Showing papers in "IEEE Transactions on Applied Superconductivity in 2000"
CERN1
TL;DR: In this article, known expressions for the critical temperature, critical field and pinning force in NbTi are combined into a self-consistent fit formula that provides the critical current density as a function of temperature and field.
Abstract: Known expressions, for the critical temperature, critical field and pinning force in NbTi are combined into a self-consistent fit formula that provides the critical current density as a function of temperature and field. The main advantage of such a fit is the extended validity range. Data available in literature and measurements on LHC strands are used to demonstrate the accuracy of the fit. The J/sub c/ data-sets used to cover a range of field from 0 T to 9 T and temperature from 1.9 K to 9 K. The standard deviation of the fits presented is of the order of 5% or better. This accuracy is generally sufficient for design purposes, extrapolation and scaling of measured results. Better accuracy, e.g. for short sample limit prediction, can be achieved restricting the domain of validity.
268Â citations
TL;DR: The Inductrack as mentioned in this paper is a model-scale magnetic levitation system, which employs special arrays of permanent magnets on the moving car to induce repelling currents in a close-packed array of shorted circuits in the track.
Abstract: Arising out of research at the Lawrence Livermore National Laboratory on passive magnetic bearings, a new magnetic levitation system, the Inductrack, has been developed and tested at model scale. The system employs special arrays of permanent magnets (Halbach arrays) on the moving car. The magnetic field from the arrays induces repelling currents in a close-packed array of shorted circuits in the track. Above a low transition speed (a few kilometers per hour), levitation forces approach a constant value, while drag forces decrease inversely with speed, with L/D reaching 200:1 or more at operating speeds. The high magnetic efficiency of the Halbach arrays, plus the use of close-packed track circuits, results in levitating forces approaching 40 metric tonnes per square meter (using NdFeB permanent magnet arrays, whose weight in typical cases is a few percent of the levitated weight). The system is passively stable: only motion is required for levitation. Failure of the drive system only results in the train slowing down and settling onto auxiliary wheels at a low speed. A detailed theoretical analysis of the Inductrack was made, on the basis of which a small-scale model was constructed and operated. The Laboratory is building a new small-scale model system (under NASA sponsorship) to demonstrate the acceleration rates and speeds (10-g and Mach 0.4 in the model) needed to magnetically launch rockets.
136Â citations
TL;DR: In this paper, the feasibility of a direct magnetic separation device for white blood cells and plasma from whole blood is discussed based on the analysis, and the experimental results have shown good agreements with the theoretical model taking into account the gravitational force.
Abstract: Direct magnetic separations of red blood cells from whole blood have been carried out using a continuous magnetic separation method based on high gradient magnetic separation (HGMS) and a gas-permeable membrane with nitrogen gas. The experimental results have shown good agreements with the theoretical model taking into account the gravitational force. Based on the analysis, the feasibility of a direct magnetic separation device for white blood cells and plasma from whole blood is discussed.
85Â citations
TL;DR: A 15 kV class high temperature superconducting fault current limiter that can double as a fast sub-cycle solid state breaker and has the potential to become the first major commercial product for HTS power utility application is developed.
Abstract: A 15 kV class high temperature superconducting fault current limiter was developed as part of a Department of Energy Superconductivity Partnership Initiative (SPI) Phase II effort. This is an inductive/electronic fault current limiter (FCL) that can double as a fast sub-cycle solid state breaker. The said device was shipped to Southern California Edison (SCE) Center Substation at Norwalk, CA from General Atomics on June 15, 1999. Preliminary high voltage and high current testing was conducted. The pre-commercial FCL unit houses three of the world's largest Bi-2223 coils (solenoids each with an outside diameter of 1 m and a coil length of 0.75 m), collaborated by GA and IGC. These coils will operate at 35 K and be able to carry a continuous DC current of 2000 A as well as an AC pulsed current of 9000 A. Detailed specification of the FCL device and a brief description of its various subsystems will be given. Finally, test results at Center Substation are summarized and future work outlined. This Phase II FCL device is important as it has the potential to become the first major commercial product for HTS power utility application.
