Science.gov

Sample records for poloidal field coils

  1. Conceptual Design of Alborz Tokamak Poloidal Coils System

    NASA Astrophysics Data System (ADS)

    Mardani, M.; Amrollahi, R.

    2013-04-01

    The Alborz tokamak is a D-shape cross section tokamak that is under construction in Amirkabir University of Technology. One of the most important parts of tokamak design is the design of the poloidal field system. This part includes the numbers, individual position, currents and number of coil turns of the magnetic field coils. Circular cross section tokamaks have Vertical Field system but since the elongation and triangularity of plasma cross section shaping are important in improving the plasma performance and stability, the poloidal field coils are designed to have a shaped plasma configuration. In this paper the design of vertical field system and the magnetohydrodynamic equilibrium of axisymmetric plasma, as given by the Grad-Shafranov equation will be discussed. The poloidal field coils system consists of 12 circular coils located symmetrically about the equator plane, six inner PF coils and six outer PF coils. Six outer poloidal field coils (PF) are located outside of the toroidal field coils (TF), and six inner poloidal field coils are wound on the inner legs and are located outside of a vacuum vessel.

  2. PC-based package for interactive assessment of MHD equilibrium and poloidal field coil design in axisymmetric toroidal geometry

    SciTech Connect

    Kelleher, W.P.

    1987-01-01

    In the assessment of Magnetohydrodynamic (MHD) equilibrium and Poloidal Field Coil (PFC) arrangement for toroidal axisymmetric geometry, the Grad-Shafranov equation must be solved, either analytically or numerically. Existing numerical tools have been developed primarily for mainframe usage and can prove cumbersome for screening assessments and parametric evaluations. The objective of this thesis was to develop a personal computer (PC)-based calculational tool for assessing MHD/PFC problems in a highly interactive mode, well suited for scoping studies. The approach adopted involves a two-step process: first the MHD equilibrium is calculated and then the PFC arrangement, consistent with the equilibrium, is determined in an interactive design environment. The PC-based system developed consists of two programs: (1) PCEQ, which solve the MHD equilibrium problem and (2) PFDE-SIGN, which is employed to arrive at a PFC arrangement. PCEQ provides an output file including, but not limited to, the following: poloidal beta, total beta, safety factors, q, on axis and on edge. PCEQ plots the following contours and/or profiles: flux, pressure and toroidal current density, safety factor, and ratio of plasma toroidal field to vacuum field.

  3. A method for determining poloidal coil configurations for tokamak devices

    SciTech Connect

    Evans, K. Jr.

    1990-12-01

    This paper presents a method for obtaining the locations and currents of the poloidal coil systems for a tokamak, given an desirable magnetohydrodynamic equilibrium for the device. The method involves a simultaneous minimization of the match to the desired poloidal field and the stored energy in the coils, subject to the constraints necessary to achieve decoupling of the equilibrium and inductive-current-drive (ohmic-heating) systems and to achieve a given coupling of the current-drive system with the plasma. A compendium of mutual and self-inductance formulas as they apply to tokamak systems is presented, as well as examples of how the method has been used in the design of several tokamaks. Finally, a user manual for a computer code that implements this method is provided. 14 refs., 11 figs., 1 tab.

  4. EU contribution to the test and analysis of the ITER poloidal field conductor insert and the central solenoid model coil

    NASA Astrophysics Data System (ADS)

    Zanino, R.; Bagnasco, M.; Ciazynski, D.; Lacroix, B.; van Lanen, E. P. A.; Nicollet, S.; Nijhuis, A.; Savoldi Richard, L.; Sborchia, C.; Torre, A.; Vostner, A.; Zani, L.

    2009-08-01

    The PFCI is a single-layer solenoid wound from a 45 m long ITER-type NbTi dual-channel cable-in-conduit conductor, designed to be representative of the one currently proposed for the ITER PF1&6 coils. The PFCI, installed in the bore of the ITER central solenoid model coil (CSMC) at JAEA Naka, Japan, and well instrumented from both the thermal hydraulic and the electromagnetic points of view, has been successfully tested in June-August 2008. The test concentrated on DC performance (current sharing temperature and critical current measurements) and AC loss measurements. The results of the analysis of those measurements are reported in the paper, with particular attention to the comparison with the PFCI short sample, which was previously tested in the SULTAN facility. The evolution of the DC performance of the CSMC is also discussed.

  5. NCSX Toroidal Field Coil Design

    SciTech Connect

    Kalish, M.; Rushinski, J.; Myatt, L.; Brooks, A.; Dahlgren, F.; Chrzanowski, J.; Reiersen, W.; Freudenberg, K.

    2005-10-07

    The National Compact Stellarator Experiment (NCSX) is an experimental device whose design and construction is underway at the Department of Energy's Princeton Plasma Physics Laboratory (PPPL). The primary coil systems for the NCSX device consist of the twisted plasma-shaping Modular Coils, the Poloidal Field Coils, and the Toroidal Field (TF) Coils. The TF Coils are D-shaped coils wound from hollow copper conductor, and vacuum impregnated with a glass-epoxy resin system. There are 18 identical, equally spaced TF coils providing 1/R field at the plasma. They operate within a cryostat, and are cooled by LN2, nominally, to 80K. Wedge shaped castings are assembled to the inboard face of these coils, so that inward radial loads are reacted via the nesting of each of the coils against their adjacent partners. This paper outlines the TF Coil design methodology, reviews the analysis results, and summarizes how the design and analysis support the design requirements.

  6. Performance of current measurement system in poloidal field power supply for Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Liu, D. M.; Li, J.; Wan, B. N.; Lu, Z.; Wang, L. S.; Jiang, L.; Lu, C. H.; Huang, J.

    2016-11-01

    As one of the core subsystems of the Experimental Advanced Superconducting Tokamak (EAST), the poloidal field power system supplies energy to EAST's superconducting coils. To measure the converter current in the poloidal field power system, a current measurement system has been designed. The proposed measurement system is composed of a Rogowski coil and a newly designed integrator. The results of the resistor-inductor-capacitor discharge test and the converter equal current test show that the current measurement system provides good reliability and stability, and the maximum error of the proposed system is less than 1%.

  7. Poloidal field amplification in a coaxial compact toroid accelerator

    NASA Astrophysics Data System (ADS)

    Horton, R. D.; Hwang, D. Q.; Howard, S.; Brockington, S. J.; Evans, R. W.

    2008-09-01

    The Compact Toroid Injection Experiment (CTIX) produces spheromak-like compact toroids (SCTs) without external power switching, initiating a discharge by pulsed gas injection into a formation region containing a seed magnetic field generated by a solenoidal coil. After formation, the plasma is driven by an inductively delayed capacitor bank into an acceleration region, where surface axial and toroidal magnetic fields are measured at several axial positions. Due to strong eddy-current effects, formation-region magnetic field cannot be simply computed; instead, it is measured using the response of axial and radial test coils in the formation region to short solenoid test current pulses. A temporal and spatial reconstruction method is developed allowing formation-region field to be computed from the test-coil data for any CTIX discharge of identical solenoid geometry. By varying the peak value and timing of solenoidal current, curves of peak accelerator-region field as a function of initial formation-region field are developed. Curves of peak accelerator-region axial magnetic field are thereby found to be highly nonlinear functions of formation-region field, showing a threshold value for the formation-region field of approximately 5 G, above which acceleration-region field saturates at values between 2 and 12 kG. The direction of acceleration-region axial field reverses sign when the direction of solenoid current is reversed. Saturated accelerator-region axial field is a function of axial position and accelerator voltage, and is typically comparable to toroidal field at the same location. The ratio of accelerator-region to formation-region axial field commonly exceeds 1000 near the onset of saturation. This large amplification is of practical advantage for delayed plasma breakdown on CTIX, allowing a modest seed field to produce high poloidal fields, which are necessary for intense SCT acceleration. The results may also provide a useful benchmark for numerical

  8. Air core poloidal magnetic field system for a toroidal plasma producing device

    DOEpatents

    Marcus, Frederick B.

    1978-01-01

    A poloidal magnetics system for a plasma producing device of toroidal configuration is provided that reduces both the total volt-seconds requirement and the magnitude of the field change at the toroidal field coils. The system utilizes an air core transformer wound between the toroidal field (TF) coils and the major axis outside the TF coils. Electric current in the primary windings of this transformer is distributed and the magnetic flux returned by air core windings wrapped outside the toroidal field coils. A shield winding that is closely coupled to the plasma carries a current equal and opposite to the plasma current. This winding provides the shielding function and in addition serves in a fashion similar to a driven conducting shell to provide the equilibrium vertical field for the plasma. The shield winding is in series with a power supply and a decoupling coil located outside the TF coil at the primary winding locations. The present invention requires much less energy than the usual air core transformer and is capable of substantially shielding the toroidal field coils from poloidal field flux.

  9. Poloidal rotation in tokamaks with large electric field gradients

    SciTech Connect

    Hinton, F.L.; Kim, Y.

    1995-01-01

    The ion poloidal flow velocity near the plasma edge in a tokamak has been calculated by extending neoclassical theory to include orbit squeezing, which is the reduction of the ion banana widths due to radial electric field shear. The pressure gradient-driven ion parallel flow is reduced by orbit squeezing, and then no longer cancels the diamagnetic flow in its contribution to poloidal flow. This allows the poloidal flow velocity to be a significant fraction of the ion diamagnetic velocity, which can be much larger than the standard neoclassical value (proportional to the ion temperature gradient). Equations for determining the poloidal flow and radial electric field profiles self-consistently are given. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. Flux Consumption and Poloidal Magnetic Field Measurements in the MEDUSA TOKAMAK

    NASA Astrophysics Data System (ADS)

    Garstka, G. D.; Fonck, R. J.; Intrator, T.

    1996-11-01

    The Madison EDUcational Small-Aspect-ratio (MEDUSA) tokamak is a small (R=12 cm, a=8 cm) spherical tokamak designed to investigate features of ST plasmas on a laboratory scale. Recent experiments have been performed on MEDUSA to determine the consumption of ohmic flux during startup for several different operating scenarios. The primary diagnostic tool for these experiments was a low profile (0.3 cm diameter) internal magnetic probe array that provided poloidal field measurements crucial to the determination of the plasma internal inductance l_i. This probe consists of five fifteen-turn, 0.9 mm diameter coils. The coils are spaced at 1.5 cm intervals in the z direction at an installed major radius of 12 cm, and measure the radial component of the poloidal field (B_R). The flux consumption analysis was performed using the Poynting method, using the magnetic probe and the MEDUSA external magnetics to reconstruct the evolution of the MHD equilibria during startup. Results will be presented that identify the partition of poloidal flux into inductive and dissipative components. The magnetic probe array was also used to observe the redistribution of plasma current and the corresponding change in li caused by internal reconnection events. Results from these measurements will be presented.

  11. Divertor with a third-order null of the poloidal field

    SciTech Connect

    Ryutov, D. D.; Umansky, M. V.

    2013-09-15

    A concept and preliminary feasibility analysis of a divertor with the third-order poloidal field null is presented. The third-order null is the point where not only the field itself but also its first and second spatial derivatives are zero. In this case, the separatrix near the null-point has eight branches, and the number of strike-points increases from 2 (as in the standard divertor) to six. It is shown that this magnetic configuration can be created by a proper adjustment of the currents in a set of three divertor coils. If the currents are somewhat different from the required values, the configuration becomes that of three closely spaced first-order nulls. Analytic approach, suitable for a quick orientation in the problem, is used. Potential advantages and disadvantages of this configuration are briefly discussed.

  12. POLOIDAL MAGNETIC FIELD TOPOLOGY FOR TOKAMAKS WITH CURRENT HOLES

    SciTech Connect

    Puerta, Julio; Martin, Pablo; Castro, Enrique

    2009-07-26

    The appearance of hole currents in tokamaks seems to be very important in plasma confinement and on-set of instabilities, and this paper is devoted to study the topology changes of poloidal magnetic fields in tokamaks. In order to determine these fields different models for current profiles can be considered. It seems to us, that one of the best analytic descriptions is given by V. Yavorskij et al., which has been chosen for the calculations here performed. Suitable analytic equations for the family of magnetic field surfaces with triangularity and Shafranov shift are written down here. The topology of the magnetic field determines the amount of trapped particles in the generalized mirror type magnetic field configurations. Here it is found that the number of maximums and minimums of Bp depends mainly on triangularity, but the pattern is also depending of the existence or not of hole currents. Our calculations allow comparing the topology of configurations of similar parameters, but with and without whole currents. These differences are study for configurations with equal ellipticity but changing the triangularity parameters. Positive and negative triangularities are considered and compared between them.

  13. Correction of the axial asymmetry of the poloidal magnetic field in the Globus-M spherical tokamak

    SciTech Connect

    Petrov, Yu. V.; Patrov, M. I.; Varfolomeev, V. I.; Gusev, V. K.; Lamzin, E. A.; Sakharov, N. V.; Sychevskii, S. E.

    2010-06-15

    The toroidal inhomogeneity of the poloidal magnetic field-the so-called error fields that arise due to imperfections in manufacturing and assembling of the electromagnetic system-was measured in the Globus-M spherical tokamak. A substantial inhomogeneity corresponding to the n = 1 mode, which gave rise to a locked mode and led to discharge disruption, was revealed. After compensation of this inhomogeneity with the help of special correction coils, the discharge duration increased and the global plasma parameters improved substantially. A technique for determining and compensating the n = 1 mode inhomogeneity is described, the measured dependences of the penetration threshold of the m = 2/n = 1 mode on the plasma parameters are given, and results of experiments in which record parameters for the Globus-M tokamak were achieved after correction of the poloidal magnetic field are presented.

  14. Lower-hybrid poloidal current drive for fluctuation reduction in a reversed field pinch

    SciTech Connect

    Uchimoto, E.; Cekic, M.; Harvey, R.W.; Litwin, C.; Prager, S.C.; Sarff, J.S.; Sovinec, C.R.

    1994-06-01

    Current drive using the lower-hybrid slow wave is shown to be a promising candidate for improving confinement properties of a reversed field pinch (RFP). Ray-tracing calculations indicate that the wave will make a few poloidal turns while spiraling radially into a target zone inside the reversal layer. The poloidal antenna wavelength of the lower hybrid wave can be chosen so that efficient parallel current drive will occur mostly in the poloidal direction in this outer region. Three-dimensional resistive magnetohydrodynamic (MHD) computation demonstrates that an additive poloidal current in this region will reduce the magnetic fluctuations and magnetic stochasticity.

  15. Self-consistent poloidal electric field and neoclassical angular momentum flux

    SciTech Connect

    Wong, S. K.; Chan, V. S.

    2009-12-15

    A complete expression is obtained for the poloidal variation of the electrostatic potential in the banana regime for large aspect ratio flux surfaces using the method of matched asymptotic expansions. The result exhibits a finite discontinuity at the innermost point of a flux surface instead of a divergence as previously reported. Using this expression in combination with the solution of the linearized drift kinetic equation with a model collision operator, the part of the toroidal angular momentum flux due to the poloidal electric field is calculated. The result is larger than the one in existing works, which neglect the poloidal electric field, by the order of the square root of the aspect ratio.

  16. Ion orbit loss and the poloidal electric field in a tokamak

    SciTech Connect

    Xiao, H.; Hazeltine, R.D.; Valanju, P.M.

    1994-07-29

    Monte Carlo simulation studies for ion orbit loss in limiter tokamaks show a poloidal asymmetry in ion loss arising from differences in ion orbit geometry. Since electron loss to the limiter is uniformly distributed because of its tiny orbit width, the nonuniform ion loss could cause a poloidal electric field that would tend to make the ion loss to the limiter more uniform. A simple analytical derivation of this poloidal electric field and a discussion of its effects ion movement and transport are also presented.

  17. Bow-shaped toroidal field coils

    SciTech Connect

    Bonanos, P.

    1981-05-01

    Design features of Bow-Shaped Toroidal Field Coils are described and compared with circular and D shaped coils. The results indicate that bow coils can produce higher field strengths, store more energy and be made demountable. The design offers the potential for the production of ultrahigh toroidal fields. Included are representative coil shapes and their engineering properties, a suggested structural design and an analysis of a specific case.

  18. Spheromak reactor with poloidal flux-amplifying transformer

    DOEpatents

    Furth, Harold P.; Janos, Alan C.; Uyama, Tadao; Yamada, Masaaki

    1987-01-01

    An inductive transformer in the form of a solenoidal coils aligned along the major axis of a flux core induces poloidal flux along the flux core's axis. The current in the solenoidal coil is then reversed resulting in a poloidal flux swing and the conversion of a portion of the poloidal flux to a toroidal flux in generating a spheromak plasma wherein equilibrium approaches a force-free, minimum Taylor state during plasma formation, independent of the initial conditions or details of the formation. The spheromak plasma is sustained with the Taylor state maintained by oscillating the currents in the poloidal and toroidal field coils within the plasma-forming flux core. The poloidal flux transformer may be used either as an amplifier stage in a moving plasma reactor scenario for initial production of a spheromak plasma or as a method for sustaining a stationary plasma and further heating it. The solenoidal coil embodiment of the poloidal flux transformer can alternately be used in combination with a center conductive cylinder aligned along the length and outside of the solenoidal coil. This poloidal flux-amplifying inductive transformer approach allows for a relaxation of demanding current carrying requirements on the spheromak reactor's flux core, reduces plasma contamination arising from high voltage electrode discharge, and improves the efficiency of poloidal flux injection.

  19. Hall probe measurements of the poloidal magnetic field in Compact Toroidal Hybrid plasmas

    NASA Astrophysics Data System (ADS)

    Stevenson, B. A.; Knowlton, S. F.; Hartwell, G. J.; Hanson, J. D.; Maurer, D. A.

    2014-09-01

    A linear array of 16 Hall effect sensors has been developed to directly measure the poloidal magnetic field inside the boundary of a non-axisymmetric hybrid torsatron/tokamak plasma. The array consists of miniature gallium arsenide Hall sensor elements mounted 8 mm apart on a narrow, rotatable printed circuit board inserted into a re-entrant stainless steel tube sheathed in boron nitride. The sensors are calibrated on the bench and in situ to provide accurate local measurements of the magnetic field to aid in reconstructing the equilibrium plasma current density profiles in fully three-dimensional plasmas. Calibrations show that the sensor sensitivities agree with the nominal manufacturers specifications of 1.46 V/T. Poloidal fields measured with the Hall sensor array are found to be within 5% of poloidal fields modeled with a Biot-Savart code.

  20. Hall probe measurements of the poloidal magnetic field in Compact Toroidal Hybrid plasmas

    SciTech Connect

    Stevenson, B. A.; Knowlton, S. F.; Hartwell, G. J. Hanson, J. D.; Maurer, D. A.

    2014-09-15

    A linear array of 16 Hall effect sensors has been developed to directly measure the poloidal magnetic field inside the boundary of a non-axisymmetric hybrid torsatron/tokamak plasma. The array consists of miniature gallium arsenide Hall sensor elements mounted 8 mm apart on a narrow, rotatable printed circuit board inserted into a re-entrant stainless steel tube sheathed in boron nitride. The sensors are calibrated on the bench and in situ to provide accurate local measurements of the magnetic field to aid in reconstructing the equilibrium plasma current density profiles in fully three-dimensional plasmas. Calibrations show that the sensor sensitivities agree with the nominal manufacturers specifications of 1.46 V/T. Poloidal fields measured with the Hall sensor array are found to be within 5% of poloidal fields modeled with a Biot-Savart code.

  1. Hall probe measurements of the poloidal magnetic field in Compact Toroidal Hybrid plasmas.

    PubMed

    Stevenson, B A; Knowlton, S F; Hartwell, G J; Hanson, J D; Maurer, D A

    2014-09-01

    A linear array of 16 Hall effect sensors has been developed to directly measure the poloidal magnetic field inside the boundary of a non-axisymmetric hybrid torsatron/tokamak plasma. The array consists of miniature gallium arsenide Hall sensor elements mounted 8 mm apart on a narrow, rotatable printed circuit board inserted into a re-entrant stainless steel tube sheathed in boron nitride. The sensors are calibrated on the bench and in situ to provide accurate local measurements of the magnetic field to aid in reconstructing the equilibrium plasma current density profiles in fully three-dimensional plasmas. Calibrations show that the sensor sensitivities agree with the nominal manufacturers specifications of 1.46 V/T. Poloidal fields measured with the Hall sensor array are found to be within 5% of poloidal fields modeled with a Biot-Savart code.

  2. Poloidal electric field due to ICRH and its effect on neoclassical transport

    SciTech Connect

    Vacca, L. )

    1994-10-15

    We study the transport of a plasma in which a minority ion species is heated by fast Alfven waves. The strong anisotropy of the minority distribution function gives origin to a poloidal electric field. We calculate the poloidal dependence of the electric potential by numerically integrating the leading order minority distribution function. When the amplitude of this field is such that electrostatic trapping is not negligible in comparison to the magnetic trapping then neoclassical transport can be enhanced as found in previous work. The linearized kinetic equations are solved using a variational method in the banana regime. Approximate analytic expressions for the transport coefficients are given.

  3. Current density and poloidal magnetic field for toroidal elliptic plasmas with triangularity

    SciTech Connect

    Martin, P.; Haines, M.G.; Castro, E.

    2005-08-15

    Changes in the poloidal magnetic field around a tokamak magnetic surface due to different values of triangularity and ellipticity are analyzed in this paper. The treatment here presented allows the determination of the poloidal magnetic field from knowledge of the toroidal current density. Different profiles of these currents are studied. Improvements in the analytic forms of the magnetic surfaces have also been found. The treatment has been performed using a recent published system of coordinates. Suitable analytic equations have been used for the elliptic magnetic surfaces with triangularity and Shafranov shift.

  4. Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

    DOEpatents

    Woolley, Robert D.

    1998-01-01

    A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators.

  5. Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

    DOEpatents

    Woolley, R.D.

    1998-09-08

    A method and apparatus are disclosed for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators. 6 figs.

  6. Magnetic Fields at the Center of Coils

    ERIC Educational Resources Information Center

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-01-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = µ[subscript 0] (N/L) I, (1) where I is the current, N…

  7. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R.

    1987-12-01

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  8. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, J.R.

    1987-05-15

    A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

  9. The Magnetic Field of Helmholtz Coils

    ERIC Educational Resources Information Center

    Berridge, H. J. J.

    1975-01-01

    Describes the magnetic field of Helmholtz coils qualitatively and then provides the basis for a quantitative expression. Since the mathematical calculations are very involved, a computer program for solving the mathematical expression is presented and explained. (GS)

  10. Confinement improvement with rf poloidal current drive in the reversed-field pinch

    SciTech Connect

    Hokin, S.; Sarff, J.; Sovinec, C.; Uchimoto, E.

    1994-03-08

    External control of the current profile in a reversed-field pinch (RFP), by means such as rf poloidal current drive, may have beneficial effects well beyond the direct reduction of Ohmic input power due to auxiliary heating. Reduction of magnetic turbulence associated with the dynamo, which drives poloidal current in a conventional RFP, may allow operation at lower density and higher electron temperature, for which rf current drive becomes efficient and the RFP operates in a more favorable regime on the n{tau} vs T diagram. Projected parameters for RFX at 2 MA axe studied as a concrete example. If rf current drive allows RFX to operate with {beta} = 10% (plasma energy/magnetic energy) at low density (3 {times} 10{sup 19} m{sup {minus}3}) with classical resistivity (i.e. without dynamo-enhanced power input), 40 ms energy confinement times and 3 keV temperatures will result, matching the performance of tokamaks of similar size.

  11. Gyrokinetic full f analysis of electric field dynamics and poloidal velocity in the FT2-tokamak configuration

    SciTech Connect

    Leerink, S.; Heikkinen, J. A.; Janhunen, S. J.; Kiviniemi, T. P.; Nora, M.; Ogando, F.

    2008-09-15

    The ELMFIRE gyrokinetic simulation code has been used to perform full f simulations of the FT-2 tokamak. The dynamics of the radial electric field and the creation of poloidal velocity in the presence of turbulence are presented.

  12. Experimental Measurement of Asymmetric Fluctuations of Poloidal Magnetic Field in Damavand Tokomak at Different Plasma Currents

    NASA Astrophysics Data System (ADS)

    Moslehi-Fard, Mahmoud; Alinejad, Naser; Rasouli, Chapar; Sadigzadeh, Asghar

    2012-08-01

    Toroidal and Poloidal magnetic fields have an important effect on the tokomak topology. Damavand Tokomak is a small size tokomak characterized with k = 1.2, B t = 1T, R 0 = 36 cm, maximum plasma current is about 35 KA with a discharge time of 21 ms. In this experimental work, the variation of poloidal magnetic field on the torodial cross section is measured and analyzed. In order to measure the polodial magnetic field, 18 probes were installed on the edge of tokomak plasma with ∆θ = 18°, while a limiter was installed inside the torus. Plasma current, I p, induces a polodial magnetic field, B p, smaller than the torodial magnetic field B t. Magnetic lines B produced as a combination of B t and B p, are localized on the nested toroidal magnetic surfaces. The presence of polodial magnetic field is necessary for particles confinement. Mirnov oscillations are the fluctuations of polodial magnetic field, detected by magnetic probes. Disrupted instability in Tokomak typically starts with mirnov oscillations which appear as fluctuations of polodial magnetic field and is detected by magnetic probes. Minor disruptions inside the plasma can contain principal magnetic islands and their satellites can cause the annihilation of plasma confinement. Production of thin layer of turbulent magnetic field lines cause minor disruption. Magnetic limiter may cause the deformation of symmetric equilibrium configuration and chaotic magnetic islands reveal in plasma occurring in thin region of chaotic field lines close to their separatrix. The width of this chaotic layer in the right side of poloidal profile of Damavand Tokomak is smaller than the width in the left side profile because of Shafranov displacement. Ergodic region in the left side of profile develops a perturbation on the magnetic polodial field lines, B p, that are greater in magnitude than that in the right side, although the values of B p on the left side are smaller than that on the right side of the profile. The Left

  13. Inertial-acoustic oscillations of black hole accretion discs with large-scale poloidal magnetic fields

    NASA Astrophysics Data System (ADS)

    Yu, Cong; Lai, Dong

    2015-07-01

    We study the effect of large-scale magnetic fields on the non-axisymmetric inertial-acoustic modes (also called p modes) trapped in the innermost regions of accretion discs around black holes (BHs). These global modes could provide an explanation for the high-frequency quasi-periodic oscillations (HFQPOs) observed in BH X-ray binaries. There may be observational evidence for the presence of such large-scale magnetic fields in the discs since episodic jets are observed in the same spectral state when HFQPOs are detected. We find that a large-scale poloidal magnetic field can enhance the corotational instability and increase the growth rate of the purely hydrodynamic overstable p modes. In addition, we show that the frequencies of these overstable p modes could be further reduced by such magnetic fields, making them agree better with observations.

  14. On the Sequential Control of ITER Poloidal Field Converters for Reactive Power Reduction

    NASA Astrophysics Data System (ADS)

    Yuan, Hongwen; Fu, Peng; Gao, Ge; Huang, Liansheng; Song, Zhiquan; He, Shiying; Wu, Yanan; Dong, Lin; Wang, Min; Fang, Tongzhen

    2014-12-01

    Sequential control applied to the International Thermonuclear Experimental Reactor (ITER) poloidal field converter system for the purpose of reactive power reduction is the subject of this investigation. Due to the inherent characteristics of thyristor-based phase-controlled converter, the poloidal field converter system consumes a huge amount of reactive power from the grid, which subsequently results in a voltage drop at the 66 kV busbar if no measure is taken. The installation of a static var compensator rated for 750 MVar at the 66 kV busbar is an essential way to compensate reactive power to the grid, which is the most effective measure to solve the problem. However, sequential control of the multi-series converters provides an additional method to improve the natural power factor and thus alleviate the pressure of reactive power demand of the converter system without any additional cost. In the present paper, by comparing with the symmetrical control technique, the advantage of sequential control in reactive power consumption is highlighted. Simulation results based on SIMULINK are found in agreement with the theoretical analysis.

  15. A poloidal field measurement technique: Pitch angle measurements via injected He/sup +/ ions

    SciTech Connect

    Jobes, F.C.

    1989-07-01

    The poloidal field of a tokamak can be determined by observing the light emitted by He/sup +/ ions injected into the plasma by a perpendicular He/sup 0/ beam. These ions will orbit in small circles located where the neutral atom became ionized, and they will remain there for a few microseconds. During this time, some of these ions will also emit light at various spectral lines. The observed spectrum of any of these lines will have a peculiar and very wide shape, and it will be offset (Doppler shifted) with respect to the natural line location. The location and width of the spectral pattern provide independent information about the components of the poloidal field which are parallel and perpendicular to the beam velocity, and this information is local to the point where the light is emitted. For a horizontal beam, these components are b/sub x/ and b/sub y/, respectively. The difference in Doppler shift between two measurement points above one another (at the top and bottom of the beam) is directly proportional to /delta/b/sub x/, which in turn is proportional to the transform on that flux surface. Thus, this technique provides a means to measure directly local values of q(r). Simulation studies indicate that accurate measurements can be made in milliseconds. 6 refs., 8 figs.

  16. Non-axisymmetric magnetic modes of neutron stars with purely poloidal magnetic fields

    NASA Astrophysics Data System (ADS)

    Asai, Hidetaka; Lee, Umin; Yoshida, Shijun

    2016-01-01

    We calculate non-axisymmetric oscillations of neutron stars magnetized by purely poloidal magnetic fields. We use polytropes of index n = 1 and 1.5 as a background model, where we ignore the equilibrium deformation due to the magnetic field. Since separation of variables is not possible for the oscillation of magnetized stars, we employ finite series expansions for the perturbations using spherical harmonic functions. Solving the oscillation equations as the boundary and eigenvalue problem, we find two kinds of discrete magnetic modes, that is, stable (oscillatory) magnetic modes and unstable (monotonically growing) magnetic modes. For isentropic models, the frequency or the growth rate of the magnetic modes is exactly proportional to BS, the strength of the field at the surface. The oscillation frequency and the growth rate are affected by the buoyant force in the interior, and the stable stratification tends to stabilize the unstable magnetic modes.

  17. High-field superconducting nested coil magnet

    NASA Technical Reports Server (NTRS)

    Laverick, C.; Lobell, G. M.

    1970-01-01

    Superconducting magnet, employed in conjunction with five types of superconducting cables in a nested solenoid configuration, produces total, central magnetic field strengths approaching 70 kG. The multiple coils permit maximum information on cable characteristics to be gathered from one test.

  18. 2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoyi; Xiao, Chijie; Chen, Yihang; Xu, Tianchao; Lin, Chen; Wang, Long; Xu, Min; Yu, Yi

    2016-11-01

    Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (Bp) and radial electric field (Er) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D Bp profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.

  19. The importance of matched poloidal spectra to error field correction in DIII-D

    SciTech Connect

    Paz-Soldan, C. Lanctot, M. J.; Buttery, R. J.; La Haye, R. J.; Strait, E. J.; Logan, N. C.; Park, J.-K.; Solomon, W. M.; Shiraki, D.; Hanson, J. M.

    2014-07-15

    Optimal error field correction (EFC) is thought to be achieved when coupling to the least-stable “dominant” mode of the plasma is nulled at each toroidal mode number (n). The limit of this picture is tested in the DIII-D tokamak by applying superpositions of in- and ex-vessel coil set n = 1 fields calculated to be fully orthogonal to the n = 1 dominant mode. In co-rotating H-mode and low-density Ohmic scenarios, the plasma is found to be, respectively, 7× and 20× less sensitive to the orthogonal field as compared to the in-vessel coil set field. For the scenarios investigated, any geometry of EFC coil can thus recover a strong majority of the detrimental effect introduced by the n = 1 error field. Despite low sensitivity to the orthogonal field, its optimization in H-mode is shown to be consistent with minimizing the neoclassical toroidal viscosity torque and not the higher-order n = 1 mode coupling.

  20. Laboratory formation of a scaled protostellar jet by coaligned poloidal magnetic field.

    PubMed

    Albertazzi, B; Ciardi, A; Nakatsutsumi, M; Vinci, T; Béard, J; Bonito, R; Billette, J; Borghesi, M; Burkley, Z; Chen, S N; Cowan, T E; Herrmannsdörfer, T; Higginson, D P; Kroll, F; Pikuz, S A; Naughton, K; Romagnani, L; Riconda, C; Revet, G; Riquier, R; Schlenvoigt, H-P; Skobelev, I Yu; Faenov, A Ya; Soloviev, A; Huarte-Espinosa, M; Frank, A; Portugall, O; Pépin, H; Fuchs, J

    2014-10-17

    Although bipolar jets are seen emerging from a wide variety of astrophysical systems, the issue of their formation and morphology beyond their launching is still under study. Our scaled laboratory experiments, representative of young stellar object outflows, reveal that stable and narrow collimation of the entire flow can result from the presence of a poloidal magnetic field whose strength is consistent with observations. The laboratory plasma becomes focused with an interior cavity. This gives rise to a standing conical shock from which the jet emerges. Following simulations of the process at the full astrophysical scale, we conclude that it can also explain recently discovered x-ray emission features observed in low-density regions at the base of protostellar jets, such as the well-studied jet HH 154. PMID:25324383

  1. Laboratory formation of a scaled protostellar jet by coaligned poloidal magnetic field.

    PubMed

    Albertazzi, B; Ciardi, A; Nakatsutsumi, M; Vinci, T; Béard, J; Bonito, R; Billette, J; Borghesi, M; Burkley, Z; Chen, S N; Cowan, T E; Herrmannsdörfer, T; Higginson, D P; Kroll, F; Pikuz, S A; Naughton, K; Romagnani, L; Riconda, C; Revet, G; Riquier, R; Schlenvoigt, H-P; Skobelev, I Yu; Faenov, A Ya; Soloviev, A; Huarte-Espinosa, M; Frank, A; Portugall, O; Pépin, H; Fuchs, J

    2014-10-17

    Although bipolar jets are seen emerging from a wide variety of astrophysical systems, the issue of their formation and morphology beyond their launching is still under study. Our scaled laboratory experiments, representative of young stellar object outflows, reveal that stable and narrow collimation of the entire flow can result from the presence of a poloidal magnetic field whose strength is consistent with observations. The laboratory plasma becomes focused with an interior cavity. This gives rise to a standing conical shock from which the jet emerges. Following simulations of the process at the full astrophysical scale, we conclude that it can also explain recently discovered x-ray emission features observed in low-density regions at the base of protostellar jets, such as the well-studied jet HH 154.

  2. STRUCTURAL RESPONSE OF THE DIII-D TOROIDAL FIELD COIL TO INCREASED LATERAL LOADS

    SciTech Connect

    REIS,E.E; CHIN,E

    2003-10-01

    OAK-B135 Recent calibration shots in which full toroidal field (TF) coil current interacted with the maximum poloidal field coils have produced increased lateral loads on the outer sections of the TF-coil. The increased lateral loads have resulted in deflections that have been sufficient to cause the TF-coil to contact adjacent equipment and produce a transient short to ground within the coil. The six outer turns of each TF-coil bundle are clamped together by insulated preloaded studs to provide increased bending stiffness. These sections of the outer bundles depend on friction to react the lateral loads as a bundle rather than six individual turns. A major concern is that the increased loads will produce slip between turns resulting in excessive lateral deflections and possible damage to the insulating sleeve on the preloaded studs. A finite element structural model of the TF-coil was developed for the calculation of deflections and the shear load distribution throughout the coil for the applied lateral loads from a full current calibration shot. The purpose of the updated structural model is to correlate the applied lateral loads to the total shear force between the unbonded sections of the outer turns. An allowable integrated lateral load applied to the outer turns is established based on the maximum shear force that can be reacted by friction. A program that calculates the magnetic fields and integrated lateral load along the outer turns can be incorporated into the plasma control system. The integrated load can then be compared to the calculated allowable value prior to execution of calibration shots. Calibration shots with a calculated total lateral load greater than the allowable value will be prevented.

