 | In the SSC main collider up to five orders of superconducting corrector magnets will be incorporated into the spool pieces to correct for component and machine aberrations. Each order of corrector magnet will be separately powered. This will require a corrector element power lead (CEPL) with a single, room temperature-to-4K interface with multiple leads. CEPLs represent a potentially significant heat load to the 4K helium and must be vapor-cooled to meet heat leak requirements. Analysis and design of vaporcooled power leads for cryogenic systems have been extensively documented in the literature ^1,2. The purpose of this paper is to focus on the requirements and associated issues for this particular application. | Development of A Corrector Element Power Lead | 10.1007/978-1-4615-2439-7_130 |
1994-01-01 | PSI has supplied three equal capacity helium cryogenic plants^1 (dubbed ASST, MTL, and N15B). The first two plants will provide the helium refrigeration and liquefaction required for magnet testing in the Accelerator System String Test (ASST) facility and the Magnet Test Laboratory (MTL). The third plant (N15B) will supplement the ASST plant and will eventually be utilized for the N15 Sector Refrigeration System (SRS) requirements. | Initial Operation and Performance Test Results of The Accelerator System String Test (Asst) Cryogenic System | 10.1007/978-1-4615-2439-7_109 |
1994-01-01 | For purposes of testing the present LEP superconducting resonant cavities and the future LHC magnets, CERN built a test station the cryogenic power of which is presently supplied by a dedicated 6 kW at 4.5 K helium refrigerator. The thermodynamic cycle is discussed and special emphasis is put on a new cryogenic expansion turbine operating in the liquid phase. Information is given about : the cycle screw compressors’ performances, the general performance of the refrigerator, the expected efficiency enhancement due to the liquid turbine, an off-design turn down operation. | A 6 kW at 4.5 K Helium Refrigerator for CERN’s Cryogenic Test Station | 10.1007/978-1-4615-2522-6_66 |
1994-01-01 | The design, implementation and use of a control system for the cryogenic magnet test stands at General Dynamics’ Hammond, Louisiana facility is discussed. Batch control techniques are used to automate and assist the testing of magnets in a production environment. The test stand control system is integrated into the overall facility control and information systems. | The Control and Operation of A Test Stand for The Cryogenic Testing of Superconducting Magnets | 10.1007/978-1-4615-2439-7_112 |
1994-01-01 | The formation of liquid oxygen on the outside of liquid hydrogen vent lines poses a potential safety hazard on engine test stands at the NASA Stennis Space Center (SSC). Traditional foam insulations and other commercially available materials did not stand-up to the environment and were costly to install and re-install. To meet this need, an insulating material was developed by Composite Technology Development, Inc. (CTD). The material, CTD-620, is a 2-part epoxy system that cures at temperatures down to 10°C, in high humidity (85%), in less than 8 hours, and utilizes microspheres as the acting insulating component. Extensive cryogenic testing was performed at CTD on adhesion, thermal contraction, thermal conductivity, and LOX flammability. Field trials were conducted at SSC. Results of these tests are reported. In addition to the insulating properties, excellent adhesive properties were observed. Standard spray equipment was adapted by Venus-Gusmer, to make it easier to coat large areas. This equipment can apply over 3.2 kg (7 lbs) of material per minute. For smaller areas the material can be applied with a trowel. | A Spray-On Cryogenic Insulating Material for NASA Which Prevents the Formation of Liquid Oxygen on Liquid Hydrogen Vent Lines | 10.1007/978-1-4757-9053-5_149 |
1994-01-01 | The Magnet Test Laboratory (MTL) will test a considerable portion of the total SSC superconducting magnet production in order to control the manufacturing process and verify magnet performance requirements. With ten cryogenic test stands, MTL is capable of housing tests for 30 dipoles and 5 quadrupoles per month. For further understanding and improving the performance of the SSC magnets, there will be two R&D test stands for extensively instrumented magnets, and there will also be three-magnet string test facilities.^1 A large number of instruments were allocated and installed inside the prototype and first production magnets, as well as in the feed and end cans. A data acquisition and control system is developed. A comprehensive cryogenic system (including refrigerator, cryogenic distribution box and, feed/end cans), vapor-cooled power leads, anticryostats (warm bore), and other associated systems, have been designed, developed and tested. This paper will briefly discuss the progress to date. | Development of Cryogenic Instruments and Equipment For SSC Magnet Cryogenic Tests at The Mtl | 10.1007/978-1-4615-2439-7_113 |
1994-01-01 | Cryogenic systems constitute a rather unique set of chemical process plants. Although the basic unit operations are similar to those at warmer temperatures, cryogenic equipment have some distinctive features which influence their design procedure. The differences arise mainly due to (a) large absolute temperature range with consequent changes in thermophysical properties, (b) operation in the vicinity of critical points of fluids, (c) highly efficient components (e.g. heat exchangers) demanding consideration of otherwise minor sources of irreversibility, (d) multi-stream heat exchangers with internal pinch points, (e) double column distillation units, and (f) absence of chemical reactions. | CRESP - A Steady State Simulator for Cryogenic Process Plants | 10.1007/978-1-4615-2522-6_152 |
1994-01-01 | In previous work we have proved that heavy rare earth compounds with low magnetic transition temperature T_c are very useful as regenerator materials in low temperature range. Applying the magnetic material Er_3Ni particles to the 2nd regenerator of the GM refrigerator, we were able to reach the 2 K range but could not obtain high refrigeration power at 4.2 K. This is thought to be due to the temperature dependence of the magnetic specific heat. We present here a method by which high refrigeration power is obtained at low temperature. The simplest means of obtaining high power is with a hybrid structure regenerator which is composed of two kinds of magnetic materials, high T_c and low T_c materials. Computer simulation and experiments were carried out to verify the superiority of the hybrid regenerator. We succeeded experimentally in obtaining the high power of ~1.1 watt at 4.2 K. We will report other detailed results and discuss developing way of the magnetic regenerator in future. | Effect of High Entropy Magnetic Regenerator Materials on Power of the GM Refrigerator | 10.1007/978-1-4757-9053-5_83 |
1994-01-01 | The photon’s journey through the sensor ends with its conversion to an electronic signal at the focal plane. However, as seen in the previous chapter, focal plane arrays (FPAs) frequently require some type of cryogenic cooling. Cryogenic cooling is an integral part of infrared sensor architecture. Such cooling is inherent to an infrared sensor and is essential for two reasons. First, the detectors may require cooling just to function, or for increased sensitivity. Second, cryogenic cooling reduces thermal noise from filters, baffles, and even the optics themselves. The extent to which this refrigeration is applied depends on the system design, detector material, bandpass, desired sensitivity, and the expected background. For example, it is not uncommon to gain a factor of two or three in sensitivity with a low background HgCdTe-based FPA by cooling it and its surroundings an additional 10 K. | Cryocooling Systems | 10.1007/978-1-4615-7664-8_5 |