64Â citations
CERN1
Abstract: We describe here a new harmonic coil system for the field measurement of the superconducting, twin aperture LHC dipoles and the associated corrector magnets. Besides field measurements the system can be used as an antenna to localize the quench origin. The main component is a 16 m long rotating shaft, made up of 13 ceramic segments, each carrying two tangential coils plus a central radial coil, all working in parallel. The segments are connected with flexible Ti-alloy bellows, allowing the piecewise straight shaft to follow the curvature of the dipole while maintaining high torsional rigidity. At each interconnection the structure is supported by rollers and ball bearings, necessary for the axial movement for installation and for the rotation of the coil during measurement. Two such shafts are simultaneously driven by a twin-rotating unit, thus measuring both apertures of a dipole at the same time. This arrangement allows very short measurement times (typically 10 s) and is essential to perform cold magnetic measurements of all dipoles. The coil surface and direction are calibrated using a reference dipole. In this paper we describe the twin rotating coil system and its calibration facility, and we give the typical resolution and accuracy achieved with the first commissioned unit.
62Â citations
CERN1
TL;DR: The Large Hadron Collider (LHC) as discussed by the authors is a superconducting accelerator equipped with high-field magnets operating in superfluid helium below 1.9 K. The heart of the LHC cryogenic system is the quasi-isothermal magnet cooling scheme, in which flowing two-phase saturated superfluid liquid removes the heat load from the 36000 ton cold mass, immersed in some 400 m/sup 3/static pressurised liquid nitrogen.
Abstract: The Large Hadron Collider (LHC), a 26.7 km circumference superconducting accelerator equipped with high-field magnets operating in superfluid helium below 1.9 K, has now fully entered construction at CERN, the European Laboratory for Particle Physics. The heart of the LHC cryogenic system is the quasi-isothermal magnet cooling scheme, in which flowing two-phase saturated superfluid helium removes the heat load from the 36000 ton cold mass, immersed in some 400 m/sup 3/ static pressurised superfluid helium. The LHC also makes use of supercritical helium for nonisothermal cooling of the beam screens which intercept most of the dynamic heat loads at higher temperature. Although not used in normal operation, liquid nitrogen will provide the source of refrigeration for precooling the machine. Refrigeration for the LHC is produced in eight large refrigerators, each with an equivalent capacity of about 18 kW at 4.5 K, completed by 1.8 K refrigeration units making use of several stages of hydrodynamic cold compressors. The cryogenic fluids are distributed to the cryomagnet strings by a compound cryogenic distribution line circling the tunnel. Procurement contracts for the major components of the LHC cryogenic system have been adjudicated to industry, and their progress will be briefly reported. Besides construction proper, the study and development of cryogenics for the LHC has resulted in salient advances in several fields of cryogenic engineering, which we shall also review.
60Â citations
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TL;DR: The Compact Muon Solenoid (CMS) is one of the experiments being designed in the framework of the Large Hadron Collider (LHC) project at CERN, the design field of the CMS magnet is 4 T, the magnetic length is 13 m and the aperture is 6 m as discussed by the authors.
Abstract: The Compact Muon Solenoid (CMS) is one of the experiments, which are being designed in the framework of the Large Hadron Collider (LHC) project at CERN, the design field of the CMS magnet is 4 T, the magnetic length is 13 m and the aperture is 6 m. This high magnetic field is achieved by means of a 4 layer, 5 modules superconducting coil. The coil is wound from an Al-stabilized Rutherford type conductor. The nominal current of the magnet is 20 kA at 4.5 K. In the CMS coil the structural function is ensured, unlike in other existing Al-stabilized thin solenoids, both by the Al-alloy reinforced conductor and the external former. In this paper the retained manufacturing process of the 50-km long reinforced conductor is described. In general the Rutherford type cable is surrounded by high purity aluminium in a continuous co-extrusion process to produce the Insert. Thereafter the reinforcement is joined by Electron Beam Welding to the pure Al of the insert, before being machined to the final dimensions. During the manufacture the bond quality between the Rutherford cable and the high purity aluminium as well as the quality of the EB welding are continuously controlled by a novel ultrasonic phased array system. The dimensions of the insert and the final conductor are measured by laser micrometer.
58Â citations
TL;DR: In this paper, a powder-in-tube (PIT) based Nb/sub 3/Sn conductor was developed for application in accelerator magnets and high-field solenoids.