  3. Far-infrared polarimetry/interferometry for poloidal magnetic field measurement on ZT-40M

    SciTech Connect

    Erickson, R.M.

    1986-06-01

    The measurement of internal magnetic field profiles may be a very important step in the understanding of magnetic confinement physics issues. The measurement of plasma-induced Faraday rotation is one of the more promising internal magnetic field diagnostics. This thesis describes the development of a heterodyne polarimeter/interferometer for internal poloidal magnetic field measurement on ZT-40M. Heterodyne techniques were employed because of the insensitivity to spurious signal amplitude changes that cause errors in other methods. Initial problems in polarimetric sensitivity were observed that were ultimately found to be related to discharge-induced motions of the constrained diagnostic access on ZT-40M. Grazing incidence motions of the constrained diagnostic access on ZT-40M. Grazing incidence reflections on metallic surfaces of the diagnostic ports caused polarization changes that affected the measurement accuracy. Installation of internally threaded sleeves to baffle the reflections eliminated the sensitivity problem, and allowed useful Faraday rotation measurements to be made. Simultaneous polarimetric and interferometric measurements have also been demonstrated. The ability to assemble a working heterodyne polarimeter/interferometer is no longer in question. The extension of the present system to multichord operation requires increased laser power and efficiency.

  4. Adaptation of TRIPND Field Line Tracing Code to a Shaped, Poloidal Divertor Geometry

    NASA Astrophysics Data System (ADS)

    Monat, P.; Moyer, R. A.; Evans, T. E.

    2001-10-01

    The magnetic field line tracing code TRIPND(T.E. Evans, Proc. 18th Conf. on Control. Fusion and Plasma Phys., Berlin, Germany, Vol. 15C, Part II (European Physical Society, 1991) p. 65.) has been modified to use the axisymmetric equilibrium magnetic fields from an EFIT reconstruction in place of circular equilibria with multi-filament current profile expansions. This adaptation provides realistic plasma current profiles in shaped geometries. A major advantage of this modification is that it allows investigation of magnetic field line trajectories in any device for which an EFIT reconstruction is available. The TRIPND code has been used to study the structure of the magnetic field line topology in circular, limiter tokamaks, including Tore Supra and TFTR and has been benchmarked against the GOURDON code used in Europe for magnetic field line tracing. The new version of the code, called TRIP3D, is used to investigate the sensitivity of various shaped equilibria to non-axisymmetric perturbations such as a shifted F coil or error field correction coils.

  5. POLOIDAL MAGNETIC FIELD MEASUREMENTS AND ANALYSIS WITH THE DIII-D LIBEAM SYSTEM

    SciTech Connect

    D.M. THOMAS

    2002-08-01

    For over thirty years, neutral lithium beams have been employed as a localized, noninvasive diagnostic on a variety of plasma experiments worldwide, providing a number of key physics measurements. On DIII-D the LIBEAM diagnostic has been designed to provide precise measurements of the local poloidal magnetic field in the edge region, a parameter of basic importance to understanding the stability of high performance tokamaks. We utilize the Zeeman splitting and known polarization characteristics of the collisionally excited 670.8 nm Li resonance line to interpret local magnetic field components viewed using a closely packed ({Delta}R {approx} 5 mm) array of 32 viewchords. A dual photoelastic modulator/linear polarizer combination serves to amplitude modulate the light in exact correspondence to its input polarization state. Subsequent narrowband spectral filtering using etalons and standard interference filters is used to isolate one of the three Zeeman components, and the polarization state of that component is recovered using a PC-based, multichannel digital lock-in detection system. Edge magnetic pitch angle profiles for a variety of shots have been reconstructed using a small number of chords and detailed analysis of the lockin and d.c. signal levels. Present system performance appears to be limited by etalon performance as well as various broadening mechanisms in the beam that tend to decrease the polarization fraction in the observed component. A careful analysis of this effect and some strategies for improving the measured polarization will be presented.

  6. Resistive demountable toroidal-field coils for tokamak reactors

    SciTech Connect

    Jassby, D.L.; Jacobsen, R.A.; Kalnavarns, J.; Masson, L.S.; Sekot, J.P.

    1981-07-01

    Readily demountable TF (toroidal-field) coils allow complete access to the internal components of a tokamak reactor for maintenance of replacement. The requirement of readily demountable joints dictates the use of water-cooled resistive coils, which have a host of decisive advantages over superconducting coils. Previous papers have shown that resistive TF coils for tokamak reactors can operate in the steady state with acceptable power dissipation (typically, 175 to 300 MW). This paper summarizes results of parametric studies of size optimization of rectangular TF coils and of a finite-element stress analysis, and examines several candidate methods of implementing demountable joints for rectangular coils constructed of plate segments.

  7. Analysis of Thermal-Hydraulic Gravity/ Buoyancy Effects in the Testing of the ITER Poloidal Field Full Size Joint Sample (PF-FSJS)

    SciTech Connect

    Zanino, R.; Savoldi Richard, L.; Bruzzone, P.; Ciazynski, D.; Nicollet, S.

    2004-06-23

    The PF-FSJS is a full-size joint sample, based on the NbTi dual-channel cable-in-conduit conductor (CICC) design currently foreseen for the International Thermonuclear Experimental Reactor (ITER) Poloidal Field coil system. It was tested during the summer of 2002 in the Sultan facility of CRPP at a background peak magnetic field of typically 6 T. It includes about 3 m of two jointed conductor sections, using different strands but with identical layout. The sample was cooled by supercritical helium at nominal 4.5-5.0 K and 0.9-1.0 MPa, in forced convection from the top to the bottom of the vertical configuration. A pulsed coil was used to test AC losses in the two legs resulting, above a certain input power threshold, in bundle helium backflow from the heated region. Here we study the thermal-hydraulics of the phenomenon with the M and M code, with particular emphasis on the effects of buoyancy on the helium dynamics, as well as on the thermal-hydraulic coupling between the wrapped bundles of strands in the annular cable region and the central cooling channel. Both issues are ITER relevant, as they affect the more general question of the heat removal capability of the helium in this type of conductors.

  8. Flat RF coils in static field gradient nuclear magnetic resonance.

    PubMed

    Stork, H; Gädke, A; Nestle, N; Fujara, F

    2009-10-01

    The use of flat RF coils allows considerable gains in the sensitivity of static field gradient (SFG) nuclear magnetic resonance (NMR) experiments. In this article, this effect is studied theoretically as well as experimentally. Additionally, the flat coil geometry has been studied theoretically depending on magnetic field gradient, pulse sequence and amplifier power. Moreover, detecting the signal directly from the free induction decay (FID) turned out to be quite attractive for STRAFI-like microimaging experiments, especially when using flat coils. In addition to wound rectangular flat coils also spiral flat coils have been developed which can be manufactured by photolithography from printed circuit boards.

  9. Coiled tubing sidetrack: Slaughter Field case history

    SciTech Connect

    Hightower, C.M.; Blount, C.G.; Ward, S.L.; Martin, R.F.; Cantwell, D.L.; Ackers, M.J.

    1995-03-01

    The paper describes the successful sidetrack of an oil well in the Slaughter Field in West Texas using coiled tubing (CT). Several first-time CT operations performed during this workover include: setting a whipstock in casing on CT; cutting a window with CT; using mud pulse measurement-while-drilling (MWD) with CT in a real well; use of a fluid-operated orientation tool for in-hole toolface changes; successful use of an autodriller to maintain weight on bit while drilling. Directional control of the sidetracked hole proved to be ineffective due to a surface software problem. The resultant wellbore was not horizontal as planned, but instead closely paralleled the original well for much of its length. However, the previously non-productive well flowed 1,000 barrels of fluid per day (BFPD) from the sidetrack following the workover.

  10. Heat flux due to poloidal electric field in the banana regime

    SciTech Connect

    Taguchi, M. )

    1992-02-01

    The heat flux due to poloidally varying electrostatic potential is calculated in the banana regime. This electrostatic potential determined self-consistently from charge neutrality is shown to increase the electron heat flux by a factor {radical}{ital m}{sub {ital i}}/{ital m}{sub {ital e}} compared with that when this potential is neglected, where {ital m}{sub {ital e}} and {ital m}{sub {ital i}} are the masses of electron and ion, respectively.

  11. The Theory of Field Parameters for Helmholtz Coil

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Li, Guofeng; Liang, Ke; Gao, Xianhu

    In this paper, the field parameters for the magnetic field of a Helmholtz coil is defined, as predicted by the theory of magnetic multipolar fields. In accordance with Biot-Savart law, eleven series of field parameters for the Helmholtz coil are calculated and the effect of each parameter thoroughly analyzed. This is then shown to provide a theoretical basis for obtaining a uniform magnetic field.

  12. Advanced COIL technologies for field applications

    NASA Astrophysics Data System (ADS)

    Tei, Kazuyoku; Sugimoto, Daichi; Ito, T.; Watanabe, G.; Vyskubenko, O.; Takeuchi, N.; Muto, S.; Kenzo, N.; Fujioka, Tomoo

    2005-01-01

    Chemical oxygen-iodine laser (COIL) has a great potential for applications such as decommissioning and dismantlement (D&D) of nuclear reactor, rock destruction and removal and extraction of a natural resource (Methane hydrate) because of the unique characteristics such as power scalability, high optical beam quality and optical fiber beam. Five-kilowatt Chemical oxygen-iodine laser (COIL) test facility has been developed. The chemical efficiency of 27% has been demonstrated with a moderate beam quality for optical fiber coupling. Our research program contains conventional/ejector-COIL scheme, Jet-SOG/Mist-SOG optimization, fiber delivery and long-term operation.

  13. Modification of far-SOL flow by substantial gas injection in the inboard poloidal field null configuration on QUEST

    NASA Astrophysics Data System (ADS)

    Onchi, T.; Zushi, H.; Oyama, Y.; Mishra, K.; Nagashima, Y.; Hanada, K.; Idei, H.; Hasegawa, M.; Kuzmin, A.; Nakamura, K.; Fujisawa, A.; Nagaoka, K.; Quest Team

    2015-11-01

    Spontaneous plasma flow is generated in the inboard poloidal field null (IPN) configuration on QUEST spherical tokamak. Previous research has found that there is a significant relationship between plasma current and far-SOL flow. Consequently, the SOL flow is influenced by global modification of IPN plasma. For further understanding of the far-SOL flow, a hybrid probe measuring plasma flow, electron density ne, and temperature Te, was installed in the far-SOL. Using the hybrid probe and divertor probe array, two-point observation on an open flux surface was performed to study the SOL-divertor relationship and the particle transport. Substantial gas injection (GI) from private region of the IPN configuration leads to high core density but Ip-drop by 50 %. ne and Te in the far-SOL and divertor region are modified appreciably due to the GI. Poloidal flow reversal occurs and toroidal velocity drops by about 50 % in the far-SOL. We investigate modifications of pressure gradient, electric field and particle transport, and study complex structure of the far-SOL flow. This work is supported by Grants-in-aid for Scientific Research (S24226020, 15K17800) and the Collaborative Research Program of Research Institute for Applied Mechanics.

  14. Measuring the off axis magnetic field within a Helmholtz Coil

    NASA Astrophysics Data System (ADS)

    Pluhar, Edward; Martell, Eric

    2013-03-01

    Helmholtz coils are used because they produce nearly uniform magnetic fields on-axis. Prior research, namely Graf's thin coil experiment [The Physics Teacher, pp. 360 (2012)], has accurately measured the axial magnetic field produced by a thin coil; however, the magnetic field off-axis is known to be significantly more complicated and cannot be calculated analytically. In this research, I have numerically determined the magnetic field off-axis in the region between the two coils and compared those calculations with measured values. I then determined the effect the deviation from uniformity has on the behavior of a charged particle moving through this region, such as in the well-known electron charge-to-mass ratio experiment.

  15. Magnetic Field Modeling with a Set of Individual Localized Coils

    PubMed Central

    Juchem, Christoph; Nixon, Terence W.; McIntyre, Scott; Rothman, Douglas L.; de Graaf, Robin A.

    2010-01-01

    A set of generic, circular individual coils is shown to be capable of generating highly complex magnetic field distributions in a flexible fashion. Arbitrarily oriented linear field gradients can be generated in three-dimensional as well as sliced volumes at amplitudes that allow imaging applications. The multi-coil approach permits the simultaneous generation of linear MRI encoding fields and complex shim fields by the same setup, thereby reducing system complexity. The choice of the sensitive volume over which the magnetic fields are optimized remains temporally and spatially variable at all times. The restriction of the field synthesis to experimentally relevant, smaller volumes such as single slices directly translates into improved efficiency, i.e. higher magnetic field amplitudes and/or reduced coil currents. For applications like arterial spin labeling, signal spoiling and diffusion weighting, perfect linearity of the gradient fields is not required and reduced demands on accuracy can also be readily translated into improved efficiency. The first experimental realization was achieved for mouse head MRI with 24 coils that were mounted on the surface of a cylindrical former. Oblique linear field gradients of 20 kHz/cm (47 mT/m) were generated with a maximum current of 1.4 A which allowed radial imaging of a mouse head. The potential of the new approach for generating arbitrary magnetic field shapes is demonstrated by synthesizing the more complex, higher order spherical harmonic magnetic field distributions X2-Y2, Z2 and Z2X. The new multi-coil approach provides the framework for the integration of conventional imaging and shim coils into a single multi-coil system in which shape, strength, accuracy and spatial coverage of the magnetic field can be specifically optimized for the application at hand. PMID:20347360

  16. Magnetic field modeling with a set of individual localized coils.

    PubMed

    Juchem, Christoph; Nixon, Terence W; McIntyre, Scott; Rothman, Douglas L; de Graaf, Robin A

    2010-06-01

    A set of generic, circular individual coils is shown to be capable of generating highly complex magnetic field distributions in a flexible fashion. Arbitrarily oriented linear field gradients can be generated in three-dimensional as well as sliced volumes at amplitudes that allow imaging applications. The multi-coil approach permits the simultaneous generation of linear MRI encoding fields and complex shim fields by the same setup, thereby reducing system complexity. The choice of the sensitive volume over which the magnetic fields are optimized remains temporally and spatially variable at all times. The restriction of the field synthesis to experimentally relevant, smaller volumes such as single slices directly translates into improved efficiency, i.e. higher magnetic field amplitudes and/or reduced coil currents. For applications like arterial spin labeling, signal spoiling and diffusion weighting, perfect linearity of the gradient fields is not required and reduced demands on accuracy can also be readily translated into improved efficiency. The first experimental realization was achieved for mouse head MRI with 24 coils that were mounted on the surface of a cylindrical former. Oblique linear field gradients of 20 kHz/cm (47 mT/m) were generated with a maximum current of 1.4A which allowed radial imaging of a mouse head. The potential of the new approach for generating arbitrary magnetic field shapes is demonstrated by synthesizing the more complex, higher order spherical harmonic magnetic field distributions X2-Y2, Z2 and Z2X. The new multi-coil approach provides the framework for the integration of conventional imaging and shim coils into a single multi-coil system in which shape, strength, accuracy and spatial coverage of the magnetic field can be specifically optimized for the application at hand.

  17. Design of Rectangular Coils for Control of Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Daniels, Ryan; Zhou, Changgong

    2014-03-01

    Over the last decade, cylindrical cross-section (CCS) coils have encompassed the majority of studies (i.e., ``Double-Helix'' coils): predominantly for use in particle accelerators (Goodzeit et al., Rochford et al., and Tominaka et al.). In this study, we investigate single and double-layered rectangular cross-section (RCS) coils of different inclination angles. RCS coils are a novel design, which does not require special machining of grooves on supporting structure for precise assembly of coils, and may lead to cost reduction. Numerical calculation of the field based on Biot-Savart's Law is conducted using Mathematica. Our goal is to generate a static and controllable time-varying magnetic field using a special configuration of four RCS coils, and impose the field on magnetic nanoparticles levitated by optical forces to study their behavior. The calculation provides guidance for optimizing the magnetic field in this application. Our current results indicate that the configuration produces highly uniform and controllable magnetic fields in the region where the nanoparticles are levitated. Natural Sciences Department at Lawrence Technological University.

  18. Resistive toroidal-field coils for tokamak reactors

    SciTech Connect

    Kalnavarns, J.; Jassby, D.L.

    1980-11-01

    This paper analyzes the optimization of the geometry of resistive TF coils of rectangular bore for tokamak fusion test reactors and practical neutron generators. In examining the trade-offs between geometric parameters and magnetic field for reactors giving a specified neutron wall loading, either the resistive power loss or the lifetime coil cost can be minimized. Aspects of cooling, magnetic stress, and construction are addressed for several reference designs. Bending moment distributions in closed form have been derived for rectangular coils on the basis of the theory of rigid frames. Candidate methods of fabrication and of implementing demountable joints are summarized.

  19. Thermal and electrical joint test for the helical field coils in the Advanced Toroidal Facility

    SciTech Connect

    Brown, R.L.; Johnson, R.L.

    1985-01-01

    Initial feasibility studies of a number of configurations for the Advanced Toroidal Facility (ATF) resulted in the selection of a resistive copper continuous-coil torsatron as the optimum device considering the physics program, cost, and schedule. Further conceptual design work was directed toward optimization of this configuration and, if possible, a shorter schedule. It soon became obvious that in order to shorten the schedule, a number of design and fabrication activities should proceed in parallel. This was most critical for the vacuum vessel and the helical field (HF) coils. If the HF coils were wound in place on a completed vacuum vessel, the overall schedule would be significantly (greater than or equal to12 months) longer. The approach of parallel scheduel paths requires that the HF coils be segmented into parts of less than or equal to180 of poloidal angle and that joints be made on a turn-by-turn basis when the segments are installed. It was obvious from the outset that the compact and complex geometry of the joint design presented a special challenge in the areas of reliability, assembly, maintenance, disassembly, and cost. Also, electrical, thermal, and force excursions are significant for these joints. A number of soldered, welded, brazed, electroplated, and bolted joints were evaluated. The evaluations examined fabrication feasibility and complexity, thermal-electrical performance at approximately two-thirds of the steady-state design conditions, and installation and assembly processes. Results of the thermal-electrical tests were analyzed and extrapolated to predict performance at peak design parameters. The final selection was a lap-type joint clamped with insulated bolts that pass through the winding packing. 3 refs., 4 figs.

  20. Intelligent shell feedback control in EXTRAP T2R reversed field pinch with partial coverage of the toroidal surface by a discrete active coil array

    NASA Astrophysics Data System (ADS)

    Yadikin, D.; Brunsell, P. R.; Drake, J. R.

    2006-01-01

    An active feedback system is required for long pulse operation of the reversed field pinch (RFP) device to suppress resistive wall modes (RWMs). A general feature of a feedback system using a discrete active coil array is a coupling effect which arises when a set of side band modes determined by the number of active coils is produced. Recent results obtained on the EXTRAP T2R RFP demonstrated the suppression of independent m = 1 RWMs using an active feedback system with a two-dimensional array of discrete active coils in the poloidal and toroidal directions. One of the feedback algorithms used is the intelligent shell feedback scheme. Active feedback systems having different number of active coils in the poloidal (Mc) and toroidal (Nc) directions (Mc × Nc = 2 × 32 and Mc × Nc = 4 × 16) are studied. Different side band effects are seen for these configurations. A significant prolongation of the plasma discharge is achieved for the intelligent shell feedback scheme using the 2 × 32 active coil configuration. This is attributed to the side band sets including only one of the dominant unstable RWMs and avoiding coupling to resonant modes. Analog proportional-integral-derivative controllers are used in the feedback system. Regimes with different values of the proportional gain are studied. The requirement of the proportional-integral control for low proportional gain and proportional-derivative control for high proportional gain is seen in the experiments.

  1. On the toroidal current density flowing across a poloidal-magnetic-field null in an axisymmetric plasma

    SciTech Connect

    Rodrigues, Paulo; Bizarro, Joao P. S.

    2013-04-15

    The axisymmetry condition and two of Maxwell's equations are used to show that, in general, there are no nested magnetic surfaces around a poloidal-magnetic-field null for a sufficiently small value of the toroidal current density flowing there. Hence, the toroidal current density at the axis of a magnetic configuration with extreme shear reversal cannot continuously approach zero unless nested surfaces are first broken or particular values are assigned to boundary conditions and other plasma parameters. The threshold of the toroidal current-density at which the topology changes is shown to be set by such parameters, and some examples of the predicted topology transition are presented using analytical solutions of the Grad-Shafranov equation.

  2. Self organization of high βp plasma equilibrium with an inboard poloidal magnetic field null in QUEST

    NASA Astrophysics Data System (ADS)

    Mishra, Kishore; Zushi, H.; Idei, H.; Hasegawa, M.; Onchi, T.; Tashima, S.; Banerjee, S.; Hanada, H.; Togashi, H.; Yamaguchi, T.; Ejiri, A.; Takase, Y.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Kuzmin, A.; QUEST Team

    2015-08-01

    Successful production of high βp plasmas (ɛβp ⩾ 1) fully non-inductively (NI) and their long pulse sustainment with the help of modest power (<100 kW) of electron cyclotron waves is demonstrated. High βp plasmas are found for the first time to be naturally self organized to form a stable natural inboard poloidal field null (IPN) equilibrium. A critical βp value is identified, which defines the transition boundary from inboard limiter (IL) to IPN equilibrium. A new feature of plasma self organization is evidenced, which enhances its negative triangular shape to sustain high βp. These results show a relatively simple method to produce and sustain high βp plasma close to the equilibrium limit in a stable configuration exploiting its self organization property.

  3. Design and numerical evaluation of a volume coil array for parallel MR imaging at ultrahigh fields

    PubMed Central

    Pang, Yong; Wong, Ernest W.H.; Yu, Baiying

    2014-01-01

    In this work, we propose and investigate a volume coil array design method using different types of birdcage coils for MR imaging. Unlike the conventional radiofrequency (RF) coil arrays of which the array elements are surface coils, the proposed volume coil array consists of a set of independent volume coils including a conventional birdcage coil, a transverse birdcage coil, and a helix birdcage coil. The magnetic fluxes of these three birdcage coils are intrinsically cancelled, yielding a highly decoupled volume coil array. In contrast to conventional non-array type volume coils, the volume coil array would be beneficial in improving MR signal-to-noise ratio (SNR) and also gain the capability of implementing parallel imaging. The volume coil array is evaluated at the ultrahigh field of 7T using FDTD numerical simulations, and the g-factor map at different acceleration rates was also calculated to investigate its parallel imaging performance. PMID:24649435

  4. Miniature coils for producing pulsed inplane magnetic fields for nanospintronics

    SciTech Connect

    Pawliszak, Łukasz; Zgirski, Maciej

    2015-03-15

    Nanospintronic and related research often requires the application of quickly rising magnetic field pulses in the plane of the studied planar structure. We have designed and fabricated sub-millimeter-sized coils capable of delivering pulses of the magnetic field up to ∼500 Oe in the plane of the sample with the rise time of the order of 10 ns. The placement of the sample above the coil allows for easy access to its surface with manipulators or light beams for, e.g., Kerr microscopy. We use the fabricated coil to drive magnetic domain walls in 1 μm wide permalloy wires and measure magnetic domain wall velocity as a function of the applied magnetic field.

  5. MAGNETIC FIELD CONFIGURATION AT THE GALACTIC CENTER INVESTIGATED BY WIDE-FIELD NEAR-INFRARED POLARIMETRY: TRANSITION FROM A TOROIDAL TO A POLOIDAL MAGNETIC FIELD

    SciTech Connect

    Nishiyama, Shogo; Yoshikawa, Tatsuhito; Nagata, Tetsuya; Hatano, Hirofumi; Nagayama, Takahiro; Tamura, Motohide; Matsunaga, Noriyuki; Suenaga, Takuya; Hough, James H.; Sugitani, Koji; Kato, Daisuke

    2010-10-10

    We present a large-scale view of the magnetic field (MF) in the central 2{sup 0} x 2{sup 0} region of our Galaxy. The polarization of point sources has been measured in the J, H, and K{sub S} bands using the near-infrared polarimetric camera SIRPOL on the 1.4 m Infrared Survey Facility telescope. Comparing the Stokes parameters between high extinction stars and relatively low extinction ones, we obtain polarization originating from magnetically aligned dust grains in the central few hundred parsecs of our Galaxy. We find that near the Galactic plane, the MF is almost parallel to the Galactic plane (i.e., toroidal configuration), but at high Galactic latitudes (|b | >0.{sup 0}4) the field is nearly perpendicular to the plane (i.e., poloidal configuration). This is the first detection of a smooth transition of the large-scale MF configuration in this region.

  6. Spitzer or neoclassical resistivity: A comparison between measured and model poloidal field profiles on PBX-M

    SciTech Connect

    Kaye, S.M.; Levinton, F.M.; Hatcher, R.; Kaita, R.; Kessel, C.; LeBlanc, B.; McCune, D.C.; Paul, S. )

    1992-03-01

    Direct measurements of the radial profile of the magnetic field line pitch on PBX-M (Phys. Fluids B {bold 2}, 1271 (1990)), coupled with model predictions of these profiles allow a critical comparison with the Spitzer and neoclassical models of plasma parallel resistivity. The measurements of the magnetic field line pitch are made by motional Stark effect polarimetry, while the model profiles are determined by solving the poloidal field diffusion equation in the TRANSP transport code using measured plasma profiles and assuming either Spitzer or neoclassical resistivity. The measured field pitch profiles were available for only seven cases, and the model profiles were distinguishable from each other in only three of those cases due to finite resistive diffusion times. The data in two of these three were best matched by the Spitzer model, especially in the inner-half of the plasma. Portions of the measured pitch profiles for these two cases and the full profiles for other cases, however, departed significantly from both the Spitzer and neoclassical models, indicating a plasma resistivity profile different from either model.

  7. A current limiter with superconducting coil for magnetic field shielding

    NASA Astrophysics Data System (ADS)

    Kaiho, K.; Yamaguchi, H.; Arai, K.; Umeda, M.; Yamaguchi, M.; Kataoka, T.

    2001-05-01

    The magnetic shield type superconducting fault current limiter have been built and successfully tested in ABB corporate research and so on. The device is essentially a transformer in which the secondary winding is the superconducting tube. However, due to the large AC losses and brittleness of the superconducting bulk tube, they have not yet entered market. A current limiter with superconducting coil for the magnetic field shielding is considered. By using the superconducting coil made by the multi-filamentary high Tc superconductor instead of the superconducting bulk tube, the AC losses can be reduced due to the reduced superconductor thickness and the brittleness of the bulk tube can be avoidable. This paper presents a preliminary consideration of the magnetic shield type superconducting fault current limiter with superconducting coil as secondary winding and their AC losses in comparison to that of superconducting bulk in 50 Hz operation.

  8. Dependence of neoclassical toroidal viscosity on the poloidal spectrum of applied nonaxisymmetric fields

    NASA Astrophysics Data System (ADS)

    Logan, N. C.; Park, J.-K.; Paz-Soldan, C.; Lanctot, M. J.; Smith, S. P.; Burrell, K. H.

    2016-03-01

    This paper presents a single mode model that accurately predicts the coupling of applied nonaxisymmetric fields to the plasma response that induces neoclassical toroidal viscosity (NTV) torque in DIII-D H-mode plasmas. The torque is measured and modeled to have a sinusoidal dependence on the relative phase of multiple nonaxisymmetric field sources, including a minimum in which large amounts of nonaxisymmetric drive is decoupled from the NTV torque. This corresponds to the coupling and decoupling of the applied field to a NTV-driving mode spectrum. Modeling using the perturbed equilibrium nonambipolar transport (PENT) code confirms an effective single mode coupling between the applied field and the resultant torque, despite its inherent nonlinearity. The coupling to the NTV mode is shown to have a similar dependence on the relative phasing as that of the IPEC dominant mode, providing a physical basis for the efficacy of this linear metric in predicting error field correction optima in NTV dominated regimes.

  9. Dependence of neoclassical toroidal viscosity on the poloidal spectrum of applied nonaxisymmetric fields

    DOE PAGES

    Logan, Nikolas C.; Park, Jong -Kyu; Paz-Soldan, Carloa; Lanctot, Matthew J.; Smith, Sterling P.; Burrell, K. H.

    2016-02-05

    This paper presents a single mode model that accurately predicts the coupling of applied nonaxisymmetric fields to the plasma response that induces neoclassical toroidal viscosity (NTV) torque in DIII-D H-mode plasmas. The torque is measured and modeled to have a sinusoidal dependence on the relative phase of multiple nonaxisymmetric field sources, including a minimum in which large amounts of nonaxisymmetric drive is decoupled from the NTV torque. This corresponds to the coupling and decoupling of the applied field to a NTV-driving mode spectrum. Modeling using the perturbed equilibrium nonambipolar transport (PENT) code confirms an effective single mode coupling between themore » applied field and the resultant torque, despite its inherent nonlinearity. Lastly, the coupling to the NTV mode is shown to have a similar dependence on the relative phasing as that of the IPEC dominant mode, providing a physical basis for the efficacy of this linear metric in predicting error field correction optima in NTV dominated regimes.« less

  10. Tokamak with liquid metal toroidal field coil

    DOEpatents

    Ohkawa, Tihiro; Schaffer, Michael J.

    1981-01-01

    Tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. Electric current is passed through the liquid metal over a conductive path linking the toroidal space to produce a toroidal magnetic field within the toroidal space about the major axis thereof. Toroidal plasma is developed within the toroidal space about the major axis thereof.

  11. On the role of poloidal and toroidal fluctuating electric fields in tokamak transport

    SciTech Connect

    Isichenko, M.B.; Wootton, A.J.

    1995-04-03

    The two different expressions for the radial particle flux {Lambda} found in the literature, as given by equations (2) and (4), are identical if the parallel electric field is small. The first expression is derivable in a fluid approach, whereas the second follows from the analysis of individual particle orbits. These expressions, without change, are also valid for an arbitrary axisymmetric magnetic geometry. In a situation where the parallel electric field is significant, the more accurate expression for the particle flux is in terms of the standard E x B velocity.

  12. Particle Confinement in Axisymmetric Poloidal Magnetic Field Configurations with Zeros of B: Methodological Note

    SciTech Connect

    Arsenin, V.V.; Skovoroda, A.A.

    2005-12-15

    Collisionless particle confinement in axisymmetric configurations with magnetic field nulls is analyzed. The existence of an invariant of motion--the generalized azimuthal momentum--makes it possible to determine in which of the spatial regions separated by magnetic separatrices passing through the magnetic null lines the particle occurs after it leaves the vicinity of a magnetic null line. In particular, it is possible to formulate a sufficient condition for the particle not to escape through the separatrix from the confinement region to the external region. In the configuration under analysis, the particles can be lost from a separatrix layer with a thickness on the order of the Larmor radius because of the nonconservation of the magnetic moment {mu}. In this case, the variations in {mu} are easier to describe in a coordinate system associated with the magnetic surfaces. An analysis is made of the applicability of expressions for the single-pass change {delta}{mu} in the magnetic moment that were obtained in different magnetic field models for a confinement system with a divertor (such that there is a circular null line)

  13. Petal Resonator Surface Coil with a Circular Envelope for High Field Magnetic Resonance Imaging

    NASA Astrophysics Data System (ADS)

    Hidalgo, S. S.; Cuellar, G.; Solis, S. E.; Alejski, A.; Rodríguez, A. O.

    2008-08-01

    A modified version of the petal resonator surface (PERES) coil is proposed in which the petal coils are located inside a circular-shaped coil as opposed to the previous PERES version which did not have a circular envelope. An 8-petal coil was simulated using a finite element method and the quasi-static approach to numerically investigate its electromagnetic characteristics. Numerical simulations showed that the field uniformity is not greatly affected by the use of circular-shaped coil inside in the circular envelope. A coil prototype was developed using the same coil configuration as above and tested on a commercial 3 T imager and a General Electric phantom. Phantom images also demonstrated that the mutual inductance between petals does not alter the coil performance. Standard pulse sequences were used to acquire phantom images with the petal resonator surface coil. It was shown that this prototype resonator coil is fully compatible with clinical high field MR imagers and clinical pulse sequences.

  14. High field volume coil with unbalance current distribution for MRI applications of rodents

    NASA Astrophysics Data System (ADS)

    Marrufo, O. R.; Hernández, J.; Rodríguez, A. O.

    2010-12-01

    The development of transceiver volume coils for high field MRI is still a very dynamic field of investigation and development Temnikov has been recently proposed a new volume coil design, similar to the to the gradiometer coil. It is also claimed that it is possible to individually tune it with a single chip capacitor. This motivated the development of a coil prototype based on this idea for whole-body MRI of rodents at 7 Tesla. Electromagnetic simulations of the RF field generated by this coil design were previously performed to study its properties. Electromagnetic simulations were also conducted for a standard birdcage coil with similar dimensions for fare comparison. In all numerical simulations, an unbalanced currents distribution was assumed by applying half the current intensity to designated legs. This coil design operated in the transceiver mode and was linear-driven. The coil size was manufactured to accommodate small rodents. Numerical simulations showed a field uniformity improvement of our coil over the standard birdcage coil. A popular birdcage coil was also constructed to compare their performances. Phantom and rat images were acquired for both volume coils to prove the viability of this coil design for high field MRI applications and standard spin echo pulse sequences Thus, these preliminary results make this coil design a good candidate for MRI and MRS applications of high magnetic fields.

  15. Laboratory formation of a scaled protostellar jet by coaligned poloidal magnetic field: recent results and new exeprimental studies

    NASA Astrophysics Data System (ADS)

    Vinci, Tommaso; Revet, Guilhem; Higginson, Drew; Béard, Jérome; Burdonov, K.; Chen, Sophia; Khagani, D.; Khiar, B.; Naughton, K.; Pikuz, S.; Riconda, Caterina; Riquier, R.; Soloviev, A.; Willi, O.; Portugall, O.; Pépin, Henry; Ciardi, Andrea; Fuchs, Julien; Albertazzi, Bruno

    2015-08-01

    Accretion shocks in Young Stellar Objects (YSO) are a subject of great interest in astrophysics; they exhibit intense magnetic activity and are surrounded by an accretion disk from which matter falls down onto the stellar surface in the form of columns following the magnetic lines (B ~ kG) at the free-fall velocity (100-500 km/s). As a column impacts the stellar surface, a radiative shock is created which heats up the infalling flow. As a consequence, a new reverse shock forms and some oscillations are expected in the emitted radiation as a proof of this periodic dynamic, but no periodicity has yet been detected in observations.To understand the reasons for this apparent inconsistency, we have recently developped an experimental setup [B. Albertazzi et al. Science 346, 325 (2014)] in which a plasma flow (generated by a high energy laser: 1013 W/cm2 - 0.6 ns pulse) is confined inside a poloidal magnetic field (20 T). This jet has an aspect ratio >10, a temperature of tens of eV, an electron density of 1018 cm-3 and propagates at 700 km/s as show by our previous numerical work [A. Ciardi et al. Physical Review Letters, 110 (2013)]. To investigate the accretion dynamics, the jet acts as the accretion column and hits a secondary target acting as the stellar surface. We will present the recent results on generation and dynamics of the jet and the new experimental results of this configuration, namely of a supersonic reverse shock traveling within the accretion column with a speed of 100 km/s, representing a Mach number of ~ 30, and the observation of increased density structures along the edges of the interaction. This will be discussed in the light of 3D-magneto-hydrodynamic simulations which parametric variations allow to understand how the various plasma parameters affect the accretion.

