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Quasi-continuous magnets

Description: The National High Magnetic Field Laboratory is completing a quasi-continuous magnet which will sustain a constant field of 60 T for 100 ms in a 32-mm 77 K bore. This magnet consists of 9 mechanically independent, nested, liquid nitrogen-cooled coils which are individually reinforced by high-strength stainless steel outer shells. The coils were wound from rectangular large cross-section, high-strength, high-conductivity copper conductor insulated wtih polyimide and fiberglass tapes. After winding, the coils were inserted into closely fitted, stainless steel reinforcing shells and impregnated with epoxy resin. Design, analysis, material, fabrication and operational issues for this class of magnets are reviewed. Fabrication and quality assurance testing of the 60 T coil set are covered in detail. Future growth of and possible links from this technology to other magnet systems are discussed. Needed improvements in design, analysis, materials, and fabrication are outlined.
Date: May 1, 1996
Creator: Sims, J.R.; Naumovich, G.J.; Hoang, T.A. & Dent, P.C.
Partner: UNT Libraries Government Documents Department

The {open_quotes}INVERSE PROBLEM{close_quotes} to the evaluation of the magnetic fields

Description: In the design of superconducting magnet elements, such as may be required to guide and focus ions in a particle accelerator, one frequently premises some particular current distribution and then proceeds to compute the consequent magnetic field through use of the laws of Blot and Savart or of Ampere. When working in this manner one of course may need to revise frequently the postulated current distribution before arriving at a resulting magnetic field of acceptable field quality. It therefore is of interest to consider an alternative ({open_quotes}inverse{close_quotes}) procedure in which one specifies a desired character for the field required in the region interior to the winding and undertakes then to evaluate the current distribution on the specified winding surface that would provide this desired field. By evaluating the specified potential in the region interior to the winding along the interface, the authors have determined that a relaxation solution to the potential in the region outside the winding can be converged and used to calculate wire location. They have demonstrated this method by applying a slightly modified version of the program POISSON to a periodic alternating sinusoidal quadrupole field.
Date: June 1, 1995
Creator: Caspi, S.; Helm, M. & Laslett, L.J.
Partner: UNT Libraries Government Documents Department

Magnet coil electrical gaskets of high compliance and ampacity

Description: Coils employed in the magnets of the PHENIX Detector, presently under construction for RHIC (Relativistic Heavy Ion Collider) at the Brookhaven National Laboratory, are massive (weight {approximately} 8000 kG each). For that reason we subdivided them into a series of manageable subcoils that we will subsequent bolt together. Electrical terminals attached to the subcoils conductors are rigidly embedded and precisely located during vacuum impregnation. However; we anticipate some misalignment and nonuniform gaping to occur between terminals at assembly. We have elected to use electrical gaskets of compliance and ampacity between the bolted terminals to enhance the current carrying capability of the electrical joints. This paper describes the material candidates selected, the tests performed, and the relative ranking of the materials tested.
Date: May 17, 1995
Creator: Harvey, A.R. & Yamamoto, R.M.
Partner: UNT Libraries Government Documents Department

Design of a coil to correct magnetic field errors on the DIII-D tokamak

Description: Small toroidally asymmetric errors on the ideally symmetric magnetic field of a tokamak are of concern for the design of next-generation devices and the performance of existing machines. Errors as small as one part in 10{sup 4} or less can be enough to cause detrimental effects on the stability and confinement of the plasma. Previously, we have used a simple perturbation coil mounted on top of the DIII-D tokamak (``n = 1 coil``) to enhance or partially reduce the error fields, resulting in significant effects on the stability of the plasma. Recently, careful measurements were made of the error fields created by the 18 field-shaping coils on DIII-D. Spectral analysis has yielded a better understanding of the source of the toroidal and poloidal field errors existing on the tokamak. With this new information, a much better error-field correction coil (``C-coil``) has been designed which should be able to nearly eliminate the m=2, n=1 component of the error field without introducing other toroidal modes. By dividing the C-coil into segments which can be connected in different configurations, we will be able to program the phase and amplitude of a variety of perturbation fields for experimentation. Alternatively, the coil can be configured and programmed to provide the maximum reduction of error fields for routine plasma operations, enabling a wider stable operating parameter space for the tokamak. Details of the C-coil design and its harmonic spectrum are presented.
Date: November 1, 1991
Creator: Scoville, J. T. & LaHaye, R. J.
Partner: UNT Libraries Government Documents Department

Center column design of the PLT

Description: The center column of the PLT machine is a secondary support member for the toroidal field coils. Its purpose is to decrease the bending moment at the nose of the coils. The center column design was to have been a stainless steel casting with the toroidal field coils grouped around the casting at installation, trapping it in place. However, the castings developed cracks during fabrication and were unsuitable for use. Installation of the coils proceeded without the center column. It then became necessary to redesign a center column which would be capable of installation with the toroidal field coils in place. The final design consists of three A-286 forgings. This paper discusses the final center column design and the influence that new knowledge, obtained during the power tests, had on the new design. (auth)
Date: January 1, 1975
Creator: Citrolo, J. & Frankenberg, J.
Partner: UNT Libraries Government Documents Department