Abstract: New Nb/sub 3/Sn conductors, based on the powder-in-tube (PIT) process, have been developed for application in accelerator magnets and high-field solenoids. For application in accelerator magnets, SMI has developed a binary 504 filament PIT conductor by optimizing the manufacturing process and adjustment of the conductor lay-out. It uniquely combines a non-copper current density of 2680 A/mm/sup 2/@10 T with an effective filament diameter of about 20 /spl mu/m. This binary conductor may be used in a 10 T, wide bore model separator dipole magnet for the LHC, which is being developed by a collaboration of the University of Twente and CERN. A ternary (Nb/7.5wt%Ta)/sub 3/Sn conductor containing 37 filaments is particularly suited for application in extremely high-field superconducting solenoids. This wire features a copper content of 43%, a non-copper current density of 217 A/mm/sup 2/@20 T and a B/sub c2/ of 25.6 T. The main issues and the experimental results of the development program of PIT Nb/sub 3/Sn conductors are presented and discussed in this paper.
54Â citations
TL;DR: A superconducting magnet assembly for an ECR (Electron Cyclotron Resonance) ion source at the 88-inch cyclotron at LBL is described in this article, which achieves a field on axis of 4 T and 3 T at the mirrors with 0.4 T between and a sextupole field of 2.0 T at 15 cm diameter in the confinement volume.
Abstract: A superconducting magnet assembly has been built for an ECR (Electron Cyclotron Resonance) ion source at the 88-inch cyclotron at LBL. Three 34-cm ID solenoids provide axial plasma confinement and a sextupole assembly in the solenoid bore provides radial stability. Two large solenoids are spaced 50 cm. Apart with a smaller opposing solenoid between. The sextupole assembly is 92 cm long with winding inner diameter of 20 cm. And outer diameter of 27.2 cm. The design goal is to achieve a field on axis of 4 T and 3 T at the mirrors with 0.4 T between and a sextupole field of 2.0 T at 15-cm diameter in the confinement volume. Each solenoid uses rectangular conductor wish copper/SC ratio of 4; the three coils are wet-wound on a one-piece aluminum bobbin with aluminum banding for radial support. The sextupole uses rectangular conductor with copper/SC ratio of 3. Each of the 6 coils is wet-wound with filled epoxy on a metal pole; the ends of the pole are aluminum and the central 34-cm is iron to augment the sextupole field. The six coils are assembled on a 20-cm-OD stainless steel tube with a 1.4-cm thick 30.0-cm OD aluminum tube over the assembly for structural support. Thin metal bladders are expanded azimuthally between each coil and axially at tire ends to pre-load the assembly. The sextupole assembly fits inside the solenoid bobbin, which provides support for the magnetic forces. The magnet exceeds design requirements with minimum training.
54Â citations
TL;DR: In this article, an outline of the Nb/sub 3/Al conductor prepared by rapid-heating, quenching and transformation (RHQT) process is described, together with that of Nb sub 3/al conductors fabricated by other process.
Abstract: An outline of the Nb/sub 3/Al conductor prepared by rapid-heating, quenching and transformation (RHQT) process is described, together with that of Nb/sub 3/Al conductors fabricated by other process. The RHQT process produces highly stoichiometric Nb/sub 3/Al with fine grains, via supersaturated-solid solution Nb(Al)/sub ss/. The RHQT Nb/sub 3/Al exhibits a quite high critical current density J/sub c/ over the whole range of magnetic fields, in particular, in fields above 20 T. The achieved high stoichiometry accounts for the substantially improved high field performance and is compatible with the excellent strain tolerance which makes Nb/sub 3/Al superior over Nb/sub 3/Sn conductors. Deformability of as-quenched Nb/Nb(Al)/sub ss/ is enough for the conductor to be externally stabilized with Cu, stranded to a cable, flat-roll formed and wound to a coil, before transforming Nb(Al)/sub ss/ to A15-type Nb/sub 3/Al. The current carrying capacity has been enhanced through increasing wire diameter and reduced Nb matrix ratio. Incorporation of stabilizer has been externally and internally made for RHQT JR Nb/sub 3/Al conductors.
53Â citations
TL;DR: The evolution of superconducting MRI magnet systems are traced-taking note of the importance of advances in cryogenic technology and design practice-as they have responded to both market forces and competing magnet technologies.
