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Quenches in the superconducting magnet CELLO

Description: The superconducting magnet CELLO was tested with currents up to 3200 A at Saclay and has been installed at DESY in Hamburg where it will be used for particle physics experiments requiring colliding beams of electrons and positrons. The testing of this unique, large, one-layer solenoid provides an excellent opportunity to evaluate the theory of quench propagation under adiabatic conditions, that is, in a coil in which the conductors are not in direct contact with helium. In an early test of this coil, quenches that occurred, gives the details of the damaged conductor, and includes an analysis of the quenches. Observed axial quench velocities are compared to the calculated values based on both measurements and calculations of the thermal conductivity of the fabricated coil.
Date: January 1, 1979
Creator: Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Cost of high field Nb/sub 3/Sn and Nb-Ti accelerator dipole magnets

Description: Future high-energy proton accelerators will likely require very high magnetic fields if the size of the accelerator and associated experimental areas are to be limited to dimensions that can be accommodated by the terrain at convenient sites. For example, the circumference of a 20 TeV, 10 T accelerator will be about 60 km. Two commercially available superconductors can be used to produce fields of 10 T or greater. The first is Nb/sub 3/Sn, which can operate in pool boiling helium at 4.4 K, the second is Nb-Ti, which must be cooled to about 1.9 K in superfluid helium. In this paper the costs of 7 to 11 T, 5 cm bore, 6 m long magnets made of these materials are compared. At 10 T the capital cost of Nb-Ti coils operating in superfluid helium is 35% less than the cost of Nb/sub 3/Sn coils and the cost is still 10% less after the differential operating costs over the life of the accelerator are included. 10 references, 11 figures, 16 tables.
Date: June 1, 1983
Creator: Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

A study of the effects of copper to superconductor ratio on stability

Description: Accelerator dipole magnets operate with very low copper to superconductors ratios (R). This ability to operate with low R is significant in its impact on cost. The optimum value of R has been an issue of considerable debate. This study shows that the minimum propagating zone length is greatest for copper to superconductor ratios well below 1.5, which appears to be in contradiction with some of the data. 4 refs., 7 figs.
Date: August 1, 1988
Creator: Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Cost of high-field Nb/sub 3/Sn and NbTi accelerator dipole magnets

Description: Future high-energy proton accelerators will likely require very high magnetic fields if the size of the accelerator and associated experimental areas are to be limited to dimensions that can be accomodated by the terrain at convenient sites. Two commercially available superconductors can be used to produce magnetic fields of 10T or more. The first is Nb/sub 3/Sn, which can operate in pool boiling helium at 4.4 K. The second is NbTi, which must be cooled to about 1.9 K in superfluid helium. In this paper the costs of 5-cm-bore, 6-m-long magnets made of these materials and operating at fields from 5 to 11 T are compared. At 10 T the capital cost of a NbTi coil operating in superfluid helium is 35% less than the cost of a Nb/sub 3/Sn coil. The cost of the NbTi coil is still 10% less after the differential operating costs that will be incurred over the life of the accelerator are included. The results presented here are a summary of a detailed analysis of these costs given in a separate report.
Date: November 1, 1982
Creator: Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Source, origin, and propagation of quenches measured in superconducting dipole magnets

Description: Transitions from the superconducting to normal state at 4.4 and 1.8 K in several model accelerator dipoles were recorded by a fast data-acquisition system. The resistive voltage rise in the conductor during the transitions is used to determine accurately the location of the quench source in the magnets and to estimate the axial and turn-to-turn quench velocities. The quench velocity, temperature evolution and energy deposition in the coil were calculated using the program QUENCH, and are in reasonable agreement with the data. In the two dipole magnets studied, the transitions almost always occurred in the regions of highest field. In one coil the high field region is in the straight section because the field in this region is enhanced by iron support rings. In the other magnet the high field region is at the end, in the innermost turn of the first layer. Some quenches were preceded by large voltage spikes that can be ascribed to conductor motion. Other quenches do not appear to be associated with any large energy release. Acoustic emission (AE) was monitored during the tests and AE bursts were observed simultaneous with the initial voltage spike. An increased AE signal continued as the quench progressed.
Date: November 1, 1982
Creator: Caspi, S. & Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Application of superconducting coils to VAR control in electric power systems: a proposal

