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Coil winding development support for the Large Coil Program

Description: A coil winding facility at Oak Ridge National Laboratory has been utilized for the practice winding of the type of conductors used in the Large Coil Program (LCP) on a D shaped bobbin that is approximately 2.5 m x 3.0 m. Pancake and layer windings using copper conductors that simulate LCP-type superconductors have been wound both flat and on edge at tensions up to 8500 N. A method has been developed for winding a pancake coil without splicing the conductor. A small pulsed superconducting coil has been fabricated (63.5-mm bore, 7-T field) to illustrate this spliceless pancake method. This coil also demonstrates that by winding several different superconductors simultaneously, grading can be achieved and space and cost can be optimized. A concept is proposed for winding large Nb/sub 3/Sn superconducting coils before reacting, thus avoiding damage from winding stresses after the conductor is brittle. Also described is a method of insulating after winding and reacting.
Date: January 1, 1979
Creator: Brown, R.L.
Partner: UNT Libraries Government Documents Department

Magnetic field, vector potential, and their partial derivatives due to a current-carrying straight wire of finite length

Description: A numerical study is made of a problem dealing with calculation of the magnetic field B vector, the magnetic vector potential A vector, and first partial derivatives of the B vector field and A vector components for two kinds of magnetic sources: (1) current-carrying straight wire of finite length; and (2) current-carrying closed polygon. No restrictions are imposed on the type of the polygon and hence it need not be plane and can consist of arbitrary number of straight wires of arbitrary lengths. Separate consideration of the polygon case makes the numerical procedure more efficient than that based on the linear superposition of the straight-wire sources. All necessary quantities are derived analytically in simple and closed forms without use of any approximations and exact relations are utilized to the greatest possible extent to give an efficient algorithm. Thus, the involved numerical procedures are quite simple, fast, accurate, and straightforward. Results are given in four different coordinate systems (cartesian, cylindrical, spherical, and local toroidal) and results in any other orthogonal coordinates can be obtained with only a few minor modifications.
Date: December 1, 1981
Creator: Lee, D.K.
Partner: UNT Libraries Government Documents Department

Optimization of a bundle divertor for FED

Description: Optimal double-T bundle divertor configurations have been obtained for the Fusion Engineering Device (FED). On-axis ripple is minimized, while satisfying a series of engineering constraints. The ensuing non-linear optimization problem is solved via a sequence of quadratic programming subproblems, using the VMCON algorithm. The resulting divertor designs are substantially improved over previous configurations.
Date: January 1, 1982
Creator: Hively, L.M.; Rothe, K.E. & Minkoff, M.
Partner: UNT Libraries Government Documents Department

Compressed magnetic flux amplifier with capacitive load

Description: A first-order analysis is presented for a compressed magnetic flux (CMF) current amplifier working into a load with a capacitive component. Since the purpose of the investigation was to gain a general understanding of the arrangement, a number of approximations and limitations were accepted. The inductance of the transducer varies with time; the inductance/resistance/capacitance (LRC) circuit therefore is parametric and solutions are different for the stable regime (high C), the oscillation regime (low C), and the transition case. Solutions and performance depend strongly on circuit boundary conditions, i.e., energization of the circuit by either an injected current or by an applied capacitor charge. The behavior of current and energy amplification for the various cases are discussed in detail. A number of experiments with small CMF devices showed that the first-order theory presented predicts transducer performance well in the linear regime.
Date: March 1, 1980
Creator: Stuetzer, O.M.
Partner: UNT Libraries Government Documents Department

Assembly and installation of the large coil test facility test stand

Description: The Large Coil Test Facility (LCTF) was built to test six tokamak-type superconducting coils, with three to be designed and built by US industrial teams and three provided by Japan, Switzerland, and Euratom under an international agreement. The facility is designed to test these coils in an environment which simulates that of a tokamak. The heart of this facility is the test stand, which is made up of four major assemblies: the Gravity Base Assembly, the Bucking Post Assembly, the Torque Ring Assembly, and the Pulse Coil Assembly. This paper provides a detailed review of the assembly and installation of the test stand components and the handling and installation of the first coil into the test stand.
Date: January 1, 1983
Creator: Queen, C.C. Jr.
Partner: UNT Libraries Government Documents Department

Radial electric fields from larmor radius effects in the field-reversed theta pinch