Abstract: Since its appearance in the early 1980's, Magnetic Resonance Imaging (MRI) has taken its place as a major player in the noninvasive diagnosis of disease. It is the imaging modality of choice for detecting abnormalities of the brain, spine and musculoskeletal systems. It is on the verge of widespread application in diagnosis of cardiovascular disease and in image guided surgery. While permanent and resistive magnets are used for low field applications ("open" MRI) most systems use high field superconducting magnets making MRI the largest commercial application of superconductivity. The MRI magnet is the largest and most expensive component in the MRI system. Magnet configuration is the determining factor in MRI system architecture and directly connected to issues such as patient comfort, ease of siting, life cycle cost and functionality. All of these factors drive magnet requirements. Thus, MRI magnet requirements are determined by a combination of MRI system needs, technical requirements and market forces, plus the need for continuous reduction of both magnet-acquisition cost and total cost of ownership. Cost of ownership, in turn, includes siting, installation, operation and service. In this paper we trace the evolution of superconducting MRI magnet systems-taking note of the importance of advances in cryogenic technology and design practice-as they have responded to both market forces and competing magnet technologies.
TL;DR: In this article, the alignment of high-gradient superconducting quadrupole magnets is performed using a single stretched wire system with very long wire lengths, up to 20 m.
Abstract: High-gradient superconducting quadrupole magnets are being developed by the US LHC Accelerator Project for the Interaction Regions of the Large Hadron Collider. Determination of the magnetic axis for alignment of these magnets will be performed using a single stretched wire system. These measurements will be done both at room and cryogenic temperatures with very long wire lengths, up to 20 m. This paper reports on the stretched wire alignment methodology to be employed: and the results of recent room-temperature measurements on a 2 m model magnet with long wire lengths.
TL;DR: In this article, cable insulation and thermo-mechanical properties of epoxy impregnated Nb/sub 3/Sn composite were studied within the framework of the Fermilab high field magnet program.
Abstract: Within the framework of the Fermilab high field magnet program, cable insulation and thermo-mechanical properties of epoxy impregnated Nb/sub 3/Sn composite were studied As a part of cable insulation development, a new wrappable ceramic insulation was investigated to understand its mechanical properties and its influence on magnet fabrication technology Measurements of modulus of elasticity and Poisson's ratio of Nb/sub 3/Sn composite made out of ten-stack samples were performed under compression at room temperature and at 42 K The results from both monotonic and cyclic loading tests are presented Finally, measurements of the coefficient of thermal contraction for the composite using strain gauges is discussed
TL;DR: In this article, a three phase saturated core HTS fault current limiter (FCL) was developed and tested with a small (several hundred watts) model of a three-phase saturated core HMTS core.
Abstract: A small (several hundred watts) model of a three phase saturated core HTS fault current limiter (FCL) was developed and tested. Iron yokes of all three phases were saturated by a single DC HTS coil. The coil comprised a 60 turns single pancake (ID 135 mm), wound after heat treatment from Bi-2223 multifilamentary tape in Ag matrix. The critical current of the pancake in liquid nitrogen was 8 A. The tests have shown that the limiting value of the AC current (at 50 Hz) can be easily adjusted in the range from 8 A to 20 A depending on the value of the DC current in the HTS coil. The optimum value of the latter is 4 A, corresponding to the 8 times increase of the differential resistance in the current limiting mode. The response time is very short (less that 1 ms). Under tests the short-circuiting event was made in one, two and all three phases. The case of short-circuiting of one phase in the three-phase FCL is especially favorable from the standpoint of the voltages induced in HTS coil compared to the one-phase FCL.
TL;DR: The ATLAS central solenoid magnet is being developed to provide a magnetic field of 2 Tesla in the central tracking volume of the ATLAS detector under construction at the CERN/LHC project.
Abstract: The ATLAS central solenoid magnet is being developed to provide a magnetic field of 2 Tesla in the central tracking volume of the ATLAS detector under construction at the CERN/LHC project. The solenoid coil design features high-strength aluminum stabilized superconductor to make the coil thinnest while maintaining its stability and the pure-aluminum strip technique for quench protection and safety. The solenoid coil is installed in a common cryostat with the LAr calorimeter in order to minimize the cryostat wall. A transparency of 0.66 radiation length is achieved with these integrated efforts. The progress in the solenoid coil fabrication is reported.