Description: During the last eight years, static VAR-control systems with thyristor-controlled, room-temperature reactors have been used in electrical systems for voltage control and system stabilization. In this proposal, we describe a new static VAR-control system that uses an asymmetrically controlled Graetz bridge and a superconducting dc coil. Preliminary studies indicate that the proposed system will have lower overall losses and that its capital cost and electrical characteristics are comparable to those of a conventional system. Three- and four-year programs for developing the electronic circuitry and superconducting coils for VAR control, culminating in the installation and testing of an approx. 40-MVAR system, are proposed.
Date: November 1, 1979
Creator: Boenig, H.J. & Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Workshop on stability in superconducting magnets, Los Alamos, New Mexico, July 25--29, 1977

Description: The week-long Workshop on Stability in Superconducting Magnets sponsored by the Los Alamos Scientific Laboratory was a delightful technical success. Experts in theory and practice from all areas of the superconducting community met to discuss the intricacies of the stability problem. Detailed theory, recent data, computer interpretations of both, and engineering or design solutions to assure stability were presented. Emphasis of the workshop was mostly on the aspects of heat transfer necessary to promote stability and recovery. For the use of the attendees we have compiled Martin Wilson's talk of July 31; several summaries of the main sessions, as presented by rapporteurs on August 4; brief synopses of some of the working group sessions; a conference review by Wilson; and a list of attendees.
Date: June 1, 1978
Creator: Hassenzahl, W.V. & Rogers, J.D. (comps.)
Partner: UNT Libraries Government Documents Department

Sextupole correction coils for SSC model dipoles

Description: Local correction of the sextupole error field is proposed for the dipoles of the SSC. This requirement is imposed on the design by the high field quality required both during injection at low fields and during colliding beam operation at high fields. Error fields in the main dipole windings due to superconductor magnetization and conductor misplacements and unwanted sextupole and decapole magnetic field terms. To correct the sextupole error field we have constructed sextupole coils made of a single layer of superconducting wire and have mounted them with high precision on the stainless steel bore tube. These correction coils have been operated with 1 meter long SSC model dipoles in both the self-powered and externally-powered modes. The sextupole field in the bore has been reduced by as much as a factor of 50. The level of correction depends strongly on the angular alignment of the correction coil with respect to the sextupole error field it is to correct. Results of tests, performance of the correction coils and alignment requirements for the system are presented.
Date: May 1, 1985
Creator: Rechen, J.B.; Gilbert, W.S. & Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Technology of superconducting accelerator dipoles

Description: We discuss accelerator dipoles and their characteristics. Other types of magnets, in particular bubble chamber magnets have been quite successful. Their performance is based on cryogenic stability which is addressed only briefly in this chapter. This type of stability is not available to the accelerator designer because of the large quantities of copper or other stabilizer that would reduce the current density in the windings to an unacceptably low value.
Date: June 1, 1983
Creator: Hassenzahl, W.V.; Meuser, R.B. & Taylor, C.
Partner: UNT Libraries Government Documents Department

1-GWh diurnal load-leveling Superconducting Magnetic Energy Storage system reference design

Description: A point reference design has been completed for a 1-GWh Superconducting Magnetic Energy Storage system. The system is for electric utility diurnal load-leveling but can also function to meet much faster power demands including dynamic stabilization. This study explores several concepts of design not previously considered in the same detail as treated here. Because the study is for a point design, optimization in all respects is not complete. This report examines aspects of the coil, the superconductor supported off of the dewar shell, the dewar shell, and its configuration and stresses, the underground excavation and construction for holding the superconducting coil and its dewar, the helium refrigeration system, the electrical converter system, the vacuum system, the guard coil, and the costs. This report is divided into two major portions. The first is a general treatment of the work and the second is seven detailed technical appendices issued as separate reports. The information presented on the aluminum stabilizer for the conductor, on the excavation, and on the converter is based upon industrial studies contracted for this work.
Date: September 1, 1979
Creator: Rogers, J.D.; Hassenzahl, W.V. & Schermer, R.I. (comps.)
Partner: UNT Libraries Government Documents Department