Application data for the PLT stabilizing field rectifier

Description: This paper describes the 12-pulse stabilizing field rectifier used for vertical field production in the Princeton Large Torus (PLT). It is essential that the rectifier be reliable, and protect itself from all faults including induced transient overvoltage produced by switching and plasma instabilities. To this end, computer simulations were run to insure protection under various fault conditions. (auth)
Date: November 1, 1975
Creator: Bronner, G.; Murray, J.G. & Oliaro, G.E.
Partner: UNT Libraries Government Documents Department

Uncertainties in calculated heating and radiation damage in the toroidal field coil of a tokamak experimental power reactor due to neutron cross-section errors

Description: Calculated results are presented of the uncertainties in the neutron scalar flux, the energy deposition per unit volume, and the displacements per atom in the toroidal field coil of a tokamak experimental power reactor due to neutron cross-section errors in iron and carbon which are major constituents of the blanket-shield-coil configuration considered. The calculations were carried out using perturbation theory to obtain sensitivity profiles for the various cross sections of interest, and these profiles were then combined with cross- section error estimates, including correlations, to obtain the uncertainties. Each of the three responses--the neutron scalar flux, the energy deposition per unit volume, and the displacements per atom--is found to be very sensitive to the cross sections in the energy group which contains the source (approximately 14 MeV since a D-T source is assumed), and each of the responses is found to have a relative standard deviation of approximately 100 percent due to neutron cross- section errors in iron.
Date: March 1, 1976
Creator: Alsmiller, R.G. Jr.; Barish, J. & Weisbin, C.R.
Partner: UNT Libraries Government Documents Department

Discrete coil torus with lower field ripple

Description: A new toroidal field coil configuration is described which allows one to reduce the volume of a toroidal field coil system or the number of coils constituting such a system without increasing the toroidal field ripple. (auth)
Date: October 1, 1975
Creator: Sheffield, G.V.
Partner: UNT Libraries Government Documents Department

Test facility for PLT TF coils

Description: Past experience with the model C stellerator and other toroidal field devices indicates that mechanical and electrical tests of a toroidal field coil prior to maximum field operation of the device is prudent and desirable. This paper describes a test program for the PLT-TF coils. The test stand consists of one test coil, two background coils and a steel supporting structure. The three coil configuration produces a 67.5 kG field at the inner conductor (38 kG at the bore center) and simulates a 1/R field distribution in the bore of the test coil. The resolution of the field force system and resultant stresses within the test structure are discussed. A test procedure is described which maximizes the information obtained from a 100,000 pulse program. (auth)
Date: January 1, 1975
Creator: Hearney, J.; File, J. & Dreskin, S.
Partner: UNT Libraries Government Documents Department

PDX toroidal field coils stress analysis

Description: A method used in the stress analysis of the PDX toroidal field coil is developed. A multilayer coil design of arbitrary dimensions in the shape of either a circle or an oval is considered. The analytical model of the coil and the supporting coil case with connections to the main support structure is analyzed using the finite element technique. The three dimensional magnetic fields and the non-uniform body forces which are a loading condition on a coil due to toroidal and poloidal fields are calculated. The method of analysis permits rapid and economic evaluations of design changes in coil geometry as well as in coil support structures. Some results pertinent to the design evolution and their comparison are discussed. The results of the detailed stress analysis of the final coil design due to toroidal field, poloidal field and temperature loads are presented. (auth)
Date: January 1, 1975
Creator: Nikodem, Z. D. & Smith, R. A.
Partner: UNT Libraries Government Documents Department

Stress analysis of PLT coil

Description: The toroidal field coils of tokamak devices create a field within the torus whose strength varies inversely with distance from the machine center. This field, crossing the current in the TF coils, creates a magnetic pressure on the coil. The pressure produces a net inward centering force, countered by pressure on the wedge face, and a vertical separating force, causing tensile stress across the horizontal mid-plane. In the past these forces have been analyzed by superposition and beam theory. Because of the size and complexity of the PLT machine it was decided to also initiate a finite element analysis of the coil. This paper describes both methods of analysis. (auth)
Date: January 1, 1975
Creator: Frankenberg, J. & Smith, R. A.
Partner: UNT Libraries Government Documents Department

Analyses of laminated beams for us in coil design

Description: Recent experimental data obtained from PLT has shown that equivalent beam theory is inadequate for predicting the deformation of large circular toroidal field coils. The PLT coils are much more flexible than equivalent beam theory predicts. The latest analyses have shown that shear plays an important role in the deformation of the PLT TF coils. This situation has indicated the need to analyze in explicit detail, the layer to layer behavior of simple laminated structures. The progress made to date in analyzing a laminated beam is summarized. By using variational techniques, the deflections and stresses in each layer of a laminated beam are modeled. To date, reasonable results have been obtained for either deflection or stress separately but a single model that simultaneously gives good agreement for both deflection and stress has not yet been determined. Brief descriptions of the mathematical models used and the results obtained with each are presented. (auth)
Date: January 1, 1975
Creator: Bialek, J.
Partner: UNT Libraries Government Documents Department