1994-01-01 | A Magnet Test Facility (MTF) is currently being built by Babcock and Wilcox (B&W) to perform prototype and production testing of Superconducting Supercollider Laboratory (SSCL) Collider Quadrupole Magnets. The facility will consist of 3 major sections: the cryogenic (refrigerator) system, the magnet test area, and the magnet preparation area. An overview of the facility will be presented which will emphasize the operational requirements and modes for the cryogenic system. | B&W’s Magnet Test Facility for SSC Collider Quadrupole Magnets | 10.1007/978-1-4615-2522-6_89 |
1994-01-01 | In order to minimize parasitic heat loads and achieve a five-year mission lifetime, the NICMOS solid nitrogen dewar has been designed with a single fluid line serving as both fill and vent for the cryogen tank. A no-vent fill of liquid nitrogen (LN_2) is necessary to achieve a reasonable fill time with this configuration. High density of the solid nitrogen (SN_2) is also desired in order to maximize dewar efficiency. A test was conducted at Ball Electro-Optics and Cryogenics Division in December of 1992 to demonstrate the capability to perform a no-vent fill of LN_2 and to determine the attainable solid nitrogen density. The test was successful in achieving a complete no-vent fill of the 67 L test tank with LN_2. The loaded LN_2 was then solidified using cold helium gas circulated through the tank wall heat exchanger. A series of additional loading steps achieved a bulk cryogen fill density of 94% of the maximum SN_2 density at 60K. The no-vent fill procedure should be applicable to other solid cryogen systems in which the cryogen can exist in a liquid phase, and could be a candidate method for on-orbit replenishment of certain spaceborne liquid cryogen systems. | Demonstration of No-Vent Fill and Solidification of Nitrogen for the Nicmos Dewar | 10.1007/978-1-4615-2522-6_17 |
1994-01-01 | Experimental studies of catastrophic loss of insulating vacuum for RHIC dipoles to air and to helium have been performed in the Brookhaven MAGCOOL magnet test facility. A RHIC dipole was cooled to 4.5 Kelvin and powered to its 5000 Ampere design current prior to the test. Ambient air or helium was then introduced into the enclosure to simulate the vacuum loss conditions. The response of the cryogenic system, including the insulating vacuum, pressure, temperature and flow rate for the cooling helium, temperatures on the vacuum tank and heat shield are given as a function of time. The heat load is calculated from the sum of the heat into the magnet and the adjacent helium cooling pipes. The results indicate that for this system the heat load from a sudden loss of vacuum is of the order of 10 kW [0.086 W/cm^2] for the helium test and 20 kW [0.17 W/cm^2] for the air test. These are approximately one order of magnitude larger than the magnet quench heat load, and thus require special consideration of a pressure relief system for the helium cooling circuit. | An Experimental Study of Catastrophic Loss of Vacuum for RHIC Dipole in MAGCOOL | 10.1007/978-1-4615-2522-6_120 |
1994-01-01 | Cryogenic systems for commercial superconducting magnetic energy storage systems must operate unattended at remote locations for extended periods of time. The magnet cryostat is a central element of these cryogenic systems. Superconductivity, Inc.’s (SI’s) energy storage system, called the SSD_®, is also designed to be mobile so the cryostat must be able to support the magnet against dynamic transportation loading in addition to static and seismic loads. This paper reports on the design and operation of SI’s newest cryostat, which contains the superconducting energy storage magnet, current leads and liquid helium inventory. During normal operation the cryostat functions as part of a closed system connected to a helium refrigerator-liquefier. The refrigeration system collects and reliquefies helium boiloff and transfers the liquid back to the cryostat to maintain a constant liquid level. Due to its low heat leak and relatively large helium inventory the cryostat is capable of maintaining operation of the superconducting energy storage magnet for 55 to 60 hours in open cycle mode without refrigerator-liquefier assistance. This allows the energy storage system to continue to operate during planned semi-annual refrigerator maintenance and in the event of an unscheduled refrigerator outage. This has significantly improved overall system reliability. | Design and Operation of a Robust Cryostat for Commercial Superconducting Energy Storage Systems | 10.1007/978-1-4615-2522-6_103 |
1994-01-01 | Thermal characteristics of the MAGCOOL cryogenic system after both natural and heater-induced quenches of the RHIC dipoles have been investigated. For natural quench currents around 6700 amperes, the pressure in the cooling loop exceeded the 15 atmosphere (15.2 MPa) setting of the quench relief valve causing helium to vent through the valve. The initial pressure rise rate was approximately 18 atm/min and the loop pressure increased from 5 to 15 atm in about 30 seconds. To ensure that no helium was vented from the MAGCOOL cooling loop in order to minimize uncertainties in the thermal measurements and better understand the heating/cooling process, the RHIC magnet was then quenched at lower currents between 2000 and 5000 amperes using a strip heater on the magnet coils. A series of tests with the cooling loop connected to a large volume surge tank was also performed to show the dependence of loop pressure on the loop volume. The peak pressure and temperature in the magnet cooling loop were found to be linearly proportional to the energy released for a given loop volume. The time lag of temperature along the cooling loop during quench recovery was determined. Very good agreement between total cooling provided and the magnetic stored energy was found for each of the several values of quench current. | Thermal Characteristics of the Magcool Cryogenic System After Quenches of Rhic Dipoles | 10.1007/978-1-4615-2522-6_42 |
1994-01-01 | This Report presents a method for calculating the Jc, B, T critical surface for commercial grade niobium tin given an effective T_c and B_c2 and J_c over a range of magnetic inductions B. Given the effective T_c and B_c2 and J_c, one can estimate the J_c over a range of magnetic inductions from 0.1 T to 0.8 times effective B_c2 and a range of temperatures from 1.5 K to about 14 K. The effects of conductor strain can also be estimated using this method. A comparison between calculated values of J_c and measurements is illustrated for a number of cases. The method presented in this report can be used to estimate the performance of niobium tin in magnets at temperatures different from those where measured data is available. The method of calculating the J_c can also be used to estimate the effects of superconductor magnetization on the field quality at low fields. | Calculating the J_c, B, T Surface for Commercial Niobium Tin Conductors Using a Reduced State Model | 10.1007/978-1-4757-9053-5_93 |
1994-01-01 | The 45 Tesla hybrid magnet system will consist of a 14 Tesla superconducting outsert magnet and a 31 Tesla water cooled insert. The magnet is planned for operation in early 1995 at the National High Magnetic Field Laboratory. Its purpose is to provide the highest DC magnetic fields for the materials research community. The present paper discusses the overall design of the cryogenic system for the superconducting magnet. Unique features of this system include static 1.8 K pressurized He II as a coolant for the magnet and a refrigerated structural support system for load transfer during fault conditions. The system will consist of two connected cryostats. The magnet is contained within one cryostat which has a clear warm bore of 616 mm and is designed to be free of system interfaces and therefore minimize interference with the magnet user. A second supply cryostat provides the connections to the refrigeration system and magnet power supply. The magnet and supply cryostats are connected to each other through a horizontal services duct section. Issues to be discussed in the present paper include design and thermal analysis of the magnet system during cooldown and in steady state operation and overall cryogenic system design. | Cryogenic System for the 45 Tesla Hybrid Magnet | 10.1007/978-1-4615-2522-6_44 |