Superconducting magnetic energy storage for electric utilities and fusion systems

Description: Superconducting inductors provide a compact and efficient means of storing electrical energy without an intermediate conversion process. Energy storage inductors are under development for load leveling and transmission line stabilization in electric utility systems and for driving magnetic confinement and plasma heating coils in fusion energy systems. Fluctuating electric power demands force the electric utility industry to have more installed generating capacity than the average load requires. Energy storage can increase the utilization of base-load fossil and nuclear power plants for electric utilities. The Los Alamos Scientific Laboratory and the University of Wisconsin are developing superconducting magnetic energy storage (SMES) systems, which will store and deliver electrical energy for load leveling, peak shaving, and the stabilization of electric utility networks. In the fusion area, inductive energy transfer and storage is being developed. Both 1-ms fast-discharge theta-pinch systems and 1-to-2-s slow energy transfer tokamak systems have been demonstrated. The major components and the method of operation of a SMES unit are described, and potential applications of different size SMES systems in electric power grids are presented. Results are given of a reference design for a 10-GWh unit for load leveling, of a 30-MJ coil proposed for system stabilization, and of tests with a small-scale, 100-kJ magnetic energy storage system. The results of the fusion energy storage and transfer tests are presented. The common technology base for the various storage systems is discussed.
Date: January 1, 1978
Creator: Rogers, J.D.; Boenig, H.J. & Hassenzahl, W.V.
Partner: UNT Libraries Government Documents Department

Coil protection for a utility scale superconducting magnetic energy storage plant

Description: Superconducting Magnetic Energy Storage (SMES) is proposed for electric utility load leveling. Attractive costs, high diurnal energy efficiency (greater than or equal to 92%), and rapid response are advantages relative to other energy storage technologies. Recent industry-led efforts have produced a conceptual design for a 5000 MWh/1000 MW energy storage plant which is technically feasible at commercially attractive estimated costs. The SMES plant design includes a protection system which prevents damage to the magnetic coil if events require a rapid discharge of stored energy. This paper describes the design and operation of the coil protection system, which is primarily passive and uses the thermal capacity of the coil itself to absorb the stored electromagnetic energy.
Date: January 1, 1986
Creator: Loyd, R.J.; Schoenung, S.M.; Hassenzahl, W.V.; Rogers, J.D. & Purcell, J.R.
Partner: UNT Libraries Government Documents Department

Development of multielement SQUID arrays for magnetic source imaging. Final report

Description: Superconducting quantum interference devices (SQUIDs) were initially developed in the late 1960s as biomagnetic detectors to monitor electrical activity in the body. Research in this area has increased in recent years as electronics and computer diagnositcs have improved. The basis of this proposal was to asses: (1) the advantages of using this technique over other technologies and (2) the requirements for development of a complete system that would advance the state of the art. In our assessment of this technology, we collaborated with the Medical School at the University of California, San Francisco (UCSF), General Electric (GE), Biomagnetic Technologies (BTi), and Conductus, each of which has unqiue expertise in biomedical applications. UCSF is one of the foremost clinical institutions in the US developing imaging techniques. GE is the primary US supplier of medical imaging systems. Conductus is the major US supplier of SQUIDs and BTi is a developer of SQUID array systems.
Date: June 1, 1995
Creator: Hassenzahl, W.V.; Casper, T.A. & Miller, D.E.
Partner: UNT Libraries Government Documents Department

Investigation on the enhancement of the critical current densities in bronze-process Nb/sub 3/Sn