  16. Detailed 3D models of the induced electric field of transcranial magnetic stimulation coils

    NASA Astrophysics Data System (ADS)

    Salinas, F. S.; Lancaster, J. L.; Fox, P. T.

    2007-05-01

    Previous models neglected contributions from current elements spanning the full geometric extent of wires in transcranial magnetic stimulation (TMS) coils. A detailed account of TMS coil wiring geometry is shown to provide significant improvements in the accuracy of electric field (E-field) models. Modeling E-field dependence based on the TMS coil's wire width, height, shape and number of turns clearly improved the fit of calculated-to-measured E-fields near the coil body. Detailed E-field models were accurate up to the surface of the coil body (within 0.5% of measured) where simple models were often inadequate (up to 32% different from measured).

  17. Special Coils Development at the National High Magnetic Field Laboratory in Toulouse

    NASA Astrophysics Data System (ADS)

    Béard, J.; Billette, J.; Frings, P.; Suleiman, M.; Lecouturier, F.

    2013-03-01

    The Laboratoire National des Champs Magnétiques Intenses (LNCMI) develops different types of coils suited to specific experiments. We present some recent developments on magnet design. Several coils are dedicated to experiments in large scale facilities in France and Switzerland. A 30 T split-pair coil for X-rays diffraction and one 40 T coil for plasma physics at the LULI, two 30 T coils with axial access (one with an conical bore) for X-ray diffraction and absorption experiments. A 40 T wide angle conical access solenoid with a high duty-cycle for neutron scattering at the ILL is being constructed. For use at the installation in Toulouse we have developed, apart from our standard 60 and 70 T coils, several special coils: a coil with a long optical path with 30 T transverse magnetic field and a 90 T long pulse dual coil system.

  18. Open half-volume quadrature transverse electromagnetic coil for high-field magnetic resonance imaging.

    PubMed

    Peshkovsky, A S; Kennan, R P; Fabry, M E; Avdievich, N I

    2005-04-01

    A half-volume quadrature head transverse electromagnetic (TEM) coil has been constructed for 4 T imaging applications. This coil produces a sufficiently large homogeneous B(1) field region for the use as a volume coil. It provides superior transmission efficiency, resulting in significantly lower power deposition, as well as greater sensitivity and improved patient comfort and accessibility compared with conventional full-volume coils. Additionally, this coil suppresses the RF penetration artifact that distorts the RF magnetic field profile and alters the intensity in high-field images recorded with linear surface and volume coils. These advantages make it possible to apply this device as an efficient transmit/receive coil for high-field imaging with a restricted field of view.

  19. Diamagnetic flux measurement using the PDX TF coils

    SciTech Connect

    Thomas, P.

    1983-02-01

    The diamagnetism of plasmas in PDX has been measured using the toroidal field coils as the equivalent of the conventional diamagnetic loop. The extremely low inductive coupling between the toroidal and poloidal coil systems makes the measurement feasible. The main difficulty arises from the change in the TF coil resistance due to Joule heating, compounded by the nonlinearity and sharp temperature dependence of the resistance of the joints in the TF coils. The measurement method, details of the experimental system, and illustrative results are presented.

  20. Models of the uniformity of electro-magnetic fields generated for biological experiments by Merritt coils.

    PubMed

    Vesper, D N; Swez, J A; Nindl, G; Fox, M T; Sandrey, M A; Balcavage, W X

    2000-01-01

    Electromagnetic field (EMF) producing wire coils were described by Merritt et al, Rev. Sci. Instrum. 54 (7), 1983. Merritt coils produce large volume EMFs in which statistical numbers of biological experiments are performed. We build and use Merritt coils for cell/animal studies and are developing therapeutic EMF systems. Here we present models illustrating the EMFs produced by our coils and discuss the criteria that should be applied to the use of Merritt and other coils to achieve valid experimental results. In a companion paper at this meeting Nindl et al, describe biological experiments, using these Merritt coils, showing that EMFs may be useful in treating many inflammatory disease states. Although the large-volume EMFs produced by Merritt coils are convenient for biological experiments the EMFs are not perfectly uniform and the deviations can be a significant source of experimental error. The orientation and size of experimental objects are key contributors to these deviations. To evaluate our Merritt coils we solved the Biot-Savart law explicitly for ideal 3-coil and 4-coil Merritt systems and compared these theoretical EMFs with those of our systems. We present a detailed examination of deviations in magnetic field amplitude, as well as magnetic field direction, as a function of location within the coils. We find that spherically shaped experimental sets minimize these deviations. We developed simple formulae for accurately predicting deviations associated with Merritt coils. PMID:10834267

  1. Measuring Earth's Local Magnetic Field Using a Helmholtz Coil

    NASA Astrophysics Data System (ADS)

    Williams, Jonathan E.

    2014-04-01

    In this paper, I present a low-cost interactive experiment for measuring the strength of Earth's local magnetic field. This activity can be done in most high schools or two-year physics laboratories with limited resources, yet will have a tremendous learning impact. This experiment solidifies the three-dimensional nature of Earth's magnetic field vector and helps reinforce the aspect of the vertical component of Earth's magnetic field. Students should realize that Earth's magnetic field is not fully horizontal (except at the magnetic equator) and that a compass simply indicates the direction of the horizontal component of Earth's magnetic field. A magnetic dip needle compass can be used to determine the angle (known as the "dip angle" or "inclination angle") measured from the direction in which Earth's magnetic field vector points to the horizontal. In this activity, students will be able to determine the horizontal component of the field using a Helmholtz coil and, knowing the dip angle, the Earth's magnetic field strength can be determined.

  2. Toroidal current induced by particle trapping inside a new toroidal laboratory magnetized plasma device with poloidal magnetic field induced by a central conductor

    NASA Astrophysics Data System (ADS)

    Pierre, Th.; Caron, X.; Gravier, E.; Antar, G.

    2012-10-01

    In the laboratory toroidal device MISTOR, a poloidal field is created by a current (1200 A) flowing along a central toroidal conductor. A security factor q=1 is obtained at radial position r = 5 cm. Helium plasma is produced by electric discharge using a tungsten filament. When Bpol= 0, the whole plasma is turbulent that is a standard in a Simple Magnetized Torus. As Bpol is increased, the turbulence level decreases and a stable plasma is obtained. This is correlated with the decrease of the radial electric field. The confinement time is estimated in the afterglow decaying plasma. It increases from 50 microsec. without poloidal field to 0.5 millisec. when q=1 at mid-radius. The trapping of the particles inside the mirror-traps inherent in this topology (banana orbits) is studied. The precession of the banana orbits seems to be the dominant mechanism. The measurement of the toroidal current using a probe indicates that the electrons experience an oriented toroidal drift along the field lines. Detailed measurements of the EEDF are compared with theory. The influence of detrapping is investigated in order to estimate the bootstrap current induced in this device.

  3. Poloidal OHMIC heating in a multipole

    SciTech Connect

    Holly, D.J.

    1982-01-01

    The feasibility of using poloidal currents to heat plasmas confined by a multipole field has been examined experimentaly in Tokapole II. The machine is operated as a toroidal octupole, with a time-varying toroidal magnetic field driving poloidal plasma currents I/sub plasma/ - 20 kA to give densities n/sub e/ - 10/sup 13/ cm/sup -3/ and temperatures T/sub e/ - 30 eV.

  4. Field Demonstraton of Existing Microhole Coiled Tubing Rig (MCTR) Technology

    SciTech Connect

    Kent Perry; Samih Batarseh; Sheriff Gowelly; Thomas Hayes

    2006-05-09

    The performance of an advanced Microhole Coiled Tubing Rig (MCTR) has been measured in the field during the drilling of 25 test wells in the Niobrara formation of Western Kansas and Eastern Colorado. The coiled tubing (CT) rig designed, built and operated by Advanced Drilling Technologies (ADT), was documented in its performance by GTI staff in the course of drilling wells ranging in depth from 500 to nearly 3,000 feet. Access to well sites in the Niobrara for documenting CT rig performance was provided by Rosewood Resources of Arlington, VA. The ADT CT rig was selected for field performance evaluation because it is one of the most advanced commercial CT rig designs that demonstrate a high degree of process integration and ease of set-up and operation. Employing an information collection protocol, data was collected from the ADT CT rig during 25 drilling events that encompassed a wide range of depths and drilling conditions in the Niobrara. Information collected included time-function data, selected parametric information indicating CT rig operational conditions, staffing levels, and field observations of the CT rig in each phase of operation, from rig up to rig down. The data obtained in this field evaluation indicates that the ADT CT rig exhibited excellent performance in the drilling and completion of more than 25 wells in the Niobrara under varied drilling depths and formation conditions. In the majority of the 25 project well drilling events, ROP values ranged between 300 and 620 feet per hour. For all but the lowest 2 wells, ROP values averaged approximately 400 feet per hour, representing an excellent drilling capability. Most wells of depths between 500 and 2,000 feet were drilled at a total functional rig time of less than 16 hours; for wells as deep at 2,500 to 3,000 feet, the total rig time for the CT unit is usually well under one day. About 40-55 percent of the functional rig time is divided evenly between drilling and casing/cementing. The balance of

  5. Numerical study of the magnetic field diffusion in the toroidal field coils of the TFTR

    SciTech Connect

    Preis, H.

    1983-01-01

    The diffusion of the vertical magnetic field through the toroidal field coils is numerically analyzed in TFTR. Two different excitations of the vertical field are assumed whose behavior can be described by either a step function or a ramp function. Using the computer code FEDIFF, the distribution of the eddy currents in the windings and casing of the toroidal field coils, as well as their time behavior, is calculated for these functions. From integration of the eddy current functions over their pulse length, the energy dissipated by them is obtained. Finally, the magnetic field of the eddy currents within the torous is calculated. Based upon this field, which is represented as a function of time and space coordinates, the influence of this diffusion upon the field curvature index is described.

  6. A high temperature superconductor tape RF receiver coil for a low field magnetic resonance imaging system

    NASA Astrophysics Data System (ADS)

    Cheng, M. C.; Yan, B. P.; Lee, K. H.; Ma, Q. Y.; Yang, E. S.

    2005-08-01

    High temperature superconductor (HTS) thin films have been applied in making a low loss RF receiver coil for improving magnetic resonance imaging image quality. However, the application of these coils is severely limited by their limited field of view (FOV). Stringent fabrication environment requirements and high cost are further limitations. In this paper, we propose a simpler method for designing and fabricating HTS coils. Using industrial silver alloy sheathed Bi(2-x)PbxSr2Ca2Cu3O10 (Bi-2223) HTS tapes, a five-inch single-turn HTS solenoid coil has been developed, and human wrist images have been acquired with this coil. The HTS tape coil has demonstrated an enhanced FOV over a six-inch YBCO thin film surface coil at 77 K with comparable signal-to-noise ratio.

  7. Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST

    SciTech Connect

    Onchi, T.; Zushi, H.; Hanada, K.; Idei, H.; Hasegawa, M.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K.; Kuzmin, A.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Watanabe, O.; Mishra, K.; Mahira, Y.; Tashima, S.; Banerjee, S.; Nagaoka, K.

    2015-08-15

    Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current (I{sub p}) ramp-up phase, high heat flux (>1 MW/m{sup 2}) and supersonic flow (Mach number M > 1) are found to be present simultaneously in the far-SOL. The heat flux is generated by energetic electrons excursed from the last closed flux surface. Supersonic flows in the poloidal and toroidal directions are correlated with each other. In the quasi-steady state, sawtooth-like oscillation of I{sub p} at 20 Hz is observed. Heat flux and subsonic plasma flow in the far-SOL are modified corresponding to the I{sub p}-oscillation. The heat flow caused by motion of energetic electrons and the bulk-particle transport to the far-SOL is enhanced during the low-I{sub p} phase. Modification of plasma flow in the far SOL occurs earlier than the I{sub p} crash. The M–I{sub p} curve has a limit-cycle characteristic with sawtooth-like oscillation. Such a core–SOL relationship indicates that the far-SOL flow plays an important role in sustaining the oscillation of I{sub p} in the IPN configuration.

  8. Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST

    NASA Astrophysics Data System (ADS)

    Onchi, T.; Zushi, H.; Mishra, K.; Mahira, Y.; Nagaoka, K.; Hanada, K.; Idei, H.; Hasegawa, M.; Nakamura, K.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K.; Tashima, S.; Banerjee, S.; Kuzmin, A.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Watanabe, O.

    2015-08-01

    Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current (Ip) ramp-up phase, high heat flux (>1 MW/m2) and supersonic flow (Mach number M > 1) are found to be present simultaneously in the far-SOL. The heat flux is generated by energetic electrons excursed from the last closed flux surface. Supersonic flows in the poloidal and toroidal directions are correlated with each other. In the quasi-steady state, sawtooth-like oscillation of Ip at 20 Hz is observed. Heat flux and subsonic plasma flow in the far-SOL are modified corresponding to the Ip-oscillation. The heat flow caused by motion of energetic electrons and the bulk-particle transport to the far-SOL is enhanced during the low-Ip phase. Modification of plasma flow in the far SOL occurs earlier than the Ip crash. The M-Ip curve has a limit-cycle characteristic with sawtooth-like oscillation. Such a core-SOL relationship indicates that the far-SOL flow plays an important role in sustaining the oscillation of Ip in the IPN configuration.

  9. Superconducting toroidal field coil current densities for the TFCX

    SciTech Connect

    Kalsi, S.S.; Hooper, R.J.

    1985-04-01

    A major goal of the Tokamak Fusion Core Experiment (TFCX) study was to minimize the size of the device and achieve lowest cost. Two key factors influencing the size of the device employing superconducting magnets are toroidal field (TF) winding current density and its nuclear heat load withstand capability. Lower winding current density requires larger radial build of the winding pack. Likewise, lower allowable nuclear heating in the winding requires larger shield thickness between the plasma and coil. In order to achieve a low-cost device, it is essential to maximize the winding's current density and nuclear heating withhstand capability. To meet the above objective, the TFCX design specification adopted as goals a nominal winding current density of 3500 A/cm/sup 2/ with 10-T peak field at the winding and peak nuclear heat load limits of 1 MW/cm/sup 3/ for the nominal design and 50 MW/cm/sup 3/ for an advanced design. This study developed justification for these current density and nuclear heat load limits.

  10. Magnetic-field sensing coil embedded in ceramic for measuring ambient magnetic field

    SciTech Connect

    Takahashi, Hironori

    2004-02-10

    A magnetic pick-up coil for measuring magnetic field with high specific sensitivity, optionally with an electrostatic shield (24), having coupling elements (22) with high winding packing ratio, oriented in multiple directions, and embedded in ceramic material for structural support and electrical insulation. Elements of the coil are constructed from green ceramic sheets (200) and metallic ink deposited on surfaces and in via holes of the ceramic sheets. The ceramic sheets and the metallic ink are co-fired to create a monolithic hard ceramic body (20) with metallized traces embedded in, and placed on exterior surfaces of, the hard ceramic body. The compact and rugged coil can be used in a variety of environments, including hostile conditions involving ultra-high vacuum, high temperatures, nuclear and optical radiation, chemical reactions, and physically demanding surroundings, occurring either individually or in combinations.

  11. Levitation in the field of a nonsuperconducting coil with magnetic flux stabilization

    NASA Astrophysics Data System (ADS)

    Koshurnikov, E. K.

    2013-09-01

    A method providing the "frozen flux" conditions in a nonsuperconducting coil is suggested and demonstrated with a model. The feasibility of permanent magnet stable levitation in the field of the coil with magnetic flux stabilization and mean current control is shown. The method allows researchers to exploit permanent magnet-superconducting body interaction in physical devices, for example, to reproduce, using nonsuperconducting coils, the frozen magnetic flux conditions required for the stable levitation of the magnet over a superconducting body.

  12. Superconducting FCL using a combined inducted magnetic field trigger and shunt coil

    DOEpatents

    Tekletsadik, Kasegn D.

    2007-10-16

    A single trigger/shunt coil is utilized for combined induced magnetic field triggering and shunt impedance. The single coil connected in parallel with the high temperature superconducting element, is designed to generate a circulating current in the parallel circuit during normal operation to aid triggering the high temperature superconducting element to quench in the event of a fault. The circulating current is generated by an induced voltage in the coil, when the system current flows through the high temperature superconducting element.

  13. Generation of long prolate volumes of uniform magnetic field in cylindrical saddle-shaped coils

    NASA Astrophysics Data System (ADS)

    Dinale, Justin; Vrbancich, Julian

    2014-03-01

    We investigate the uniformity of the magnetic flux density (referred to as the field uniformity) within a series of coils designed to provide a prolate volume of field uniformity. Computational modelling of two cylindrical coil systems which have a sinusoidal current density distributed on the surface of the cylinder, shows the extent of prolate field uniformity along the cylindrical axis, with height and width of the magnetic volume limited by the radius of the cylinder. The first coil system consists of a cos θ coil--a series of saddle-shaped filament loops spaced uniformly with respect to cos θ on the curved cylindrical surface, where θ is the angle between the radius of the cylinder and the horizontal radial axis (assuming a horizontal cylinder). The second coil system, named the ‘ELFcage’ coil, consists of saddle-shaped filament loops spaced uniformly with respect to a fixed Δθ, on the cylindrical surface. The volume of field uniformity is also compared with volumes generated by circular Helmholtz and Barker coil designs. For coil diameters of 2 m, the Helmholtz and Barker coils generate a volume of field uniformity within 1% to 3% of the field at the centre that extends ˜0.8 m and ˜1.4 m respectively along the axis of symmetry. This compares to an extent of 3 m and 6 m for both the cos θ and ELFcage coils wound on a 2 m diameter cylinder (8 m length), for 1% and 3% field uniformity respectively. Importantly, the ELFcage coil shows significantly greater field uniformity along the radial axis compared to the cos θ coil. An array of triaxial magnetometers was used to measure the volume of field uniformity within the cos θ coil system, consisting of two sets of orthogonal cos θ windings to generate radial fields and a solenoid winding to generate an axial field. These measurements confirmed the results obtained from computational modelling. The cos θ coil system is currently in use for calibration of magnetometers and for measuring the magnetic

  14. INTERCOMPARISON OF PERFORMANCE OF RF COIL GEOMETRIES FOR HIGH FIELD MOUSE CARDIAC MRI

    PubMed Central

    Constantinides, Christakis; Angeli, S.; Gkagkarellis, S.; Cofer, G.

    2012-01-01

    Multi-turn spiral surface coils are constructed in flat and cylindrical arrangements and used for high field (7.1 T) mouse cardiac MRI. Their electrical and imaging performances, based on experimental measurements, simulations, and MRI experiments in free space, and under phantom, and animal loading conditions, are compared with a commercially available birdcage coil. Results show that the four-turn cylindrical spiral coil exhibits improved relative SNR (rSNR) performance to the flat coil counterpart, and compares fairly well with a commercially available birdcage coil. Phantom experiments indicate a 50% improvement in the SNR for penetration depths ≤ 6.1 mm from the coil surface compared to the birdcage coil, and an increased penetration depth at the half-maximum field response of 8 mm in the 4-spiral cylindrical coil case, in contrast to 2.9 mm in the flat 4-turn spiral case. Quantitative comparison of the performance of the two spiral coil geometries in anterior, lateral, inferior, and septal regions of the murine heart yield maximum mean percentage rSNR increases of the order of 27–167% in vivo post-mortem (cylindrical compared to flat coil). The commercially available birdcage outperforms the cylindrical spiral coil in rSNR by a factor of 3–5 times. The comprehensive approach and methodology adopted to accurately design, simulate, implement, and test radiofrequency coils of any geometry and type, under any loading conditions, can be generalized for any application of high field mouse cardiac MRI. PMID:23204945

  15. Application of NASTRAN to TFTR toroidal field coil structures

    NASA Technical Reports Server (NTRS)

    Chen, S. J.; Lee, E.

    1978-01-01

    The primary applied loads on the TF coils were electromagnetic and thermal. The complex structure and the tremendous applied loads necessitated computer type of solutions for the design problems. In the early stage of the TF coil design, many simplified finite element models were developed for the purpose of investigating the effects of material properties, supporting schemes, and coil case material on the stress levels in the case and in the copper coil. In the more sophisticated models that followed the parametric and scoping studies, the isoparametric elements, such as QUAD4, HEX8, and HEXA, were used. The analysis results from using these finite element models and the NASTRAN system were considered accurate enough to provide timely design information.

  16. Field quality measurements of Fermilab Nb(3)Sn common coil dipole model

    SciTech Connect

    Kashikhin, V.S.; Andreev, N.; Dimarco, J.; Feher, S.; Kashikhin, V.V.; Lamm, M.; Novitski, I.; Orris, D.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Velev, G.; Zlobin, A.V.; Fermilab

    2003-11-01

    A short model of single-layer Nb{sub 3}Sn common coil magnet has been fabricated and is being tested at Fermilab. This paper summarizes results of magnetic measurements in this model. The geometrical harmonics, coil magnetization and iron saturation effects, ramp-rate dependence, field decay and the ''snap-back'' effect at injection are presented.

  17. Simulation and optimization of the magnetic field in an electroplated copper micro-coil

    NASA Astrophysics Data System (ADS)

    Matar, Maher; Al-Halhouli, Alaaldeen T.; Büttgenbach, Stephanus; Dietzel, Andreas H.

    2013-05-01

    This work aims at simulating and optimizing the magnetic field intensity in different electroplated copper micro-coil designs that can be integrated in a recently developed electromagnetic micro-pump. The results of this study will be used in fabricating new optimized micro-coil designs that may enhance the performance of the developed synchronous micro-pump (i.e., the maximum back pressures and flow rates). The synchronous micro-pump concept depends on managing the movement of two magnets in an annular fluidic channel. Magnet rotation is achieved by sequentially activating a set of planar micro-coils to repel or attract the first magnet (traveling magnet) through the channel, while the second one is anchored between the inlet and the outlet ports. At the end of each pumping cycle, the magnets exchange their anchored and traveling functions. To achieve the maximum back pressure and flow rate (highest performance) in such micro-pump, higher magnetic fields without exceeding the material temperature limitation are required. The stronger the magnetic fields that can be generated, the higher the hydraulic power that can the pump deliver. This study presents extensive numerical simulations using the commercial software package COMSOL and presents also optimizations for the effect of the main micro-coil parameters on the generated magnetic field: coil wire width and height, the coil turns offset distance, the effect of including an iron core inside the coil area, and the number of coil turns. The main analyzed results are: the normal magnetic flux contours at the top (upper) surface of the coil - where the permanent magnets rotate in the micro-pump channel -, the distribution of the magnetic field streams and the area averaging of the magnetic field intensity all over the micro-coil sector.

  18. A Modified Alderman-Grant Coil makes possible an efficient cross-coil probe for high field solid-state NMR of lossy biological samples

    NASA Astrophysics Data System (ADS)

    Grant, Christopher V.; Yang, Yuan; Glibowicka, Mira; Wu, Chin H.; Park, Sang Ho; Deber, Charles M.; Opella, Stanley J.

    2009-11-01

    The design, construction, and performance of a cross-coil double-resonance probe for solid-state NMR experiments on lossy biological samples at high magnetic fields are described. The outer coil is a Modified Alderman-Grant Coil (MAGC) tuned to the 1H frequency. The inner coil consists of a multi-turn solenoid coil that produces a B 1 field orthogonal to that of the outer coil. This results in a compact nested cross-coil pair with the inner solenoid coil tuned to the low frequency detection channel. This design has several advantages over multiple-tuned solenoid coil probes, since RF heating from the 1H channel is substantially reduced, it can be tuned for samples with a wide range of dielectric constants, and the simplified circuit design and high inductance inner coil provides excellent sensitivity. The utility of this probe is demonstrated on two electrically lossy samples of membrane proteins in phospholipid bilayers (bicelles) that are particularly difficult for conventional NMR probes. The 72-residue polypeptide embedding the transmembrane helices 3 and 4 of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) (residues 194-241) requires a high salt concentration in order to be successfully reconstituted in phospholipid bicelles. A second application is to paramagnetic relaxation enhancement applied to the membrane-bound form of Pf1 coat protein in phospholipid bicelles where the resistance to sample heating enables high duty cycle solid-state NMR experiments to be performed.

  19. Uniform magnetic fields generated by circular current-carrying coils. [for spacecraft

    NASA Technical Reports Server (NTRS)

    Williams, V. L.; Cain, J. C.

    1975-01-01

    The study described was carried out to evaluate known systems of circular coils with a view toward their application on board the space probes Ranger 1, Ranger 2, and Explorer 10. Particular attention is given to a new method, developed during the investigation, for determining the constants of systems composed of 6 to 8 coils. Such systems were found to generate magnetic fields of very high uniformity. By using advanced computational techniques, it proved possible to evaluate the field uniformity of various systems without recourse to complex analytical methods. Means of evaluating the influence of coil dimensions on the uniformity of the field of any system are described.

  20. Magnetic Field Alignment of PS-P4VP: a Non-Liquid Crystalline Coil-Coil Block Copolymer

    NASA Astrophysics Data System (ADS)

    Rokhlenko, Yekaterina; Zhang, Kai; Larson, Steven; Gopalan, Padma; O'Hern, Corey; Osuji, Chinedum

    2015-03-01

    Magnetic fields provide the ability to control alignment of self-assembled soft materials such as block copolymers. Most prior work in this area has relied on the presence of ordered assemblies of anisotropic liquid crystalline species to ensure sufficient magnetic anisotropy to drive alignment. Recent experiments with poly(styrene-b-4-vinylpyridine), a non-liquid crystalline BCP, however, show field-induced alignment of a lamellar microstructure during cooling across the order-disorder transition. Using in situ x-ray scattering, we examine the roles of field strength and cooling rate on the alignment response of this low MW coil-coil BCP. Alignment is first observed at field strengths as low as 1 Tesla and improves markedly with both increasing field strength and slower cooling. We present a geometric argument to illustrate the origin of a finite, non-trivial magnetic susceptibility anisotropy for highly stretched surface-tethered polymer chains and corroborate this using coarse-grained molecular dynamics simulations. We rationalize the magnetic field response of the system in terms of the mobility afforded by the absence of entanglements, the intrinsic anisotropy resulting from the stretched polymer chains and sterically constrained conjugated rings, and the large grain size in these low molecular weight materials.

  1. Measurement of Poloidal Velocity on the National Spherical Torus Experiment

    SciTech Connect

    Ronald E. Bell and Russell Feder

    2010-06-04

    A diagnostic suite has been developed to measure impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both active emission in the plane of the neutral heating beams and background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent chargeexchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. Local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. Radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  2. Bucking Coil Efficiency Correction for 5'' PMT Exposed to an External Magnetic Field

    NASA Astrophysics Data System (ADS)

    Llodra, Anthony; Reinhold, Joerg

    2014-03-01

    This research was conducted in support of the Hall C upgrade activities at Thomas Jefferson National Accelerator Facility (JLab). We propose to employ bucking coils in order to maximize the collection efficiency of the 5'' PMTs installed on the Cherenkov detector, which could potentially be exposed to external magnetic field produced by the Super Conducting Super High Momentum Spectrometer (SHMS) magnet. In this research project a 5'' PMT was placed in a light tight cylinder with a fiber optic cable. The cylinder was centered within a set of Helmholtz coils to produce a constant external magnetic field. Furthermore, the cylinder was wrapped with 20 coils of standard 12 gauge cable to act as the bucking coil. With the intensity of the LED source, and the magnitude of the external magnetic field fixed at a carefully determined value, data was taken to determine if the collection efficiency of the PMT was indeed affected. With a decrease in collection efficiency confirmed, further data were taken. A range of current (0-6 A) was applied to the bucking coils, while ADC spectra were analyzed in intervals of 0.25 A. The data indicated that in an external magnetic field of approximately 3 Gauss, the 5'' PMT collection efficiency is maximized with the bucking coil current set to approximately 3.5 A. Thus, the data conclusively indicates that the bucking coil system will indeed maximize the collection efficiency of the 5'' PMT. Florida International University.

  3. Finite size disc gradient coil set for open vertical field magnets.

    PubMed

    Petropoulos, L S

    2000-06-01

    A new analytical approach is used in the design of disc-like gradient coils suitable for magnet geometries with main field direction perpendicular to the surface of the disc. An inverse procedure is used to optimize the coil's characteristics, subject to the restrictions imposed by the desired field behavior over a certain set of constraint points inside a predetermined imaging volume. Excellent agreement between the expected values of the gradient magnetic field and the numerical values generated by applying the Biot-Savart law to a discrete current pattern of the perspective disc coil was found. A Finite Element Analysis package was used to predict the fringe gradient field levels for a non-shielded axial disc coil and for a self-shielded transverse disc coil in the vicinity of the magnet poles. The numerical results indicate that for the self-shielded design the gradient fringe field is 1000 times smaller than the corresponding fringe field for the non-shielded disc case. Also no significant spatial dependence was noticed for the shielded coil's fringe field. PMID:10913723

  4. A simple model for estimating a magnetic field in laser-driven coils

    NASA Astrophysics Data System (ADS)

    Fiksel, Gennady; Fox, William; Gao, Lan; Ji, Hantao

    2016-09-01

    Magnetic field generation by laser-driven coils is a promising way of magnetizing plasma in laboratory high-energy-density plasma experiments. A typical configuration consists of two electrodes—one electrode is irradiated with a high-intensity laser beam and another electrode collects charged particles from the expanding plasma. The two electrodes are separated by a narrow gap forming a capacitor-like configuration and are connected with a conducting wire-coil. The charge-separation in the expanding plasma builds up a potential difference between the electrodes that drives the electrical current in the coil. A magnetic field of tens to hundreds of Teslas generated inside the coil has been reported. This paper presents a simple model that estimates the magnetic field using simple assumptions. The results are compared with the published experimental data.

  5. Effects of coil orientation on the electric field induced by TMS over the hand motor area

    NASA Astrophysics Data System (ADS)

    Laakso, Ilkka; Hirata, Akimasa; Ugawa, Yoshikazu

    2014-01-01

    Responses elicited by transcranial magnetic stimulation (TMS) over the hand motor area depend on the position and orientation of the stimulating coil. In this work, we computationally investigate the induced electric field for multiple coil orientations and locations in order to determine which parts of the brain are affected and how the sensitivity of motor cortical activation depends on the direction of the electric field. The finite element method is used for calculating the electric field induced by TMS in two individual anatomical models of the head and brain. The orientation of the coil affects both the strength and depth of penetration of the electric field, and the field strongly depends on the direction of the sulcus, where the target neurons are located. The coil position that gives the strongest electric field in the target cortical region may deviate from the closest scalp location by a distance on the order of 1 cm. Together with previous experimental data, the results support the hypothesis that the cortex is most sensitive to fields oriented perpendicular to the cortical layers, while it is relatively insensitive to fields parallel to them. This has important implications for targeting of TMS. To determine the most effective coil position and orientation, it is essential to consider both biological (the direction of the targeted axons) and physical factors (the strength and direction of the electric field).

  6. Effects of coil orientation on the electric field induced by TMS over the hand motor area.

    PubMed

    Laakso, Ilkka; Hirata, Akimasa; Ugawa, Yoshikazu

    2014-01-01

    Responses elicited by transcranial magnetic stimulation (TMS) over the hand motor area depend on the position and orientation of the stimulating coil. In this work, we computationally investigate the induced electric field for multiple coil orientations and locations in order to determine which parts of the brain are affected and how the sensitivity of motor cortical activation depends on the direction of the electric field. The finite element method is used for calculating the electric field induced by TMS in two individual anatomical models of the head and brain. The orientation of the coil affects both the strength and depth of penetration of the electric field, and the field strongly depends on the direction of the sulcus, where the target neurons are located. The coil position that gives the strongest electric field in the target cortical region may deviate from the closest scalp location by a distance on the order of 1 cm. Together with previous experimental data, the results support the hypothesis that the cortex is most sensitive to fields oriented perpendicular to the cortical layers, while it is relatively insensitive to fields parallel to them. This has important implications for targeting of TMS. To determine the most effective coil position and orientation, it is essential to consider both biological (the direction of the targeted axons) and physical factors (the strength and direction of the electric field).

  7. A monopole/loop dual-tuned RF coil for ultrahigh field MRI

    PubMed Central

    Yan, Xinqiang

    2014-01-01

    Proton and heteronuclear MRI/MRS using dual-tuned (DT) coils could provide both anatomical and metabolic images without repositioning the subject. However, it is technologically challenging to attain sufficiently electromagnetic (EM) decoupling between the heteronuclear channel and proton channel, and keep the imaging areas and profiles of two nuclear channels highly matched. In this study, a hybrid monopole/loop technique was proposed for DT coil design and this technique was validated by implementing and testing a DT 1H/23Na coil for MR imaging at 7T. The RF fields of the monopole (1H channel) and regular L/C loop (23Na channel) were orthogonal and intrinsically EM decoupled. Bench measurement results demonstrated the isolation between the two nuclear channels was better than -28 dB at both nuclear frequencies. Compared with the conventional DT coil using trap circuits, the monopole/loop DT coil had higher MR sensitivity for sodium imaging. The experimental results indicated that the monopole/loop technique might be a simple and efficient design for multinuclear imaging at ultrahigh fields. Additionally, the proposed DT coils based on the monopole/loop technique can be used as building blocks in designing multichannel DT coil arrays. PMID:25202657

  8. Insert Coil Test for HEP High Field Magnets Using YBCO Coated Conductor Tapes

    SciTech Connect

    Lombardo, V.; Barzi, E.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2011-06-15

    The final beam cooling stages of a Muon Collider may require DC solenoid magnets with magnetic fields of 30-50 T. In this paper we present progress in insert coil development using commercially available YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} Coated Conductor. Technological aspects covered in the development, including coil geometry, insulation, manufacturing process and testing are summarized and discussed. Test results of double pancake coils operated in liquid nitrogen and liquid helium are presented and compared with the performance of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} tape short samples.

  9. DESIGN NOTE: Design of convex-surface gradient coils for a vertical-field open MRI system

    NASA Astrophysics Data System (ADS)

    Moon, C. H.; Park, H. W.; Cho, M. H.; Lee, S. Y.

    2000-08-01

    Open MRI systems usually use vertical-field magnets because interventional studies can be performed more conveniently with them. In this paper, we have designed convex-surface gradient coils for a vertical-field open MRI system. To obtain stronger gradient field strength with a smaller coil inductance while maintaining enough space for interventional operations, we have designed gradient coils on convex, rather than planar, surfaces. The convex-surface gradient coils are designed using the finite element method where the convex surfaces are defined at the prolate spheroidal coordinate. We present evaluation results of the convex-surface gradient coils designed with various rates of convexity.

  10. Decoupling of excitation and receive coils in pulsed magnetic resonance using sinusoidal magnetic field modulation

    NASA Astrophysics Data System (ADS)

    Tseytlin, Mark; Epel, Boris; Sundramoorthy, Subramanian; Tipikin, Dmitriy; Halpern, Howard J.

    2016-11-01

    In pulsed magnetic resonance, the excitation power is many orders of magnitude larger than that induced by the spin system in the receiving coil or resonator. The receiver must be protected during and immediately after the excitation pulse to allow for the energy stored in the resonator to dissipate to a safe level. The time during which the signal is not detected, the instrumental dead-time, can be shortened by using magnetically decoupled excitation and receive coils. Such coils are oriented, with respect to each other, in a way that minimizes the total magnetic flux produced by one coil in the other. We suggest that magnetically decoupled coils can be isolated to a larger degree by tuning them to separate frequencies. Spins are excited at one frequency, and the echo signal is detected at another. Sinusoidal magnetic field modulation that rapidly changes the Larmor frequency of the spins between the excitation and detection events is used to ensure the resonance conditions for both coils. In this study, the relaxation times of trityl-CD3 were measured in a field-modulated pulsed EPR experiment and compared to results obtained using a standard spin echo method. The excitation and receive coils were tuned to 245 and 256.7 MHz, respectively. Using an available rapid-scan, cross-loop EPR resonator, we demonstrated an isolation improvement of approximately 20-30 dB due to frequency decoupling. Theoretical analysis, numerical simulations, and proof-of-concept experiments demonstrated that substantial excitation-detection decoupling can be achieved. A pulsed L-band system, including a small volume bi-modal resonator equipped with modulation coils, was constructed to demonstrate fivefold dead-time reduction in comparison with the standard EPR experiment. This was achieved by detuning of the excitation and receive coils by 26 MHz and using sinusoidal modulation at 480 kHz.