1994-01-01 | Three liquid argon calorimeters were cooled down and operated as part of the D-Zero detector at Fermi National Accelerator laboratory. The largest vessel contains 248 metric tons of uranium and copper plates and 19 kL (5000 gal.) of liquid argon. The other two vessels are mirror images, each containing 185 metric tons of uranium and stainless steel plates and 12.1 kL (3200 gal.) of liquid argon. The cooldown was accomplished by convection heat transfer between boiling liquid nitrogen filled finned heat exchangers and argon gas inside the vessels. Information regarding the general internal geometry of the calorimeters, cooldown, operation, and steady state heat loads will be presented. | Thermal Information Regarding the Cooldown and Operation of Liquid Argon Calorimeters | 10.1007/978-1-4615-2522-6_132 |
1994-01-01 | The paper will report upon the final design, manufacturing and tests of CEBAF’s HMS Dipole cryogenic equipment. The liquid nitrogen circuits, the helium circuits and thermal insulation of the magnet will be addressed. The cryogenic reservoir and control module as an integral part of the HMS Dipole magnet will be presented. The construction, manufacturing, tests and final performance of the HMS Dipole cryogenic system will be reported. The LN_2 circuit and the He circuit are tied together by the control system for cool down, normal operation and standby. This system monitors proper temperature differences between both circuits and controls the cryogenic supply to meet the constraints. Implementation of the control features for the cryogenic system into the control system will be reported. | Cryogenics in CEBAF HMS Dipole | 10.1007/978-1-4615-2522-6_45 |
1994-01-01 | The tensile properties and fracture characteristics of two kinds of Ag-containing Al-Li-Cu-Mg-Zr alloys with different aging conditions have been studied from 290 to 77 K. The results show that the tensile strength and ductility of the alloys improved significantly with a decrease in test temperature from 153 to 77 K, except for the elongation of some alloys in certain aging conditions. Planar slip behavior is the predominant deformation mode for the natural-, under-, and peak-aged samples when tested at room temperature, but the slip distribution is fairly homogeneous as the test temperature is reduced to 77 K. The different modes of tensile fracture are closely associated with the aging time and test temperatures. The improvement in cryogenic ductility of the alloys can be attributed to an increase in deformation homogeneity. The tensile fracture behavior of the alloys at ambient and cryogenic temperatures are discussed. | The Tensile Fracture of Ag-Containing Al-Li-Cu-Mg-Zr Alloys | 10.1007/978-1-4757-9053-5_171 |
1994-01-01 | A new technique is proposed to provide a balanced representation of liquid-vapour coexistence densities by means of a cubic equation of state of the van der Waals type, without causing undue deviations in the calculated saturated vapor densities ( ρ ^ V ) due to the improvement in the saturated liquid density ( ρ ^ L ) calculations. The reduced temperature T _ r at the condition of ∆ Z = Z ^ V - Z ^ L = 0.5 is chosen for preserving the proper location of the dome-shaped saturation curve. This condition represents a value of T _ r in the vicinity of 0.92 – 0.94. The average absolute deviations in the calculated ρ ^ V and ρ ^ L values for H_2, N_2, O_2, A_r, CH_4, and CO_2 are about 1%. | Balanced Representation of Liquid-Vapour Coexistence Densities at Cryogenic Temperatures | 10.1007/978-1-4615-2522-6_232 |
1994-01-01 | The Superconducting Super Collider (SSC) Gammas, Electrons, Muons (GEM) magnet is a large superconducting solenoid with a total mass of 1.05×10^6 kg and a stored energy of 2.5 GJ. A cryogenic system to cool and to maintain the GEM magnet to liquid helium temperature is described. The system is designed to operate effectively under a variety of operating conditions, including cooldown/warm-up, steady state operations, and quench. Primary cooling during steady-state operation is based on natural circulation thermosiphon flow through cooling tubes in the solenoid support bobbin. Additional cooling loops are included for lead and joint cooling and conductor stabilization. A helium refrigerator/liquefier rated at 2 kW and 20 gls will be specified to meet the refrigeration requirements. Cooldown of the magnet from 300 K to liquid nitrogen temperatures is accomplished using a counterflow helium-to- liquid-nitrogen heat exchanger independent of the helium refrigerator. The system incorporates provisions for maintenance access during accelerator beam operation. | A Liquid Helium Cryogenic System Design for the Gem Magnet | 10.1007/978-1-4615-2522-6_46 |
1994-01-01 | Some of the proposed magnet case alloys for the International Thermonuclear Experimental Reactor (TIER) are metastable austenitic stainless steels. The case will be subjected to high loads and can be as much as 100 mm thick in some proposed designs. Case assembly will probably require thick section welding with its attendant chemical inhomogeneity. Even alloys that are thermally stable with respect to martensitic transformation can, under these conditions of high stresses, cryogenic temperature, and high magnetic fields, undergo transformation. Previous work at 8 T has shown a measurable magnetic field effect on the 4.2 K tensile and fracture toughness properties of AISI300 series metastable austenitic stainless steels. Thus, it is important to understand how these alloys will behave under conditions of high magnetic fields and cryogenic temperature, particularly at the higher magnetic fields that will be used in ITER. 4.2 K data for 316LN indicates that the change in fracture toughness is not monotonic. It initially decreases and then later increases with applied field. | Cryogenic Fracture Behavior of 316LN in Magnetic Fields up to 14.6 T | 10.1007/978-1-4757-9053-5_154 |
1994-01-01 | When complete, the Continuous Electron Beam Accelerator Facility (CEBAF) will be centered on a 4 GeV recirculating linac. Each of the two linacs contains 160 superconducting radio frequency (SRF) 1497 MHz niobium cavities^1 in 20 cryomodules operating between 2 and 2.3 K. Minimization of the total heat load is critical to machine performance, since the refrigeration capacity is fixed. The total heat load of the cryomodule consists of the static load (fixed heat leak) and the dynamic load (proportional to the cavity performance Q o, or quality factor). The heat load of the cryomodules is the single largest load to both the primary and secondary cooling circuits of the refrigerator. The optimization of the thermal performance of the cryomodule considers recent test data of multilayer insulation (MLI) systems developed for the SSC, in addition to the effect of the dynamic heat load on the design of the cryostat. The design of the cryomodule and the measured thermal performance of the installed north and south linac cryomodules are discussed. The performance to date is shown to meet the design heat loads for the accelerator. | Thermal Performance of the Cebaf Superconducting Linac Cryomodule | 10.1007/978-1-4615-2522-6_71 |
1994-01-01 | An oxygen deficiency exists when the concentration of oxygen, by volume, drops to a level at which atmosphere supplying respiratory protection must be provided. Since liquid cryogens can expand by factors of 700 (LN_2) to 850 (LH_e), the uncontrolled release into an enclosed space can easily cause an oxygen-deficient condition. An oxygen deficiency hazard (ODH) fatality rate per hour (Ø) is defined as: Ø = Σ NiPiFi, where Ni = number of components, Pi = probability of failure or operator error, and Fi = fatality factor. ODHs range from “unclassified” (Ø<l0^-9 l/h) to class 4, which is the most hazardous (Ø>l0^-1 lh). For Superconducting Super Collider Laboratory (SSCL) buildings where cryogenic systems exist, failure rate, fatality factor, reduced oxygen ratio, and fresh air circulation are examined. | ODH, Oxygen Deficiency Hazard Cryogenic Analysis | 10.1007/978-1-4615-2522-6_119 |