Description: The work reported here addressed the problem of improving the critical current characteristic of a comercial multifilamentary Nb/sub 3/Sn strand by varying its heat treatment. The work was done from the perspective that the critical current characteristic is controlled by the metallurgical state of the reacted layer, which is, in turn, fixed by the processing the wire has undergone. The research was carried out in parallel with metallographic studies which analyzed the microstructure and composition profile within the reacted Nb/sub 3/Sn layer as a function of heat treatment. The combined results of metallographic and processing research suggest that it is possible to engineer the microstructure of the reacted layer to improve J/sub c/(H). The specific product of the work is a tailored double-aging treatment which introduces a favorable combination of microstructure and composition in the reacted layer and causes a substantial improvement in the critical current characteristic of the strand.
Date: October 1, 1981
Creator: Hong, M.; Wu, I.W.; Morris, J.W. Jr.; Gilbert, W.; Hassenzahl, W.V. & Taylor, C.
Partner: UNT Libraries Government Documents Department

Influence of microstructure on the properties of bronze-processed multifilamentary wire

Description: The A15 layer of a commercial Airco wire containing 2869 Nb filaments was analyzed as a function of heat treatment. Its microstructure is composed of three morphologically concentric shells. The central shell consists of fine equiaxed grains and has a nearly stoichiometric Sn concentration. High resolution electron microscopic analysis suggests that the fine grains are formed through the polygonization of dislocations. The homogeneous composition through the fine-grained layer is a probable consequence of the small grain size, which permits relatively rapid chemical redistributions through grain boundary diffusion. In contrast, the chemical gradient in the large-grained inner and outer sheels is steep. The microstructure is established by the reaction heat treatment, and determines the critical current. The best combination of grain size, composition, and volume of the fine-grained shell is obtained with an intermediate reaction temperature (700 to 730/sup 0/C); this temperature range also yields the best values of J/sub c/. Various two-step heat treatments were studied and compared to isothermal aging. The best microstructure and, hence, the best critical current characteristic was obtained by aging the specimen at 700/sup 0/C for 4 days followed by 730/sup 0/ for 2 days.
Date: May 1, 1983
Creator: Wu, I.W.; Dietderich, D.R.; Hassenzahl, W.V. & Morris, J.W. Jr.
Partner: UNT Libraries Government Documents Department

Field quality of the end sections of SSC (Superconducting Super Collider) dipoles

Description: The central or two-dimensional field of a dipole magnet can be calculated with some precision. The fields at the end of the magnet, which are three-dimensional in nature, provide a more complicated problem. Starting with an end design that produced a relatively good end in terms of multipole components, a method of extending parts of the straight section was used to reduce the most important harmonics, the sextupole and decapole, to a negligible level. In addition, the effect of extending an iron yoke over the ends of a magnet was investigated and it was found to have little effect on the harmonics, though it will raise the dipole field. These results are encouraging as they imply that good ends can be developed with relative ease should the two dimensional cross-section of a dipole magnet such as the SSC have to be changed.
Date: September 1, 1986
Creator: Hassenzahl, W.V.; Caspi, S.; Gilbert, W.; Helm, M.; Laslett, L.J. & Morgan, G.A.
Partner: UNT Libraries Government Documents Department

Four-layer, two-inch bore, superconducting dipole magnet

Description: Superconductors provide the accelerator designer with a unique opportunity to construct machines that can achieve high particle energies and yet have low operating costs. This paper describes the design, fabrication and testing of a 4 layer, 50 mm bore superconducting dipole magnet, D-9A. The magnet reached short sample, 5.8 T at 4.4 K and 8.0 T and 1.8 K, with little training, and exhibited low losses and low ramp rate sensitivity.
Date: November 1, 1982
Creator: Hassenzahl, W.V.; Peters, C.; Gilbert, W.; Taylor, C. & Meuser, R.
Partner: UNT Libraries Government Documents Department

Magnetic field measurements of model SSC (Superconducting Super Collider) dipoles