  11. Heat flux and plasma flow in the scrape off layer on the spherical tokamak QUEST with inboard poloidal field null configuration

    NASA Astrophysics Data System (ADS)

    Onchi, Takumi; Zushi, Hideki; Mishra, Kishore; Hanada, Kazuaki; Idei, Hiroshi; Nakamura, Kazuo; Fujisawa, Akihide; Nagashima, Yoshihiko; Hasegawa, Makoto; Kuzmin, Arseny; Nagaoka, Kenichi; QUEST Team

    2014-10-01

    Heat flux and plasma flow in the scrape off layer (SOL) are examined in the inboard poloidal null (IPN) configuration on the spherical tokamak (ST) QUEST. In the ST, trapped energetic electrons on the low field side are widely excursed from the last closed flux surface to SOL so that significant heat loss occurs. Interestingly, plasma flows in the core and the SOL are also observed in IPN though no inductive force like ohmic heating is applied. High heat flux (>1 MW/m2) and sonic flow (M > 1) in far-SOL arise in current ramp-up phase. In quasi-steady state, sawtooth-like oscillation of plasma current with 20 Hz has been observed. Heat flux and subsonic plasma flow in far-SOL are well correlated to plasma current oscillation. The toroidal Mach number largely increases from Mφ ~ 0.1 to ~ 0.5 and drops although the amplitude of plasma current is about 10% of that. Note that such flow modification occurs before plasma current crash, there may be some possibility that phenomena in the SOL or the edge trigger reactions in the core plasma. This work is supported by Grants-in-aid for Scientific Research (S24226020), NIFS Collaboration Research Program (NIFS12KUTR081), and the Collaborative Research Program of Research Institute for Applied Mechanics, Kyushu University.

  12. Simulation of concomitant magnetic fields on fast switched gradient coils used in advanced application of MRI

    NASA Astrophysics Data System (ADS)

    Salinas-Muciño, G.; Torres-García, E.; Hidalgo-Tobon, S.

    2012-10-01

    The process to produce an MR image includes nuclear alignment, RF excitation, spatial encoding, and image formation. To form an image, it is necessary to perform spatial localization of the MR signals, which is achieved using gradient coils. MRI requires the use of gradient coils that generate magnetic fields, which vary linearly with position over the imaging volume. Safety issues have been a motivation to study deeply the relation between the interaction of gradient magnetic field and the peripheral nerve stimulation. In this work is presented a numerical modeling between the concomitant magnetic fields produced by the gradient coils and the electric field induced in a cube with σ conductivity by the gradient field switching in pulse sequences as Eco planar Imaging (EPI), due to this kind of sequence is the most used in advance applications of magnetic resonance imaging as functional MRI, cardiac imaging or diffusion.

  13. Construction of Specialty Guide Field Coils Using an Industrial Robotic Arm

    NASA Astrophysics Data System (ADS)

    Berry, William; Crawford, Christopher; Fugal, Mario; Martin, Elise; Wagner, Daniel; Milburn, Robert

    2011-10-01

    Many contemporary nuclear physics experiments require precise control of the magnetic field within key regions of the experimental apparatus. The nEDM experiment, for instance, requires uniform guide fields (produced by guide field coils) to transport neutron spin polarization from the polarizer to the measurement cell. Guide field coils in general are subject to tight geometrical constraints, and must not produce any external fields which would affect the results of the experiment. In order to produce a satisfactory coil in light of these constraints, a systematic design technique is needed. We introduce the magnetic scalar potential technique, which calculates the exact coil windings required on a specified boundary to produce any desired field distribution inside that satisfies Maxwell's equations. Realizing the designs produced by this technique introduces an additional difficulty: winding many turns according to the exact calculated paths. This is addressed by ``printing'' our coils onto a copper-plated G10 form using a calibrated robot arm and spindle, resulting in a 3-d printed circuit board. To correct for deviations in the actual shape of the form, we use a laser displacement sensor to capture the actual geometry as input into the calculation of the windings. Supported in part by NSF grant PHY-0855584.

  14. Studies of high-field sections of a muon helical cooling channel with coil separation

    SciTech Connect

    Lopes, M.L.; Kashikhin, V.S.; Yonehara, K.; Yu, M.; Zlobin, A.V.; /Fermilab

    2011-03-01

    The Helical Cooling Channel (HCC) was proposed for 6D cooling of muon beams required for muon collider and some other applications. HCC uses a continuous absorber inside superconducting magnets which produce solenoidal field superimposed with transverse helical dipole and helical gradient fields. HCC is usually divided into several sections each with progressively stronger fields, smaller aperture and shorter helix period to achieve the optimal muon cooling rate. This paper presents the design issues of the high field section of HCC with coil separation. The effect of coil spacing on the longitudinal and transverse field components is presented and its impact on the muon cooling discussed. The paper also describes methods for field corrections and their practical limits. The magnetic performance of the helical solenoid with coil separation was discussed in this work. The separation could be done in three different ways and the performances could be very different which is important and should be carefully described during the beam cooling simulations. The design that is currently being considered is the one that has the poorest magnetic performance because it presents ripples in all three components, in particular in the helical gradient which could be quite large. Moreover, the average gradient could be off, which could affect the cooling performance. This work summarized methods to tune the gradient regarding the average value and the ripple. The coil longitudinal thickness and the helix period can be used to tune G. Thinner coils tend to reduce the ripples and also bring G to its target value. However, this technique reduces dramatically the operational margin. Wider coils can also reduce the ripple (not as much as thinner coils) and also tune the gradient to its target value. Longer helix periods reduce ripple and correct the gradient to the target value.

  15. Anisotropy of 2G HTS racetrack coils in external magnetic fields

    NASA Astrophysics Data System (ADS)

    Chudy, Michal; Chen, Yiran; Zhang, Min; Coombs, T. A.

    2013-07-01

    Pancake or racetrack coils wound with second generation high-temperature superconductors (2G HTSs) are important elements for numerous applications of HTS. The applications of these coils are primarily in rotating machines such as motors and generators where they must withstand external magnetic fields from various orientations. The characterization of 2G HTS coils is mostly focused on AC loss assessment, critical current and maximum magnetic field evaluation. In this study, racetrack coils will be placed in different orientations of external magnetic fields—Jc (Ic) versus angle measurements will be performed and interpreted. Full attention is paid to studies of anisotropy Jc versus angle curves for short samples of 2G HTS tapes. As will be shown, the shape of the Jc versus angle curves for tapes has a strong influence on the Jc (Ic) versus angle curves for coils. In this work, a unique and unpredicted behavior of the Jc versus angle curves for the 2G HTS racetrack coils was found. This will be analyzed and fully explained.

  16. 3D vacuum magnetic field modelling of the ITER ELM control coil during standard operating scenarios

    NASA Astrophysics Data System (ADS)

    Evans, T. E.; Orlov, D. M.; Wingen, A.; Wu, W.; Loarte, A.; Casper, T. A.; Schmitz, O.; Saibene, G.; Schaffer, M. J.; Daly, E.

    2013-09-01

    In-vessel, non-axisymmetric, control coils have proven to be an important option for mitigating and suppressing edge-localized modes (ELMs) in high performance operating regimes on a growing number of tokamaks. Additionally, an in-vessel non-axisymmetric ELM control coil is being considered in the ITER baseline design. In preparing for the initial operation of this coil set, a comprehensive study was carried out to characterize the linear superposition of the 3D vacuum magnetic field, produced by the ELM coil, on a series of equilibria representing nine standard ITER operating scenarios. Here, the spatial phase angle of toroidally distributed currents, specified with a cosine waveform, in the upper and lower rows of the ITER ELM coil (IEC) set is varied in 2° steps while holding the current in the equatorial row of coils constant. The peak current in each of the three toroidal rows of window-frame coils making up the IEC is scanned between 5 kAt and 90 kAt in 5 kAt steps and the width of the edge region covered by overlapping vacuum field magnetic islands is calculated. This width is compared to a vacuum field ELM suppression correlation criterion found in DIII-D. A minimum coil current satisfying the DIII-D criterion, along with an associated set of phase angles, is identified for each ITER operating scenario. These currents range from 20 kAt to 75 kAt depending on the operating scenario being used and the toroidal mode number (n) of the cosine waveform. Comparisons between the scaling of the divertor footprint area in cases with n = 3 perturbation fields versus those with n = 4 show significant advantages when using n = 3. In addition, it is found that the DIII-D correlation criterion can be satisfied in the event that various combinations of individual IEC window-frame coils need to be turned off due to malfunctioning components located inside the vacuum vessel. Details of these results for both the full set of 27 window-frame coils and various reduced sets

  17. Formation of sheet plumes, current coils, and helical magnetic fields in a spherical magnetohydrodynamic dynamo

    NASA Astrophysics Data System (ADS)

    Miyagoshi, Takehiro; Kageyama, Akira; Sato, Tetsuya

    2011-07-01

    Aiming at understanding of magnetic field generation process in rapidly rotating stars and planets represented by the Earth, computer simulations of magnetohydrodynamic (MHD) dynamo were performed in a rotating spherical shell geometry. Thermal convection and dynamo process with Ekman number of the order of 10-7 were studied. New structures of convection motion, dynamo-generated electrical current, and magnetic field are found. The flow is organized as a set of thin, sheet-like plumes. The current is made of small-scale coil structure with magnetic flux tubes within each of the coil. These flux tubes are connected each other to form a large scale helical magnetic field structure.

  18. Integrated Design System of Toroidal Field Coil for CFETR

    NASA Astrophysics Data System (ADS)

    Luo, Zhiren; Liu, Xufeng; Du, Shuangsong; Wang, Zhongwei; Song, Yuntao

    2016-09-01

    Integrating engineering software is meaningful but challenging for a system code of a fusion device. This issue is seldom considered by system codes currently. Therefore, to discuss the issue, the Integrated Design System of TF Coil (IDS-TFC) has been worked out, which consists of physical calculation, CAD, and Finite Element Analysis (FEA). Furthermore, an Integrated and Automatically Optimized Method (IAOM) has been created to address the integration and interfaces. The method utilizes a geometry parameter to connect each design submodule and achieve automatic optimization. Double-objectives optimization has been realized, confirming it is feasible to integrate and optimize engineering design and physical calculation. Moreover, IDS-TFC can also serve as a useful reference of integrated design processing for subsequent fusion design. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2014GB110000, 2014GB110002)

  19. Dipole antennas for ultrahigh-field body imaging: a comparison with loop coils.

    PubMed

    Raaijmakers, A J E; Luijten, P R; van den Berg, C A T

    2016-09-01

    Although the potential of dipole antennas for ultrahigh-field (UHF) MRI is largely recognized, they are still relatively unknown to the larger part of the MRI community. This article intends to provide electromagnetic insight into the general operating principles of dipole antennas by numerical simulations. The major part focuses on a comparison study of dipole antennas and loop coils at frequencies of 128, 298 and 400 MHz. This study shows that dipole antennas are only efficient radiofrequency (RF) coils in the presence of a dielectric and/or conducting load. In addition, the conservative electric fields (E-fields) at the ends of a dipole are negligible in comparison with the induced E-fields in the center. Like loop coils, long dipole antennas perform better than short dipoles for deeply located imaging targets and vice versa. When the optimal element is chosen for each depth, loop coils have higher B1 (+) efficiency for shallow depths, whereas dipole antennas have higher B1 (+) efficiency for large depths. The cross-over point depth decreases with increasing frequency: 11.6, 6.2 and 5.0 cm for 128, 298 and 400 MHz, respectively. For single elements, loop coils demonstrate a better B1 (+) /√SARmax ratio for any target depth and any frequency. However, one example study shows that, in an array setup with loop coil overlap for decoupling, this relationship is not straightforward. The overlapping loop coils may generate increased specific absorption rate (SAR) levels under the overlapping parts of the loops, depending on the drive phase settings. Copyright © 2015 John Wiley & Sons, Ltd.

  20. On steady poloidal and toroidal flows in tokamak plasmas

    SciTech Connect

    McClements, K. G.

    2010-08-15

    The effects of poloidal and toroidal flows on tokamak plasma equilibria are examined in the magnetohydrodynamic limit. ''Transonic'' poloidal flows of the order of the sound speed multiplied by the ratio of poloidal magnetic field to total field B{sub {theta}/}B can cause the (normally elliptic) Grad-Shafranov (GS) equation to become hyperbolic in part of the solution domain. It is pointed out that the range of poloidal flows for which the GS equation is hyperbolic increases with plasma beta and B{sub {theta}/}B, thereby complicating the problem of determining spherical tokamak plasma equilibria with transonic poloidal flows. It is demonstrated that the calculation of the hyperbolicity criterion can be easily modified when the assumption of isentropic flux surfaces is replaced with the more tokamak-relevant one of isothermal flux surfaces. On the basis of the latter assumption, a simple expression is obtained for the variation of density on a flux surface when poloidal and toroidal flows are simultaneously present. Combined with Thomson scattering measurements of density and temperature, this expression could be used to infer information on poloidal and toroidal flows on the high field side of a tokamak plasma, where direct measurements of flows are not generally possible. It is demonstrated that there are four possible solutions of the Bernoulli relation for the plasma density when the flux surfaces are assumed to be isothermal, corresponding to four distinct poloidal flow regimes. Finally, observations and first principles-based theoretical modeling of poloidal flows in tokamak plasmas are briefly reviewed and it is concluded that there is no clear evidence for the occurrence of supersonic poloidal flows.

  1. Electric and magnetic fields in solenoidal coils from statics to MHz frequencies

    NASA Astrophysics Data System (ADS)

    Henjes, Katja

    1996-01-01

    The time-varying electric and magnetic fields inside a solenoidal coil have recently been calculated by Harmon. He modeled the coil by a cylindrical current sheet, used a physical approach starting from the Maxwell equations, and found results very different from what was believed from circuit theory since the 1920's. Harmon's derivation neglects the electric field-current relation in the wire, i.e., it violates Ohm's law. In this article, the fields are derived from the Maxwell equations with this omission amended. Instead of the current, the terminal voltage of the coil is taken as the independent input. The relation between the current and the electric field in the coil wire constitutes an additional boundary condition. It allows as additional variable an energy influx from the power source, whereas Harmon considered radiation from the coil outward only. With these modifications, the old circuit theory results are recovered again. Implications are outlined for the physical legitimacy of other models involving a given current sheet.

  2. Design and Performance of the First Dual-Coil Magnet at the Wuhan National High Magnetic Field Center

    NASA Astrophysics Data System (ADS)

    Peng, T.; Sun, Q. Q.; Zhang, X.; Xu, Q.; Xiao, H. X.; Herlach, F.; Pan, Y.; Li, L.

    2013-03-01

    The first 80 T dual-coil magnet was manufactured and tested at the Wuhan National High Magnetic Field Center (WHMFC). The inner coil consists of 8 layers of 2.8 mm × 4.3 mm CuNb microcomposite wire developed in China; the bore diameter is 14 mm and the outer diameter 135 mm. The outer coil was wound directly on the inner coil with 12 layers of 3 mm × 6 mm soft copper. Each conductor layer of both coils was reinforced by Zylon/epoxy composite. The inner and outer coil were driven by a 1.6 MJ/5.12 mF capacitor bank and by eight 1 MJ/3.2 mF modules, respectively. At the voltage of 14.3 kV for the inner coil and 22 kV for the outer coil, the inner and outer coils produced peak fields of 48.5 T and 34.5 T respectively, which gave a total field of 83 T. This was the first combined operation of the new capacitor banks installed at the WHMFC. We present details of the design, manufacture and test of the dual-coil magnet and discuss crucial material properties. Based on this experience, a second dual-coil magnet will be designed; the enhanced design will be discussed. With the total energy of 12.6 MJ, peak field up to 90 T is expected.

  3. Electromagnetic fields in the human body due to switched transverse gradient coils in MRI.

    PubMed

    While, Peter T; Forbes, Larry K

    2004-07-01

    Magnetic resonance imaging scans impose large gradient magnetic fields on the patient. Modern imaging techniques require this magnetic field to be switched rapidly for good resolution. However, it is believed that this can also lead to the unwanted side effect of peripheral nerve stimulation, which proves to be a limiting factor to the advancement of MRI technology. This paper establishes an analytical model for the fields produced within an MRI scanner by transverse gradient coils of known current density. Expressions are obtained for the magnetic induction vector and the electric field vector, as well as for the surface charge and current densities that are induced on the patient's body. The expressions obtained are general enough to allow the study of any combination of gradient coils whose behaviour can be approximated by Fourier series. For a realistic example coil current density and switching function, it is found that spikes of surface charge density are induced on the patient's body as the gradient field is switched, as well as loops of surface current density that mimic the coil current density. For a 10 mT m(-1) gradient field with a rise time of 100 micros, the magnitude of the radial electric field at the body is found to be 10.3 V m(-1). It is also found that there is a finite limit to radial electric field strength as rise time approaches zero.

  4. Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

    DOE PAGES

    Gao, Lan; Ji, Hantao; Fiksel, Gennady; Fox, William; Evans, Michelle; Alfonso, Noel

    2016-04-15

    Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ~ 1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ~ 3 x 1016 W/cm2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ~ 40-50 T magnetic fields at the center of the coil ~ 3-4 ns after laser irradiation. In conclusion, the experiments providemore » significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.« less

  5. Ultrafast proton radiography of the magnetic fields generated by a laser-driven coil current

    NASA Astrophysics Data System (ADS)

    Gao, Lan; Ji, Hantao; Fiksel, Gennady; Fox, William; Evans, Michelle; Alfonso, Noel

    2016-04-01

    Magnetic fields generated by a current flowing through a U-shaped coil connecting two copper foils were measured using ultrafast proton radiography. Two ˜1.25 kJ, 1-ns laser pulses propagated through laser entrance holes in the front foil and were focused to the back foil with an intensity of ˜3 × 1016 W/cm2. The intense laser-solid interaction induced a high voltage between the copper foils and generated a large current in the connecting coil. The proton data show ˜40-50 T magnetic fields at the center of the coil ˜3-4 ns after laser irradiation. The experiments provide significant insight for future target designs that aim to develop a powerful source of external magnetic fields for various applications in high-energy-density science.

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

    SciTech Connect

    Kalsi, S.S.; Lousteau, D.C.; Miller, J.R.

    1987-01-01

    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.

  7. Experimental study of the effects of alternating fields on HTS coils according to the winding insulation conditions

    NASA Astrophysics Data System (ADS)

    Hwang, Y. J.; Ahn, M. C.; Lee, T. S.; Lee, W. S.; Ko, T. K.

    2013-08-01

    This paper examines the effects of alternating fields on high-temperature superconducting (HTS) coils according to the winding insulation condition. Alternating fields can occur in synchronous machines (armature reaction, faults) and other devices. In superconducting synchronous machines, alternating fields affect the operational characteristics of the machine and the superconducting field coil. Therefore, a method of reducing the effects of alternating fields is necessary in superconducting synchronous design. In this study, the effects of alternating fields on the HTS field coil according to the winding insulation condition were experimentally evaluated. The experimental results show that HTS coils made using the no-insulation technique can be a solution for reducing the effects of the alternating field. These results are expected to suggest useful data for applications of HTS field coils in superconducting synchronous machines.

  8. Experimental study on a Nb3Al insert coil under high magnetic field

    NASA Astrophysics Data System (ADS)

    Zhu, Guang; Dai, Yinming; Cheng, Junsheng; Chang, Kun; Liu, Jianhua; Wang, Qiuliang; Pan, Xifeng; Li, Chao

    2016-06-01

    Nb3Al is one of the most promising superconductors to replace Nb3Sn in large scale, high field superconducting magnet. Since the complicated conductor manufacturing process, long and stable Nb3Al conductor is difficult to acquire in a commercial scale. Based on a 70 m length of Nb-Al precursor conductor, we designed and fabricated a Nb3Al coil. The coil winding, low temperature diffusion heat treatment and epoxy impregnation are described in detail. The finished Nb3Al coil is tested as an insert in a background magnet. The test is performed at the background field from 7 T to 15 T. The test results are analyzed and presented in this paper.

  9. Boost of plasma current with active magnetic field shaping coils in rotamak discharges

    SciTech Connect

    Yang Xiaokang; Goss, Jermain; Kalaria, Dhara; Huang, Tian Sen

    2011-08-15

    A set of magnetic shaping coils is installed on the Prairie View (PV) rotamak for the study of active plasma shape control in the regimes with and without toroidal field (TF). In the spherical tokamak regime (with TF), plasma current I{sub p} can be boosted by 200% when all five shaping coils (connected in series) are energized. The enhancement of current drive efficiency is mainly attributed to the radial compression and the substantially axial extension of the plasma column; this in turn improves the impedance matching and thus increases antenna input power. In the field-reversed configuration (without TF), plasma current can be boosted by 100% when one middle coil is used; the appearance of radial shift mode limits the achievable value of I{sub p}. The experiments clearly demonstrate that the plasma shape control plays a role in effectively driving plasma current in rotamaks.

  10. Calculation of impurity poloidal rotation from measured poloidal asymmetries in the toroidal rotation of a tokamak plasma

    SciTech Connect

    Chrystal, C.; Burrell, K. H.; Groebner, R. J.; Kaplan, D. H.; Grierson, B. A.

    2012-10-15

    To improve poloidal rotation measurement capabilities on the DIII-D tokamak, new chords for the charge exchange recombination spectroscopy (CER) diagnostic have been installed. CER is a common method for measuring impurity rotation in tokamak plasmas. These new chords make measurements on the high-field side of the plasma. They are designed so that they can measure toroidal rotation without the need for the calculation of atomic physics corrections. Asymmetry between toroidal rotation on the high- and low-field sides of the plasma is used to calculate poloidal rotation. Results for the main impurity in the plasma are shown and compared with a neoclassical calculation of poloidal rotation.

  11. A Common Coil Design for High Field 2-in-1 Accelerator Magnets^*.

    NASA Astrophysics Data System (ADS)

    Gupta, R.

    1997-05-01

    This paper presents a common coil design concept for 2-in-1 superconducting accelerator magnets. It practically eliminates the major problems in the ends of high field magnets built with either high temperature or conventional superconductors. Racetrack coils, consisting of rectangular blocks built with either superconducting cables or tapes, are common to both apertures with each aperture containing one half of each coil. The two apertures are in the same vertical plane in an over-under geometry. A set of common flat coils are placed vertically on left and right side of the two apertures producing field in the opposite directions. The ends are easy to wind with the conductors experiencing little strain. The ends can be fully supported by a simple 2-d geometry to contain the large Lorentz forces. The overall magnet design, construction and tooling are also expected to be simpler than in conventional cosine theta magnets. The block design for high field magnets uses more conductor than the cosine theta design but is preferred for dealing with the large Lorentz forces in the body of the magnet. The concept is also suitable for a variety of other high field superconducting, moderate field superferric, multi-aperture and combined function magnet designs. ^*Work supported by the U.S. Department of Energy.

  12. A method for determining poloidal rotation from poloidal asymmetry in toroidal rotation (invited)

    SciTech Connect

    Chrystal, C.; Burrell, K. H.; Lao, L. L.; Pace, D. C.; Grierson, B. A.

    2014-11-15

    A new diagnostic has been developed on DIII-D that determines the impurity poloidal rotation from the poloidal asymmetry in the toroidal angular rotation velocity. This asymmetry is measured with recently added tangential charge exchange viewchords on the high-field side of the tokamak midplane. Measurements are made on co- and counter-current neutral beams, allowing the charge exchange cross section effect to be measured and eliminating the need for atomic physics calculations. The diagnostic implementation on DIII-D restricts the measurement range to the core (r/a < 0.6) where, relative to measurements made with the vertical charge exchange system, the spatial resolution is improved. Significant physics results have been obtained with this new diagnostic; for example, poloidal rotation measurements that significantly exceed neoclassical predictions.

  13. Enhanced trapped field performance of bulk high-temperature superconductors using split coil, pulsed field magnetization with an iron yoke

    NASA Astrophysics Data System (ADS)

    Ainslie, M. D.; Fujishiro, H.; Mochizuki, H.; Takahashi, K.; Shi, Y.-H.; Namburi, D. K.; Zou, J.; Zhou, D.; Dennis, A. R.; Cardwell, D. A.

    2016-07-01

    Investigating and predicting the magnetization of bulk superconducting materials and developing practical magnetizing techniques is crucial to using them as trapped field magnets in engineering applications. The pulsed field magnetization (PFM) technique is considered to be a compact, mobile and relative inexpensive way to magnetize bulk samples, requiring shorter magnetization times (on the order of milliseconds) and a smaller and less complicated magnetization fixture; however, the trapped field produced by PFM is generally much smaller than that of slower zero field cooling or field cooling techniques, particularly at lower operating temperatures. In this paper, the PFM of two, standard Ag-containing Gd–Ba–Cu–O samples is carried out using two types of magnetizing coils: (1) a solenoid coil, and (2) a split coil, both of which make use of an iron yoke to enhance the trapped magnetic field. It is shown that a significantly higher trapped field can be achieved using a split coil with an iron yoke, and in order to explain these how this arrangement works in detail, numerical simulations using a 2D axisymmetric finite element method based on the H -formulation are carried to qualitatively reproduce and analyze the magnetization process from both electromagnetic and thermal points of view. It is observed that after the pulse peak significantly less flux exits the bulk when the iron core is present, resulting in a higher peak trapped field, as well as more overall trapped flux, after the magnetization process is complete. The results have important implications for practical applications of bulk superconductors as such a split coil arrangement with an iron yoke could be incorporated into the design of a portable, high magnetic field source/magnet to enhance the available magnetic field or in an axial gap-type bulk superconducting electric machine, where iron can be incorporated into the stator windings to (1) improve the trapped field from the magnetization

  14. Enhanced trapped field performance of bulk high-temperature superconductors using split coil, pulsed field magnetization with an iron yoke

    NASA Astrophysics Data System (ADS)

    Ainslie, M. D.; Fujishiro, H.; Mochizuki, H.; Takahashi, K.; Shi, Y.-H.; Namburi, D. K.; Zou, J.; Zhou, D.; Dennis, A. R.; Cardwell, D. A.

    2016-07-01

    Investigating and predicting the magnetization of bulk superconducting materials and developing practical magnetizing techniques is crucial to using them as trapped field magnets in engineering applications. The pulsed field magnetization (PFM) technique is considered to be a compact, mobile and relative inexpensive way to magnetize bulk samples, requiring shorter magnetization times (on the order of milliseconds) and a smaller and less complicated magnetization fixture; however, the trapped field produced by PFM is generally much smaller than that of slower zero field cooling or field cooling techniques, particularly at lower operating temperatures. In this paper, the PFM of two, standard Ag-containing Gd-Ba-Cu-O samples is carried out using two types of magnetizing coils: (1) a solenoid coil, and (2) a split coil, both of which make use of an iron yoke to enhance the trapped magnetic field. It is shown that a significantly higher trapped field can be achieved using a split coil with an iron yoke, and in order to explain these how this arrangement works in detail, numerical simulations using a 2D axisymmetric finite element method based on the H -formulation are carried to qualitatively reproduce and analyze the magnetization process from both electromagnetic and thermal points of view. It is observed that after the pulse peak significantly less flux exits the bulk when the iron core is present, resulting in a higher peak trapped field, as well as more overall trapped flux, after the magnetization process is complete. The results have important implications for practical applications of bulk superconductors as such a split coil arrangement with an iron yoke could be incorporated into the design of a portable, high magnetic field source/magnet to enhance the available magnetic field or in an axial gap-type bulk superconducting electric machine, where iron can be incorporated into the stator windings to (1) improve the trapped field from the magnetization process

  15. Electromagnetic modeling of REBCO high field coils by the H-formulation

    NASA Astrophysics Data System (ADS)

    Xia, Jing; Bai, Hongyu; Lu, Jun; Gavrilin, Andrew V.; Zhou, Youhe; Weijers, Hubertus W.

    2015-12-01

    In this paper, we employ the anisotropic bulk approximation to successfully implement the electromagnetic modeling of superconducting coils wound with rare-earth-barium-copper-oxide (REBCO) tapes based on the H-formulation, in which the field-dependent critical current density and highly nonlinear E-J characteristic are considered. The total number of turns in the stacks of REBCO pancake coils is up to several thousand. We validate the anisotropic bulk model by comparing the ac loss of a small four-pancake coil between the bulk model and the original model which takes the actual thickness of the superconducting layer into account. Then, the anisotropic bulk model is used to investigate the self-field problem of the REBCO prototype coils of the National High Magnetic Field Laboratory 32 {{T}} all-superconducting magnet. The field and current density distributions are obtained, and an obvious shielding effect is observed at the top and bottom of the coils. The ac losses in the first and second cycles are calculated. The former is crucial to the design of the cooling system and the latter relates to the routine consumption of the liquid helium. It is found that the ac loss in the first cycle is 2.6 times as large as that in the second cycle. We also study the ac loss dependences on some key parameters (the critical current, n-value and ramp rate of the applied current). It is found that both in the first and second cycles, the ac loss increases with decreasing critical current. Moreover, the influence of the n-value on the ac loss is negligible. In addition, the ac loss decreases logarithmically with increasing ramp rate. However, the average power loss increases linearly with increasing ramp rate. We also compare some analytical estimates with the simulation result for the ac loss of the dual prototype coils. It is found that the results of Bean’s slab model are closer to the simulation result. The presented model is a useful tool to help us understand

  16. Team one (GA/MCA) effort of the DOE 12 Tesla Coil Development Program. 12 Tesla ETF toroidal field coil helium bath cooled NbTi alloy concept

    SciTech Connect

    Not Available

    1980-07-01

    This report presents the conceptual design of an ETF compatible toroidal field coil, employing helium bath cooled NbTi alloy conductor. The ten TF-coil array generates a peak field of 11-1/2 tesla at 2.87 m radius, corresponding to a major axis field of 6.1 tesla. The 10 kA conductor is an uninsulated, unsoldered Rutherford cable, employing NbTiTa ally as developed in Phase I of this effort. The conductor is encased within a four element frame of stainless steel strips to provide hoop and bearing load support.

  17. Improved field free line magnetic particle imaging using saddle coils.

    PubMed

    Erbe, Marlitt; Sattel, Timo F; Buzug, Thorsten M

    2013-12-01

    Magnetic particle imaging (MPI) is a novel tracer-based imaging method detecting the distribution of superparamagnetic iron oxide (SPIO) nanoparticles in vivo in three dimensions and in real time. Conventionally, MPI uses the signal emitted by SPIO tracer material located at a field free point (FFP). To increase the sensitivity of MPI, however, an alternative encoding scheme collecting the particle signal along a field free line (FFL) was proposed. To provide the magnetic fields needed for line imaging in MPI, a very efficient scanner setup regarding electrical power consumption is needed. At the same time, the scanner needs to provide a high magnetic field homogeneity along the FFL as well as parallel to its alignment to prevent the appearance of artifacts, using efficient radon-based reconstruction methods arising for a line encoding scheme. This work presents a dynamic FFL scanner setup for MPI that outperforms all previously presented setups in electrical power consumption as well as magnetic field quality.

  18. Inverse design of an organ-oriented RF coil for open, vertical-field, MR-guided, focused ultrasound surgery.

    PubMed

    Xin, Xuegang; Han, Jijun; Feng, Yanqiu; Feng, Qianjin; Chen, Wufan

    2012-12-01

    The advantages of open, vertical-field, magnetic resonance-guided, focused ultrasound surgery (MRgFUS) are attractive. The inverse technique using the bi-boundary conditions is proposed to design a uterine-oriented intraoperative RF coil with an ultrasound aperture for the MRgFUS system. In the current proposed scheme, the desired magnetic field of the RF coil was set to completely overlap the target organ. The current density distribution on the RF coil surface, accounting for the expected magnetic field, was solved using the inverse technique. The stream function was available through the 'discretization' of the current density distribution on the RF coil surface. The coil windings were obtained from the contour plot of the stream function. As a modification of previous designs, the bi-boundary conditions are proposed in the inverse technique for the existence of the ultrasound aperture. Based on the obtained coil windings, a prototype coil was constructed. MR imaging of the phantom and the human body was performed to show the efficacy of the prototype coil. The results of temperature measurement using the prototype coil in a 0.4-T MR system were satisfactory. The performance of the prototype coil improved compared with the previously reported design.

  19. Plasma response based RMP coil geometry optimization for an ITER plasma

    NASA Astrophysics Data System (ADS)

    Zhou, Lina; Liu, Yueqiang; Liu, Yue; Yang, Xu

    2016-11-01

    Based on an ITER 15MA Q  =  10 inductive scenario, a systematic numerical investigation is carried out in order to understand the effect of varying the geometry of the magnetic coils, used for controlling the edge localized modes in tokamaks, on the plasma response to the resonant magnetic perturbation (RMP) fields produced by these coils. Toroidal computations show that both of the plasma response based figures of merit—one is the pitch resonant radial field component near the plasma edge and the other is the plasma displacement near the X-point of the separatrix—consistently yield the same prediction for the optimal coil geometry. With a couple of exceptions, the presently designed poloidal location of the ITER upper and lower rows of RMP coils is close to the optimum, according to the plasma response based criteria. This holds for different coil current configurations with n  =  2, 3, 4, as well as different coil phasing between the upper and lower rows. The coils poloidal width from the present design, on the other hand, is sub-optimal for the upper and lower rows. Modelling also finds that the plasma response amplitude sharply decreases by moving the middle row RMP coils of ITER from the designed radial location (just inside the inner vacuum vessel) outwards (outside the outer vacuum vessel). The decay rate is sensitively affected by the middle row coils’ poloidal coverage for low-n (n  =  1, 2) RMP fields, but not for high-n (n  =  4) fields.

  20. Toroid field coil shear key installation study, DOE task No. 22

    SciTech Connect

    Jones, C.E.; Meier, R.W.; Yuen, J.L.

    1995-01-09

    Concepts for fitting and installation of the scissor keys, triangular keys, and truss keys in the ITER Toroidal Field (TF) Coil Assembly were developed and evaluated. In addition, the process of remote removal and replacement of a failed TF coil was considered. Two concepts were addressed: central solenoid installed last (Naka Option 1) and central solenoid installed first (Naka Option 2). In addition, a third concept was developed which utilized the favorable features of both concepts. A time line for installation was estimated for the Naka Option 1 concept.

  1. Strong magnetic fields generated with a simple open-ended coil irradiated by high power laser pulses

    NASA Astrophysics Data System (ADS)

    Zhu, B. J.; Li, Y. T.; Yuan, D. W.; Li, Y. F.; Li, F.; Liao, G. Q.; Zhao, J. R.; Zhong, J. Y.; Xue, F. B.; He, S. K.; Wang, W. W.; Lu, F.; Zhang, F. Q.; Yang, L.; Zhou, K. N.; Xie, N.; Hong, W.; Wei, H. G.; Zhang, K.; Han, B.; Pei, X. X.; Liu, C.; Zhang, Z.; Wang, W. M.; Zhu, J. Q.; Gu, Y. Q.; Zhao, Z. Q.; Zhang, B. H.; Zhao, G.; Zhang, J.