Description: The generation of radial electric field from the different Larmor radii between the diffusing ions and electrons in Field-Reversed Theta Pinch (FR theta P) has been evaluated by developing a new computer code, FLR. The code treats the background electrons at point particles, while for large-orbit ions the effects of finite Larmor radius are incorporated into an accurate density formulation. This is necessary since in a small device whose size is comparable to an ion gyroradius (e.g., FR theta P) most ions will contribute to the density over a fairly large region of the plasma. The actual ion density at any point in the plasma represents a time-averaged contribution from all particles whose gyro-orbits pass through that point. The FLR code has predicted the electric field strengths between 10/sup 3/ and 10/sup 4/ volts/cm, which is in good agreement with the experimental values of FRX-A measurements which correspond roughly to the order of 10/sup 3/ volts/cm.
Date: January 1, 1980
Creator: Hu, Y.
Partner: UNT Libraries Government Documents Department

Hamiltonian mechanics and divergence-free fields

Description: The field lines, or integral curves, of a divergence-free field in three dimensions are shown to be topologically equivalent to the trajectories of a Hamiltonian with two degrees of freedom. The consideration of fields that depend on a parameter allow the construction of a canonical perturbation theory which is valid even if the perturbation is large. If the parametric dependence of the magnetic, or the vorticity field is interpreted as time dependence, evolution equations are obtained which give Kelvin's theorem or the flux conservation theorem for ideal fluids and plasmas. The Hamiltonian methods prove especially useful for study of fields in which the field lines must be known throughout a volume of space.
Date: August 1, 1986
Creator: Boozer, A.H.
Partner: UNT Libraries Government Documents Department

High current density, cryogenically cooled sliding electrical joint development

Description: In the past two years, conceptual designs for fusion energy research devices have focussed on compact, high magnetic field configurations. The concept of sliding electrical joints in the large magnets allows a number of technical advantages including enhanced mechanical integrity, remote maintainability, and reduced project cost. The rationale for sliding electrical joints is presented. The conceptual configuration for this generation of experimental devices is highlghted by an approx. 20 T toroidal field magnet with a flat top conductor current of approx. 300 kA and a sliding electrical joint with a gross current density of approx. 0.6 kA/cm/sup 2/. A numerical model was used to map the conductor current distribution as a function of time and position in the conductor. A series of electrical joint arrangements were produced against the system code envelope constraints for a specific version of the Ignition Studies Project (ISP) which is designated as 1025.
Date: September 1, 1986
Creator: Murray, H.
Partner: UNT Libraries Government Documents Department

Simulation of poloidal divertors in one-dimensional tokamak transport codes

Description: The two-dimensional effect of plasma flow along the field lines in the scrape-off zone of a poloidal divertor has been modeled phenomenologically in a one-dimensional tokamak transport code. Some results of the profiles in the scrape-off zone, as well as in the main plasma, are given in this paper. These calculations suggest some approximations, which have been used to develop a zero-dimensional model of the divertor.
Date: April 1, 1978
Creator: Mense, A. T. & Emmert, G. A.
Partner: UNT Libraries Government Documents Department

Dynamo theory: can amplification of magnetic-field profiles arise from a cross-field alpha effect

Description: The answer to the title question is here provided in cylindrical geometry for an essentially arbitrary radial dependence of this alpha effect, except that it is subject to a simple, physically required constraint. The interest in this type of alpha effect derives from its connection with compressible turbulence, which is usually not considered in kinematic dynamo theory.
Date: April 1, 1982
Creator: Gerwin, R. & Keinigs, R.
Partner: UNT Libraries Government Documents Department

Ohm's law for mean magnetic fields

Description: Spatially complicated magnetic fields are frequently treated as the sum of a large, slowly varying, mean field and a small, rapidly varying, field. The primary effect of the small field is to modify the Ohm's law of the mean field. A set of plausible assumptions leads to a form of the mean field Ohm's law which is fundamentally different from the conventional alpha effect of dynamo theory.
Date: November 1, 1984
Creator: Boozer, A.H.
Partner: UNT Libraries Government Documents Department

Programmer's guide to FFE: a fast front-end data-acquisition program

Description: The Large Coil Test Facility project of the Fusion Energy Division has a data acquisition system which includes a large host computer and several small, peripheral front-end computers. The front-end processors handle details of data acquisition under the control of the host and pass data back to the host for storage. Some of the front ends are known as fast front ends and are required to collect a maximum of 64,000 samples each second. This speed and other hardware constraints resulted in a need for a stand-alone, assembly language task which could be downline loaded from the host system into the fast front ends. FFE (Fast Front End) was written to satisfy this need. It was written in the PDP-11 MACRO-11 assembly language for an LSI-11/23 processor. After the host loads the task into the front end, it controls the data acquisition process with a series of commands and parameters. This Programmer's Guide describes the structure and operation of FFE in detail from a programming point of view. A companion User's guide provides more information on the use of the program from the host system.
Date: May 1, 1983
Creator: Million, D.L.
Partner: UNT Libraries Government Documents Department