1994-01-01 | A trial forging for advanced cryogenic machinery, which was made of a modified 706-type Ni-base superalloy with reduced Nb, Ti and other minor elements such as C, Si and B to improve toughness and weldability, was manufactured from a 12-ton electro-slag remelted ingot with an 810 mm diameter. The tensile properties and fracture toughness of this large Ni-base superalloy forging were investigated at 293 K and 4 K. At 4 K, the yield strength and fracture toughness were, 1149 MPa and 293 MPa % MathType!MTEF!2!1!+- % feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaaOaaaeaaca % qGTbaaleqaaaaa!36FF! $$\sqrt {\text{m}} $$ , respectively. The results indicated that the balance of toughness and yield strength was excellent. Also, a 40-mm-thick ring with a 600 mm outer diameter cut from the same forging was welded using the TIG welding process, and the properties of the weldment were investigated. | Mechanical Properties of Large Ni-Base Superalloy Forgings at Cryogenic Temperatures | 10.1007/978-1-4757-9053-5_169 |
1994-01-01 | Piezoresistive pressure transducers are being used in cryogenic environments for measuring dynamic and absolute pressures without the use of capillary tubes. A common type of piezoresistive pressure transducer is constructed on a micromachined silicon diaphragm that has an implanted resistance bridge on its surface. It is well known that these transducers have temperature dependent properties that are regular and reproducible and which can be accommodated via standard calibration techniques. However, we have found that at temperatures below 30 K some of these sensors display secondary effects caused by self heating. Self heating in a piezoresistive pressure sensor operating at cryogenic temperatures causes calibration errors due to the thermally dependent sensitivity changes of the transducer (about 1%/K). A similar calibration problem occurs when the sensors are used to measure pressure fluctuations in a cryogenic gas that is also changing temperature, especially below 30 K. Although the self heating problem can be avoided by the use of very low excitation currents, the problem of measuring pressure fluctuations in a gas undergoing temperature changes is much more difficult and less tractable. | Self Heating in Piezoresistive Pressure Sensors at Cryogenic Temperatures | 10.1007/978-1-4615-2522-6_137 |
1994-01-01 | An unrecrystallized structure is found to significantly improve the work hardening characteristics by lowering the work hardening rate during the early stages of deformation. This is in contrast to a recrystallized structure, which requires a higher work hardening rate to accommodate the greater degree of multiple slip necessary to maintain strain compatibility between the more randomly oriented grains. The stronger texture associated with the unrecrystallized structure allows deformation to occur more efficiently. The addition of magnesium also improves the work hardening characteristics by increasing the overall level of the work hardening rate. The improved characteristics of the work hardening behavior result in a parallel increase in both the strength and ductility at cryogenic temperatures. These findings are positive since they suggest a method by which improvements in the work hardening behavior and subsequent mechanical properties may be obtained through practical modifications of the microstructure and composition. | Influence of Grain Structure and Solute Composition on the Work Hardening Behavior of Aluminum at Cryogenic Temperatures | 10.1007/978-1-4757-9053-5_172 |
1994-01-01 | Developmental or “model” SSC quadrupole cold masses and collared coils are successfully being tested at the Vertical Test Facility (VTF) in Lynchburg, Virginia. Within this facility, a vertical dewar maintains a pool boiling liquid helium environment of 3.85 K to 4.5 K in order to observe the quenching and magnetic field characteristics of these coils. A description of the facility performance an its contents, including the dewar and ancillary equipment, is described hereafter. | B&W Vertical Test Facility for SSC Collider Quadrupole Magnets | 10.1007/978-1-4615-2522-6_90 |
1994-01-01 | The vibration produced by Stirling cryocoolers is incompatible with precision-pointing imaging instruments. This paper reviews vibration reduction techniques and then examines a vibration cancellation system that was designed for the displacer of a Hughes tactical cooler. This system uses a custom-designed multi-axis counterbalance and an analog implementation of an adaptive feedforward compensator. In an initial test, the third harmonic of the displacer’s axial force was cancelled by 22 to 38 dB over a wide range of drive frequencies, with little effect on the other harmonics or the lateral vibrations. | Adaptive Vibration Cancellation for Split-Cycle Stirling Cryocoolers | 10.1007/978-1-4615-2522-6_169 |
1994-01-01 | The measurement of control parameters in cryogenic systems such as temperature, pressure, fluid velocity, mass flow, fluid density, liquid level etc is limited in accuracy by degradation of analogue signals passing from the cold sensors to ambient temperature data handling equipment. Recent developments at Southampton show how significant improvement in accuracy can be achieved to the point where the normal expectation of accuracy for sensor-generated data is 0.01% limited only by calibration errors and drifts. This accuracy can be achieved in cryogenic systems and plant using CMOS based hybrid silicon circuitry, in which the analogue signals from the sensors are converted to digital signals at the cold end before transmission without degradation. | Instrumentation of Cryogenic Systems and Plant to Accuracy of 0.01% Using Cold Electronics | 10.1007/978-1-4615-2522-6_123 |
1994-01-01 | A vital and integral part of the European fusion experiment JET is a large cryo-system consisting of large scale cryopumps, a nitrogen system ( 110 000 L storage capacity, daily usage of 25 000 L, and the ability to produce 1 500 m^3/h gaseous nitrogen), and two helium refrigerators (with a total capacity of 1300W/4.4K or 450 L/h liquefaction). Peripheral equipment includes 15000 L liquid and 6 000m^3 gaseous storage, 15 g/s 200 bar recovery compressors, and 15g/s purification capacity. The liquid nitrogen and liquid helium distribution systems have more than 30 individual outlets to different users around the JET site. The major users are supplied in a closed loop using low loss individual flexible cryolines. The cryoplant operates fully automatically and has been built for maximum operational flexibility, in particular to be compatible with the future tritium phase of JET. In addition to the tritium compatibility, remote handling requirements and the predicted effects of heating and activation by the expected neutron flux have been included in the overall design. | The JET Cryosystem, Overview and Experience | 10.1007/978-1-4615-2522-6_59 |
1994-01-01 | Cryogenic wind tunnels are capable of testing at flight equivalent conditions on scaled models to obtain full size results. To reach cryogenic temperatures the gas and much of the tunnel mass is cooled by injecting liquid nitrogen into the tunnel. During the cooling from ambient to cryogenic temperatures the thermal stress, liquid nitrogen consumption, time, and test gas dew point are critical to insure uniform and good flow quality in the test section. The dew point is critical because it shows the amount of water vapor within the tunnel circuit. A cooldown is not a problem if the gas dew point is low (< 233K) before the gas temperature drops below the dew point. If the dew point is not low while cooling, frost will from on the model and sections of the tunnel. This paper examines the sources of water vapor in a cryogenic wind tunnel, the effects it has on the tunnel operation, and the methods to manage the water vapor. The tunnel used in this study is the U.S. National Transonic Facility located at NASA Langley. Research Center. | Effects of Water Vapor on Cryogenic Wind Tunnels | 10.1007/978-1-4615-2522-6_11 |