    2015-12-01

    A simple scheme to produce strong magnetic fields due to cold electron flow in an open-ended coil heated by high power laser pulses is proposed. It differs from previous generation of magnetic fields driven by fast electron current in a capacitor-coil target [S. Fujioka et al., Sci. Rep. 3, 1170 (2013)]. The fields in our experiments are measured by B-dot detectors and proton radiography, respectively. A 205 T strong magnetic field at the center of the coil target is generated in the free space at Iλ2 of 6.85 × 1014 W cm-2 μm2, where I is the laser intensity, and λ is the laser wavelength. The magnetic field strength is proportional to Iλ2. Compared with the capacitor-coil target, the generation mechanism of the magnetic field is straightforward and the coil is easy to be fabricated.

  2. Recent advances in quasi-poloidal stellarator physics issues

    NASA Astrophysics Data System (ADS)

    Spong, D. A.; Hirshman, S. P.; Lyon, J. F.; Berry, L. A.; Strickler, D. J.

    2005-08-01

    The quasi-poloidal stellarator (QPS) hybrid has been developed using a stellarator optimization approach that has proven to be compatible with both low aspect ratio and significantly reduced neoclassical transport relative to anomalous levels. A unique characteristic of this type of quasi-symmetry is a reduced viscous damping level for poloidal plasma flows. Since the plasma-generated E × B and diamagnetic flows are nearly poloidal, minimal parallel flows (and viscous stress) are required to achieve parallel pressure balance in comparison with configurations such as the tokamak, in which the plasma induced flows are nearly perpendicular to the direction of minimum viscosity and relatively larger parallel flows are required. In addition to this impact on neoclassical flows it is also anticipated that quasi-poloidal symmetry will minimize resistance to self-organized plasma-turbulence-driven shear flows and ease access to enhanced confinement states. In order to test these and other transport issues, the QPS device has been designed with a high degree of flexibility by allowing variable current capability not only in its vertical and toroidal coilsets but also in each separate modular coil group. Numerical optimizations have demonstrated that this flexibility can be used not only to modify transport properties, such as the poloidal viscosity, but also to directly suppress magnetic islands.

  3. Elastic-plastic analysis of the toroidal field coil inner leg of the compact ignition tokamak

    SciTech Connect

    Horie, T.

    1987-07-01

    Elastic-plastic analyses were made for the inner leg of the Compact Ignition Tokamak toroidal field (TF) coil, which is made of copper-Inconel composite material. From the result of the elastic-plastic analysis, the effective Young's moduli of the inner leg were determined by the analytical equations. These Young's moduli are useful for the three-dimensional, elastic, overall TF coil analysis. Comparison among the results of the baseline design (R = 1.324 m), the bucked pressless design, the 1.527-m major radius design, and the 1.6-m major radius design was also made, based on the elastic-plastic TF coil inner leg analyses.

  4. Zylon-reinforced high magnetic field coils for the K.U. Leuven pulsed field laboratory

    NASA Astrophysics Data System (ADS)

    Rosseel, K.; Herlach, F.; Boon, W.; Bruynseraede, Y.

    2001-01-01

    PBO Zylon ® fibers have been used for the internal reinforcement of pulsed magnets. Due to the very high packing density (80%) of these fibers, vacuum impregnation of Zylon reinforced coils is difficult. Impregnation test were performed using pressure-vacuum impregnation and wet winding. A prototype series of coils for 60-70 T with 1-2 ms pulse duration was designed and wound, using wet winding for both the internal Zylon and external carbon fiber reinforcement. Special precautions were taken to avoid insulation breakdown at the transitions between conductor layers. Furthermore, axial movement of the conductor wires was restrained by strong axial compression of the coil with a steel shell casing. These modifications were incorporated into an 80 T coil made of Zylon and soft Cu. The design, construction and performance of this coil are discussed.

  5. Passive magnetic field cancellation device by multiple high-Tc superconducting coils

    NASA Astrophysics Data System (ADS)

    Gu, C.; Zou, S.; Han, Z.; Qu, T.-M.

    2010-04-01

    A passive magnetic field cancellation device (PMFCD) is designed. The PMFCD could automatically cancel the field as an active cancellation system did; however it requires no power sources and feedback systems. The capability of the PMFCD is based on the principle that a closed loop can resist flux variation and keep the flux constant inside. The closed loop in the PMFCD is formed by connecting two pairs of high temperature superconductor Helmholtz coils with different radii in series. More important thing is that the ratio of the radius and the turn number between the coils has to satisfy a number of conditions, with which 100% cancellation can be reached. Theoretical methods to obtain the turn number ratio and radius ratio are the major part of the paper. Numerical simulation was followed, aiming to evaluate field distribution under a cancellation state and correct the theoretical values.

  6. Electromagnetic fields inside a lossy, multilayered spherical head phantom excited by MRI coils: models and methods.

    PubMed

    Liu, Feng; Crozier, Stuart

    2004-05-21

    The precise evaluation of electromagnetic field (EMF) distributions inside biological samples is becoming an increasingly important design requirement for high field MRI systems. In evaluating the induced fields caused by magnetic field gradients and RF transmitter coils, a multilayered dielectric spherical head model is proposed to provide a better understanding of electromagnetic interactions when compared to a traditional homogeneous head phantom. This paper presents Debye potential (DP) and Dyadic Green's function (DGF)-based solutions of the EMFs inside a head-sized, stratified sphere with similar radial conductivity and permittivity profiles as a human head. The DP approach is formulated for the symmetric case in which the source is a circular loop carrying a harmonic-formed current over a wide frequency range. The DGF method is developed for generic cases in which the source may be any kind of RF coil whose current distribution can be evaluated using the method of moments. The calculated EMFs can then be used to deduce MRI imaging parameters. The proposed methods, while not representing the full complexity of a head model, offer advantages in rapid prototyping as the computation times are much lower than a full finite difference time domain calculation using a complex head model. Test examples demonstrate the capability of the proposed models/methods. It is anticipated that this model will be of particular value for high field MRI applications, especially the rapid evaluation of RF resonator (surface and volume coils) and high performance gradient set designs.

  7. Decoding 3D search coil signals in a non-homogeneous magnetic field.

    PubMed

    Thomassen, Jakob S; Benedetto, Giacomo Di; Hess, Bernhard J M

    2010-06-18

    We present a method for recording eye-head movements with the magnetic search coil technique in a small external magnetic field. Since magnetic fields are typically non-linear, except in a relative small region in the center small field frames have not been used for head-unrestrained experiments in oculomotor studies. Here we present a method for recording 3D eye movements by accounting for the magnetic non-linearities using the Biot-Savart law. We show that the recording errors can be significantly reduced by monitoring current head position and thereby taking the location of the eye in the external magnetic field into account. PMID:20359490

  8. An optimized target-field method for MRI transverse biplanar gradient coil design

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Xu, Jing; Fu, Youyi; Li, Yangjing; Huang, Kefu; Zhang, Jue; Fang, Jing

    2011-12-01

    Gradient coils are essential components of magnetic resonance imaging (MRI) systems. In this paper, we present an optimized target-field method for designing a transverse biplanar gradient coil with high linearity, low inductance and small resistance, which can well satisfy the requirements of permanent-magnet MRI systems. In this new method, the current density is expressed by trigonometric basis functions with unknown coefficients in polar coordinates. Following the standard procedures, we construct an objective function with respect to the total square errors of the magnetic field at all target-field points with the penalty items associated with the stored magnetic energy and the dissipated power. By adjusting the two penalty factors and minimizing the objective function, the appropriate coefficients of the current density are determined. Applying the stream function method to the current density, the specific winding patterns on the planes can be obtained. A novel biplanar gradient coil has been designed using this method to operate in a permanent-magnet MRI system. In order to verify the validity of the proposed approach, the gradient magnetic field generated by the resulted current density has been calculated via the Biot-Savart law. The results have demonstrated the effectiveness and advantage of this proposed method.

  9. Efficient field emission from coiled carbon nano/microfiber on copper substrate by dc-PECVD

    NASA Astrophysics Data System (ADS)

    Banerjee, D.; Jha, A.; Chattopadhyay, K. K.

    2010-10-01

    Crystalline coiled carbon nano/micro fibers in thin film form have been synthesized via direct current plasma enhanced chemical vapor deposition (PECVD) on copper substrates with acetylene as a carbon precursor at 10 mbar pressure and 750 °C substrate temperature. The as-prepared samples were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). XRD pattern as well as selected area electron diffraction (SAED) pattern showed that the samples were crystalline in nature. SEM and HRTEM studies showed that as synthesized coiled carbon fibers are having average diameter ˜100 nm and are several micrometers in length. The as-prepared samples showed moderately good electron field emission properties with a turn-on field as low as 1.96 V/μm for an inter-electrode distance 220 μm. The variation of field emission properties with inter-electrode distance has been studied in detail. The field emission properties of the coiled carbon fibrous thin films are compared with that of crystalline multiwalled carbon nanotubes and other carbon nanostructures.

  10. Status of poloidal divertor experiments

    SciTech Connect

    Mahdavi, M.A.

    1986-01-01

    The poloidal divertor was originally proposed as a means of impurity control and helium ash removal. Some variations of the concept were also proposed to achieve radiative cooling of the boundary plasma. The discovery of a regime of improved confinement in beam-heated diverted plasmas has further increased the potential value of this concept for tokamak reactors. This paper reviews the poloidal divertor experiments in ASDEX, Doublet III, and PDX and reviews the status of divertor theory and some aspects of the next-generation experiments.

  11. Synchronous Generator with HTS-2G field coils for Windmills with output power 1 MW

    NASA Astrophysics Data System (ADS)

    Kovalev, K.; Kovalev, L.; Poltavets, V.; Samsonovich, S.; Ilyasov, R.; Levin, A.; Surin, M.

    2014-05-01

    Nowadays synchronous generators for wind-mills are developed worldwide. The cost of the generator is determined by its size and weight. In this deal the implementation of HTS-2G generators is very perspective. The application of HTS 2G field coils in the rotor allows to reduce the size of the generator is 1.75 times. In this work the design 1 MW HTS-2G generator is considered. The designed 1 MW HTS-2G generator has the following parameters: rotor diameter 800 mm, active length 400 mm, phase voltage 690V, rotor speed 600 min-1 rotor field coils with HTS-2G tapes. HTS-2G field coils located in the rotating cryostat and cooled by liquid nitrogen. The simulation and optimization of HTS-2G field coils geometry allowed to increase feed DC current up to 50A. Copper stator windings are water cooled. Magnetic and electrical losses in 1 MW HTS-2G generator do not exceed 1.6% of the nominal output power. In the construction of HTS-2G generator the wave multiplier with ratio 1:40 is used. The latter allows to reduce the total mass of HTS-2G generator down to 1.5 tons. The small-scale model of HTS-2G generator with output power 50 kW was designed, manufactured and tested. The test results showed good agreement with calculation results. The manufacturing of 1 MW HTS-2G generator is planned in 2014. This work is done under support of Rosatom within the frames of Russian Project "Superconducting Industry".

  12. Repair of a water-cooled field coil for a hydroelectric motor/generator

    SciTech Connect

    Miller, L.J. III

    1983-01-01

    Four reversible pump/turbine units at TVA's Raccoon Mountain Pumped-Storage Plant were placed in service in 1978 to 1979. The stator and rotor windings for the motor/generators are direct water cooled. This paper describes repairs to a water-cooled coil of one of the 24 field poles of Unit No. 3 motor/generator placed in service in February 1979.

  13. The Influence of Eddy Effect of Coils on Flow and Temperature Fields of Molten Droplet in Electromagnetic Levitation Device

    NASA Astrophysics Data System (ADS)

    Feng, Lin; Shi, Wan-Yuan

    2015-08-01

    In this work, the influence of eddy effect of coils on magnetic, flow, and temperature fields in an electromagnetically levitated molten droplet was investigated by a serial of axisymmetric numerical simulations. In an electromagnetic levitation device, both metal droplet and coils are conductive materials, therefore the distributions of current density in them should be non-uniform as a result of the eddy effect. However, in previous works, the eddy effect was considered alone in metal droplet but ignored in coils usually. As the distance of coils and metal droplet is several millimetres in general, the non-uniform distribution of current density in coils actually gives important influences on calculations of magnetic, flow, and temperature fields. Here, we consider the eddy effect both in metal droplet as well as that in coils simultaneously. Lifting force, absorbed power, fluid flow, and temperature field inside a 4-mm radius molten copper droplet as a typical example are then calculated and analyzed carefully under such condition. The results show that eddy effect leads to higher magnetic force, velocity, and temperature in both levitating and melting processes than those when the eddy effect is ignored. What is more, such influence increases as the distance of droplet and coils becomes closer, which corresponds to experimental measurement. Therefore, we suggest that eddy effect of coils should be considered in numerical simulation on this topic to obtain more reliable result.

  14. Evaluation of cancellation coil for precision magnetic measurements with strong prepolarization field inside shielded environment

    NASA Astrophysics Data System (ADS)

    Hwang, Seong-min; Kim, Kiwoong; Seok Kang, Chan; Lee, Seong-Joo; Lee, Yong-Ho

    2012-04-01

    Many precision magnetic measurements can benefit significantly from or even require strong prepolarization fields (Bp) and magnetically shielded environments. We describe here in detail a cancellation coil (CC) which can neutralize the Bp on the electrically conductive shield walls that may otherwise induce currents on the walls to produce a lingering transient residual field (Btr) inside the shielded environment and disrupt the measurement operations. The CC was designed using the inverse problem method to effectively neutralize magnetic fields generated on the shield walls by the Bp coil. The implemented CC was evaluated by measuring Btr using a fluxgate magnetometer at different magnetometer positions and cancellation coil currents (ICC). Multi-mode component analysis on the Btr measurements revealed two dominant components, where the component with shorter time constant comes from the current induced around the shield side walls and the other with longer time constant from the current induced on the ceiling and floor of the magnetically shielded room. The analysis also revealed the optimal ICC for each of the top, side, and bottom sections of the CC, which enables significantly easier fine-tuning of individual sections of the CC to enhance CC performance.

  15. Understanding the Dynamics of Magnetic Field Alignment for Rod-Coil Block Copolymers

    NASA Astrophysics Data System (ADS)

    McCulloch, Bryan; Portale, Giuseppe; Bras, Wim; Hexemer, Alexander; Segalman, Rachel A.

    2012-02-01

    Alignment of semiconducting block copolymer nanostructures is crucial to optimize charge transport in these materials. Magnetic fields can act on the liquid crystalline conjugated polymers, inducing alignment in rod-coil block copolymers. By using a combination of small angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) we have studied the magnetic field alignment of poly(alkoxy phenylene vinylene-b-isoprene) (PPV-PI) rod-coil block copolymers. In situ measurements have also shown the magnetic field leads to a stabilization of the ordered phase. Furthermore, there appear to be two distinct timescales for alignment: at short times the alignment of these materials is fast likely caused by preferential growth of aligned domains, and at long times alignment increases by the very slow process of defect annihilation. Further, there is an optimum temperature where the kinetics and thermodynamic driving forces for alignment are balanced, producing very highly aligned samples. Understanding the mechanisms by which alignment occurs has lead to knowledge helping to rationally optimize the magnetic alignment of rod-coil block copolymers.

  16. Bucking Coil Implementation on PMT for Active Cancelling of Magnetic Field

    SciTech Connect

    Gogami, T; Asaturyan, A; Bono, J; Baturin, P; Chen, C; Chiba, A; Chiga, N; Fujii, Y; Hashimoto, O; Kawama, D; Maruta, T; Maxwell, V; Mkrtchyan, A; Nagao, S; Nakamura, S N; Reinhold, J; Shichijo, A; Tang, L; Taniya, N; Wood, S A; Ye, Z

    2013-11-01

    Aerogel and water Cerenkov detectors were employed to tag kaons for a lambda hypernuclear spectroscopic experiment which used the (e,e'K{sup +}) reaction in experimental Hall C at Jefferson Lab (JLab E05-115). Fringe fields from the kaon spectrometer magnet yielded ~5 Gauss at the photomultiplier tubes (PMT) for these detectors which could not be easily shielded. As this field results in a lowered kaon detection efficiency, we implemented a bucking coil on each photomultiplier tubes to actively cancel this magnetic field, thus maximizing kaon detection efficiency.

  17. DESIGN, FABRICATION, INSTALLATION AND TESTING OF IN-VESSEL CONTROL COILS FOR DIII-D

    SciTech Connect

    ANDERSON, PM; BAXI, CB; KELLMAN, AG; REIS, EE; ROBINSON, JI

    2002-10-01

    OAK A271 DESIGN, FABRICATION, INSTALLATION AND TESTING OF IN-VESSEL CONTROL COILS FOR DIII-D. Since 1995, DIII-D has performed correction of magnetic field imperfections using a set of six external picture frame coils located on the vessel mid-plane. Recently, these coils have also demonstrated significant benefits when used for feedback of the resistive wall mode, an instability that limits the plasma performance at high beta. Modeling has shown that substantial performance improvements can be achieved by installing new coils inside the vessel and expanding the poloidal coverage above and below the mid-plane. Two prototype internal coils were installed in 2001 and have been tested successfully. installation of a set of twelve internal coils and magnetic sensors in the DIII-D tokamak is to be completed in December 2002. The design requirement for the new coil system was to maximize the magnetic field at the plasma edge, operate with a frequency range of dc to 1000 Hz, and fit behind the existing graphite wall tiles. The coil design adopted and installed is a water-cooled hollow copper conductor insulated with polyamide and housed inside a stainless steel tube that forms a vacuum boundary. The coil is rigidly mounted to the inside of the vacuum vessel. The primary challenge in the design of these coils was in joining of both the copper conductor and the stainless tube without overheating the polyamide insulator.

  18. Predictive study of current sharing temperature test in the Toroidal Field Model Coil without LCT coil using the M&M code

    NASA Astrophysics Data System (ADS)

    Savoldi, L.; Zanino, R.

    2000-08-01

    The Toroidal Field Model Coil (TFMC) will be tested next year at Forschungszentrum Karlsruhe, Germany, in the frame of the International Thermonuclear Experimental Reactor (ITER). The TFMC is pancake-wound on radial plates using 10 Nb 3Sn two-channel cable-in-conduit conductors, jointed on the inner- and outer-side of the coil. The drivers for the test of current sharing temperature ( Tcs) are the resistive heaters located on the inlet plumbing to each conductor (DP1.1, DP1.2) of the first double pancake (DP1). Since all available sensors are outside the coil, Tcs in the conductor must be measured indirectly, which requires sophisticated analysis tools because of the complexity of the system. In the present work we use the recently developed Multi-conductor Mithrandir (M&M) code. The main aim of the paper is of assessing computationally possible scenarios of normal zone initiation in the high field region of the conductor, without quench propagation out of the inlet joint, in the test configuration without LCT coil.

  19. Modified Solenoid Coil That Efficiently Produces High Amplitude AC Magnetic Fields With Enhanced Uniformity for Biomedical Applications

    PubMed Central

    Bordelon, David E.; Goldstein, Robert C.; Nemkov, Valentin S.; Kumar, Ananda; Jackowski, John K.; DeWeese, Theodore L.; Ivkov, Robert

    2014-01-01

    In this paper, we describe a modified solenoid coil that efficiently generates high amplitude alternating magnetic fields (AMF) having field uniformity (≤10%) within a 125-cm3 volume of interest. Two-dimensional finite element analysis (2D-FEA) was used to design a coil generating a targeted peak AMF amplitude along the coil axis of ~100 kA/m (peak-to-peak) at a frequency of 150 kHz while maintaining field uniformity to >90% of peak for a specified volume. This field uniformity was realized by forming the turns from cylindrical sections of copper plate and by adding flux concentrating rings to both ends of the coil. Following construction, the field profile along the axes of the coil was measured. An axial peak field value of 95.8 ± 0.4 kA/m was measured with 650 V applied to the coil and was consistent with the calculated results. The region of axial field uniformity, defined as the distance over which field ≥90% of peak, was also consistent with the simulated results. We describe the utility of such a device for calorimetric measurement of nanoparticle heating for cancer therapy and for magnetic fluid hyperthermia in small animal models of human cancer. PMID:25392562

  20. Performance assessment and optimization of the ITER toroidal field coil joints

    NASA Astrophysics Data System (ADS)

    Rolando, G.; Foussat, A.; Knaster, J.; Ilin, Y.; Nijhuis, A.

    2013-08-01

    The ITER toroidal field (TF) system features eighteen coils that will provide the magnetic field necessary to confine the plasma. Each winding pack is composed of seven double pancakes (DP) connected through praying hands joints. Shaking hands joints are used to interface the terminals of the conductor with the feeder and inter-coil U-shaped bus bars. The feasibility of operating plasma scenarios depends on the ability of the magnets to retain sufficient temperature and current margins. In this respect, the joints represent a possible critical region due to the combination of steady state Joule heating in the resistance of the joint and coupling losses and currents in ramped operation. The temperature and current margins of both DP and terminal joints are analysed during the 15 and 17 MA plasma scenarios. The effect on the joint performance of feasible optimization solutions, such as rotation of the terminal joints and sole RRR increase, is explored. The characterization of the TF coil joints is completed by the estimation of the coupling loss time constant for different inter-strand and strand-to-joint resistance values. The study is carried out with the code JackPot-ACDC, allowing the analysis of lap-type joints with a strand-level detail.

  1. Highlights from the assembly of the helical field coils for the Advanced Toroidal Facility

    SciTech Connect

    Benson, R.D.

    1985-01-01

    The helical field (HF) coils in the Advanced Toroidal Facility (ATF) device consist of a set of 24 identical segments connected to form a continuous pair of helical coils wrapped around a toroidal vacuum vessel. Each segment weighs approximately 1364 kg (3000 lb) and is composed of 14 water-cooled copper plate conductors bolted to a cast stainless steel structural support member with a T-shape cross section (known as the structural tee). The segment components are electrically insulated with Kapton adhesive tape, G-10, Tefzel, and rubber to withstand 2.5 kV. As a final insulator and structural support, the entire segment is vacuum impregnated with epoxy. This paper offers a brief overview of the processes used to assemble the component parts into a completed segment, including identification of items that required special attention. 4 figs.

  2. Phase diagram of rod-coil diblock copolymer melts by self-consistent field theory

    NASA Astrophysics Data System (ADS)

    Yan, Dadong; Tang, Jiuzhou; Jiang, Ying; Zhang, Xinghua; Chen, Jeff

    A unified phase diagram is presented for rod-coil diblock copolymer melts in the isotropic phase regime as a function of the asymmetric parameter. The study is based on free-energy calculation, which incorporates three-dimensional spatial variations of the volume fraction with angular dependence. The wormlike-chain model is used in a self-consistent field treatment. Body-centered cubic, A15, hexagonal, gyroid, and lamellar structures where the rod segments are packed inside the convex rod-coil interface are found stable. As the conformational asymmetric parameter increases, the A15 phase region expands and the gyroid phase region reduces. The stability of the structures is analyzed by concepts such as packing frustration, spinodal limit, and interfacial curvature.

  3. Feasibility Study on Welding Structure of the HT-7U Toroidal Field Coil Case

    NASA Astrophysics Data System (ADS)

    Chen, Wen-ge; Pan, Yin-nian; Wu, Jie-feng; Wei, Jing; Wu, Song-tao; Weng, Pei-de

    2001-06-01

    The Toroidal Field (TF) coil case of the HT-7U superconducting tokamak device is made of austenitic stainless steel 316LN and is designed to operate at cryogenic temperature (4 K). 316LN can retain high strength and fracture toughness at 4 K. Feasibility study on technical process of welding has been experimentally considered as a hopeful joint method for suppression of post-welding deformation and reduction of over-heating. Meanwhile the final range of stress intensity and the stress intensity factor (K) for pre-cracks of welding structure have been determined by using J-integral. These related results are optimistic and have shown that there's no problem in strength and fracture toughness at the vicinity of the pre-crack tip. This paper introduces the welding structure of TF coil case in detail.

  4. Development of effective power supply using electric double layer capacitor for static magnetic field coils in fusion plasma experiments.

    PubMed

    Inomoto, M; Abe, K; Yamada, T; Kuwahata, A; Kamio, S; Cao, Q H; Sakumura, M; Suzuki, N; Watanabe, T; Ono, Y

    2011-02-01

    A cost-effective power supply for static magnetic field coils used in fusion plasma experiments has been developed by application of an electric double layer capacitor (EDLC). A prototype EDLC power supply system was constructed in the form of a series LCR circuit. Coil current of 100 A with flat-top longer than 1 s was successfully supplied to an equilibrium field coil of a fusion plasma experimental apparatus by a single EDLC module with capacitance of 30 F. The present EDLC power supply has revealed sufficient performance for plasma confinement experiments whose discharge duration times are an order of several seconds. PMID:21361590

  5. Feasibility study for reduction of the screening current induced field in a 2G high temperature superconducting coil

    NASA Astrophysics Data System (ADS)

    Hwang, Y. J.; Jang, J. Y.; Ahn, M. C.; Park, Y. G.; Lee, S. G.

    2016-10-01

    This paper reports the effects of thermal energy on reducing the overshoot of the current sweep cycle method to reduce the screening current-induced field (SCF) in a 2G high temperature superconducting (HTS) coil. A disadvantage of the current sweep cycle method is the necessity for large overshoot in the coil current. For a 2G HTS coil, excessive overshooting of the coil current is undesirable (Yanagisawa et al 2012 AIP Conf. Proc. 1434 1373-8). In an effort to circumvent this overshooting problem, the thermal energy effect was investigated in combination with the current sweep cycle method based on experiments in this study. The experimental results show that greater SCF reduction in the HTS coil was obtained upon increasing thermal energy by heater current.

  6. Vertical poloidal asymmetries of low-Z element radiation in the PDX tokamak

    SciTech Connect

    Brau, K.; Suckewer, S.; Wong, S.K.

    1983-06-01

    Vertical poloidal asymmetries of hydrogen isotopes and low-Z impurity radiation in the PDX tokamak may be caused by poloidally asymmetric sources of these elements at gas inlet valves, limiters or vacuum vessel walls, asymmetric magnetic field geometry in the region beyond the plasma boundary, or by ion curvature drifts. Low ionization states of carbon (C II- C IV) are more easily influenced by edge conditions than is CV. Vertical poloidal asymmetries of CV are correlated with the direction of the toroidal field. The magnitude of the asymmetry agrees with the predictions of a quasifluid neoclassical model. Experimental data and numerical simulations are presented to investigate different models of impurity poloidal asymmetries.

  7. Mechanical testing and development of the helical field coil joint for the Advanced Toroidal Facility

    SciTech Connect

    Nelson, B.E.; Bryan, W.E.; Goranson, P.L.; Warwick, J.E.

    1985-01-01

    The helical field (HF) coil set for the Advanced Toroidal Facility (ATF) is an M = 12, l = 2, constant-ratio torsatron winding consisting of 2 coils, each with 14 turns of heavy copper conductor. The coils are divided into 24 identical segments to facilitate fabrication and minimize the assembly schedule. The segments are connected across through-bolted lap joints that must carry up to 124,000 A per turn for 5 s or 62,500 A steady-state. In addition, the joints must carry the high magnetic and thermal loads induced in the conductor and still fit within the basic 140- by 30-mm copper envelope. Extensive testing and development were undertaken to verify and refine the basic joint design. Tests included assembly force and clamping force for various types of misalignment; joint resistance as a function of clamping force; clamp bolt relaxation due to thermal cycling; fatigue testing of full-size, multiturn joint prototypes; and low-cycle fatigue and tensile tests of annealed CDA102 copper. The required performance parameters and actual test results, as well as the final joint configuration, are presented. 2 refs., 9 figs., 4 tabs.

  8. Geometrical Design of a Scalable Overlapping Planar Spiral Coil Array to Generate a Homogeneous Magnetic Field

    PubMed Central

    Jow, Uei-Ming; Ghovanloo, Maysam

    2014-01-01

    We present a design methodology for an overlapping hexagonal planar spiral coil (hex-PSC) array, optimized for creation of a homogenous magnetic field for wireless power transmission to randomly moving objects. The modular hex-PSC array has been implemented in the form of three parallel conductive layers, for which an iterative optimization procedure defines the PSC geometries. Since the overlapping hex-PSCs in different layers have different characteristics, the worst case coil-coupling condition should be designed to provide the maximum power transfer efficiency (PTE) in order to minimize the spatial received power fluctuations. In the worst case, the transmitter (Tx) hex-PSC is overlapped by six PSCs and surrounded by six other adjacent PSCs. Using a receiver (Rx) coil, 20 mm in radius, at the coupling distance of 78 mm and maximum lateral misalignment of 49.1 mm (1/√3 of the PSC radius) we can receive power at a PTE of 19.6% from the worst case PSC. Furthermore, we have studied the effects of Rx coil tilting and concluded that the PTE degrades significantly when θ > 60°. Solutions are: 1) activating two adjacent overlapping hex-PSCs simultaneously with out-of-phase excitations to create horizontal magnetic flux and 2) inclusion of a small energy storage element in the Rx module to maintain power in the worst case scenarios. In order to verify the proposed design methodology, we have developed the EnerCage system, which aims to power up biological instruments attached to or implanted in freely behaving small animal subjects’ bodies in long-term electrophysiology experiments within large experimental arenas. PMID:24782576

  9. Coil system for plasmoid thruster

    NASA Technical Reports Server (NTRS)

    Eskridge, Richard H. (Inventor); Lee, Michael H. (Inventor); Martin, Adam K. (Inventor); Fimognari, Peter J. (Inventor)

    2010-01-01

    A coil system for a plasmoid thruster includes a bias coil, a drive coil and field coils. The bias and drive coils are interleaved with one another as they are helically wound about a conical region. A first field coil defines a first passage at one end of the conical region, and is connected in series with the bias coil. A second field coil defines a second passage at an opposing end of the conical region, and is connected in series with the bias coil.

  10. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    SciTech Connect

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-15

    An X-mode polarized V band (50 GHz–75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz–19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from −1 km/s to −3 km/s.

  11. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

    NASA Astrophysics Data System (ADS)

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  12. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak.

    PubMed

    Qu, Hao; Zhang, Tao; Han, Xiang; Wen, Fei; Zhang, Shoubiao; Kong, Defeng; Wang, Yumin; Gao, Yu; Huang, Canbin; Cai, Jianqing; Gao, Xiang

    2015-08-01

    An X-mode polarized V band (50 GHz-75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz-19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured by the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from -1 km/s to -3 km/s.

  13. Using a modified 3D-printer for mapping the magnetic field of RF coils designed for fetal and neonatal imaging

    NASA Astrophysics Data System (ADS)

    Vavoulas, Alexander; Vaiopoulos, Nicholas; Hedström, Erik; Xanthis, Christos G.; Sandalidis, Harilaos G.; Aletras, Anthony H.

    2016-08-01

    An experimental setup for characterizing the magnetic field of MRI RF coils was proposed and tested. The setup consisted of a specially configured 3D-printer, a network analyzer and a mid-performance desktop PC. The setup was tested on a single loop RF coil, part of a phased array for fetal imaging. Then, the setup was used for determining the magnetic field characteristics of a high-pass birdcage coil used for neonatal MR imaging with a vertical static field. The scattering parameter S21, converted into power ratio, was used for mapping the B1 magnetic field. The experimental measurements from the loop coil were close to the theoretical results (R = 0.924). A high degree of homogeneity was measured for the neonatal birdcage RF coil. The development of MR RF coils is time consuming and resource intensive. The proposed experimental setup provides an alternative method for magnetic field characterization of RF coils used in MRI.

  14. Using a modified 3D-printer for mapping the magnetic field of RF coils designed for fetal and neonatal imaging.

    PubMed

    Vavoulas, Alexander; Vaiopoulos, Nicholas; Hedström, Erik; Xanthis, Christos G; Sandalidis, Harilaos G; Aletras, Anthony H

    2016-08-01

    An experimental setup for characterizing the magnetic field of MRI RF coils was proposed and tested. The setup consisted of a specially configured 3D-printer, a network analyzer and a mid-performance desktop PC. The setup was tested on a single loop RF coil, part of a phased array for fetal imaging. Then, the setup was used for determining the magnetic field characteristics of a high-pass birdcage coil used for neonatal MR imaging with a vertical static field. The scattering parameter S21, converted into power ratio, was used for mapping the B1 magnetic field. The experimental measurements from the loop coil were close to the theoretical results (R=0.924). A high degree of homogeneity was measured for the neonatal birdcage RF coil. The development of MR RF coils is time consuming and resource intensive. The proposed experimental setup provides an alternative method for magnetic field characterization of RF coils used in MRI. PMID:27310429

  15. Using a modified 3D-printer for mapping the magnetic field of RF coils designed for fetal and neonatal imaging.

    PubMed

    Vavoulas, Alexander; Vaiopoulos, Nicholas; Hedström, Erik; Xanthis, Christos G; Sandalidis, Harilaos G; Aletras, Anthony H

    2016-08-01

    An experimental setup for characterizing the magnetic field of MRI RF coils was proposed and tested. The setup consisted of a specially configured 3D-printer, a network analyzer and a mid-performance desktop PC. The setup was tested on a single loop RF coil, part of a phased array for fetal imaging. Then, the setup was used for determining the magnetic field characteristics of a high-pass birdcage coil used for neonatal MR imaging with a vertical static field. The scattering parameter S21, converted into power ratio, was used for mapping the B1 magnetic field. The experimental measurements from the loop coil were close to the theoretical results (R=0.924). A high degree of homogeneity was measured for the neonatal birdcage RF coil. The development of MR RF coils is time consuming and resource intensive. The proposed experimental setup provides an alternative method for magnetic field characterization of RF coils used in MRI.

  16. Unscented transform-based uncertainty analysis of rotating coil transducers for field mapping

    NASA Astrophysics Data System (ADS)

    Arpaia, P.; De Matteis, E.; Schiano Lo Moriello, R.

    2016-03-01

    The uncertainty of a rotating coil transducer for magnetic field mapping is analyzed. Unscented transform and statistical design of experiments are combined to determine magnetic field expectation, standard uncertainty, and separate contributions of the uncertainty sources. For nonlinear measurement models, the unscented transform-based approach is more error-proof than the linearization underlying the "Guide to the expression of Uncertainty in Measurements" (GUMs), owing to the absence of model approximations and derivatives computation. When GUM assumptions are not met, the deterministic sampling strategy strongly reduces computational burden with respect to Monte Carlo-based methods proposed by the Supplement 1 of the GUM. Furthermore, the design of experiments and the associated statistical analysis allow the uncertainty sources domain to be explored efficiently, as well as their significance and single contributions to be assessed for an effective setup configuration. A straightforward experimental case study highlights that a one-order-of-magnitude reduction in the relative uncertainty of the coil area produces a decrease in uncertainty of the field mapping transducer by a factor of 25 with respect to the worst condition. Moreover, about 700 trials and the related processing achieve results corresponding to 5 × 106 brute-force Monte Carlo simulations.

  17. Superelliptical Insert Gradient Coil with a Field Modifying Layer for Breast Imaging

    PubMed Central

    Moon, Sung M.; Goodrich, K. Craig; Hadley, J. Rock; Kim, Seong-Eun; Zeng, Gengsheng L.; Morrell, Glen R.; McAlpine, Matthew A.; Chronik, Blaine A.; Parker, Dennis L.