Model for magnetic reconnection

Description: A forced reconnection problem was modeled by two infinite wires that are embedded in a plasma which carry parallel currents. They are brought together at a specified rate. The distance between the wires is taken as 2a(1-e/sup ..omega..t/). For small displacements, the hydromagnetic equations can be linearized and solved asymptotically. For larger displacements, the plasma behavior can be estimated by use of scaling arguments. We determine a local velocity of magnetic reconnection and show that it is essentially equal to the maximum possible reconnection velocity (that of the corresponding vacuum case) up to the time when this velocity approaches the local Alfven speed. We compare the details of our solution with the Sweet-Parker and Petschek reconnection theories.
Date: March 1, 1978
Creator: Adler, E.A. & Kulsrud, R.M.
Partner: UNT Libraries Government Documents Department

Comparative anatomy of dipole magnets or the magnet designer's coloring book

Description: A collection of dipole magnet cross sections is presented together with an indication of how they are related geometrically. The relationships indicated do not necessarily imply the actual path of evolutionary development. Brief consideration is given to magnets of higher multipole order, i.e., quadrupole magnets, etc.). The magnets under consideration have currents parallel to the axis except at the ends, and are long. The relationship between current distribution and magnetic field is essentially two-dimensional. The coils are usually surrounded by an iron yoke, but the emphasis is on conductor-dominated configurations capable of producing a rather uniform magnetic field in the aperture; the iron usually has a small effect.
Date: April 1, 1983
Creator: Meuser, R.B.
Partner: UNT Libraries Government Documents Department

Analysis of quench-vent pressures for present design of ITER (International Thermonuclear Experimental Reactor) TF (toroidal field) coils

Description: The International Thermonuclear Experimental Reactor (ITER) is a new tokamak design project with joint participation from Japan, the European Community, the Union of the Soviet Union, and the United States. This paper examines the effects of a quench within the toroidal field (TF) coils based on current ITER design. It is a preliminary, rough analysis. Its intent is to assist ITER designers while more accurate computer codes are being developed and to provide a check against these more rigorous solutions. Rigorous solutions to the quench problem are very complex involving three- dimensional heat transfer, extreme changes in heat capacities and copper resistivity, and varying flow dynamics within the conductors. This analysis addresses all these factors in an approximate way. The result is much less accurate than a rigorous analysis. Results here could be in error as much as 30 to 40 percent. However, it is believed that this paper can still be very useful to the coil designer. Coil pressures and temperatures vs time into a quench are presented. Rate of helium vent, energy deposition in the coil, and depletion of magnetic stored energy are also presented. Peak pressures are high (about 43 MPa). This is due to the very long vent path length (446 m), small hydraulic diameters, and high current densities associated with ITER's cable-in-conduit design. The effects of these pressures as well as the ability of the coil to be self protecting during a quench are discussed. 3 refs., 1 fig., 3 tabs.
Date: September 20, 1989
Creator: Slack, D.S.
Partner: UNT Libraries Government Documents Department

Recent progress on the HESS (High Explosive Spheromak Source) experiment

Description: The new objective of the Los Alamos spheromak program is to assess the use of magnetized plasmas as an energy transfer medium to accelerate material objects to hyper-velocities ({approx gt} 20 km/s). In meeting this objective, we are committed to the subordinate goals of creating high field, long-lived spheromak discharges, examining the technical feasibility of employing High Explosives (HE) to compress seed spheromaks, and investigate the technical requirements involved in forming spheromaks by Mechanical Helicity Injection (MHI) using HE. This paper describes the recent efforts of the CTR-5, M-4, and M-6 groups at Los Alamos in assessing the feasibility of generating magnetic helicity by mechanical means in the High Explosive Spheromak Source (HESS) experiment. 3 refs., 3 figs.
Date: January 1, 1989
Creator: Mayo, R.M.; Barnes, D.C.; Freeman, B.; Henins, I.; Jarboe, T.R.; Platts, D. (Los Alamos National Lab., NM (USA) et al.
Partner: UNT Libraries Government Documents Department

Transient voltage oscillations in coils

Description: Magnet coils may be excited into internal voltage oscillations by transient voltages. Such oscillations may electrically stress the magnet's dielectric components to many times its normal stress. This may precipitate a dielectric failure, and the attendant prolonged loss of service and costly repair work. Therefore, it is important to know the natural frequencies of oscillations of a magnet during the design stage, and to determine whether the expected switching transient voltages can excite the magnet into high-voltage internal oscillations. The series capacitance of a winding significantly affects its natural frequencies. However, the series capacitance is difficult to calculate, because it may comprise complex capacitance network, consisting of intra- and inter-coil turn-to-turn capacitances of the coil sections. A method of calculating the series capacitance of a winding is proposed. This method is rigorous but simple to execute. The time-varying transient voltages along the winding are also calculated.
Date: January 1, 1985
Creator: Chowdhuri, P.
Partner: UNT Libraries Government Documents Department