TL;DR: The European Home Team is responsible for the design, fabrication and the test of the Toroidal Field Model Coil (TFMC) of the International Thermonuclear Experimental Reactor (ITER) as discussed by the authors.
Abstract: The European Home Team is responsible for the design, the fabrication and the test of the Toroidal Field Model Coil (TFMC) of the International Thermonuclear Experimental Reactor (ITER). Within this task, three full-size samples had to be fabricated by industry and to be tested in the SULTAN facility (Villigen, Switzerland). Each sample is composed of two parallel straight bars of full-size conductor, connected at bottom through a joint. This paper reports on the test results and analysis of the first two samples. We present the results of the critical current measurements performed on each conductor leg, the results of the measurements of the joint DC resistance and of the joint quench temperature, the results of joint loss and conductor loss measured under pulsed magnetic field. The results are analysed through comparisons with predictions given by theoretical models. Conclusions are drawn for the expected performances of the TFMC and of the ITER coils.
TL;DR: In this paper, the authors present a relative assessment of the most suitable spiral structure for the ITER magnets for the toroidal field model coil (TFMC) production, which is used in the manufacture of the two model coils for ITER.
Abstract: In the framework of the controlled nuclear fusion by magnetic confinement programme, a particular design of a Cable-in-Conduit Conductor (CICC) is being developed, including two parallel cooling channels. The central channel is separated from the strand channel by a spiral structure whose geometry can substantially influence the overall pressure drop. The thermo-hydraulics of this so called dual channel CICC is not well known. Hence various experiments with pressurised nitrogen at room temperature, on straight and curved unit lengths from the ITER toroidal field model coil (TFMC) production, have been performed at both Ansaldo and CEA-Cadarache to characterise the friction factor of the two parallel cooling regions, in a range of representative Reynolds numbers. These experimental results are presented. It has been possible to characterise different kinds of spiral geometries used in the manufacture of the two model coils for ITER: the TFMC and the Central Solenoid Model Coil. A relative assessment of the most suitable spiral for the ITER magnets is presented. This discussion includes: (i) manufacturing aspects with the capability of the spiral to support the cabling process as a function of the geometry of the spiral and the compaction of the cable; (ii) pressure drop considerations, as a function of the spiral geometry which plays an important role in the cooling process and the required cold pump power. Conclusions and recommendations are drawn.
CERN1
TL;DR: The Compact Muon Solenoid (CMS) detector as mentioned in this paper is a general-purpose detector designed to run in mid-2005 at the highest luminosity at the LHC at CERN.
Abstract: CMS (Compact Muon Solenoid) is a general-purpose detector designed to run in mid-2005 at the highest luminosity at the LHC at CERN. Its distinctive features include a 6 m free bore diameter, 12.5 m long, 4 T superconducting solenoid enclosed inside a 10,000 tonne return yoke. The magnet will be assembled and tested on the surface by the end of 2003 before being transferred by heavy lifting means to a 90 m deep underground experimental area. The design and construction of the magnet is a 'common project' of the CMS Collaboration. It is organized by a CERN based group with strong technical and contractual participation by CEA Saclay, ETH Zurich, Fermilab Batavia IL, INFN Geneva, ITEP Moscow, University of Wisconsin and CERN. The return yoke, 21 m long and 14 m in diameter, is equivalent to 1.5 m of saturated iron interleaved with four muon stations. The yoke and the vacuum tank are being manufactured. The indirectly-cooled, pure-aluminium-stabilized coil is made up from five modules internally wound with four layers of a 20 kA mechanically reinforced conductor. The contracts for the conductor and the outer cryogenics have just been awarded, and the remaining coil parts, including winding, are being tendered worldwide in industry. The project is described, with emphasis on the present status.
TL;DR: In this article, two Bi-2212 double-pancake coils (Coil A and Coil B) were installed in the high-field superconducting magnet system at the Tsukuba Magnet Laboratory of the National Research Institute for Metals.