1994-01-01 | A computer program to simulate the Fermilab Tevatron liquid helium satellite refrigeration system has been developed. The simulator program takes advantage of the Macintosh platform upon which it was developed to produce a unique, easy to use Macintosh interface to facilitate ease of cycle design and modification. The user can drag icons representing refrigerator components around on the screen and piece them together to form a variety of liquid helium refrigeration cycle configurations. Extensive use of the icons, windows, and pull-down menus of the Macintosh interface allows the user to easily alter refrigeration component configurations and parameters. Calculation accuracy is retained by using existing helium property subroutines and component models. The user interface, program output, and code details are described. Sample configurations and results are presented. | Simulating the Tevatron Liquid Helium Satellite Refrigerators | 10.1007/978-1-4615-2522-6_151 |
1994-01-01 | A cryogenic system with the capacity of 200 l/h or 500 W at 4.4 K has been operated to develop the superconducting conductors and coils for the LHD. The system has contributed in various superconducting technologies along with the dc 75kA power supply and 10 MN mechanical testing machine, and completed the basic R&D works of the LHD. While operating the cryogenic system, impurity densities of hydrocarbon gases in circulating helium gas became much larger than expected for this cryogenic system. The densities of some impurity gases were carefully monitored in reference to the operational conditions of the circulating compressor by using gas chromatography. Impurity gas densities of oxygen, nitrogen and ethane increased observably, when the output capacity of the compressor was reduced. In a two-stage oil injected compression system with a variable stroke mechanism for a first stage, a reduction in the capacity of the first stage leads to a larger compression ratio for the second stage, and the temperature of the injected oil increases. The production of the impurities in the helium might be caused by cracking a part of the injected oil in the compressor. The compressor, therefore, was reconstructed such that sufficient injection oil is supplied and the compression ratio division becomes even. It was confirmed that the impurities are not produced after modification. | Reduction of Hydrocarbon Impurities in 200 L/H Helium Liquefier-Refrigerator System | 10.1007/978-1-4615-2522-6_76 |
1994-01-01 | The SSC cryogenic system consists of 12 sectors—ten in the collider and two in the HEB. Each sector, in turn, consists of a surface refrigerator system (SRS) and a tunnel refrigerator system (SRT), interfacing at a surface distribution box, where a cryogenic transfer line connects them. Proposals for the sector refrigerator surface system (SRS) are presently in review for vendor selection. This paper reviews the requirements and status of the SRT subsystems—cold compressor; transfer lines; distribution box; nitrogen pump box, dump tanks, and subcooler box; and auxiliary end box. | Cryogenic Systems for the SSC and the Status of their Development | 10.1007/978-1-4615-2522-6_84 |
1994-01-01 | The cryogenic system of the HERA superconducting proton accelerator has a total cooling capacity of 3 times 6500 Watts at 4.3 K and 3 times 20 KW around 60 K. Its first operation started in 1987 and since the end of 1990 the complete system operated continuously at 4.3 K. We report on the experience gathered during 30000 operating hours of the three cold boxes and the corresponding 14 screw compressors together with the helium distribution system and the purification system. Maintenance experience and statistics of some failures of different components are described and we give information about the consumption of helium, liquid nitrogen and electrical power. Data about lifetime of adsorber fillings and compressor oil are given. Experience on normal operation stability and during magnet quenches are discussed. We give a summary of the availability and the reliability of the system. | Report on Operational Experience and Reliabllity of the HERA Cryogenic System | 10.1007/978-1-4615-2522-6_69 |
1994-01-01 | Protons to the CERN LHC will be supplied from the SPS accelerator via two new injection lines. The lines include three bending arcs for horizontal beam deflection and are characterized by a strong inclination (7.2 % maximum slope) to overcome the difference in height (40 m) between the two machines. They will be equipped with superconducting dipoles operated at a field of 5.4 T and 4.4 K. The distribution to the magnets of liquid helium in strongly inclined channels and over a distance of several hundred meters represents a considerable cryogenic challenge. A preliminary design of the cryogenic system is under way and the cooling schemes suitable to the unusual geometry are reviewed. The basic requirements of the refrigerating system and a tentative layout of the cryoplants are presented. | Design Criteria of the Cryogenic System for the CERN LHC Injection Lines | 10.1007/978-1-4615-2522-6_77 |
1994-01-01 | We employ a technique which uses superfluid ^4He as a delicate, low noise suspension medium. The goal is to create a new type of torsion balance for earth based gravitational experiments requiring very high sensitivity. As a fluid bearing replacing the classical torsion fiber suspension, liquid helium II offers several unique advantages. Most notable are its extremely low viscosity, high thermal stability, inertness and small thermally driven fluctuations. We present the design and performance aspects of buoyant torsional oscillators and the cryogenic system used to maintain the superfluid medium. | The Design, Construction and Testing of Floats for Use in Superfluid Helium | 10.1007/978-1-4615-2522-6_138 |
1994-01-01 | Composite insulation systems to be used in the International Thermonuclear Experimental Reactor (ITER) must meet demanding design requirements, including combined shear and compressive stresses, performance at cryogenic temperatures, and continued mechanical and electrical performance after exposure to high levels of neutron and gamma radiation. Several polymeric insulation systems that are reinforced with boron-free glass fabric and are suitable for the vacuum-pressure impregnation (VPI) method of fabrication were screened at 76 K using the short-beam-shear (SBS) test, with the leading candidates then tested in combined shear/compression at cryogenic temperatures. The shear/compression specimens were comprised of two, 12.7.mm diameter, stainless steel chips bonded together by the composite insulation, allowing characterization of its adhesive and cohesive properties. Using the shear/compression test at different ratios of shear to compression, a shear/compression failure envelope for each insulation system can be determined. Production variables of the shear/compression specimens, including molding techniques, were also investigated. The effects of desizing (4 h at 400°C) and heat treating (50 h at 700°C) the glass fabric to simulate the heat treatment of Nb_3Sn superconductor, prior to vacuum impregnation, were also examined. | Properties of Candidate ITER Vacuum Impregnation Insulation Systems | 10.1007/978-1-4757-9053-5_128 |
1994-01-01 | The analytical perturbed hard-sphere equation of state (EOS), recently developed from the square-well-linear-extension potential function, has been simplified. The resulting EOS is cubic in terms of volume while retaining the structure of the original equation. It was successfully applied to the prediction of thermodynamic properties of the molecular model fluids (square-well and Lennard-Jones), and saturated properties for seven cryogenic fluids (methane, argon, nitrogen, neon, oxygen, krypton and xenon). | A Semi-Theoretical Cubic Equation of State for Calculating Properties of Cryogenic Fluids | 10.1007/978-1-4615-2522-6_230 |