Description: To qualify for use in the Superconducting Super Collider, the 8000 or so 16 m long dipole magnets must pass a series of tests. One of these will be a set of warm measurements of field quality, which must be precise to about 0.001% of the 100 G field produced by 10 A, the maximum current the coils are allowed to carry for an extended period at room temperature. Field measurements of better than this accuracy have already been carried out on 1 m long model dipoles. These measurements have included determinations of the dipole fields and the higher harmonics in the central or two dimensional region and in the total magnet. In addition, axial scans of the dipole and higher harmonic magnetic fields have been made to determine the local variations, which might reflect fabrication and assembly tolerances. This paper describes the equipment developed for these measurements, the results of a representative set of measurements of the central and integral fields and axial scans, and a comparison between warm and cold measurements. Reproducibility, accuracy and precision will be described for some of the measurements. The significance of the warm measurements as a part of the certification process for the SSC dipoles will be discussed.
Date: October 1, 1986
Creator: Hassenzahl, W.V.; Gilbert, W.S.; Green, M.I. & Barale, P.J.
Partner: UNT Libraries Government Documents Department

Superconducting magnetic energy storage

Description: Long-time varying-daily, weekly, and seasonal-power demands require the electric utility industry to have installed generating capacity in excess of the average load. Energy storage can reduce the requirement for less efficient excess generating capacity used to meet peak load demands. Short-time fluctuations in electric power can occur as negatively damped oscillations in complex power systems with generators connected by long transmission lines. Superconducting inductors with their associated converter systems are under development for both load leveling and transmission line stabilization in electric utility systems. Superconducting magnetic energy storage (SMES) is based upon the phenomenon of the nearly lossless behavior of superconductors. Application is, in principal, efficient since the electromagnetic energy can be transferred to and from the storage coils without any intermediate conversion to other energy forms. Results from a reference design for a 10-GWh SMES unit for load leveling are presented. The conceptual engineering design of a 30-MJ, 10-MW energy storage coil is discussed with regard to system stabilization, and tests of a small scale, 100-KJ SMES system are presented. Some results of experiments are provided from a related technology based program which uses superconducting inductive energy storage to drive fusion plasmas.
Date: January 1, 1978
Creator: Rogers, J.D.; Boenig, H.J.; Hassenzahl, W.V. & Schermer, R.I.
Partner: UNT Libraries Government Documents Department

Thermo-hydraulic analysis of the TPX superconducting TF magnets

Description: The superconducting magnets in Fusion Reactors are subjected to pulsed, nuclear, and resistive heating. The thermo-hydraulic response of the helium forced-flow cooled conductors to the various heat sources is critical to magnet design and performance. Recently developed computer codes allow accurate modeling of conductor response and have been used as an aid to design of the toroidal field (TF) magnets for the Tokamak Physics eXperiment (TPX). The authors present results of design studies that determine the trade-off between double- and single-pancake helium-flow configurations.
Date: October 6, 1993
Creator: Wong, R. L.; Zbasnik, J. P. & Hassenzahl, W. V.
Partner: UNT Libraries Government Documents Department

Thermo-hydraulic analysis of superconducting toroidal-field magnets for the Tokamak Physics Experiment

Description: The superconducting magnets in Fusion Reactors are subjected to pulsed, nuclear, and resistive heating. The thermo-hydraulic response of the helium forced-flow cooled conductors to the various heat sources is critical to magnet design and performance. Recently developed computer codes allow accurate modeling of conductor response and have been used as an aid to design of the toroidal field (TF) magnets for the Tokamak Physics experiment (TPX). We present results of design studies that determine the trade-off between double- and single-pancake helium flow configurations, the minimum-temperature margin, and the stability against rapid heat input. The results guide the choice and design of the liquid helium refrigerator.
Date: July 9, 1993
Creator: Wong, R. L.; Zbasnik, J. P. & Hassenzahl, W. V.
Partner: UNT Libraries Government Documents Department