    2010-01-01

    Many Magnetic Resonance Imaging (MRI) applications such as Dynamic Contrast Enhanced MRI (DCE-MRI) of the breast require high spatial and temporal resolution, and can benefit from improved gradient performance, e.g. increased gradient strength, and reduced gradient rise time. The improved gradient performance required to achieve high spatial and temporal resolution for this application may be achieved by using local insert gradients specifically designed for a target anatomy. Current flat gradient systems cannot create an imaging volume large enough to accommodate both breasts, further, their gradient fields are not homogeneous, dropping off rapidly with distance from the gradient coil surface. To attain an imaging volume adequate for bilateral breast MRI, a planar local gradient system design has been modified into a superellipse shape, creating homogeneous gradient volumes (HGVs) that are 182% (Gx), 57% (Gy), and 75% (Gz) wider (left/right direction) than those of the corresponding standard planar gradient. Adding an additional field-modifying (FM) gradient winding results in an additional improvement of the homogeneous gradient field near the gradient coil surface over the already enlarged HGVs of the superelliptical gradients (67%, 89%, and 214% for Gx, Gy, and Gz respectively). A prototype y-gradient insert has been built to demonstrate imaging and implementation characteristics of the superellipse gradient in a 3T MRI system. PMID:20939085

  18. Unscented transform-based uncertainty analysis of rotating coil transducers for field mapping.

    PubMed

    Arpaia, P; De Matteis, E; Schiano Lo Moriello, R

    2016-03-01

    The uncertainty of a rotating coil transducer for magnetic field mapping is analyzed. Unscented transform and statistical design of experiments are combined to determine magnetic field expectation, standard uncertainty, and separate contributions of the uncertainty sources. For nonlinear measurement models, the unscented transform-based approach is more error-proof than the linearization underlying the "Guide to the expression of Uncertainty in Measurements" (GUMs), owing to the absence of model approximations and derivatives computation. When GUM assumptions are not met, the deterministic sampling strategy strongly reduces computational burden with respect to Monte Carlo-based methods proposed by the Supplement 1 of the GUM. Furthermore, the design of experiments and the associated statistical analysis allow the uncertainty sources domain to be explored efficiently, as well as their significance and single contributions to be assessed for an effective setup configuration. A straightforward experimental case study highlights that a one-order-of-magnitude reduction in the relative uncertainty of the coil area produces a decrease in uncertainty of the field mapping transducer by a factor of 25 with respect to the worst condition. Moreover, about 700 trials and the related processing achieve results corresponding to 5 × 10(6) brute-force Monte Carlo simulations.

  19. Physical and engineering constraints for tokamak reactors with helical coils

    SciTech Connect

    Potok, R.E.; Becker, H.

    1983-09-01

    The authors present an analytical and numerical analysis of a tokamak reactor with a set of helical coils added in order to eliminate plasma disruptions. The optimal helical configuration was found to be a set of continuous, l = 2 stellarator coils which are made of copper and are internal to the toroidal field coils, l being the number of poloidal field periods. (The optimization process did not include evaluation of the viability of a modular stellarator reactor). Scaling laws were developed for this optimal configuration, and a series of parametric scans are performed with varying assumptions for the forces on the helical coils and the ratio of helical coil transform to plasma transform (M). The option space available for attractive reactor designs is strongly constrained and involves large forces on the helical coils, low q plasma operation (q being the plasma safety factor), and moderately low M (3 to 5). Numerical calculations showed that M must be > 3 in order to obtain well defined flux surfaces. This is in agreement with results from the JIPP-T-II Tokomak.

  20. Intraoral approach for imaging teeth using the transverse B1 field components of an occlusally oriented loop coil

    PubMed Central

    Idiyatullin, Djaudat; Corum, Curtis A.; Nixdorf, Donald R.; Garwood, Michael

    2013-01-01

    Purpose The signal-to-noise ratio and resolution are two competing parameters for dental MRI and are highly dependent on the radiofrequency (RF) coil configuration and performance. The purpose of this work is to describe an intraoral approach for imaging teeth with the RF coil plane oriented orthogonally to the Zeeman field to use the transverse components of the B1 field for transmitting and receiving the NMR signal. Methods A single loop coil with shape and size fitted to the average adult maxillary arch was built and tested with a phantom and human subjects in vivo on a whole-body 4T MRI scanner. Supporting Biot-Savart law simulations were performed with Matlab. Results In the occlusion position (in bite plane between the upper and lower teeth), the sensitive volume of the coil encompasses the most important dental structures, the teeth and their supporting structures, while uninteresting tissues containing much higher proton density (cheeks, lips, and tongue) are outside the sensitive volume. The presented images and simulated data show the advantages of using a coil in the orthogonal orientation for dental applications. Conclusion The transverse components of the B1 field of a surface coil can effectively be used for imaging of teeth and associated structures. PMID:23900995

  1. Initial feasibility testing of limited field of view magnetic resonance thermometry using a local cardiac radiofrequency coil.

    PubMed

    Volland, Nelly A; Kholmovski, Eugene G; Parker, Dennis L; Hadley, J Rock

    2013-10-01

    The visualization of lesion formation in real time is one potential benefit of carrying out radiofrequency ablation under magnetic resonance (MR) guidance in the treatment of atrial fibrillation. MR thermometry has the potential to detect such lesions. However, performing MR thermometry during cardiac radiofrequency ablation requires high temporal and spatial resolution and a high signal-to-noise ratio. In this study, a local MR coil (2-cm diameter) was developed to investigate the feasibility of performing limited field of view MR thermometry with high accuracy and speed. The local MR coil allowed high-resolution (1 × 1 × 3 mm(3)) image acquisitions in 76.3 ms with a field of view 64 × 32 mm(2) during an open-chest animal experiment. This represents a 4-fold image acquisition acceleration and an 18-fold field of view reduction compared to that achieved using external MR coils. The signal sensitivity achieved using the local coil was over 20 times greater than that achievable using external coils with the same scan parameters. The local coil configuration provided fewer artifacts and sharper and more stable images. These results demonstrate that MR thermometry can be performed in the heart wall and that lesion formation can be observed during radiofrequency ablation procedures in a canine model.

  2. Nonlinear Dynamics of a Magnetically Driven Duffing-Type Spring-Magnet Oscillator in the Static Magnetic Field of a Coil

    ERIC Educational Resources Information Center

    Donoso, Guillermo; Ladera, Celso L.

    2012-01-01

    We study the nonlinear oscillations of a forced and weakly dissipative spring-magnet system moving in the magnetic fields of two fixed coaxial, hollow induction coils. As the first coil is excited with a dc current, both a linear and a cubic magnet-position dependent force appear on the magnet-spring system. The second coil, located below the…

  3. Induction coil as a non-contacting ultrasound transmitter and detector: Modeling of magnetic fields for improving the performance.

    PubMed

    Rueter, Dirk

    2016-02-01

    A simple copper coil without a voluminous stationary magnet can be utilized as a non-contacting transmitter and as a detector for ultrasonic vibrations in metals. Advantages of such compact EMATs without (electro-)magnet might be: applications in critical environments (hot, narrow, presence of iron filings…), potentially superior fields (then improved ultrasound transmission and more sensitive ultrasound detection). The induction field of an EMAT strongly influences ultrasound transduction in the nearby metal. Herein, a simplified analytical method for field description at high liftoff is presented. Within certain limitations this method reasonably describes magnetic fields (and resulting eddy currents, inductances, Lorentz forces, acoustic pressures) of even complex coil arrangements. The methods can be adapted to conventional EMATS with a separate stationary magnet. Increased distances (liftoff) are challenging and technically relevant, and this practical question is addressed: with limited electrical power and given free space between transducer and target metal, what would be the most efficient geometry of a circular coil? Furthermore, more complex coil geometries ("butterfly coil") with a concentrated field and relatively higher reach are briefly investigated. PMID:26522956

  4. Measurements on Subscale Y-Ba-Cu-O Racetrack Coils at 77 K and Self-Field

    SciTech Connect

    Wang, X.; Caspi, S.; Cheng, D. W.; Dietderich, D. R.; Felice, H.; Ferracin, P.; Godeke, A.; Joseph, J. M.; Lizarazo, J.; Prestemon, S. O.; Sabbi, G.

    2009-10-19

    YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) tapes carry significant amount of current at fields beyond the limit of Nb-based conductors. This makes the YBCO tapes a possible conductor candidate for insert magnets to increase the bore field of Nb{sub 3}Sn high-field dipoles. As an initial step of the YBCO insert technology development, two subscale racetrack coils were wound using Kapton-insulated commercial YBCO tapes. Both coils had two layers; one had 3 turns in each layer and the other 10 turns. The coils were supported by G10 side rails and waxed strips and not impregnated. The critical current of the coils was measured at 77 K and self-field. A 2D model considering the magnetic-field dependence of the critical current was used to estimate the expected critical current. The measured results show that both coils reached 80%-95% of the expected values, indicating the feasibility of the design concept and fabrication process.

  5. Magnetic Field Homogenization of the Human Prefrontal Cortex with a Set of Localized Electrical Coils

    PubMed Central

    Juchem, Christoph; Nixon, Terence W.; McIntyre, Scott; Rothman, Douglas L.; de Graaf, Robin A.

    2011-01-01

    The prefrontal cortex is a common target brain structure in psychiatry and neuroscience due to its role in working memory and cognitive control. Large differences in magnetic susceptibility between the air-filled sinuses and the tissue/bone in the frontal part of the human head cause a strong and highly localized magnetic field focus in the prefrontal cortex. As a result, image distortion and signal dropout are observed in MR imaging. A set of external, electrical coils is presented that provides localized and high amplitude shim fields in the prefrontal cortex with minimum impact on the rest of the brain when combined with regular zero-to-second order spherical harmonics shimming. The experimental realization of the new shim method strongly minimized or even eliminated signal dropout in gradient-echo images acquired at settings typically used in functional magnetic resonance at 4 Tesla. PMID:19918909

  6. Low magnetic moment PIN diodes for high field MRI surface coils.

    PubMed

    Voskoboynik, Pavel; Joos, Ronald D; Doherty, W E; Goldfarb, Ron B

    2006-12-01

    Positive-intrinsic-negative (PIN) silicon diodes are commonly used in magnetic resonance imaging (MRI) coils to perform active or passive blocking and detuning, or to disable circuit functions. However, diode packages with large magnetic moments are known to cause image artifacts in high field MRI systems. In this study, diode packages with low magnetic moment were designed by compensating components of ferromagnetic nickel and paramagnetic tungsten with diamagnetic silver. The new diodes have an initial positive susceptibility up to fields of 1 T and a negative susceptibility from 1 to 7 T. Their magnetic moments are one to two orders of magnitude smaller than those of standard diodes; moments as small as 20 nJ/T at 7 T were achieved. PMID:17278801

  7. Optimized molecular dynamics force fields applied to the helix-coil transition of polypeptides.

    PubMed

    Best, Robert B; Hummer, Gerhard

    2009-07-01

    Obtaining the correct balance of secondary structure propensities is a central priority in protein force-field development. Given that current force fields differ significantly in their alpha-helical propensities, a correction to match experimental results would be highly desirable. We have determined simple backbone energy corrections for two force fields to reproduce the fraction of helix measured in short peptides at 300 K. As validation, we show that the optimized force fields produce results in excellent agreement with nuclear magnetic resonance experiments for folded proteins and short peptides not used in the optimization. However, despite the agreement at ambient conditions, the dependence of the helix content on temperature is too weak, a problem shared with other force fields. A fit of the Lifson-Roig helix-coil theory shows that both the enthalpy and entropy of helix formation are too small: the helix extension parameter w agrees well with experiment, but its entropic and enthalpic components are both only about half the respective experimental estimates. Our structural and thermodynamic analyses point toward the physical origins of these shortcomings in current force fields, and suggest ways to address them in future force-field development.

  8. Design and Fabrication of Helmholtz Coils to Study the Effects of Pulsed Electromagnetic Fields on the Healing Process in Periodontitis: Preliminary Animal Results

    PubMed Central

    Haghnegahdar, A; Khosrovpanah, H; Andisheh-Tadbir, A; Mortazavi, Gh; Saeedi Moghadam, M; Mortazavi, SMJ; Zamani, A; Haghani, M; Shojaei Fard, M; Parsaei, H; Koohi, O

    2014-01-01

    Background: Effects of electromagnetic fields on healing have been investigated for centuries. Substantial data indicate that exposure to electromagnetic field can lead to enhanced healing in both soft and hard tissues. Helmholtz coils are devices that generate pulsed electromagnetic fields (PEMF). Objective: In this work, a pair of Helmholtz coils for enhancing the healing process in periodontitis was designed and fabricated. Method: An identical pair of square Helmholtz coils generated the 50 Hz magnetic field.  This device was made up of two parallel coaxial circular coils (100 turns in each loop, wound in series) which were separated from each other by a distance equal to the radius of one coil (12.5 cm). The windings of our Helmholtz coil was made of standard 0.95mm wire to provide the maximum possible current. The coil was powered by a function generator.  Results: The Helmholtz Coils generated a uniform magnetic field between its coils. The magnetic field strength at the center of the space between two coils was 97.6 μT. Preliminary biological studies performed on rats show that exposure of laboratory animals to pulsed electromagnetic fields enhanced the healing of periodontitis. Conclusion: Exposure to PEMFs can lead to stimulatory physiological effects on cells and tissues such as enhanced healing of periodontitis. PMID:25505775

  9. Strongly magnetized accretion discs require poloidal flux

    NASA Astrophysics Data System (ADS)

    Salvesen, Greg; Armitage, Philip J.; Simon, Jacob B.; Begelman, Mitchell C.

    2016-08-01

    Motivated by indirect observational evidence for strongly magnetized accretion discs around black holes, and the novel theoretical properties of such solutions, we investigate how a strong magnetization state can develop and persist. To this end, we perform local simulations of accretion discs with an initially purely toroidal magnetic field of equipartition strength. We demonstrate that discs with zero net vertical magnetic flux and realistic boundary conditions cannot sustain a strong toroidal field. However, a magnetic pressure-dominated disc can form from an initial configuration with a sufficient amount of net vertical flux and realistic boundary conditions. Our results suggest that poloidal flux is a necessary prerequisite for the sustainability of strongly magnetized accretion discs.

  10. Corneal temperature changes induced by high-field-strength MR imaging with a head coil.

    PubMed

    Shellock, F G; Crues, J V

    1988-06-01

    High-field-strength/high-frequency magnetic resonance (MR) imaging systems can cause tissue heating. Since the eye is particularly susceptible to temperature elevations because of its relatively poor blood supply, the authors measured corneal temperatures in 33 patients immediately before and after MR imaging performed with a 1.5-T (64-MHz) imager and a transmit/receive head coil at estimated peak specific absorption rates (SAR) ranging from 2.54 to 3.05 W/kg. There was a statistically (P less than .001) significant increase in the average corneal temperature (32.7 degrees C +/- 0.7 before imaging, 33.2 degrees C +/- 0.5 after). The changes in corneal temperature ranged from 0.0 degrees C to 1.8 degrees C (mean, 0.5 degrees C), and the highest corneal temperature measured after imaging was 34.4 degrees C. In animal models, the eye temperature threshold for radio frequency-induced cataractogenesis is between 41 degrees C and 55 degrees C. The authors conclude that clinical MR imaging with use of a head coil at the SARs studied causes relatively minor increases in corneal temperature that do not appear to pose any thermal hazard to ocular tissue. PMID:3363146

  11. A distributed equivalent magnetic current based FDTD method for the calculation of E-fields induced by gradient coils.

    PubMed

    Liu, Feng; Crozier, Stuart

    2004-08-01

    This paper evaluates a new, low-frequency finite-difference time-domain method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretization of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modelling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multi-layered spherical phantom model and a complete body model.

  12. High-field 13C NMR spectroscopy of tissue in Vivo. A double-resonance surface-coil probe

    NASA Astrophysics Data System (ADS)

    Reo, Nicholas V.; Ewy, Coleen S.; Siegfried, Barry A.; Ackerman, Joseph J. H.

    A double-resonance surface-coil NMR probe is described for performance of high-field (8.5 T) proton decoupled carbon-13 experiments with tissue in vivo. The probe may be accommodated in standard, 89 mm i.d. clear bore, commercial spectrometers and is suitable for studies utilizing small laboratory animals such as mice, hamsters, and rats. A coaxial coil design is employed (10 mm diameter 13C coil, 20 mm diameter 1H coil) which provides ca. 40 dB attenuation between the 13C observe and 1H decouple channels. The inherent efficiency of the surface-coil configuration provides a sensitivity comparable to a commercial probe of the same nominal dimension (10 mm Helmholtz coil) and assures adequate decoupling in conductive samples with ca. 3-5 W power. In the absence of 13C isotopic enrichment, NMR spectra of rat leg, liver, and brain in vivo provide signalto-noise sufficient for 10 min time resolution. Administration of 100 mg of 90% 13C-labeled glucose into a peripheral vein of a ca. 300 g rat resulted in a liver glucose resonance which could be monitored with good signal-to-noise and 3 min time resolution.

  13. Performance of pancake coils of parallel co-wound Ag/BSCCO tape conductors in static and ramped magnetic fields

    SciTech Connect

    Schwenterly, S.W.; Lue, J.W.; Lubell, M.S.; Walker, M.S.; Hazelton, D.W.; Haldar, P.; Rice, J.A.; Hoehn, J.G. Jr.; Motowidlo, L.R.

    1994-12-31

    Critical Currents are reported for several Ag/BSCCO single-pancake coils in static magnetic fields ranging from 0 to 5 T and temperatures from 4.2 K to 105 K. The sample coils were co-wound of one to six tape conductors in parallel. Since the closed loops formed in such an arrangement could lead to eddy current heating or instability in changing fields, one of the coils was also tested in helium gas, in fields ramped at rates of up to 1.5 T/s. For these quasi-adiabatic tests, at each temperature the transport current was set just below the critical value for a preset static field of 3.3 or 4.9 T. The field was then rapidly ramped down to zero, held for 20 sec, and then ramped back up to the original value. The maximum observed temperature transient of about 1.7 K occurred at 9 K, for a field change of 4.75 T. The temperature transients became negligible when the sample was immersed in liquid helium. Above 30 K, the transients were below 1 K. These results give confidence that parallel co-wound HTSC coils are stable in a rapidly-ramped magnetic field, without undue eddy current heating.

  14. Avoiding eddy-current problems in ultra-low-field MRI with self-shielded polarizing coils

    NASA Astrophysics Data System (ADS)

    Nieminen, Jaakko O.; Vesanen, Panu T.; Zevenhoven, Koos C. J.; Dabek, Juhani; Hassel, Juha; Luomahaara, Juho; Penttilä, Jari S.; Ilmoniemi, Risto J.

    2011-09-01

    In ultra-low-field magnetic resonance imaging (ULF MRI), superconductive sensors are used to detect MRI signals typically in fields on the order of 10-100 μT. Despite the highly sensitive detectors, it is necessary to prepolarize the sample in a stronger magnetic field on the order of 10-100 mT, which has to be switched off rapidly in a few milliseconds before signal acquisition. In addition, external magnetic interference is commonly reduced by situating the ULF-MRI system inside a magnetically shielded room (MSR). With typical dipolar polarizing coil designs, the stray field induces strong eddy currents in the conductive layers of the MSR. These eddy currents cause significant secondary magnetic fields that may distort the spin dynamics of the sample, exceed the dynamic range of the sensors, and prevent simultaneous magnetoencephalography and MRI acquisitions. In this paper, we describe a method to design self-shielded polarizing coils for ULF MRI. The experimental results show that with a simple self-shielded polarizing coil, the magnetic fields caused by the eddy currents are largely reduced. With the presented shielding technique, ULF-MRI devices can utilize stronger and spatially broader polarizing fields than achievable with unshielded polarizing coils.

  15. Influence of applied magnetic field strength and frequency response of pick-up coil on the magnetic barkhausen noise profile

    NASA Astrophysics Data System (ADS)

    Vashista, M.; Moorthy, V.

    2013-11-01

    The influence of applied magnetic field strength and frequency response of the pick-up coil on the shape of Magnetic Barkhausen Noise (MBN) profile have been studied. The low frequency MBN measurements have been carried out using 5 different MBN pick-up coils at two different ranges of applied magnetic field strengths on quenched and tempered (QT) and case-carburised and tempered (CT) 18CrNiMo7 steel bar samples. The MBN pick-up coils have been designed to obtain different frequency response such that the peak frequency response varies from ˜4 kHz to ˜32 kHz and the amplitude of low frequency signals decreases gradually. At lower applied magnetic field strength of ±14,000 A/m, all the pick-up coils produced a single peak MBN profile for both QT and CT sample. However, at higher applied magnetic field strength of ±22,000 A/m, the MBN profile showed two peaks for both QT and CT samples for pick-up coils with peak frequency response up to ˜17 kHz. Also, there is systematic reduction in peak 2 for QT sample and asymmetric reduction in the heights of peak 1 and peak 2 for CT sample with increase in peak frequency response of the pick-up coils. The decreasing sensitivity of pick-up coils with increasing peak frequency response to MBN signal generation is indicated by the gradual reduction in width of MBN profile and height of peak 2 in the QT sample. The drastic reduction in peak 1 as compared to peak 2 in the CT sample shows the effect of decreasing low frequency response of the pick-up coils on lowering skin-depth of MBN signal detection. This study clearly suggests that it is essential to optimise both maximum applied magnetic field strength and frequency response of the MBN pick-up coil for maximising the shape of the MBN profile for appropriate correlation with the magnetisation process and hence the material properties.

  16. Method of sustaining a radial electric field and poloidal plasma rotation over most of the cross-section of a tokamak

    DOEpatents

    Darrow, Douglass S.; Ono, Masayuki

    1990-03-06

    A radial electric field of a desired magnitude and configuration is created throughout a substantial portion of the cross-section of the plasma of a tokamak. The radial electric field is created by injection of a unidirectional electron beam. The magnitude and configuration of the radial electric field may be controlled by the strength of the toroidal magnetic field of the tokamak.

  17. Method of sustaining a radial electric field and poloidal plasma rotation over most of the cross-section of a tokamak

    DOEpatents

    Darrow, Douglass S.; Ono, Masayuki

    1990-01-01

    A radial electric field of a desired magnitude and configuration is created hroughout a substantial portion of the cross-section of the plasma of a tokamak. The radial electric field is created by injection of a unidirectional electron beam. The magnitude and configuration of the radial electric field may be controlled by the strength of the toroidal magnetic field of the tokamak.

  18. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR.

    PubMed

    Kruber, S; Farrher, G D; Anoardo, E

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α-helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm(3) the effective magnet homogeneity is lower than 130 ppm. PMID:26367321

  19. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR

    NASA Astrophysics Data System (ADS)

    Kruber, S.; Farrher, G. D.; Anoardo, E.

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α -helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm3 the effective magnet homogeneity is lower than 130 ppm.

  20. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR.

    PubMed

    Kruber, S; Farrher, G D; Anoardo, E

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α-helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm(3) the effective magnet homogeneity is lower than 130 ppm.

  1. A study of the electromagnetic characteristics of no-insulation GdBCO racetrack coils under an external magnetic ripple field

    NASA Astrophysics Data System (ADS)

    Choi, Y. H.; Yang, D. G.; Kim, Y. G.; Kim, S. G.; Song, J. B.; Lee, H. G.

    2016-04-01

    Here we report the effect of an external magnetic ripple field on the electromagnetic characteristics of GdBCO racetrack coils being operated with a constant DC current. Two types of GdBCO racetrack coils, one wound without turn-to-turn insulation (NI) and the other wound with Kapton tape (INS), were examined under external ripple fields generated by a permanent magnet mounted on a rotor, which was driven by a separate AC motor. The voltage fluctuations and magnetic field variations were measured with respect to the external ripple field intensity (B ERF), rotating speed, and the operating condition. When the INS and NI coils were exposed to an external ripple field (herein, I op = 80 A, B ERF = 2 mT, and 5 rpm), a voltage fluctuation occurred because a time-varying magnetic field interacted with an electric circuit creating an electromotive force. The peak-to-peak voltage (V pp = 0.29 mV) of the NI coil was ∼1.86 times lower than that (0.54 mV) of the INS coil, because the voltage response of the NI coil lagged behind dB/dt due to the existence of turn-to-turn contact. Furthermore, the V pp of the INS coil increased with increasing B ERF and rotating speed, while those of the NI coil were barely affected due to the delay of electromagnetic induction. In excessive current and ripple field conditions (I op = 1.125 I c, B ERF = 8 mT, and 50 rpm) the INS coil eventually quenched while the NI coil did not, implying that the electromagnetic stability of the NI coil in excessive time-varying field conditions was superior to that of the INS coil.

  2. Demonstration Model Development of the Force-Balanced Coil for SMES

    NASA Astrophysics Data System (ADS)

    Nomura, Shinichi; Kasuya, Koji; Tanaka, Norihiro; Tsuboi, Kenji; Tsutsui, Hiroaki; Shimada, Ryuichi; Ninomiya, Akira; Ishigohka, Takashi

    In large-scale SMES, the superconducting coils require special considerations for induced electromagnetic forces to limit allowable tensile stress. Force-balanced coil (FBC) is a helically wound hybrid coil of toroidal field coils and a solenoid. The FBC can significantly reduce the required mass of the structure for induced electromagnetic forces. In order to demonstrate the feasibility of the FBC concept for SMES, the authors have developed a superconducting model coil. The outer diameter of the model FBC is 0.53m. The hand-made winding, using NbTi/Cu composite strands with a diameter of 1.17mm, was finished with 10584 poloidal turns after four months. The helical windings of the model FBC were neither impregnated with epoxy resin nor reinforced with stainless steel wires. Three test runs were conducted with liquid helium cooling at intervals of several months. The number of quench tests was 81 in total. The first quench current was 293A, which was 53% of the critical coil current. The training phenomena could be observed even after the coil was warmed up to room temperature. After successive quenches the quench current was improved to 476A, corresponding to 86% of the critical coil current, and it was successfully excited up to 6.1T.

  3. Investigation of the B1 field distribution and RF power deposition in a birdcage coil as functions of the number of coil legs at 4.7 T, 7.0 T, and 11.7 T

    NASA Astrophysics Data System (ADS)

    Seo, Jeung-Hoon; Han, Sang-Doc; Kim, Kyoung-Nam

    2015-06-01

    The proper design of birdcage (BC) coils plays a very important role in the acquisition of highresolution magnetic resonance imaging (MRI) of small animals such as rodents. In this context, we investigate multiple-leg (8-, 16-, 32-, 64-, and 128-leg) BC coils operating at ultra-high fields (UHF) of 7.0 T and 11.7 T and a high-field (HF) of 4.7 T for rodent magnetic resonance imaging (MRI). Primarily, Our study comparatively examines the parameters of the radiofrequency (RF) transmission (|B1 +|)-field, the magnetic flux (|B1|)-field, and RF power deposition (RF-PD) as functions of the number of BC-coil legs via finite-difference time-domain (FDTD) calculations under realistic loading conditions with a biological phantom. In particular, the specific ratio |E/B1 +| is defined for predicting RF-PD values in different coil structures. Our results indicate that the optimal number of legs of the BC coil can be chosen for different resonance frequencies of 200 MHz, 300 MHz, and 500 MHz and that this choice can be lead to superior |B1 +|-field intensity and |B1|-field homogeneity and decreased RF-PD. We believe that our approach to determining the optimal number of legs for a BC coil can contribute to rodent MR imaging.

  4. Comparison of poloidal velocity measurements to neoclassical theory on the National Spherical Torus Experiment

    SciTech Connect

    Bell, R. E.; Andre, R.; Kaye, S. M.; Kolesnikov, R. A.; LeBlanc, B. P.; Rewoldt, G.; Wang, W. X.; Sabbagh, S. A.

    2010-08-15

    Knowledge of poloidal velocity is necessary for the determination of the radial electric field, which along with its gradient is linked to turbulence suppression and transport barrier formation. Recent measurements of poloidal flow on conventional tokamaks have been reported to be an order of magnitude larger than expected from neoclassical theory. In contrast, poloidal velocity measurements on the NSTX spherical torus [Kaye et al., Phys. Plasmas 8, 1977 (2001)] are near or below neoclassical estimates. A novel charge exchange recombination spectroscopy diagnostic is used, which features active and passive sets of up/down symmetric views to produce line-integrated poloidal velocity measurements that do not need atomic physics corrections. Inversions are used to extract local profiles from line-integrated active and background measurements. Poloidal velocity measurements are compared with neoclassical values computed with the codes NCLASS[Houlberg et al., Phys. Plasmas 4, 3230 (1997)] and GTC-NEO[Wang et al., Phys. Plasmas 13, 082501 (2006)].

  5. Capability Assessment of the Equilibrium Field System in KTX

    NASA Astrophysics Data System (ADS)

    Luo, Bing; Luo, Zhengping; Xiao, Bingjia; You, Wei; Tan, Mingsheng; Guo, Yong; Bai, Wei; Mao, Wenzhe; Li, Hong; Liu, Adi; Lan, Tao; Xie, Jinlin; Liu, Wandong

    2016-01-01

    Radial equilibrium of the KTX plasma column is maintained by the vertical field which is produced by the equilibrium field coils. The equilibrium is also affected by the eddy current, which is generated by the coupling of copper shell, plasma and poloidal field coils. An equivalent circuit model is developed to analyze the dynamic performance of equilibrium field coils, without auxiliary power input to equilibrium field coils and passive conductors. Considering the coupling of poloidal field coils, copper shell and plasma, the evolution of spatial distribution of the eddy current density on the copper shell is estimated by finite element to analyze the effect of shell to balance. The simulation results show that the copper shell and equilibrium field coils can provide enough vertical field to balance 1 MA plasma current in phase 1 of a KTX discharge. Auxiliary power supply on the EQ coils is necessary to control the horizontal displacement of KTX due to the finite resistance effect of the shell. supported by the Ministry of Science and Technology of China (No. 2011GB106000)

  6. SQUIDs vs. Faraday coils for ultlra-low field nuclear magnetic resonance: experimental and simulation comparison

    SciTech Connect

    Matlashov, Andrei N; Espy, Michelle A; Kraus, Robert H; Sayukov, Igor M; Schultz, Larry J; Urbaitis, Algis V; Volegov, Petr L; Wurden, Caroline J

    2010-01-01

    Nuclear magnetic resonance (NMR) methods are widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging or MRI. Recently it has become possible to perform NMR and MRI in ultra-low field (ULF) regime that requires measurement field strengths only of the order of 1 Gauss. These techniques exploit the advantages offered by superconducting quantum interference devices or SQUIDs. Our group at LANL has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airports security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification and security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers provide enough sensitivity in the 3-10 kHz range and can be used for fast liquid explosives detection based on ULF NMR/MRI technique. We describe an experimental and computer simulation comparison of the world's first multichannel SQUID based and Faraday coils based instruments that are capable of performing ULF MRI for liquids identification.

  7. Fast ion loss associated with perturbed field by resonant magnetic perturbation coils in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, Jun Young; Kim, Junghee; Rhee, Tongnyeol; Yoon, S. W.; Park, G. Y.; Jeon, Y. M.; Isobe, M.; Shimizu, A.; Ogawa, K.; Park, J.-K.; Garcia-Munoz, M.

    2013-10-01

    Resonant magnetic perturbation (RMP) is the most promising strategies for ELM mitigation/suppression. However, it has been found through the modeling and the experiments that RMP for the ELM mitigation can enhance the toroidally localized fast ion loss. During KSTAR experimental campaigns in 2011 and 2012, sudden increase or decrease of the fast ion loss has been observed by the scintillator-based fast ion loss detector (FILD) when the RMP is applied. Three-dimensional perturbed magnetic field by RMP coil in vacuum is calculated by Biot-Savart's law embedded in the Lorentz orbit code (LORBIT). The LORBIT code which is based on gyro-orbit following motion has been used for the simulation of the three-dimensional fast ion trajectories in presence of non-axisymmetric magnetic perturbation. It seems the measured fast ion loss rate at the localized position depends on not only the RMP field configuration but also the plasma profile such as safety factor and so on, varying the ratio between radial drift and stochastization of the fat-ion orbits. The simulation results of fast ion orbit under magnetic perturbation w/ and w/o plasma responses will be presented and compared with KSTAR FILD measurement results in various cases.

  8. SQUIDs vs. Induction Coils for Ultra-Low Field Nuclear Magnetic Resonance: Experimental and Simulation Comparison.

    PubMed

    Matlashov, Andrei N; Schultz, Larry J; Espy, Michelle A; Kraus, Robert H; Savukov, Igor M; Volegov, Petr L; Wurden, Caroline J

    2011-01-01

    Nuclear magnetic resonance (NMR) is widely used in medicine, chemistry and industry. One application area is magnetic resonance imaging (MRI). Recently it has become possible to perform NMR and MRI in the ultra-low field (ULF) regime requiring measurement field strengths of the order of only 1 Gauss. This technique exploits the advantages offered by superconducting quantum interference devices or SQUIDs. Our group has built SQUID based MRI systems for brain imaging and for liquid explosives detection at airport security checkpoints. The requirement for liquid helium cooling limits potential applications of ULF MRI for liquid identification and security purposes. Our experimental comparative investigation shows that room temperature inductive magnetometers may provide enough sensitivity in the 3-10 kHz range and can be used for fast liquid explosives detection based on ULF NMR technique. We describe experimental and computer-simulation results comparing multichannel SQUID based and induction coils based instruments that are capable of performing ULF MRI for liquid identification. PMID:21747638

  9. Application of poloidal beta and plasma internal inductance in determination of input power time of Damavand tokamak

    NASA Astrophysics Data System (ADS)

    Noori, Ehsanallah; Sadeghi, Yahya; Ghoranneviss, Mahmood

    2016-10-01

    In this study, magnetic measurement of poloidal fields were used to determine poloidal beta and plasma internal inductance of Damavand tokamak combination of poloidal beta and plasma internal inductance (β _p+{l_i}/{2} ), known as Shafranov parameter, was obtained experimentally in terms of normal and tangential components of the magnetic field. Plasma internal inductance and poloidal beta were obtained using parametrization method based on analytical solution of Grad-Shafranov equation (GSE) and compared with parabolic-like profile of toroidal current density approach for determination of the plasma internal inductance. Finding evolution of β _p+{l_i}/{2} and plasma internal inductance. Finding poloidal beta (Shafranov parameter and internal inductance) and using energy balance equation, thermal energy and energy confinement were determined qualitatively in terms of poloidal beta during a regular discharge of Damavand tokamak.

  10. Towards beyond 1 GHz NMR: Mechanism of the long-term drift of screening current-induced magnetic field in a Bi-2223 coil

    NASA Astrophysics Data System (ADS)

    Koyama, Y.; Takao, T.; Yanagisawa, Y.; Nakagome, H.; Hamada, M.; Kiyoshi, T.; Takahashi, M.; Maeda, H.

    2009-07-01

    The screening current-induced magnetic field in the (Bi,Pb) 2Sr 2Ca 2Cu 3O x (Bi-2223) insert coil proposed for a beyond 1 GHz nuclear magnetic resonance (NMR) spectrometer may generate a long-term field drift, resulting in a loss of field-frequency lock operation and an inability to make high resolution NMR measurements. The measured screening current-induced magnetic field of a Bi-2223 double-pancake coil exhibits a hysteresis effect at 4.2 K that is reproduced by a numerical simulation based on a finite thickness rectangular superconductor bar model. The screening current-induced field at the coil center is of opposite polarity to that generated by the coil current, and thus the apparent field intensity shows a positive drift with time. On the contrary, the field at a coil end is of the same polarity as the coil field, and the apparent field intensity decreases with time. If we wait for ∼1000 h after coil excitation, the field drift rate approaches the field decay rate of the persistent current of 10 -8 h -1, suitable for a long-term NMR measurement in a beyond 1 GHz NMR spectrometer.

  11. Optimum coil shape for a given volume of conductor to obtain maximum central field in an air core solenoid

    SciTech Connect

    Hernandez, P.