1994-01-01 | There is, in all of us, a certain part that lives outside of time.^1 We become aware of our mortality only at exceptional moments, a mild indisposition, a sudden handicap, or an illness that forces us to change our lifestyle and restrict our activities. But most of the time we feel immortal. First, there was a belief that if we obey nature’s commands and follow its dictates, this would “free men from an infinity of maladies both of the body and of the mind, and possibly of all the infirmities of age,”^2 then a belief that technology itself could replace nature and transcend its very limits.^3 Today, death is safely removed to a comfortable distance. Sophisticated life-saving techniques constitute society’s standing order against diseases. However, to fight death itself, has not usually been within the domain of medicine. Yet, this is the request Thomas Donaldson made to a California Court of Appeal when he sought a declaratory judgment that could give him the legal right to “mercy-freezing.”^4 | Life, Death, and the Pursuit of Destiny | 10.1007/978-1-59259-448-1_7 |
1994-01-01 | The dynamic behavior of fluids affected by asymmetric gravity jitter oscillations, in particular the effect of surface tension on partially-filled rotating fluids in a dewar tank, with and without installing baffle-board, imposed by time-dependent directions of background gravity have been investigated. Results show that lower frequency gravity jitter imposed on the time-dependent variations of the direction of background gravity induced a greater amplitude of oscillations and a stronger degree of asymmetry in liquid-vapor interface geometry than that made by the higher frequency gravity jitter. As the viscous force, between liquid and solid interface, greatly contributes to the damping effect of slosh wave excitation, a rotating dewar installed with baffles provides more area of liquid-solid interface than a rotating dewar without baffles. Results show that the damping effect provided by the baffles reduce the amplitude of slosh wave excitation, lowers the degree of asymmetry in the liquid-vapor distribution, and lowers angular momentum and fluid moment fluctuations. | Effect of the Baffle on the Cryogenic Helium Container Angular Momentum and Momentum Fluctuations due to Asymmetric Gravity Jitter Excited Slosh Waves | 10.1007/978-1-4615-2522-6_30 |
1994-01-01 | The variations of adhesive strength at cryogenic temperature of epoxy to polyimide (PI) or polyethylene (PE) films, which were exposed in plasma composed of one of nitrogen, argon and oxygen, were studied for the simulation of the interface strength between polymeric fibers and resins of advanced composite materials. Plasma surface treatments for polymeric films were performed aiming at increasing surface energy without spoiling bulk properties of films. ECR (electron cyclotron resonance) was employed for production of plasmas and its characteristics was evaluated. The results indicated that surface energies of films increased when the films were deposited to plasma. A film-resinfilm lap test were also carried out. In the case of untreated PE films, debonding at film-resin interface arised on cooling down process to cryogenic temperatures. On the other hand, in the case of plasma treated films, debonding was not induced in cooling down process. Adhesive strength between film and resin was improved by ECR plasma processing for a few ten seconds' exposure. Surface analysis revealed that the introduction of polar groups induced the improvement. The plasma treatment was found to be applicable to the organic fibers. | Effects of Surface Treatment with Plasma on Adhesive Strengths at Cryogenic Temperature | 10.1007/978-1-4757-9053-5_131 |
1994-01-01 | The MTL’s function is to test prototype and industrially manufactured magnets for the Superconducting Super Collider Laboratory (SSCL). The cryogenic system of the MTL has a main refrigeration system consisting of a two-stage compression system, a refrigerator/liquefier coldbox, a liquid helium dewar, warm gas storage, and a regeneration skid. The MTL cryogenic system also includes the following auxiliary equipment: two cleaning, cooling, warmup and purification (CCWP) coldbox modules with a regeneration skid for the charcoal beds, two CCWP compressors, a dehydration skid with its own regeneration system, a pump box, a refrigeration recovery unit, and five distribution boxes. Figure 1 describes the general flow of these systems. At any given time, the refrigeration system has the capacity to simultaneously test at least six magnets under normally required testing conditions. | Operational Modes and Control Philosophy of the SSCL Magnet Test Lab (MTL) Cryogenic System | 10.1007/978-1-4615-2439-7_214 |
1994-01-01 | Fermilab’s Tevatron accelerator is undergoing a major cryogenic system upgrade. This upgrade project is necessary to lower coil temperature of the accelerator’s magnets by approximately 1K. The new system configuration utilizes a new valve box containing a 130 liter subcooling dewar and a Cold Compressor at each of the 24 satellite refrigerators. Each Cold Compressor pumps on a dewar to maintain the two-phase pressure at 50.7 kPa (0.5 atm) producing 3.56K helium in the dewar and magnet strings. | New Cryogenic Controls for the Tevatron Low Temperature Upgrade | 10.1007/978-1-4615-2522-6_145 |
1994-01-01 | The performance of the MAGCOOL cryogenic system after low current strip heater quenches of the SSC dipoles has been investigated. For quench currents between 2000 and 3500 amperes, the loop pressure after a quench does not exceed the set relief pressure. The peak pressure and temperature in the magnet cooling loop were found to be linearly proportional to the energy released during a quench. Excellent agreement between total cooling provided and the magnetic stored energy was found for each of the several values of quench current. The results indicate that the magnetic stored energy is the key parameter; the measurements are accurate and the methodology is appropriate and one that could be applied to similar cryogenic systems. | Peak Loop Pressure and Temperature and Comparison of Total Cooling Provided to the Energy Released after Low Current Quenches of SSC Dipoles in Magcool Cryogenic System | 10.1007/978-1-4615-2522-6_95 |
1994-01-01 | A computer-controlled method that minimizes thermometric and radiation errors for the measurement of thermal conductivity of materials is presented. Initial runs with G-11 to “qualify” the apparatus brought us face to face with our naiveté when large contact resistance errors were observed. Various methods that failed to maintain good thermal contact from room to liquid-helium temperature are examined, and the solution to the problem is discussed. Thermal conductivity curves for G-10/11CR (NIST), Amodel 33% glass, Noryl SEIGFN3, and 3 types of Ultem are presented. The thermal properties of Vectra, a liquid-crystal polymer, are also mentioned because its properties are unique. | The Measurement of Thermal Conductivity of Plastics at Cryogenic Temperatures — A Discussion of Contact Resistance and One’s Naiveté | 10.1007/978-1-4757-9053-5_139 |
1994-01-01 | With the use of the primary volumetric calibrator described in another paper presented at this Conference, two Venturi flowmeters of different sizes, and covering respectively the ranges 0.5 to 4 and 3.5 to 25 g/s, were tested and calibrated in cryogenic helium under several thermodynamic conditions. Designed by scaling down ISO specifications, they are equipped with commercially available ∆P meters (Validyne DP-10 type) which are placed closed to them, that is in the low temperature environment. Results are given for saturated helium at 4.2 K, superfluid, and, only for the larger meter, supercritical helium at 4.2 K and 0.4 MPa absolute. The slight differences noticed in the tests performed under different thermodynamic conditions are discussed. Under constant conditions, short-time repeatability was fairly good and never exceeding ± 0.5 %. While the zero drift of the ∆P transducers during individual tests or even when changing the thermodynamic conditions appears negligible (generally less than 0.1 %), during the cool-down between room and LHe temperature it is generally noticeable (up to 1% or more), and is probably due to mechanical settling of the diaphragm; the instrument zero therefore must be adjusted at the beginning of low temperature operation. | Metrological Performances of Venturi Flowmeters in Normal, Supercritical and Superfluid Helium | 10.1007/978-1-4615-2522-6_128 |