FRC formation studies with Z-discharge ionization on FRX-C

Description: Recent exploratory operation at high-bias levels on FRX-C is discussed. The motivation of these in situ formation studies was to explore the use of Z-discharge ionization (Z-PI) for achieving larger trapped poloidal flux and commensurately large x/sub s/ values, where x/sub s/ is the ratio of the separatrix radius r/sub s/ to the coil radius r/sub c/. Such studies are of interest in ascertaining predicted improvements of particle confinement and degradation of stability with the associated increase of anti s, the approximate number of ion gyroradii across the minor radius of the FRC. The results of these studies may be summarized briefly as: (1) the Z-PI worked well in conjunction with conventional theta-PI to extend the level of trapped flux at high fill pressure (20 mtorr), but the Z-PI worked poorly at low fill pressure (5 mtorr), and (2) increased trapped flux at 5 mtorr quickly led to degradation of the flux lifetime and no significant increase in x/sub s/, while at 20 mtorr the initial value of x/sub s/ was increased significantly but with degraded flux lifetimes.
Date: January 1, 1985
Creator: Armstrong, W.T.; Chrien, R.E.; Hugrass, W.; Klingner, P.L.; McKenna, K.F.; Milroy, R.D. et al.
Partner: UNT Libraries Government Documents Department

Startup of Large Coil Test Facility

Description: The Large Coil Test Facility (LCTF) is being used to test superconducting toroidal field coils about one-third the size of those for INTOR. Eventually, six different coils from four countries will be tested. Operations began in 1983 with acceptance testing of the helium refrigerator/liquefier system. Comprehensive shakedown of the facility and tests with the first three coils (from Japan, the United States, and Switzerland) were successfully accomplished in the summer of 1984. Currents up to 10,200 A and fields up to 6.4 T were reached. Data were obtained on performance of refrigerator, helium distribution, power supplies, controls, and data acquisition systems and on the acoustic emission, voltages, currents, and mechanical strains during charging and discharging the coils.
Date: January 1, 1984
Creator: Haubenreich, P.N.; Bohanan, R.E.; Fietz, W.A.; Luton, J.N. & May, J.R.
Partner: UNT Libraries Government Documents Department

Design considerations for ITER (International Thermonuclear Experimental Reactor) toroidal field coils

Description: The International Thermonuclear Experimental Reactor (ITER) is a new tokamak design project with joint participation from Europe, Japan, the Union of Soviet Socialist Republics (USSR), and the United States. This paper describes a magnetic and mechanical design methodology for toroidal field (TF) coils that employs Nb/sub 3/Sn superconductor technology. Coil winding is sized by using conductor concepts developed for the US TIBER concept. The nuclear heating generated during operation is removed from the windings by helium flowing through the conductor. The heat in the coil case is removed through a separate cooling circuit operating at approximately 20 K. Manifold concepts are presented for the complete coil cooling system. Also included are concepts for the coil structural arrangement. The effects of in-plane and out-of-plane loads are included in the design considerations for the windings and case. Concepts are presented for reacting these loads with a minimum amount of additional structural material. Concepts discussed in this paper could be considered for the ITER TF coils. 6 refs., 5 figs., 1 tab.
Date: January 1, 1987
Creator: Kalsi, S.S.; Lousteau, D.C. & Miller, J.R.
Partner: UNT Libraries Government Documents Department

Influence of dump voltage and allowable temperature rise on stabilizer requirements in superconducting coils

Description: A superconducting winding must have enough stabilizer to satisfy two sets of criteria. During normal operation, the amount of stabilizer must be large enough either to make the coil unconditionally stable or to give a certain desired stability margin. Once a dump occurs, the amount of stabilizer must be large enough to carry the current without generating excessive dump voltages or allowing the winding to exceed a certain maximum temperature (and maximum pressure, in the case of force-cooled coils). The voltage criterion often dominates for very large coil systems, but it is frequently ignored in initial design studies. This paper gives some simple relations between the dump voltage and the stored energy, temperature rise, and coil geometry that are useful in scooping the required amount of stabilizer. Comparison with some recently proposed fusion magnet system designs indicates that excessive dump voltages could result in some cases. High-temperature superconductors may require more stabilizer than the conventional alloys. Calculations with simple model coil systems indicate how trade-offs between various coil parameters affect the dump voltage. 12 refs., 1 fig., 1 tab.
Date: January 1, 1988
Creator: Schwenterly, S.W.
Partner: UNT Libraries Government Documents Department