    1995-02-01

    This paper is an expansion of engineering notes prepared in 1961 to address the question of how to wind circular coils so as to obtain the maximum axial field with the minimum volume of conductor. At the time this was a germain question because of the advent of superconducting wires which were in very limited supply, and the rapid push for generation of very high fields, with little concern for uniformity.

  12. Toroidal and poloidal momentum transport studies in tokamaks

    NASA Astrophysics Data System (ADS)

    Tala, T.; Crombé, K.; de Vries, P. C.; Ferreira, J.; Mantica, P.; Peeters, A. G.; Andrew, Y.; Budny, R.; Corrigan, G.; Eriksson, A.; Garbet, X.; Giroud, C.; Hua, M.-D.; Nordman, H.; Naulin, V.; Nave, M. F. F.; Parail, V.; Rantamäki, K.; Scott, B. D.; Strand, P.; Tardini, G.; Thyagaraja, A.; Weiland, J.; Zastrow, K.-D.; Contributors, JET-EFDA

    2007-12-01

    The present status of understanding of toroidal and poloidal momentum transport in tokamaks is presented in this paper. Similar energy confinement and momentum confinement times, i.e. τE/τphi ≈ 1 have been reported on several tokamaks. It is more important though, to study the local transport both in the core and edge plasma separately as, for example, in the core plasma, a large scatter in the ratio of the local effective momentum diffusivity to the ion heat diffusivity χphieff/χi,eff among different tokamaks can be found. For example, the value of effective Prandtl number is typically around χphieff/χi,eff ≈ 0.2 on JET while still τE/τphi ≈ 1 holds. Perturbative NBI modulation experiments on JET have shown, however, that a Prandtl number χphi/χi of around 1 is valid if there is an additional, significant inward momentum pinch which is required to explain the amplitude and phase behaviour of the momentum perturbation. The experimental results, i.e. the high Prandtl number and pinch, are in good qualitative and to some extent also in quantitative agreement with linear gyro-kinetic simulations. In contrast to the toroidal momentum transport which is clearly anomalous, the poloidal velocity is usually believed to be neo-classical. However, experimental measurements on JET show that the carbon poloidal velocity can be an order of magnitude above the predicted value by the neo-classical theory within the ITB. These large measured poloidal velocities, employed for example in transport simulations, significantly affect the calculated radial electric field and therefore the E × B flow shear and hence modify and can significantly improve the simulation predictions. Several fluid turbulence codes have been used to identify the mechanism driving the poloidal velocity to such high values. CUTIE and TRB turbulence codes and also the Weiland model predict the existence of an anomalous poloidal velocity, peaking in the vicinity of the ITB and driven dominantly

  13. Influence of piston and magnetic coils on the field-dependent damping performance of a mixed-mode magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Zeinali, Mohammadjavad; Amri Mazlan, Saiful; Choi, Seung-Bok; Imaduddin, Fitrian; Hamidah Hamdan, Lailatul

    2016-05-01

    This work presents a 2D simulation study of a mixed-mode magnetorheological (MR) damper in which the influence of the geometric elements of the piston and magnetic coil on the MR damper’s performance is investigated by using the Ansoft Maxwell software tool. Four results of the simulation, which are magnetic flux density (B), MR fluid yield stress (τ 0), {τ }0{L}a and W{τ }0{L}a, are used to compare the performance of the MR damper. Multiplication of the yield stress by the active operating mode length ({τ }0{L}a) represents the variable portion of the active (on-state) damping force of the flow mode motion, while the value of W{τ }0{L}a represents the active damping force of the shear mode motion. The contribution of each operating mode (shear and flow) is related to the mixed-mode geometry and piston velocity. Therefore, each operating mode is evaluated separately. In this work, a total of 154 simulations are done in which 74, 20 and 60 simulations are conducted to analyse the effect of the piston radius, coil dimensions (width and length) and coil boundary lengths, respectively, on the performance of the MR damper. The simulation results show that increasing the piston radius can increase the W{τ }0{L}a value and reduce the value. For a given area of magnetic coil housing, a greater housing length in the axial direction of the piston can increase the achieved yield stress of the MR fluid and hence consequently the performance of the MR damper. A minimum boundary length is needed around the magnetic coil in order to attain a supreme magnetic field distribution. However, there is an optimised value for axial coil boundary lengths, which are the lengths of the upper and lower mixed-mode areas.

  14. Irradiation and testing of compact ignition tokamak toroidal field coil insulation materials

    SciTech Connect

    Kanemoto, G.K.; Sherick, M.J.; Sparks, D.C.

    1990-05-01

    This report documents the results of an irradiation and testing program performed on behalf of Martin Marietta Energy Systems, Inc. in support of the Compact Ignition Tokamak Research and Development program. The purpose of the irradiation and testing program was to determine the effects of neutron and gamma irradiation on the mechanical and electrical properties of candidate toroidal field coil insulation materials. Insulation samples were irradiated in the Advanced Test Reactor (ATR) in a large I-hole. The insulation samples were irradiated within a lead shield to reduce exposure to gamma radiation to better approximate the desired ration of neutron to gamma exposure. Two different exposure levels were specified for the insulation samples. To accomplish this, the samples were encapsulated in two separate aluminum capsules; the capsules positioned at the ATR core mid-plane and at the top of the fueled region to take advantage of the axial cosine distribution of the neutron and gamma flux; and by varying the length of irradiation time of the two capsules. Disassembly of the irradiated capsules and testing of the insulation samples were performed at the Test Reactor Area (TRA) Hot Cell Facilities. Testing of the samples included shear compression static, shear compression fatigue, flexure static, and electrical resistance measurements.

  15. Null space imaging: nonlinear magnetic encoding fields designed complementary to receiver coil sensitivities for improved acceleration in parallel imaging.

    PubMed

    Tam, Leo K; Stockmann, Jason P; Galiana, Gigi; Constable, R Todd

    2012-10-01

    To increase image acquisition efficiency, we develop alternative gradient encoding strategies designed to provide spatial encoding complementary to the spatial encoding provided by the multiple receiver coil elements in parallel image acquisitions. Intuitively, complementary encoding is achieved when the magnetic field encoding gradients are designed to encode spatial information where receiver spatial encoding is ambiguous, for example, along sensitivity isocontours. Specifically, the method generates a basis set for the null space of the coil sensitivities with the singular value decomposition and calculates encoding fields from the null space vectors. A set of nonlinear gradients is used as projection imaging readout magnetic fields, replacing the conventional linear readout field and phase encoding. Multiple encoding fields are used as projections to capture the null space information, hence the term null space imaging. The method is compared to conventional Cartesian SENSitivity Encoding as evaluated by mean squared error and robustness to noise. Strategies for developments in the area of nonlinear encoding schemes are discussed. The null space imaging approach yields a parallel imaging method that provides high acceleration factors with a limited number of receiver coil array elements through increased time efficiency in spatial encoding.

  16. Null Space Imaging: Nonlinear Magnetic Encoding Fields Designed Complementary to Receiver Coil Sensitivities for Improved Acceleration in Parallel Imaging

    PubMed Central

    Tam, Leo K.; Galiana, Gigi; Stockmann, Jason P.; Constable, R. Todd

    2012-01-01

    To increase image acquisition efficiency, we develop alternative gradient encoding strategies designed to provide spatial encoding complementary to the spatial encoding provided by the multiple receiver coil elements in parallel image acquisitions. Intuitively, complementary encoding is achieved when the magnetic field encoding gradients are designed to encode spatial information where receiver spatial encoding is ambiguous, for example, along sensitivity isocontours. Specifically, the method generates a basis set for the null space of the coil sensitivities with the singular value decomposition (SVD) and calculates encoding fields from the null space vectors. A set of nonlinear gradients is used as projection imaging readout magnetic fields, replacing the conventional linear readout field and phase encoding. Multiple encoding fields are used as projections to capture the null space information, hence the term Null Space Imaging (NSI). The method is compared to conventional Cartesian SENSitivity Encoding (SENSE) as evaluated by mean squared error and robustness to noise. Strategies for developments in the area of nonlinear encoding schemes are discussed. The NSI approach yields a parallel imaging method that provides high acceleration factors with a limited number of receiver coil array elements through increased time efficiency in spatial encoding. PMID:22190380

  17. A liquid-helium-free superconducting coil system forming a flat minimum-magnetic-field distribution of an electron cyclotron resonance ion source

    SciTech Connect

    Yoshida, Ken-ichi Nara, Takayuki; Saitoh, Yuichi; Yokota, Watalu

    2014-02-15

    A flat distribution of the minimum magnetic field (flat-B{sub min}) of an electron cyclotron resonance ion source (ECRIS) is expected to perform better in highly charged ion production than classical B{sub min}. To form a flat-B{sub min} structure with a liquid helium-free superconducting device, a coil system of seven coils with four current leads has been designed. The lead number was reduced by connecting the plural coils in series to maintain the flat-B{sub min} structure even when the coil currents are changed for adjustment. This coil system can be operated with a helium-free cryostat, since the estimation of heat from the leads to the coils is nearly equivalent to the existing superconducting ECRIS of a similar type.

  18. Poloidal rotation near the edge of a tokamak plasma in [ital H] mode

    SciTech Connect

    Hinton, F.L.; Kim, J.; Kim, Y.; Brizard, A.; Burrell, K.H. )

    1994-02-21

    Ion poloidal flow in tokamaks near the plasma edge has been calculated by extending neoclassical theory to include orbit squeezing, which is the reduction of the ion banana widths due to the gradient in the radial electric field. The calculated poloidal flow velocity is a significant fraction of the ion diamagnetic velocity, which can be much larger than the velocity predicted by neoclassical theory (proportional to the ion temperature gradient). The agreement with spectroscopic measurements of the poloidal rotation velocity in helium plasmas in the DIII-D tokamak is shown to be reasonably good very close to the plasma edge.

  19. Poloidal inhomogeneity of turbulence in the FT-2 tokamak by radial correlation Doppler reflectometry and gyrokinetic modelling

    NASA Astrophysics Data System (ADS)

    Altukhov, A. B.; Gurchenko, A. D.; Gusakov, E. Z.; Esipov, L. A.; Irzak, M. A.; Kantor, M. Yu; Kouprienko, D. V.; Lashkul, S. I.; Leerink, S.; Niskala, P.; Stepanov, A. Yu; Teplova, N. V.

    2016-11-01

    The poloidal dependence of the drift-wave turbulence characteristics is investigated at the FT-2 tokamak by radial correlation Doppler reflectometry (RCDR) technique and using the full distribution function global gyrokinetic modelling by ELMFIRE code. The poloidal variation of the turbulence radial correlation length from 0.2-0.55 cm is demonstrated both by measurement and computation. The turbulence correlation length rapidly decreases from the top of the poloidal cross-section to the high field side and then steadily grows in the poloidal direction. A well-pronounced excess of the turbulence radial correlation length in deuterium over its value in hydrogen discharges is demonstrated.

  20. Impact of plasma poloidal rotation on resistive wall mode instability in toroidally rotating plasmas

    SciTech Connect

    Aiba, N.; Shiraishi, J.; Tokuda, S.

    2011-02-15

    Stability of resistive wall mode (RWM) is investigated in a cylindrical plasma and an axisymmetric toroidal plasma by taking into account not only toroidal rotation but also poloidal rotation. Since the Doppler shifted frequency is responsible for the RWM stability, the modification of this Doppler shifted frequency by poloidal rotation affects the rotation effect on RWM. When a poloidal rotation frequency is not so large, the effect of poloidal rotation on the RWM stability can be approximately treated with the modified toroidal rotation frequency. In a toroidal plasma, this modified frequency is determined by subtracting a toroidal component of the rotation parallel to the magnetic field from the toroidal rotation frequency. The poloidal rotation that counteracts the effect of the Doppler shift strongly reduces the stabilizing effect of toroidal rotation, but by changing the rotational direction, the poloidal rotation enhances this stabilizing effect. This trend is confirmed in not only a cylindrical plasma but also a toroidal plasma. This result indicates that poloidal rotation produces the dependence of the critical toroidal rotation frequency for stabilizing RWM on the rotational direction of toroidal rotation in the same magnetic configuration.

  1. A target field design of open multi-purpose RF coil for musculoskeletal MR imaging at 3T.

    PubMed

    Gao, Fei; Zhang, Rui; Zhou, Diange; Wang, Xiaoying; Huang, Kefu; Zhang, Jue

    2016-10-01

    Musculoskeletal MR imaging under multi-angle situations plays an increasingly important role in assessing joint and muscle tissues system. However, there are still limitations due to the closed structures of most conventional RF coils. In this study, a time-harmonic target-field method was employed to design open multi-purpose coil (OMC) for multi-angle musculoskeletal MR imaging. The phantom imaging results suggested that the proposed OMC could achieve homogeneously distributed magnetic field and high signal-to-noise ratio (SNR) of 239.04±0.83 in the region of interest (ROI). The maximum temperature in the heating hazard test was 16°C lower than the standard regulation, which indicated the security of the designed OMC. Furthermore, to demonstrate the effectiveness of the proposed OMC for musculoskeletal MR imaging, especially for multi-angle imaging, a healthy volunteer was examined for MR imaging of elbow, ankle and knee using OMC. The in vivo imaging results showed that the proposed OMC is effective for MR imaging of musculoskeletal tissues at different body parts, with satisfied B1 field homogeneity and SNR. Moreover, the open structure of the OMC could provide a large joint movement region. The proposed open multi-purpose coil is feasible for musculoskeletal MR imaging, and potentially, it is more suitable for the evaluation of musculoskeletal tissues under multi-angle conditions.

  2. Coil combination for receive array spectroscopy: Are data‐driven methods superior to methods using computed field maps?

    PubMed Central

    Robson, Matthew D.

    2015-01-01

    Purpose Combining spectra from receive arrays, particularly X‐nuclear spectra with low signal‐to‐noise ratios (SNRs), is challenging. We test whether data‐driven combination methods are better than using computed coil sensitivities. Theory Several combination algorithms are recast into the notation of Roemer's classic formula, showing that they differ primarily in their estimation of coil receive sensitivities. This viewpoint reveals two extensions of the whitened singular‐value decomposition (WSVD) algorithm, using temporal or temporal + spatial apodization to improve the coil sensitivities, and thus the combined spectral SNR. Methods Radiofrequency fields from an array were simulated and used to make synthetic spectra. These were combined with 10 algorithms. The combined spectra were then assessed in terms of their SNR. Validation used phantoms and cardiac 31P spectra from five subjects at 3T. Results Combined spectral SNRs from simulations, phantoms, and humans showed the same trends. In phantoms, the combined SNR using computed coil sensitivities was lower than with WSVD combination whenever the WSVD SNR was >14 (or >11 with temporal apodization, or >9 with temporal + spatial apodization). These new apodized WSVD methods gave higher SNRs than other data‐driven methods. Conclusion In the human torso, at frequencies ≥49 MHz, data‐driven combination is preferable to using computed coil sensitivities. Magn Reson, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Magn Reson Med 75:473–487, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic

  3. Type-I superconductor pick-up coil in superconducting quantum interference device-based ultra-low field nuclear magnetic resonance

    SciTech Connect

    Hwang, Seong-min Kim, Kiwoong; Kyu Yu, Kwon; Lee, Seong-Joo; Hyun Shim, Jeong; Körber, Rainer; Burghoff, Martin

    2014-02-10

    In ultra-low field nuclear magnetic resonance (ULF-NMR) with strong prepolarization field (B{sub p}), type-II superconducting pick-up coils may be vulnerable to flux pinning from the strong B{sub p}. Pick-up coils made of NbTi, Nb, and Pb were evaluated in terms of acquired NMR signal quality. The type-II pick-up coils showed degraded signals above 61 mT maximum exposure, while the Pb pick-up coil exhibited no such degradation. Furthermore, a negative counter pulse following a strong B{sub p} was shown to follow magnetic hysteresis loop to unpin the trapped flux in the type-II pick-up coil and restore the NMR signal.

  4. Nonambipolarity, orthogonal conductivity, poloidal flow, and torque

    SciTech Connect

    Hulbert, G.W.; Perkins, F.W.

    1989-02-01

    Nonambipolar processes, such as neutral injection onto trapped orbits or ripple-diffusion loss of ..cap alpha..-particles, act to charge a plasma. A current j/sub r/ across magnetic surfaces must arise in the bulk plasma to maintain charge neutrality. An axisymmetric, neoclassical model of the bulk plasma shows that these currents are carried by the ions and exert a j/sub r/B/sub theta/R/c torque in the toroidal direction. A driven poloidal flow V/sub theta/ = E/sub r/'c/B must also develop. The average current density is related to the radial electric field E/sub r/' = E/sub r/ + v/sub /phi//B/sub theta//c in a frame moving with the plasma via the orthogonal conductivity = sigma/sub /perpendicular//E/sub r/', which has the value sigma/sub /perpendicular// = (1.65epsilon/sup 1/2/)(ne/sup 2/..nu../sub ii//M..cap omega../sub theta//sup 2/) in the banana regime. If an ignited plasma loses an appreciable fraction ..delta.. of its thermonuclear ..cap alpha..-particles by banana ripple diffusion, then the torque will spin the plasma to sonic rotation in a time /tau//sub s/ approx. 2/tau//sub E//..delta.., /tau//sub E/ being the energy confinement time. 10 refs., 1 fig.

  5. Mechanism of notable difference in the field delay times of no-insulation layer-wound and pancake-wound REBCO coils

    NASA Astrophysics Data System (ADS)

    Suetomi, Y.; Yanagisawa, K.; Nakagome, H.; Hamada, M.; Maeda, H.; Yanagisawa, Y.

    2016-10-01

    The characteristic magnetic field delay time for a no-insulation (NI) REBCO layer-wound coil is three orders of magnitude longer than that for a NI REBCO double-pancake coil. In a NI layer-wound coil, the circumferential current firstly flows along the periphery of the coil winding, and then it diffuses from the top and bottom turns into the middle turns of the winding, resulting in a long characteristic magnetic field delay time due to the current diffusion process. In contrast, the characteristic magnetic field delay time for a NI double-pancake coil is dominated by the circumferential current decay in individual turns. On the basis of a derived scaling law, the characteristic magnetic field delay time for a NI REBCO layer-wound coil for a 400 MHz LTS/REBCO nuclear magnetic resonance (NMR) magnet is 37 h, while that for a NI REBCO double-pancake coil is only <1 min. Thus, it is demonstrated that a double-pancake-winding is greatly preferred to a layer-winding for NMR applications from the view point of the characteristic magnetic field delay time.

  6. Superconducting magnetic coil

    DOEpatents

    Aized, Dawood; Schwall, Robert E.

    1996-06-11

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

  7. Superconducting magnetic coil

    DOEpatents

    Aized, Dawood; Schwall, Robert E.

    1999-06-22

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil.

  8. Superconducting magnetic coil

    DOEpatents

    Aized, D.; Schwall, R.E.

    1999-06-22

    A superconducting magnetic coil includes a plurality of sections positioned axially along the longitudinal axis of the coil, each section being formed of an anisotropic high temperature superconductor material wound about a longitudinal axis of the coil and having an associated critical current value that is dependent on the orientation of the magnetic field of the coil. The cross section of the superconductor, or the type of superconductor material, at sections along the axial and radial axes of the coil are changed to provide an increased critical current at those regions where the magnetic field is oriented more perpendicularly to the conductor plane, to thereby increase the critical current at these regions and to maintain an overall higher critical current of the coil. 15 figs.

  9. Design of Pickup Coil Made of Litz Wire and Cooled at 77 K for High Sensitive Measurement of AC Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Enpuku, Keiji; Hirakawa, Shintaro; Momotomi, Ryuji; Matsuo, Masaaki; Yoshida, Takashi; Kandori, Akihiko

    2011-07-01

    We studied the performance of a copper pickup coil for high sensitive measurements of ac magnetic fields. The coil was made of Litz wire to prevent the skin effect, and was cooled at 77 K to reduce thermal noise. We first obtained an analytical expression for the coil resistance by analyzing the eddy current loss of the coil. The analytical result explains well the measured dependences of the coil resistance on the frequency, number of turns of the coil (N), and filament diameter of the Litz wire (df). Next, we show the design of the pickup coil. When appropriate values are selected for N and df, we can expect the magnetic field noise SB1/2 < 10 fT/Hz1/2 for f > 1 kHz and SB1/2 < 2 fT/Hz1/2 for f > 10 kHz for the pickup coil with diameter of 50 mm. The experimental results agreed with the designed values.

  10. Fine positioning of a poloidal probe array

    SciTech Connect

    Yamada, T.; Nagashima, Y.; Inagaki, S.; Kawai, Y.; Yagi, M.; Itoh, S.-I.; Maruta, T.; Shinohara, S.; Terasaka, K.; Kawaguchi, M.; Fukao, M.; Fujisawa, A.; Itoh, K.

    2007-12-15

    Multipoint detection is an essential requirement for investigating plasma turbulence which is a highly nonlinear phenomenon in space and time. We have fabricated an array of 64-channel poloidal probes surrounding the linear cylindrical plasma named LMD-U in order to study turbulence properties, particularly the nonlinear mode couplings, in the domain of poloidal wave number and frequency. However, misalignments of probe tips produce spurious modes, which do not exist in the real plasma, to distort the precise wave number measurements. The paper presents the description of the 64-channel poloidal probe array with means to adjust the probe positions, with discussion on the effects of the misalignments on the wave number measurements.

  11. Improved Coil for Hydrogen Dissociators

    NASA Technical Reports Server (NTRS)

    Vessot, R.

    1984-01-01

    Flat coil has rigid printed circuit substrate. New coil structure minimizes RF electric field near glass walls of plasma vessel; therefore reduces direct electron bombardment of glass. Design lends itself well to high production and standardized dimensions.

  12. DESIGN, FABRICATION, INSTALLATION, TESTING AND INITIAL RESULTS OF IN-VESSEL CONTROL COILS FOR DIII-D

    SciTech Connect

    ANDERSON,P.M; BAXI,C.B; KELLMAN,A.G; REIS,E.E

    2003-10-01

    OAK-B135 Since 1995, DIII-D has performed correction of magnetic field imperfections using a set of six external picture frame coils located on the vessel mid-plane. In 2000, these coils also demonstrated benefits when used for feedback of the resistive wall mode, an instability that limits the plasma performance at high beta. Modeling has shown that substantial performance improvements could be achieved by installing new coils inside the vessel and expanding the poloidal coverage above and below the mid-plane. Two prototype internal coils were installed in 2001 and were power tested successfully after several bakes to 350 C. A full set of twelve internal coils and related magnetic sensors are now operational in the DIII-D tokamak. The design requirements for the new coil system was to maximize the magnetic field at the plasma edge, operate with a frequency range of dc to 1000 Hz, and fit behind the existing graphite wall tiles. The coil design adopted and installed is a water-cooled hollow copper conductor insulated with polyamide and housed inside a stainless steel tube that forms a vacuum boundary. The coil is rigidly mounted to the inside of the vacuum vessel. The primary challenge in the design of these coils wa sin joining of both the copper conductor and the stainless tube without overheating the polyamide insulator. Elastic-plastic analysis was used to demonstrate acceptable thermal stresses during baking conditions. Analysis determined the optimum water cooling channel diameter. The coils were tested in high toroidal field to the limit of the power supply of 4.5 kA DC with inductance-limited current for frequencies between 300 Hz and 1000 Hz. Recent results are presented.

  13. Proposal of High-Frequency Magnetic Field Immunity Test for Medical Devices, and Design and Development of Coil for the Test

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takahiko; Koshiji, Kohji

    Medical devices have been obliged to satisfy electromagnetic compatibility by revision of the pharmaceutical affairs law. However, even if the medical devices satisfy the electromagnetic compatibility based on the law, it is not necessarily safe. Sometimes, malfunctions of cardiac pacemaker are caused by the magnetic field leaked from an induction heating cooker. In this paper, a new method of electromagnetic susceptability (EMS) evaluation is proposed, and a loop coil for the magnetic field immunity test in the frequency range from 10kHz to 3MHz is designed and developed. As a result, the loop coil made on an experimental basis generated uniform magnetic field with a fluctuation within 3.3dB in the loop coil pane and 5.6dB along the coil axis.

  14. Defect detection in embedded reinforcing bars and cables using a multi-coil magnetic field sensor

    NASA Astrophysics Data System (ADS)

    Simmonds, John; Gaydecki, Patrick

    1999-07-01

    A nondestructive testing system which detects surface defects in steel bars or cables embedded within reinforced or pre-stressed concrete is described. The component under test is energized by an alternating current of sufficient frequency to ensure that current flows takes place on the surface of the steel. Detection coils, in conjunction with a suitable amplification system, are positioned at various alignments with respect to the steel bar or cable, and thereby detect, through mutual induction, both the dominant flow path and the deviated current flow in the vicinity of a defect. The output signals from the multi-coil array are converted and fed to a computer for storage and processing. This system has clear relevance to the civil engineering nondestructive testing industry.

  15. High-field double-pancake superconducting coils and a method of winding

    DOEpatents

    Materna, P.A.

    1984-01-31

    A double-pancake coil having first and second pancakes may comprise a plurality of conductor means, each conductor means having a different grade and having one or more conductors, wherein each pancake of said double-pancake coil is comprised of inner and outer turns; wherein said inner turns are comprised of at least one of said conductor means wound about an axis and nested within one another; wherein said outer turns are comprised of said inner conductor means and at least one other conductor means co-wound about said inner turns and nested within one another; wherein each of said conductor means is wound along said axis from said first pancake to said second pancake at a different turn.

  16. Toroidal coil chromatography: the effect of scale-up and "g" field on stage efficiency.

    PubMed

    Sutherland, Ian; Hewitson, Peter; de Folter, Joost

    2011-09-01

    Selected test results have been taken from various publications and resolution and stage efficiency measured using an established model. All experiments used the same sample and, where possible, the same sample loading. The results show that stage mixing efficiencies have increased from 1.1% in 1998 to greater than 25% in the latest scaled-up version of a Toroidal coil chromatography (TCC) instrument working at 240 g. PMID:21227439

  17. Design and construction of an actively frequency-switchable RF coil for field-dependent Magnetisation Transfer Contrast MRI with fast field-cycling.

    PubMed

    Choi, Chang-Hoon; Hutchison, James M S; Lurie, David J

    2010-11-01

    Magnetisation Transfer Contrast (MTC) is an important MR contrast-generating mechanism to characterise the MR-invisible macromolecular protons using an off-resonance pre-saturation RF irradiation pulse (or MT pulse). MTC MRI is normally implemented at a fixed magnetic field; however, it may be useful to evaluate changes of the MT effect as a function of external magnetic field strength (B₀). In order to conduct field-dependent MTC experiments with a single MR system, two techniques are crucially needed. B₀ should be able to be switched between levels during irradiation of the MT pulse. At the same time, the resonance frequency of the RF coil (f₀) should also be able to be shifted to the corresponding value. Switching B₀ is attained by the fast field-cycling technique, while in order to switch f₀, a specially designed multi-tunable RF coil is required. Here, we designed and constructed an actively frequency-switchable RF coil for frequencies at and below 2.5 MHz. The design employed PIN diodes, and enabled switching f₀ between five different values, with excellent impedance matching (approximately -37 dB S₁₁ reflection) and Q-factor of about 100 at each configuration.

  18. Collisionality scaling of main-ion toroidal and poloidal rotation in low torque DIII-D plasmas

    NASA Astrophysics Data System (ADS)

    Grierson, B. A.; Burrell, K. H.; Solomon, W. M.; Budny, R. V.; Candy, J.

    2013-06-01

    In tokamak plasmas with low levels of toroidal rotation, the radial electric field Er is a combination of pressure gradient and toroidal and poloidal rotation components, all having similar magnitudes. In order to assess the validity of neoclassical poloidal rotation theory for determining the poloidal rotation contribution to Er, Dα emission from neutral beam heated tokamak discharges in DIII-D (Luxon 2002 Nucl. Fusion 42 614) has been evaluated in a sequence of low torque (electron cyclotron resonance heating and balanced diagnostic neutral beam pulse) discharges to determine the local deuterium toroidal rotation velocity. By invoking the radial force balance relation the deuterium poloidal rotation can be inferred. It is found that the deuterium poloidal flow exceeds the neoclassical value in plasmas with collisionality \

  19. α/β coiled coils.

    PubMed

    Hartmann, Marcus D; Mendler, Claudia T; Bassler, Jens; Karamichali, Ioanna; Ridderbusch, Oswin; Lupas, Andrei N; Hernandez Alvarez, Birte

    2016-01-15

    Coiled coils are the best-understood protein fold, as their backbone structure can uniquely be described by parametric equations. This level of understanding has allowed their manipulation in unprecedented detail. They do not seem a likely source of surprises, yet we describe here the unexpected formation of a new type of fiber by the simple insertion of two or six residues into the underlying heptad repeat of a parallel, trimeric coiled coil. These insertions strain the supercoil to the breaking point, causing the local formation of short β-strands, which move the path of the chain by 120° around the trimer axis. The result is an α/β coiled coil, which retains only one backbone hydrogen bond per repeat unit from the parent coiled coil. Our results show that a substantially novel backbone structure is possible within the allowed regions of the Ramachandran space with only minor mutations to a known fold.

  20. Impact of Stationary Direct Current in the Central Solenoidal Coil on Tokamak Plasma Formation by Non-induction Heating

    NASA Astrophysics Data System (ADS)

    Watanabe, Osamu

    2016-09-01

    Stationary direct current in the central solenoidal coil (DCCS) of tokamak devices can reduce the non-induction heating energy necessary for tokamak plasma formation. The magnetic field energy in the inner region of the central solenoidal coil (CS region) is expelled during the tokamak plasma formation, because the vertical magnetic field intensity generated by the central solenoidal coil and poloidal field coils is partly cancelled by the increase in the toroidal plasma current. Because this magnetic field energy expelled from the CS region is distributed to the tokamak plasma in accordance with the mutual inductance, this expelled energy can drive the toroidal plasma current inductively. This energy expulsion in the CS region can be enhanced by the DCCS without the modification of the tokamak plasma configuration, when the CS coil current has negligible leakage magnetic field in the plasma area. Because the drive of the toroidal plasma current by non-induction heating can be assisted by this inductive current drive mechanism, the non-induction heating energy necessary for the tokamak plasma formation can be reduced by the DCCS. If the non-induction heating is constant, the tokamak plasma formation time can be shorted by the DCCS.

  1. Poloidal variation of viscous forces in the banana collisionality regime

    SciTech Connect

    Wang, J.P.; Callen, J.D. )

    1993-09-01

    The poloidal variation of the parallel viscous and heat viscous forces are determined for the first time using a rigorous Chapman--Enskog-like approach that has been developed recently. It is shown that the poloidal variation is, like the poloidal distribution of the trapped particles, concentrated on the outer edge (large major radius side) of the tokamak.

  2. Poloidal variation of viscous forces in the banana collisionality regime

    SciTech Connect

    Wang, J.P.; Callen, J.D.

    1992-12-01

    The poloidal variation of the parallel viscous and heat viscous forces are determined for the first time using a rigorous Chapman- Enskog-like approach that has been developed recently. It is shown that the poloidal variation is approximately proportional to the poloidal distribution of the trapped particles, which are concentrated on the outer edge (large major radius side) of the tokamak.

  3. MULTI-MODE ERROR FIELD CORRECTION ON THE DIII-D TOKAMAK

    SciTech Connect

    SCOVILLE, JT; LAHAYE, RJ

    2002-10-01

    OAK A271 MULTI-MODE ERROR FIELD CORRECTION ON THE DIII-D TOKAMAK. Error field optimization on DIII-D tokamak plasma discharges has routinely been done for the last ten years with the use of the external ''n = 1 coil'' or the ''C-coil''. The optimum level of correction coil current is determined by the ability to avoid the locked mode instability and access previously unstable parameter space at low densities. The locked mode typically has toroidal and poloidal mode numbers n = 1 and m = 2, respectively, and it is this component that initially determined the correction coil current and phase. Realization of the importance of nearby n = 1 mode components m = 1 and m = 3 has led to a revision of the error field correction algorithm. Viscous and toroidal mode coupling effects suggested the need for additional terms in the expression for the radial ''penetration'' field B{sub pen} that can induce a locked mode. To incorporate these effects, the low density locked mode threshold database was expanded. A database of discharges at various toroidal fields, plasma currents, and safety factors was supplement4ed with data from an experiment in which the fields of the n = 1 coil and C-coil were combined, allowing the poloidal mode spectrum of the error field to be varied. A multivariate regression analysis of this new low density locked mode database was done to determine the low density locked mode threshold scaling relationship n{sub e} {proportional_to} B{sub T}{sup -0.01} q{sub 95}{sup -0.79} B{sub pen} and the coefficients of the poloidal mode components in the expression for B{sub pen}. Improved plasma performance is achieved by optimizing B{sub pen} by varying the applied correction coil currents.

  4. Toroidal field coil design concept and structural support system for CTHR

    SciTech Connect

    Chianese, R. B.; Kelly, J. L.; Ruck, G. W.

    1980-09-01

    The CTHR conceptual design consists of a magnetically confined (tokamak) fusion reactor fitted with a fertile uranium blanket. The fusion driver concept was based on an ignited plasma. All concepts and parameters were selected on the basis that technical feasibility would be achieved by 1995 to assure a viable commercial operation in the early to mid-21st century. The reactor was designed to achieve good fissile fuel production, with electricity production being a second order priority. However, the resulting concepts that evolved were all excellent power producers which significantly improved the economic performance. The subsystems discussed in the following paragraphs provide a background of the application for the TF coil design described in this report.

  5. RF Head Coil Design with Improved RF Magnetic Near-Fields Uniformity for Magnetic Resonance Imaging (MRI) Systems

    PubMed Central

    Sohn, Sung-Min; DelaBarre, Lance; Gopinath, Anand; Vaughan, John Thomas

    2015-01-01

    Higher magnetic field strength in magnetic resonance imaging (MRI) systems offers higher signal-to-noise ratio (SNR), contrast, and spatial resolution in MR images. However, the wavelength in ultra-high fields (7 tesla and beyond) becomes shorter than the human body at the Larmor frequency with increasing static magnetic field (B0) of MRI system. At short wavelengths, interference effect appears resulting in non- uniformity of the RF magnetic near-field (B1) over the subject and MR images may have spatially anomalous contrast. The B1 near-field generated by the transverse electromagnetic (TEM) RF coil’s microstrip line element has a maximum near the center of its length and falls off towards both ends. In this study, a double trapezoidal shaped microstrip transmission line element is proposed to obtain uniform B1 field distribution by gradual impedance variation. Two multi-channel RF head coils with uniform and trapezoidal shape elements were built and tested with a phantom at 7T MRI scanner for comparison. The simulation and experimental results show stronger and more uniform B1+ near-field with the trapezoidal shape. PMID:25892746

  6. Coil Designs for Novel Magnetic Geometries to Cure the Divertor Heat Flux Problem for Reactors

    NASA Astrophysics Data System (ADS)

    Pekker, M.; Valanju, P.; Kotschenreuther, M.; Wiley, J. C.; Strickler, D.

    2004-11-01

    Coil designs are developed for novel magnetic divertor geometries with a second axi-symmetric x-point and flux expansion region along the separatrix. Adjacent posters describe how these lead to spreading of heat flux and the possibility of stable, complete detachment to overcome serious physics and engineering problems in reactors. The principal feasibility issue is creating, with simple coils, additional X-points on the separatrix without extensively deforming the magnetic field in the main plasma. For the spherical tokamak NSTX, we show that adding one or two poloidal coils suffices to create a divergent flux at the divertor, i.e., a new x-point. The currents and forces for the extra coils are small. We also modify ARIES ST design to show reactor feasibility. Optimized coil designs for PEGASUS, ARIES RS/AT, and a modular ITER retrofit are also being developed. For our calculations we used self consistent code FBEQ, which was used to design NSTX. We also use NCSX tools for optimization of designs with competing physics and engineering constraints.