1994-01-01 | The use of cryogenic technology has produced real progress in wind tunnel testing, permitting the attainment in high Reynolds numbers and precise replication of aerodynamic phenomena existing on aircraft in flight. | The T2 Cryogenic Transonic Wind Tunnel of Onera-Cert Toulouse France | 10.1007/978-1-4615-2522-6_8 |
1993-12-01 | Strengthening of steel 06Kh16N15M3B by drawing at cryogenic temperatures | 10.1007/BF00707643 | |
1993-11-01 | A nitrogen-strengthened austenitic stainless steel was tested in uniaxial tension at room temperature (295 K) and in liquid nitrogen (76 K). A transition in ductile fracture appearance from a cup-cone fracture at room temperature to shear fracture at cryogenic temperature is observed and correlated to deformation behavior and micromechanisms (void nucleation and strain localization) of fracture. The flow stresses, fracture stresses, and strain hardening rates are all higher at liquid nitrogen temperature compared to those at room temperature, and the significant increases in plastic flow stresses are accompanied by planar deformation mechanisms. At both temperatures, primary void nucleation is observed mainly at scattered, large patches of sigma phase, and initial primary void growth is associated with tensile instability (necking) in the specimen. Postuniform elongation at 295 K leads to secondary void nucleation from small, less than 1 μm in diameter, microalloy particles, leading directly to failure; the strain required for secondary void growth and coalescence is highly localized and does not contribute to macroscopic elongation. At 76 K, uniform strain increases, total strain decreases, and strain localization into shear bands between the primary voids and the surface of the neck leads directly to failure. Secondary void nucleation, growth, and coalescence are limited to shear bands and also do not contribute to the macroscopic elongation. The observations of void nucleation are characterized in terms of a continuum analysis for the interfacial stress at voidnucleating particles. The critical interfacial stress for void nucleation at the lower temperature correlates with the increased flow properties of the matrix. | Temperature-Induced Transition in Ductile Fracture Appearance of a Nitrogen-Strengthened Austenitic Stainless Steel | 10.1007/BF02646531 |
1993-09-01 | Heat transfer by ejector pumps in gaseous cryogenic machines | 10.1007/BF01148692 | |
1993-08-01 | Vacuum characteristics of structural materials in cryogenic vacuum installations | 10.1007/BF01149643 | |
1993-06-01 | A hot wire anemometer using superconducting thin films has been developed for measurements in a gaseous^4 He turbulent round jet around 4 K . Localized velocity fluctuations, down to a few microns, and high frequency events, up to 1 MHz can be detected giving access to the study of turbulent subsonic flow with Reynolds numbers ranging up to 10^6. First data analysis featuring the energy cascade in this “ideal” system are also discussed. | A hot wire anemometer for cryogenic hydrodynamic experiments | 10.1007/BF01082528 |
1993-05-01 | Damping hydraulic impacts in cryogenic systems using vapor-hydraulic domes | 10.1007/BF01150101 | |
1993-02-01 | Dissipative losses in cryogenic transport tanks | 10.1007/BF01150384 | |
1993-02-01 | Comparative analysis of cryogenic cycles of systems for reverse condensation of nitrogen vapors | 10.1007/BF01150383 | |
1993-01-01 | In the reaction center (RC) of the photosynthetic bacteria Rhodobacter (Rb.) sphaeroides , two closely overlapping bacteriochlorophyll a (BChl) molecules constitute the primary electron donor (P). Under normal conditions, charge separation occurs between P and the Q_A quinone acceptor. If Q_A is chemically prereduced, photoexcitation of P generates a triplet state (^3P) which decays in 100–150 µs at cryogenic temperatures. | FTIR Difference Spectrum of the Triplet State of the Primary Electron Donor in Photosynthetic Bacterial Reaction Centers | 10.1007/978-94-011-1934-4_114 |
1993-01-01 | Lazaroid belongs to a novel group of compounds — aminosteroids (AS) which are potent inhibitors of central nervous system tissue lipid peroxidation, and are devoid of classical glucocorticoid and mineralocorticoid activities. Recent studies have shown that aminosteroids possess cerebral-protective properties and are efficacious in attenuating damage to the CNS imparted by trauma, ischemia, and vasospasm. The purpose of this study was to determine the effect of AS on (a) brain elastance, a measure of the protective volumetric buffering capacity of the brain, and (b) on cerebral perilesional edema. We used the cryogenic brain injury rat model, the constant rate and continuous infusion method to study brain elastance, and the gravitometric method to determine brain edema. | The Effect of Lazaroid on Cerebral Elastance and Edema in a Cryogenic Injury Model | 10.1007/978-3-642-77789-9_22 |
1993-01-01 | The development of the magnetically levitating vehicle using the superconducting magnet(Maglev) was started in 1972, for the purpose of realizing a high speed railway system. The running tests of Maglev have been executed at Miyazaki test line these 15 years, setting a speed record of 517km/h on Dec. 1979. Now, a new test line is under construction in Yamanashi prefecture, to confirm the possibility of the revenue service. The superconducting magnet is one of the most important parts for Maglev. This superconducting magnet should be designed to satisfy the severe weight and heat leak restrictions. Here the superconducting magnets for Maglev system is outlined. | Current Status of Superconducting Magnet for a Maglev System | 10.1007/978-4-431-68305-6_270 |
1993-01-01 | A hot wire anemometer using superconducting thin films has been developed for measurements in a gaseous ^4 He turbulent round jet around 4 K . Localized velocity fluctuations, down to a few microns, and high frequency events, up to I MHz can be detected giving access to the study of turbulent subsonic flow with Reynolds numbers ranging up to 10^6. First data analysis featuring the energy cascade in this “ideal” system are also discussed. | A Hot Wire Anemometer for Cryogenic Hydrodynamic Experiments | 10.1007/978-94-011-1689-3_24 |
1993-01-01 | We report the first subpicosecond shock-waves ever generated and measured by electronic circuits. We have used these circuits with integrated antennas to generate and detect freely-propagating THz radiation. The circuits are monolithic nonlinear transmission lines fabricated on GaAs and, for peak efficiency, they operate at liquid nitrogen temperatures. Nonlinear transmission lines (NLTL’s) have been used by several researchers for generating electronic shock-waves with picosecond transition times by compressing the wavefront generated by a ∼0.5 W, ∼5–10 GHz microwave power source.^1,2,3 While the literature reflects continual decreases in these transition times, as measured both by diode sampling bridges and by electro-optic sampling, the fastest reported 10%–90% fall time thus far has been 1.4 ps, with a∼5V amplitude.^4 However, generating and measuring a sub-picosecond transition with an all-electronic device has been an elusive goal because a fundamental limitation has been the NLTL diode series resistance. By immersing a packaged NLTL into liquid nitrogen, we were able to lower this resistance significantly, thereby producing voltage shock-waves with 880 fs fall times and 3.5 V amplitudes, as measured by an on-chip diode sampling bridge (Figure 1). We have used these circuits with integrated slot antennas to generate freely propagating THz radiation, and we have observed measurable radiation beyond 3 THz. | All-Electronic Subpicosecond Pulses for A 3-Terahertz Free-Space Signal Generation and Detection System | 10.1007/978-1-4615-2870-8_7 |