Abstract: Development of a 1 GHz superconducting NMR magnet is in progress at the Tsukuba Magnet Laboratory (TML) of the National Research Institute for Metals (NRIM). This magnet will contain a BSCCO inner coil, which should generate a central field of 23.5 T in a backup field of 21.1 T. In order to accomplish this targeted field, we fabricated two Bi-2212 double-pancake coils (Coil A and Coil B). They were installed in the high-field superconducting magnet system at the TML/NRIM. Their performance was measured in a backup field of 18 T. Coil A was made of 20 double-pancakes wound with Ag sheathed Bi-2212 tape conductors. Ag-Mg tape was co-wound for mechanical support. Its winding was 147 mm in outer diameter and 220 mm in height. It generated a central field of 21.4 T in a clear bore of 61 mm. Coil B was located inside Coil A. Its 6 double-pancakes were wound with Bi-2212 tape conductors reinforced with Ag-Mg-Ni alloy sheath. The outer diameter and height of the winding were 48 mm and 63 mm, respectively. Coil B generated the highest field of 23.4 T in a backup field of 21.4 T. This study confirmed that the present performance of the Bi-2212 coils had already satisfied the required conditions for the inner coil of the 1 GHz NMR magnet from the viewpoint of high-field generation.
KEK1
TL;DR: In this article, a precipitation type aluminum alloys have been developed for the ATLAS thin superconducting solenoid, which achieved high yield strength of 79 MPa (R.T.) and 117 MPa(4.2 K) with high residual resistivity ratio (RRR) of 170 after cold working of 20% in area reduction.
Abstract: The precipitation type aluminum alloys have excellent performance as the increasing rate in electric resistivity with additives in the precipitation state is considerably low, compared to that of the aluminum alloy with additives in the solid-solution state. It is possible to enhance the mechanical strength without remarkable degradation in residual resistivity ratio (RRR) by increasing content of selected additive elements. Nickel is the suitable additive element because it has very low solubility in aluminum and low increasing rate in electric resistivity, and furthermore, nickel and aluminum form intermetallic compounds which effectively resist the motion of dislocations. First, Al-0.1wt%Ni alloy was developed for the ATLAS thin superconducting solenoid. This alloy achieved high yield strength of 79 MPa (R.T.) and 117 MPa (4.2 K) with high RRR of 490 after cold working of 21% in area reduction. These highly balanced properties could not be achieved with previously developed solid-solution aluminum alloys. In order to achieve higher strength than the above, Al-Ni alloys of up to 2.0 wt% Ni content were investigated. Al-2.0wt%Ni alloy achieved yield strength of 120 MPa (R.T.) and 167 MPa (4.2 K) with RRR of 170 after cold working of 20% in area reduction.
TL;DR: The 60 T Long-Pulse (60 T LP) magnet system has provided controlled power magnetic field pulses to experimentalists since August 3, 1998 as mentioned in this paper, which is installed as part of the user facility research equipment at the National High Magnetic Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory.
Abstract: The 60 T Long-Pulse (60 T LP) magnet system has provided controlled power magnetic field pulses to experimentalists since August 3, 1998. This magnet system is installed as part of the user facility research equipment at the National High Magnetic Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory. The 60 T LP magnet is the first of its kind in the United States and produces the highest field in its class, routinely providing a 60 T pulsed field of 100 ms flat-top duration in a 32 mm diameter bore. In addition, numerous other controlled pulse shapes at 60 T and lower fields have been provided. Since the start of commissioning on September 17, 1997 the magnet has been pulsed in excess of 800 times at various field levels. More than 600 magnet pulses have been provided to experiments and almost 400 of these were at 60 T. Operating statistics including coil system and inductance and resistance histories are presented. Operating and maintenance experience and issues are discussed as well as realizable improvements and upgrades to the magnet.
TL;DR: In this paper, a correlation was developed for the turbulent friction factor f of a circular channel with a helical rib roughness of rectangular cross section, which was relevant to the central channel (hole) in two-channel cable-in-conduit conductors.
Abstract: A correlation has been developed for the turbulent friction factor f of a circular channel with a helical rib roughness of rectangular cross section, which is relevant to the central channel (hole) in two-channel cable-in-conduit conductors. The correlation is based on data we measured on a pipe with three different types of helix. It relates f with the Reynolds number Re and with suitable dimensionless combinations of all relevant geometrical parameters of the problem, i.e., hole diameter and helix gap and thickness. A limited comparison with actual (QUELL) conductor data shows good agreement.