PLT toroidal field coil power tests

Description: The PLT toroidal field coil power tests were initiated in October, 1974 to gain information in several areas. The most important objectives during the tests were the verification of deflections and stresses as predicted by Frankenberg and Smith. Also, the stability of the toroidal field coils against radial self-field loading was to be determined. Lastly, the predicted thermal characteristics of the coils were to be verified. (auth)
Date: November 1, 1975
Creator: Marino, R.; Citrolo, J. & Frankenberg, J.
Partner: UNT Libraries Government Documents Department

Analytic solutions for constant tension coil shapes

Description: An analytical solution of the differential equation describing the shape of a flexible filamentary conductor (incapable of supporting bending stresses) in a toroidal magnetic field has been obtained. The solution derives from a series expansion of modified Bessel functions of integer order. The characteristics of toroidal field magnets for proposed tokamak devices are obtainable by term by term integration of the solution series. General expressions are given for the following coil characteristics: the conductor turn length, the solenoid inductance, the area enclosed by the coil and the coil support dimensions. For several particular cases of interest these coil characteristics are obtained as closed form analytical formula. (auth)
Date: January 1, 1976
Creator: Gralnick, S.L. & Tenney, F.H.
Partner: UNT Libraries Government Documents Department

Three-dimensional mechanical stresses in toroidal magnets for controlled thermonuclear reactors

Description: From fifth symposium on engineering problems of fusion research; Princeton, New Jersey, USA (6 Nov 1973). It appears that, when considering the field limits of toroidal superconducting magnets, the mechanical stresses on the coils will be a primary limitation. The results of a detailed analysis of the forces and resultant stresses imposed on the magnet coils are presented. Two coil geometries have been analyzed; the circular coil toroid similar to the Oak Ridge design, and the D'' shaped coil similar to the design proposed by the Princeton Plasma Physics Laboratory. Stresses calculated by a three-dimensional analysis are presented for the coils under normal and abnormal operating conditions. The abnormal condition considered is the unexpected quench'' of an adjacent coil resulting in asymmetric magnetic fields. The three-dimensional magnetic fields, within the current-carrying conductors, were calculated to determine the body forces. A three-dimensional, finite-element elastic stress analysis code, SOLID SAP'', was used to evaluate the resultant mechanical stresses. (23 figures) (auth)
Date: January 1, 1973
Creator: DeMichele, D.W. & Darby, J.B. Jr.
Partner: UNT Libraries Government Documents Department

Influence of the between-the-turns thermal insulation on the duty of a large, liquid-cooled pulsed coil

Description: From fifth symposium on engineering problems of fusion research; Princeton, New Jersey, USA (6 Nov 1973). The moving cold front set up by good thermal insulation between the coil turns efficiently sweeps the heat from the conductor. A quantitative description of this effect is given. The toroidal field coils of the ORMAK machines are used as an example, but the discussion is applicable to any liquid-cooled coil made from hollow conductors. (MOW)
Date: January 1, 1973
Creator: Derby, R.W.
Partner: UNT Libraries Government Documents Department

Design and fabrication of the PDX poloidal field solenoid utilizing fiberglass reinforced epoxy

Description: This paper discusses the basic design of the Poloidal Field Solenoid Coil. It will be mainly concerned with the more unique features of the Solenoid such as the copper coil windings and the design of the epoxy-glass structural support mandrels. The center solenoid coil of the PDX machine consists of five different coil systems (OH No. 8, No. 9; NF No. 11; DF No. 7; EF Solenoid and CF No. 9). Three concentric fiberglass reinforced epoxy cylinders fabricated in- house will act as mandrels to support and to house the coils that will result as an integral unit. (auth)
Date: November 1, 1975
Creator: Young, K.S.C.
Partner: UNT Libraries Government Documents Department

250-kG mirror coil development for the linear Scyllac experiment

Description: The linear Scyllac theta-pinch machine required mirror coils on each end of the 5-m-long lead coil, which would give mirror ratios of two to three times the 100-kG main coil magnetic field. A pulsed magnetic field of 250 RG was established as a design goal for the mirror coils. Several different designs were evaluated using the 178- kJ, 80-kV Scyllac prototype capacitor bank. Calculations were made to determine the coil geometry for each 250-kG cotl design. A copper-lined, steel-jacketed coil, and an all steel coil were fabricated and tested (4 to 5 cm bores). The types of materials selected for each coli, strength considerations, and fabricating techniques are discussed. The final design of the mirror coils for the 11.2-cm-bore Scyllac machine was established using an all-steel (Maraging type 250) design. An aluminium coil (2014-T652) was built and tested to failure in order to establish data as to the maximum fields that aluminum coils could be subjected to in a typical pulsed theta-pinch evironment. This program and conclusions are discussed. (auth)
Date: January 1, 1973
Creator: Hanks, K.W.; Boicourt, G.P. & Bailey, A.G.
Partner: UNT Libraries Government Documents Department