1993-01-01 | The climate in the northern hemisphere witnessed significant cooling and aridity between 23,000 and 16,000 B.P., with the furthest extension of the Weichsel (Valdai) glaciers occurring between 22,000 and 18,000 years ago. This period saw a two-stage process of accelerated loess formation—the Desna and Altyn—with each showing evidence of cryogenic processes (Velichko 1973, 1979). | The Pleistocene-Holocene Boundary | 10.1007/978-1-4899-1112-4_14 |
1993-01-01 | Aramid/aluminium laminates (ARALL^® laminates) are a family of new hybrid composites made of alternating layers of thin aluminium alloy sheets with plies of epoxy adhesive prepreg containing unidirectional aramid fibres. The effect of elevated and cryogenic temperatures on these materials is critical to aerospace applications. ARALL 1, 2, 3, and 4 laminates have been tested in tension at temperatures ranging from −300F–400 °F (−184–204 °C) and at room temperature after exposure. This paper summarizes how tensile properties depend on temperature for these four ARALL laminates under the conditions described. At cryogenic temperatures, no degradation of ultimate tensile strengths, tensile yield strengths and moduli were found for either the longitudinal or transverse directions for ARALL 1–4 laminates. Furthermore, the mechanical properties remained the same or increased slightly as the temperature decreased. Longitudinal and transverse ultimate tensile strengths, tensile yield strengths, and moduli of ARALL 1–3 laminates at room temperature remain nearly constant after the laminates were exposed for 1, 10 and 100 h to temperatures up to 250 °F (121 °C), and up to 350 °F (177 °C) for ARALL 4 laminates. However, these properties determined at the elevated temperatures after 1, 10 and 100 h exposure showed a tendency to decrease with increasing temperature. The properties of ARALL laminates are much better in the longitudinal fibre direction than those of conventional monolithic aluminium alloys. Typical failure modes of the test specimens in the high-temperature range were examined using a scanning electron microscope. The discussions are also described in the paper. | Temperature dependence of the tensile behaviour of aramid/aluminium laminates | 10.1007/BF00349028 |
1992-11-01 | An a priori assessment of the number of measuring devices and their locations in an experimental evaluation of the efficiency of a cryogenic plant | 10.1007/BF01821922 | |
1992-11-01 | We have constructed and used two dimensional arrays of both unstressed and stressed Ge:Ga photoconductive detectors for far-infrared astronomy from the Kuiper Airborne Observatory (KAO). The 25 element (5×5) arrays are designed for a new cryogenically cooled spectrometer, the MPE/UCB Far-Infrared Imaging Fabry-Perot Interferometer (FIFI). All of the pixels for the stressed array performed well on the first flights with FIFI; 25% of the detectors in the array are more sensitive than our best single element detector, with background limited noise equivalent powers (NEPs)≲3.0×10^−15 W Hz^−1/2 at 158 μm and 40 km s^−1 spectral resolution. The average array element performs within±15% of this value. With a bias field of 0.1 V/cm, the average detector response is 20±6 Amp/Watt at 158 μm. The cutoff wavelength and response also compare well with our single element detectors. The unstressed array delivers significantly better performance than our single element detector due to the lower thermal background in the new spectrometer. The average background limited NEp at 88 μm and 35 km s^−1 spectral resolution is ∼7×10^−15 W Hz^−1/2. The least sensitive pixel is only 40% less sensitive. The unstressed array response at 88 μm with a bias field of 1 V/cm is 5±1 Amp/Watt. Twenty four of the 25 elements worked on the first flights-on subsequent flights all channels have worked. Some of the exciting new science possible with far-infrared detector arrays is also discussed. | Stressed and unstressed Ge:Ga detector arrays for airborne astronomy | 10.1007/BF01010739 |
1992-11-01 | Effect of axial thermal conductivity on efficiency of heat exchangers in cryogenic refrigerators | 10.1007/BF01150924 | |
1992-10-01 | Organization of information provisions for automated planning of cryogenic pipelines of storage systems | 10.1007/BF01148862 | |
1992-10-01 | Cutting tool materials belong to a group of nonductile materials. Chipping and breaking of the cutting edge and fracturing of the tool are common types of tool failure even under conventional machining conditions. This leads to a concern about whether cutting tool materials are able to maintain their strength and toughness and withstand the low-temperature thermal shock during cryogenic machining. The objective of this investigation was to study the behaviors of these kinds of materials at cryogenic temperatures. The results will also serve as a basis in selecting the suitable cutting tool materials for cryogenic machining and in determining the cryogenic strategy and optimum cutting conditions. Several representative cutting tool materials, such as five grades of commercial carbide-cobalt alloys and M46 highspeed steel, are investigated in terms of microstructural observation, impact testing, transverse rupture strength measurement, and indentation testing. It has been shown that carbide tool materials generally retain their strength and toughness as the temperature decreases to liquid nitrogen temperature. The behaviors of carbide tool materials at cryogenic temperatures can be explained in terms of the temperature effects on the binder phase. | Cryogenic properties of some cutting tool materials | 10.1007/BF02649252 |
1992-07-01 | Results are presented for an experimental study of the effect of cooling to 77 K on resistance to crack development of chromium-nickel steels 12Kh18N10T and 03Kh20N16AG6 with impact loading. The crack resistance characteristics with a rate of crack growth of 1.5 m/sec were determined from the deformation diagram recorded during testing. Features are noted for crack advance with cooling under conditions of a dynamically applied load . | Crack resistance of chromium-nickel steels with impact loading under cryogenic temperature conditions | 10.1007/BF00777174 |
1992-02-01 | Application of optical superheating of a surface to investigation of the onset of boiling of cryogenic liquids | 10.1007/BF00851787 | |
1992-01-01 | The fracture toughness of heat treated austenitic stainless steel is measured. The data collected using a simple dynamic bend test at 77 K are compared and scaled with values measured on CT specimens at 4 K. It shows that the toughness depends strongly on the temperature and time of the heat treatment and that — as long as there is no need for values according to certain standards — expensive and time consuming 4 K tests on CT specimens can be substituted. The data are presented in three dimensional graphs. | Influence of Aging on the Fracture Toughness of Cryogenic Austenitic Materials, Evaluated by a Simple Test Method | 10.1007/978-1-4757-9050-4_24 |
1992-01-01 | Progress toward the realization of a medium size multipurpose biomagnetic system is described. Eleven second-order gradiometers are coupled with as many dc-SQUIDs manifactured in our laboratory. The geometry of the detecting coils consists of seven sensors arranged in a straight line and four sensors placed around the center. By means of this configurationit is possible to scan the chest or the abdomen with the seven aligned sensors, to measure the head with the seven central sensors whereas the whole system can provide significant information for “single shot” cardiomagnetic measurements in clinical studies. | 11-Channel Multipurpose Biomagnetic System for Operation in Unshielded Environment | 10.1007/978-3-642-77457-7_90 |
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