TL;DR: In this article, the ATLAS central solenoid magnet is constructed to provide a magnetic field of 2 Tesla in the central tracking part of the LHC detector at the LAS, and a yield strength of 110 MPa at 4.2 K has been realized keeping a residual resistivity ratio (RRR) of 590.
Abstract: The ATLAS central solenoid magnet is being constructed to provide a magnetic field of 2 Tesla in the central tracking part of the ATLAS detector at the LHC. Since the solenoid coil is placed in front of the liquid-argon electromagnetic calorimeter, the solenoid coil must be as thin (and transparent) as possible. The high-strength and high-RRR aluminum-stabilized superconductor is a key technology for the solenoid to be thinnest while keeping its stability. This has been developed with an alloy of 0.1 wt% nickel addition to 5N pure aluminum and with the subsequent mechanical cold working of 21% in area reduction. A yield strength of 110 MPa at 4.2 K has been realized keeping a residual resistivity ratio (RRR) of 590, after a heat treatment corresponding to coil curing at 130/spl deg/C for 15 hrs. This paper describes the optimization of the fabrication process and characteristics of the developed conductor.
TL;DR: In this article, the authors investigated what electrical and thermodynamic requirements have to be fulfilled by a superconductor if the fault current limiter is of a hybrid type and proposed a hybrid fault current limiter based on a novel fast acting mechanical switch for several kA at medium voltage level to commutate the rising fault current to the superconducting element within several hundred microseconds after fault detection.
Abstract: All concepts for fault current limiters employing high temperature superconductors (SCFL) have the disadvantage of significant AC losses caused by the superconductor carrying a continuous load current. Therefore, in the presented paper, it is investigated what electrical and thermodynamic requirements have to be fulfilled by a superconductor if the fault current limiter is of a hybrid type. Assuming the availability of a suitable design for a superconductor used as a delayed reacting resistive limiting element in parallel with a fast acting load switch, the concept of a hybrid fault current limiter is introduced. The concept is based on a novel fast acting mechanical switch for several kA at medium voltage level to commutate the rising fault current to the superconducting element within several hundred microseconds after fault detection. It is found that a critical current density not higher than 1.5 kA per centimeter square is adequate for the proposed system. The superconductor carries only the fault current during switching and thus the total losses of the hybrid system are only 4 percent of the losses of a conventional SCFL, which offers high economical benefits. Cooling of the superconductor by gaseous nitrogen is feasible, and presents simplicity and flexibility of operation.
TL;DR: The first 100 T non-destructive (100 T ND) magnet and power supplies as currently designed are described in this article, where the magnet will provide a 100 T pulsed field of 5 ms duration (above 90% of full field) in a 15 mm diameter bore once per hour.
Abstract: The first 100 T non-destructive (100 T ND) magnet and power supplies as currently designed are described. This magnet will be installed as part of the user facility research equipment at the National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory. The 100 T ND magnet will provide a 100 T pulsed field of 5 ms duration (above 90% of full field) in a 15 mm diameter bore once per hour. Magnet operation will be nondestructive. The magnet will consist of a controlled power outer coil set which produces a 47 T platform field in a 225 mm diameter bore. Located within the outer coil set will be a 220 mm outer diameter capacitor powered insert coil. Using inertial energy storage a synchronous motor/generator will provide AC power to a set of seven AC-DC converters rated at 64 MW/80 MVA each. These converters will energize three independent coil circuits to create 170 MJ of field energy in the outer coil set at the platform field of 47 T. The insert will then be energized to produce the balance of the 100 T peak field using a 2.3 MJ, 18 kV (charged to 15 kV), 14.4 mF capacitor bank controlled with solid-state switches. The magnet will be the first of its kind and the first non-destructive, reusable 100 T pulsed magnet. The operation of the magnet will be described along with special features of its design and construction.
TL;DR: The electrical properties of high temperature insulation coatings, which were applied by sol-gel process on Ag or AgMg sheathed Bi-2212 tapes, bronze processed Nb/sub 3/Sn wires and Ni tapes, have been studied by resistive, capacitance and high voltage breakdown techniques as discussed by the authors.
Abstract: The electrical properties of high temperature insulation coatings, which were applied by sol-gel process on Ag or AgMg sheathed Bi-2212 tapes, bronze processed Nb/sub 3/Sn wires and Ni tapes, have been studied by resistive, capacitance, and high voltage breakdown techniques. The electrical properties of the coatings with varying composition, coating type, number of dippings, and temperature and time of annealing process have been presented.
TL;DR: The first cold mass prototype has been completed and warm-measured for its multipole content at CEA/Saclay laboratory, in the frame of the special French contribution to the LHC project as mentioned in this paper.
Abstract: Each cold mass of the short straight sections in the eight LHC arcs will contain a 3.25 m long twin aperture quadrupole of a nominal gradient of 223 T/m. This magnet will be aligned in a 5.3 m long inertia tube together with auxiliary magnets on each end. On the quadrupole connection end either a pair of 38 cm long octupole or trim quadrupole magnets will be mounted, on the other end there will be combined sextupole-dipole correctors with a yoke length of 1.26 m. The powering of the main quadrupoles will be assured by two pairs of copper stabilized superconducting bus-bars placed inside the cold mass next to the bus-bars for the main dipole magnets. Each of the two quadrupole apertures will be connected to its quench protection diode. The construction of three prototypes has been entrusted to the CEA/Saclay laboratory, in the frame of the special French contribution to the LHC project. The first cold mass prototype has been completed and warm-measured for its multipole content at CEA. The second cold mass is presently under completion. The paper reviews the experience with the development of the quadrupole coils and cold mass construction and gives the results of the first warm magnetic measurements. An outlook for the series manufacture of the 400 are quadrupole magnets and their cold masses for the LHC machine completes the report.
TL;DR: In this paper, a series resistor at the end of the superconducting passive transmission line (PTL) was proposed to avoid undesirable flux trapping in the loop and for isolation in regard to the DC current.
Abstract: We report simulated results of-rapid single flux quantum (SFQ) circuits having driver, receiver, and passive transmission lines for propagating SFQ pulses to investigate the design criteria. We have studied the equivalent input/output resistance of the driver/receiver in various bias conditions and found that the resistance is almost proportional to the bias current of the driver/receiver. Furthermore, we have proposed inserting a series resistor at the end of the superconducting passive transmission line (PTL) for avoiding undesirable flux trapping in the loop and for isolation in regard to the DC current. We also found that the reduction of the bias margin due to the resistance is rather small when the resistance is much smaller than the impedance of the PTL. An operating margin of more than 30% was obtained in the driver/receiver circuits including the PTL and the series resistor.
TL;DR: The central solenoid (CS) model coil program is in progress with an international collaboration under the frame of the ITER-EDA and the installation work is underway with the inner and outer module of the CS model coil as discussed by the authors.
Abstract: The central solenoid (CS) model coil program is in progress with an international collaboration under the frame of the ITER-EDA. The purpose of the CS insert coil is to test the performance of the ITER-CS conductor. The CS insert coil is installed in the bore of the CS model coil and tested at a magnetic flux density of 13 T. The installation work is underway with the inner and outer module of the CS model coil. The superconducting characteristics of the CS conductor, the critical current and the current sharing temperature are evaluated under the operating load. The AC loss characteristics of the conductor are also evaluated under pulsed magnetic field. The fabrication of the CS insert coil was completed on May 1999. The winding tools and the results of the winding of CS insert coil are reported. The heat treatment for Nb/sub 3/Sn processing was performed successfully with no SAGBO (stress accelerated grain boundary oxidation). The procedure of the heat treatment is also reported.
TL;DR: In this article, a butt type joint has been successfully developed for the ITER magnets, where 46 kA Nb/sub 3/Sn conductors are connected by the diffusion bonding technique in vacuum.
Abstract: The conductor joint is one of the key technologies for superconducting coils. A butt type joint has been successfully developed for the ITER magnets. The 46 kA Nb/sub 3/Sn conductors are connected by the diffusion bonding technique in vacuum, after the reaction of Nb/sub 3/Sn. The advantage of this joint is low losses against pulse field, because the compacted part is very small compared with other types of joint. 15 butt joints have already been fabricated in the ITER CS Model Coil. According to the test results of the full-size conductor samples, these butt joints will be operated stably in the pulse operation, because the temperature increase due to ac losses and Joule heating by joint resistance is very small and the joint has a sufficiently high temperature margin.