  7. Tokamak Physics EXperiment (TPX): Toroidal field magnet design, development and manufacture. SDRL 32, Coil assembly documentation. Volume 5

    SciTech Connect

    Weber, C.M.

    1995-08-18

    This document is intended to address the contract requirement for providing coil assembly documentation, as required in the applicable Statement of Work: `Provide preliminary procedures and preliminary design and supporting analysis of the equipment, fixtures, and hardware required to integrate and align the impregnated coil assemblies with the coil cases and intercoil structure. Each of the three major processes associated with the coil case and intercoil structure (ICS), TF Case Fabrication, Coil Preparation for Case Assembly are examined in detail. The specific requirements, processes, equipment, and technical concerns for each of these assembly processes is presented.

  8. Poloidal asymmetries in edge transport barriersa)

    NASA Astrophysics Data System (ADS)

    Churchill, R. M.; Theiler, C.; Lipschultz, B.; Hutchinson, I. H.; Reinke, M. L.; Whyte, D.; Hughes, J. W.; Catto, P.; Landreman, M.; Ernst, D.; Chang, C. S.; Hager, R.; Hubbard, A.; Ennever, P.; Walk, J. R.

    2015-05-01

    Measurements of impurities in Alcator C-Mod indicate that in the pedestal region, significant poloidal asymmetries can exist in the impurity density, ion temperature, and main ion density. In light of the observation that ion temperature and electrostatic potential are not constant on a flux surface [Theiler et al., Nucl. Fusion 54, 083017 (2014)], a technique based on total pressure conservation to align profiles measured at separate poloidal locations is presented and applied. Gyrokinetic neoclassical simulations with XGCa support the observed large poloidal variations in ion temperature and density, and that the total pressure is approximately constant on a flux surface. With the updated alignment technique, the observed in-out asymmetry in impurity density is reduced from previous publishing [Churchill et al., Nucl. Fusion 53, 122002 (2013)], but remains substantial ( n z , H / n z , L ˜ 6 ). Candidate asymmetry drivers are explored, showing that neither non-uniform impurity sources nor localized fluctuation-driven transport are able to explain satisfactorily the impurity density asymmetry. Since impurity density asymmetries are only present in plasmas with strong electron density gradients, and radial transport timescales become comparable to parallel transport timescales in the pedestal region, it is suggested that global transport effects relating to the strong electron density gradients in the pedestal are the main driver for the pedestal in-out impurity density asymmetry.

  9. Mathematical model to determine the dimensions of superconducting cylindrical coils with a given central field - the case study for MgB2 conductors with isotropic Ic(B) characteristic

    NASA Astrophysics Data System (ADS)

    Pitel, Jozef; Melišek, Tibor; Tropeano, Matteo; Nardelli, Davide; Tumino, Andrea

    2016-08-01

    In this work, we present a mathematical model which enables to design cylindrical coils with a given central field, made of the superconducting conductor with isotropic Ic(B) characteristic. The model results in a computer code that enables to find out the coil dimensions, and to calculate the coil parameters such as critical current, maximum field in the winding and field non-uniformity on the coil axis. The Ic(B) characteristic of the conductor is represented by the set of data measured in discrete points. This approach allows us to express the Ic(B) as a function linearized in parts. Then, it is possible to involve the central field of the coil, coil dimensions, and parameters of the conductor, including its Ic(B) characteristic, in one equation which can be solved using ordinary numerical non-linear methods. Since the coil dimensions and conductor parameters are mutually linked in one equation with respect to a given coil central field, it is possible to analyze an influence of one parameter on the other one. The model was applied to three commercially available MgB2/Ni/Cu conductors produced by Columbus Superconductors. The results of simulations with the Ic(B) data at 20 K illustrate that there exists a set of winding geometries that generate a required central field, changing from a disc shape to long thin solenoid. Further, we analyze how the thickness of stabilizing copper influences the coil dimensions, overall conductor length, coil critical current, maximum field in the winding. An influence of the safety coefficient in operating current on coil dimensions and other above mentioned parameters is studied as well. Finally, we compare the coil dimensions, overall conductor length as well as coil critical current and maximum field in the winding if the value of required central field changes between 1 and 3 T.

  10. An equivalent distributed magnetic current based FDTD method for the calculation of E-fields induced by gradient coils in MRI.

    PubMed

    Crozier, S; Liu, F; Wei, Q

    2004-01-01

    This paper evaluates a low-frequency FDTD method applied to the problem of induced E-fields/eddy currents in the human body resulting from the pulsed magnetic field gradients in MRI. In this algorithm, a distributed equivalent magnetic current (DEMC) is proposed as the electromagnetic source and is obtained by quasistatic calculation of the empty coil's vector potential or measurements therein. This technique circumvents the discretizing of complicated gradient coil geometries into a mesh of Yee cells, and thereby enables any type of gradient coil modeling or other complex low frequency sources. The proposed method has been verified against an example with an analytical solution. Results are presented showing the spatial distribution of gradient-induced electric fields in a multilayered spherical phantom model and a complete body model.

  11. Addition of trim coils to the Tandem Mirror Experiment Upgrade (TMX-U) magnet system to improve the magnetic field mapping

    SciTech Connect

    Wong, R.L.; Pedrotti, L.R.; Baldwin, D.E.; Hibbs, S.M.; Hill, D.N.; Hornady, R.H.; Jackson, M.C.

    1985-11-14

    The mapping of the magnetic flux bundle from the center cell to the Plasma Potential Control plates (PPC) on the end fan of the Tandem Mirror Experiment Upgrade (TMX-U), was improved by the addition of trim coils (12,000 amp-turns) on each side of each end fan next to the pump beam magnetic shields. The coils' axes are oriented perpendicular to the machine centerline. These coils made the necessary corrections to the field-line mapping, while keeping the field in the nearby pump beam magnetic shield below the saturation threshold. This paper briefly describes the problem, discusses the design as it evolved, and presents the results of the field testing. The disturbance to the field mapping and the appropriate corrections were determined using the code GFUN (a three dimensional electromagnetic field analysis code that includes the presence of permeable materials). The racetrack-shaped coils have dimensions of 1.5 feet by 3 feet and are powered by a renovated 600 kW Bart-Messing power supply controlled by the machine's magnet control system. The magnets were fabricated from polyimide-coated magnet wire. They are rated to 200/sup 0/C, although in pulsed operation they rise only a few degrees centigrade. The coils are placed outside of the vacuum system, and thus are considerably simpler than the other machine magnets. The restraints are designed to withstand a force of 1000 pounds per coil and a turning moment of 1000 foot pounds. The calculated field strengths were verified on the machine by inserting a Hall probe along the axis. The perturbations to the neutral beam magnetic shields were also measured. A brief description of the improvement in the machine performance is also included.

  12. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    SciTech Connect

    Sorci, J.M.

    1992-02-01

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov's results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov's result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits.

  13. An analytic determination of beta poloidal and internal inductance in an elongated tokamak from magnetic probe measurements

    SciTech Connect

    Sorci, J.M.

    1992-02-01

    Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov`s results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov`s result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits.

  14. 35.4 T field generated using a layer-wound superconducting coil made of (RE)Ba2Cu3O7-x (RE = rare earth) coated conductor

    NASA Astrophysics Data System (ADS)

    Trociewitz, Ulf P.; Dalban-Canassy, Matthieu; Hannion, Muriel; Hilton, David K.; Jaroszynski, Jan; Noyes, Patrick; Viouchkov, Youri; Weijers, Hubertus W.; Larbalestier, David C.

    2011-11-01

    To explore the limits of layer wound (RE)Ba2Cu3O7-x (REBCO, RE = rare earth) coils in a high magnetic field environment >30 T, a series of small insert coils have been built and characterized in background fields. One of the coils repeatedly reached 35.4 T using a single ˜100 m length of REBCO tape wet wound with epoxy and nested in a 31 T background magnet. The coil was quenched safely several times without degradation. Contributing to the success of this coil was the introduction of a thin polyester film that surrounded the conductor. This approach introduces a weak circumferential plane in the coil pack that prevents conductor delamination that has caused degradation of several epoxy impregnated coils previously made by this and other groups.

  15. Magnetic microhelix coil structures.

    PubMed

    Smith, Elliot J; Makarov, Denys; Sanchez, Samuel; Fomin, Vladimir M; Schmidt, Oliver G

    2011-08-26

    Together with the well-known ferro- and antiferromagnetic ordering, nature has created a variety of complex helical magnetic configurations. Here, we design and investigate three-dimensional microhelix coil structures that are radial-, corkscrew-, and hollow-bar-magnetized. The magnetization configurations of the differently magnetized coils are experimentally revealed by probing their specific dynamic response to an external magnetic field. Helix coils offer an opportunity to realize microscale geometries of the magnetic toroidal moment, observed so far only in bulk multiferroic materials. PMID:21929266

  16. Magnetic Microhelix Coil Structures

    NASA Astrophysics Data System (ADS)

    Smith, Elliot J.; Makarov, Denys; Sanchez, Samuel; Fomin, Vladimir M.; Schmidt, Oliver G.

    2011-08-01

    Together with the well-known ferro- and antiferromagnetic ordering, nature has created a variety of complex helical magnetic configurations. Here, we design and investigate three-dimensional microhelix coil structures that are radial-, corkscrew-, and hollow-bar-magnetized. The magnetization configurations of the differently magnetized coils are experimentally revealed by probing their specific dynamic response to an external magnetic field. Helix coils offer an opportunity to realize microscale geometries of the magnetic toroidal moment, observed so far only in bulk multiferroic materials.

  17. Borehole induction coil transmitter

    SciTech Connect

    Holladay, Gale; Wilt, Michael J.

    2002-01-01

    A borehole induction coil transmitter which is a part of a cross-borehole electromagnetic field system that is used for underground imaging applications. The transmitter consists of four major parts: 1) a wound ferrite or mu-metal core, 2) an array of tuning capacitors, 3) a current driver circuit board, and 4) a flux monitor. The core is wound with several hundred turns of wire and connected in series with the capacitor array, to produce a tuned coil. This tuned coil uses internal circuitry to generate sinusoidal signals that are transmitted through the earth to a receiver coil in another borehole. The transmitter can operate at frequencies from 1-200 kHz and supplies sufficient power to permit the field system to operate in boreholes separated by up to 400 meters.

  18. Comparison of Poloidal Velocity Meassurements to Neoclassical Theory on the National Spherical Torus Experiment

    SciTech Connect

    Bell, R E; Kaye, S M; Kolesnikov, R A; LeBlance, B P; Rewolldt, G; Wang, W X

    2010-04-07

    Knowledge of poloidal velocity is necessary for the determination of the radial electric field, Er, which along with its gradient is linked to turbulence suppression and transport barrier formation. Recent measurements of poloidal flow on conventional tokamaks have been reported to be an order of magnitude larger than expected from neoclassical theory. In contrast, recent poloidal velocity measurements on the NSTX spherical torus [S. M. Kaye et al., Phys. Plasmas 8, 1977 (2001)] are near or below neoclassical estimates. A novel charge exchange recombination spectroscopy diagnostic is used, which features active and passive sets of up/down symmetric views to produce line-integrated poloidal velocity measurements that do not need atomic physics corrections. Local profiles are obtained with an inversion. Poloidal velocity measurements are compared with neoclassical values computed with the codes NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] and GTC-Neo [W. X. Wang, et al., Phys. Plasmas 13, 082501 (2006)], which has been updated to handle impurities. __________________________________________________

  19. Residue-specific force field based on the protein coil library. RSFF1: modification of OPLS-AA/L.

    PubMed

    Jiang, Fan; Zhou, Chen-Yang; Wu, Yun-Dong

    2014-06-26

    Traditional protein force fields use one set of parameters for most of the 20 amino acids (AAs), allowing transferability of the parameters. However, a significant shortcoming is the difficulty to fit the Ramachandran plots of all AA residues simultaneously, affecting the accuracy of the force field. In this Feature Article, we report a new strategy for protein force field parametrization. Backbone and side-chain conformational distributions of all 20 AA residues obtained from protein coil library were used as the target data. The dihedral angle (torsion) potentials and some local nonbonded (1-4/1-5/1-6) interactions in OPLS-AA/L force field were modified such that the target data can be excellently reproduced by molecular dynamics simulations of dipeptides (blocked AAs) in explicit water, resulting in a new force field with AA-specific parameters, RSFF1. An efficient free energy decomposition approach was developed to separate the corrections on ϕ and ψ from the two-dimensional Ramachandran plots. RSFF1 is shown to reproduce the experimental NMR (3)J-coupling constants of AA dipeptides better than other force fields. It has a good balance between α-helical and β-sheet secondary structures. It can successfully fold a set of α-helix proteins (Trp-cage and Homeodomain) and β-hairpins (Trpzip-2, GB1 hairpin), which cannot be consistently stabilized by other state-of-the-art force fields. Interestingly, the RSFF1 force field systematically overestimates the melting temperature (and the stability of native state) of these peptides/proteins. It has a potential application in the simulation of protein folding and protein structure refinement. PMID:24815738

  20. Residue-specific force field based on the protein coil library. RSFF1: modification of OPLS-AA/L.

    PubMed

    Jiang, Fan; Zhou, Chen-Yang; Wu, Yun-Dong

    2014-06-26

    Traditional protein force fields use one set of parameters for most of the 20 amino acids (AAs), allowing transferability of the parameters. However, a significant shortcoming is the difficulty to fit the Ramachandran plots of all AA residues simultaneously, affecting the accuracy of the force field. In this Feature Article, we report a new strategy for protein force field parametrization. Backbone and side-chain conformational distributions of all 20 AA residues obtained from protein coil library were used as the target data. The dihedral angle (torsion) potentials and some local nonbonded (1-4/1-5/1-6) interactions in OPLS-AA/L force field were modified such that the target data can be excellently reproduced by molecular dynamics simulations of dipeptides (blocked AAs) in explicit water, resulting in a new force field with AA-specific parameters, RSFF1. An efficient free energy decomposition approach was developed to separate the corrections on ϕ and ψ from the two-dimensional Ramachandran plots. RSFF1 is shown to reproduce the experimental NMR (3)J-coupling constants of AA dipeptides better than other force fields. It has a good balance between α-helical and β-sheet secondary structures. It can successfully fold a set of α-helix proteins (Trp-cage and Homeodomain) and β-hairpins (Trpzip-2, GB1 hairpin), which cannot be consistently stabilized by other state-of-the-art force fields. Interestingly, the RSFF1 force field systematically overestimates the melting temperature (and the stability of native state) of these peptides/proteins. It has a potential application in the simulation of protein folding and protein structure refinement.

  1. The discrepancy between human peripheral nerve chronaxie times as measured using magnetic and electric field stimuli: the relevance to MRI gradient coil safety.

    PubMed

    Recoskie, Bryan J; Scholl, Timothy J; Chronik, Blaine A

    2009-10-01

    Peripheral nerve stimulation (PNS) resulting from electric fields induced from the rapidly changing magnetic fields of gradient coils is a concern in MRI. Nerves exposed to either electric fields or changing magnetic fields would be expected to display consistent threshold characteristics, motivating the direct application of electric field exposure criteria from the literature to guide the development of gradient magnetic field exposure criteria for MRI. The consistency of electric and magnetic field exposures was tested by comparing chronaxie times for electric and magnetic PNS curves for 22 healthy human subjects. Electric and magnetic stimulation thresholds were measured for exposure of the forearm using both surface electrodes and a figure-eight magnetic coil, respectively. The average chronaxie times for the electric and magnetic field conditions were 109 +/- 11 micros and 651 +/- 53 micros (+/-SE), respectively. We do not propose that these results call into question the basic mechanism, namely that rapidly switched gradient magnetic fields induce electric fields in human tissues, resulting in PNS. However, this result does motivate us to suggest that special care must be taken when using electric field exposure data from the literature to set gradient coil PNS safety standards in MRI.

  2. α/β coiled coils

    PubMed Central

    Hartmann, Marcus D; Mendler, Claudia T; Bassler, Jens; Karamichali, Ioanna; Ridderbusch, Oswin; Lupas, Andrei N; Hernandez Alvarez, Birte

    2016-01-01

    Coiled coils are the best-understood protein fold, as their backbone structure can uniquely be described by parametric equations. This level of understanding has allowed their manipulation in unprecedented detail. They do not seem a likely source of surprises, yet we describe here the unexpected formation of a new type of fiber by the simple insertion of two or six residues into the underlying heptad repeat of a parallel, trimeric coiled coil. These insertions strain the supercoil to the breaking point, causing the local formation of short β-strands, which move the path of the chain by 120° around the trimer axis. The result is an α/β coiled coil, which retains only one backbone hydrogen bond per repeat unit from the parent coiled coil. Our results show that a substantially novel backbone structure is possible within the allowed regions of the Ramachandran space with only minor mutations to a known fold. DOI: http://dx.doi.org/10.7554/eLife.11861.001 PMID:26771248

  3. A poloidal section neutron camera for MAST upgrade

    SciTech Connect

    Sangaroon, S.; Weiszflog, M.; Cecconello, M.; Conroy, S.; Ericsson, G.; Wodniak, I.; Keeling, D.; Turnyanskiy, M. [EURATOM Collaboration: MAST Team

    2014-08-21

    The Mega Ampere Spherical Tokamak Upgrade (MAST Upgrade) is intended as a demonstration of the physics viability of the Spherical Tokamak (ST) concept and as a platform for contributing to ITER/DEMO physics. Concerning physics exploitation, MAST Upgrade plasma scenarios can contribute to the ITER Tokamak physics particularly in the field of fast particle behavior and current drive studies. At present, MAST is equipped with a prototype neutron camera (NC). On the basis of the experience and results from previous experimental campaigns using the NC, the conceptual design of a neutron camera upgrade (NC Upgrade) is being developed. As part of the MAST Upgrade, the NC Upgrade is considered a high priority diagnostic since it would allow studies in the field of fast ions and current drive with good temporal and spatial resolution. In this paper, we explore an optional design with the camera array viewing the poloidal section of the plasma from different directions.

  4. Development of “L-Shaped” Rotary Voice Coil Motor Actuator for Ultra Slim Optical Disk Drive Using Integrated Design Method based on Coupled-Field Analysis

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Ju; Woo, Jung-Hyun; Kim, Sa-Ung; Oh, Je-Seung; Yoo, Jeong-Hoon; Park, No-Cheol; Park, Young-Pil; Shimano, Takeshi; Nakamura, Shigeo

    2007-06-01

    In this paper, we propose an “L-shaped” rotary voice coil motor (VCM) actuator for an ultra slim optical disk drive (ODD) with a CF II card size using the integrated design method that integrates coupled-field analysis and design methods.

  5. Development of a nano-tesla magnetic field shielded chamber and highly precise AC-susceptibility measurement coil at μK temperatures

    NASA Astrophysics Data System (ADS)

    Kumar, Anil; Prakash, Om; Ramakrishanan, S.

    2014-04-01

    A special sample measurement chamber has been developed to perform experiments at ultralow temperatures and ultralow magnetic field. A high permeability material known as cryoperm 10 and Pb is used to shield the measurement space consisting of the signal detecting set-up and the sample. The detecting setup consists of a very sensitive susceptibility coil wound on OFHC Cu bobbin.

  6. An accurate magnetic field solution for medical electromagnetic tracking coils at close range

    NASA Astrophysics Data System (ADS)

    Schroeder, Tobias

    2015-06-01

    Electromagnetic tracking uses transmitter field models to determine position and orientation of an object. An important application of this technology is surgical navigation, where instruments are frequently tracked at short distances from the transmitter. At short distances, conventional and widely used dipole field models can lead to errors in tracked position and orientation. To increase tracking accuracy in this scenario, this work describes a novel transmitter field model and compares its performance against the dipole model. Demonstrated tracking accuracy improvements could have far-reaching benefits for medical navigation applications.

  7. Global electromagnetic induction in the moon and planets. [poloidal eddy current transient response

    NASA Technical Reports Server (NTRS)

    Dyal, P.; Parkin, C. W.

    1973-01-01

    Experiments and analyses concerning electromagnetic induction in the moon and other extraterrestrial bodies are summarized. The theory of classical electromagnetic induction in a sphere is first considered, and this treatment is extended to the case of the moon, where poloidal eddy-current response has been found experimentally to dominate other induction modes. Analysis of lunar poloidal induction yields lunar internal electrical conductivity and temperature profiles. Two poloidal-induction analytical techniques are discussed: a transient-response method applied to time-series magnetometer data, and a harmonic-analysis method applied to data numerically Fourier-transformed to the frequency domain, with emphasis on the former technique. Attention is given to complicating effects of the solar wind interaction with both induced poloidal fields and remanent steady fields. The static magnetization field induction mode is described, from which are calculated bulk magnetic permeability profiles. Magnetic field measurements obtained from the moon and from fly-bys of Venus and Mars are studied to determine the feasibility of extending theoretical and experimental induction techniques to other bodies in the solar system.

  8. Is turbulence indeed reduced in the tokamak edge pedestal? Mysteries of pedestal poloidal asymmetries revealed

    NASA Astrophysics Data System (ADS)

    Espinosa, Silvia; Catto, Peter J.

    2015-11-01

    It has been suggested that the L-H transition involves the reduction of turbulence by sheared radial electric fields. For H-mode pedestals, neoclassical collisional theory may thus be expected to properly treat low order phenomena, such as flows. However, Alcator H-mode edge pedestals exhibit significantly stronger poloidal asymmetry than predicted by the most comprehensive neoclassical models developed to date. We propose a novel self-consistent neoclassical theoretical model that allows us to explain these poloidal asymmetries in boron temperature and density, and hence potential. First, impurity temperature asymmetries can be driven by inertial effects, which are significant when impurities are allowed to reach sonic speeds. Second, a much stronger impurity density in-out asymmetry than given by magnetic field variation can be introduced by the poloidally varying impurity diamagnetic drift. This asymmetry is achieved by allowing the diamagnetic drift contribution to be comparable to the poloidal and toroidal flows used to measure the radial electric field. In conclusion, we provide a more realistic predictive model for pedestal observations without the need to invoke anomalous transport. Supported by DOE Grant DE-FG0291ER54109 and La Caixa Fellowship.

  9. Measuring Earth's Local Magnetic Field Using a Helmholtz Coil

    ERIC Educational Resources Information Center

    Williams, Jonathan E.

    2014-01-01

    In this paper, I present a low-cost interactive experiment for measuring the strength of Earth's local magnetic field. This activity can be done in most high schools or two-year physics laboratories with limited resources, yet will have a tremendous learning impact. This experiment solidifies the three-dimensional nature of Earth's…

  10. Construction of block-coil high-field model dipoles for future hadron colliders

    SciTech Connect

    Blackburn, Raymond; Elliott, Tim; Henchel, William; McInturff, Al; McIntyre, Peter; Sattarov, Akhdior

    2002-08-04

    A family of high-field dipoles is being developed at Texas A&M University, as part of the program to improve the cost-effectiveness of superconducting magnet technology for future hadron colliders. The TAMU technology employs stress management, flux-plate control of persistent-current multipoles, conductor optimization using mixed-strand cable, and metal-filled bladders to provide pre-load and surface compliance. Construction details and status of the latest model dipole will be presented.

  11. Tryout of the vacuum impregnation procedure for the ITER PF1 coil on the VPI mold made of plastic shell

    NASA Astrophysics Data System (ADS)

    Grigoriev, S.; Rodin, I.; Tanchuk, V.; Korban, S.; Bursikov, A.; Mednikov, A.; Pugachev, A.

    2014-05-01

    The PF1 Coil as part of the ITER superconducting magnet system is intended for positioning and shaping of the magnetic poloidal field. The technical specification for the PF1 coil requires a full-scale simulation of the basic technological processes including vacuum pressure impregnation (VPI). Usually, a VPI mold is made of massive stainless steel walls to get the required quality of the monolithic structure of the pancake insulation by hot-curing compound. As a result, we obtain a high-cost furnace with a considerable amount of steel inside to be heated up to the specified temperature; excessive energy consumption for the furnace heating system; problems with the vacuum tightness of the VPI mold. The impregnation procedure using a VPI "plastic" mold was proposed so as to avoid the above mentioned shortcomings associated with the use of the furnace made of stainless steel.

  12. Performance of the INTOR poloidal divertor

    SciTech Connect

    Post, D.E.; Petravic, M.; Schmidt, J.A.; Heifetz, D.

    1981-10-01

    The next generation of large tokamak experiments is expected to have large particle and heat outfluxes (approx. 10/sup 23/ particles/sec and 80 MW). These outfluxes must be controlled to provide adequate pumping of the helium ash and to minimize the sputtering erosion of the vacuum vessel walls, limiters, and neutralizer plates. A poloidal divertor design to solve these problems for INTOR has been done using a two-dimensional code which models the plasma as a fluid and solves equations for the flow of particles, momentum and energy, and calculates the neutral gas transport with Monte-Carlo techniques. These calculations show that there is a regime of operation where the density in the divertor is high and the temperature is low, thus easing the heat load and erosion problems. The neutral pressure at the plate is high, resulting in high gas throughputs, with modest pumping speeds.

  13. Ac losses for the self field of an ac transport current with a dc transport current offset in high {Tc} superconducting magnet coils for MagLev application

    SciTech Connect

    Koosh, V.F.

    1993-10-01

    Although much research has been conducted concerning the losses of high-{Tc} superconductors, very little has concentrated on the self-field losses in an actual magnet arrangement. The coils studied in this work were designed for use as actual magnets in an industrial application. Self field loss measurements were made upon tape-wound 2223 superconducting helix coils. The self-field losses were produced by an AC transport current with a DC transport current offset. Losses were taken for single, double and triple tape windings, giving essentially monofilament, dual, and three filament cases. The losses measured here were varied over a range of AC current values for several different DC values, and over a range of frequencies. The currents were all AC sinusoids with a DC offset. All measurements were made at T = 77K.

  14. Alternating current losses in superconducting coils

    NASA Technical Reports Server (NTRS)

    Wipf, S. L.; Guderjahn, C. A.

    1972-01-01

    Report examines relationship between coil loss and frequency and heat loss in coil as a function of the magnetic field H. Information is of value to manufacturers of superconducting magnets, motors and generators.

  15. Toroidal modelling of RMP response in ASDEX Upgrade: coil phase scan, q 95 dependence, and toroidal torques

    NASA Astrophysics Data System (ADS)

    Liu, Yueqiang; Ryan, D.; Kirk, A.; Li, Li; Suttrop, W.; Dunne, M.; Fischer, R.; Fuchs, J. C.; Kurzan, B.; Piovesan, P.; Willensdorfer, M.; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    2016-05-01

    The plasma response to the vacuum resonant magnetic perturbation (RMP) fields, produced by the ELM control coils in ASDEX Upgrade experiments, is computationally modelled using the MARS-F/K codes (Liu et al 2000 Phys. Plasmas 7 3681, Liu et al 2008 Phys. Plasmas 15 112503). A systematic investigation is carried out, considering various plasma and coil configurations as in the ELM control experiments. The low q plasmas, with {{q}95}˜ 3.8 (q 95 is the safety factor q value at 95% of the equilibrium poloidal flux), responding to low n (n is the toroidal mode number) field perturbations from each single row of the ELM coils, generates a core kink amplification effect. Combining two rows, with different toroidal phasing, thus leads to either cancellation or reinforcement of the core kink response, which in turn determines the poloidal location of the peak plasma surface displacement. The core kink response is typically weak for the n  =  4 coil configuration at low q, and for the n  =  2 configuration but only at high q ({{q}95}˜ 5.5 ). A phase shift of around 60 degrees for low q plasmas, and around 90 degrees for high q plasmas, is found in the coil phasing, between the plasma response field and the vacuum RMP field, that maximizes the edge resonant field component. This leads to an optimal coil phasing of about 100 (-100) degrees for low (high) q plasmas, that maximizes both the edge resonant field component and the plasma surface displacement near the X-point of the separatrix. This optimal phasing closely corresponds to the best ELM mitigation observed in experiments. A strong parallel sound wave damping moderately reduces the core kink response but has minor effect on the edge peeling response. For low q plasmas, modelling shows that both the resonant electromagnetic torque and the neoclassical toroidal viscous (NTV) torque (due to the presence of 3D magnetic field perturbations) contribute to the toroidal flow damping, in particular near the

  16. Toroidal modelling of RMP response in ASDEX Upgrade: coil phase scan, q 95 dependence, and toroidal torques

    NASA Astrophysics Data System (ADS)

    Liu, Yueqiang; Ryan, D.; Kirk, A.; Li, Li; Suttrop, W.; Dunne, M.; Fischer, R.; Fuchs, J. C.; Kurzan, B.; Piovesan, P.; Willensdorfer, M.; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    2016-05-01

    The plasma response to the vacuum resonant magnetic perturbation (RMP) fields, produced by the ELM control coils in ASDEX Upgrade experiments, is computationally modelled using the MARS-F/K codes (Liu et al 2000 Phys. Plasmas 7 3681, Liu et al 2008 Phys. Plasmas 15 112503). A systematic investigation is carried out, considering various plasma and coil configurations as in the ELM control experiments. The low q plasmas, with {{q}95}∼ 3.8 (q 95 is the safety factor q value at 95% of the equilibrium poloidal flux), responding to low n (n is the toroidal mode number) field perturbations from each single row of the ELM coils, generates a core kink amplification effect. Combining two rows, with different toroidal phasing, thus leads to either cancellation or reinforcement of the core kink response, which in turn determines the poloidal location of the peak plasma surface displacement. The core kink response is typically weak for the n  =  4 coil configuration at low q, and for the n  =  2 configuration but only at high q ({{q}95}∼ 5.5 ). A phase shift of around 60 degrees for low q plasmas, and around 90 degrees for high q plasmas, is found in the coil phasing, between the plasma response field and the vacuum RMP field, that maximizes the edge resonant field component. This leads to an optimal coil phasing of about 100 (‑100) degrees for low (high) q plasmas, that maximizes both the edge resonant field component and the plasma surface displacement near the X-point of the separatrix. This optimal phasing closely corresponds to the best ELM mitigation observed in experiments. A strong parallel sound wave damping moderately reduces the core kink response but has minor effect on the edge peeling response. For low q plasmas, modelling shows that both the resonant electromagnetic torque and the neoclassical toroidal viscous (NTV) torque (due to the presence of 3D magnetic field perturbations) contribute to the toroidal flow damping, in particular near the

  17. Observations of magnetospheric high-m poloidal waves by ST-5 satellites in low Earth orbit during geomagnetically quiet times

    NASA Astrophysics Data System (ADS)

    Chi, P. J.; Le, G.

    2015-06-01

    The poloidal waves with large azimuthal wave numbers (m) in the magnetosphere are known to be generated by drift or drift-bounce resonance with energetic ring current particles, and these waves may play a role in modulating the energetic particles in the inner magnetosphere. When examining the magnetic field data collected by the NASA Space Technology 5 (ST-5) satellites in the low Earth orbit, Le et al. (2011) discovered many wave events with frequencies of 30-200 mHz (in the Pc2 and Pc3 bands), and they proposed that these waves should, in fact, be Doppler-shifted high-m poloidal waves in the magnetosphere with frequencies at only a few millihertz (in the Pc5 band). Using a new method that examines the differences in wave phase detected by the three ST-5 satellites, we confirm that the frequencies in the Earth frame for the poloidal waves observed are mainly between 3 and 5 mHz. Not only were poloidal waves observed frequently by ST-5 in the dayside magnetosphere but they were also occasionally seen in the nightside when the satellites passed through the same L shells. In each wave event, the azimuthal wave number may change with L, but the wave frequency in the Earth frame remains the same. We also find that poloidal waves can last more than 9 h during geomagnetically quiet conditions, suggesting that even a very weak ring current can supply enough energetic particles to excite poloidal waves.

  18. Impurity poloidal asymmetries and plasma rotation in the PDX Tokamak

    NASA Astrophysics Data System (ADS)

    Brau, K.

    Vertical poloidal asymmetries of carbon and oxygen in the PDX Tokamak were monitored under a variety of discharge conditions in circular plasmas. Near the edge of the plasma and in the region beyond the limiter, the asymmetries appear to be caused by local impurity recycling, variations in the length of the emitting region, and effects due to vertical ion drifts. In the case of C V impurities, the sign and magnitude of the asymmetry is in qualitative agreement with the predictions of a quasi-neoclassical fluid model of impurity transport. A two dimensional computer code is used to simulate different models of poloidal asymmetries, including: (1) poloidally asymmetric source function, (2) charge exchange recombination with neutral hydrogen, (3) poloidally asymmetric electron ensity and temperature profiles, (4) poloidally varying anomalous radial diffusion coefficient, and (5) the quasi-neoclassical fluid model.

  19. Large MgB2 Superconducting Coils for the Ignitor Experiment

    NASA Astrophysics Data System (ADS)

    Tumino, A.; Grasso, G.; Coppi, B.

    2012-10-01

    Intermediate temperature, superconducting cables have been adopted for the fabrication of the largest poloidal field coils of the Ignitor experiment. This is an important step to achieve better duty cycles in Ignitor-like machines with innovative magnet technologies compared to traditional superconductors. The commercially available MgB2 strands manufactured by Columbus Superconductors meets the target specifications for the considered coils, about 5 meters of outer diameter and maximum field on the conductor below 5 T, and they are also compatible with the Ignitor cryogenic system, which is designed to cool the machine at 30 K, although MgB2 may use colder gas at 10 K. The technical feasibility of these coils, as well as their stability and protection in the unlikely case of its quench, has been studied. The final design includes about 300 MgB2 multifilamentary strands of 1 mm in diameter and a copper pipe for the He-gas flow in the center. A mock-up cable has been manufactured. Measurements of the critical current Jc as a function of magnetic field and temperature have been done for the cable bent to a curvature radius of 20 cm and compared to the results of a straight sample. The feasability of the manufacturing and jacketing processes has thus been demonstrated.

  20. High-field actively detuneable transverse electromagnetic (TEM) coil with low-bias voltage for high-power RF transmission.

    PubMed

    Avdievich, Nikolai I; Bradshaw, Ken; Kuznetsov, Andrey M; Hetherington, Hoby P

    2007-06-01

    The design and construction of a 4T (170 MHz) transverse electromagnetic (TEM) actively detuneable quadrature head coil is described. Conventional schemes for active detuning require high negative bias voltages (>300 V) to prevent leakage of RF pulses with amplitudes of 1-2 kW. To extend the power handling capacity and avoid the use of high DC bias voltages, we developed an alternate method of detuning the volume coil. In this method the PIN diodes in the detuning circuits are shorted when the RF volume coil is tuned, and negatively biased with -12 V when the coil is detuned. To preserve the high Q(U)/Q(L) ratio of the TEM coil, we modified the method of Nabetani and Watkins (Proceedings of the 13th Annual Meeting of ISMRM, Kyoto, Japan, 2004, abstract 1574) by utilizing a high-impedance (approximately 200 Omega), lumped-element, quarter-wavelength transformer. A Q(U) of 500 was achieved for the detuneable TEM, such that incorporation of the detuning network had minimal effect (<1 dB) on the performance of the coil in vivo. PMID:17534919

  1. Coil Creep and Skew-Quadrupole Field Components in the Tevatron

    SciTech Connect

    Annala, G.; Harding, D.J.; Syphers, M.J.; /Fermilab

    2011-07-11

    During the start-up of Run II of the Tevatron Collider program, several issues surfaced which were not present, or not seen as detrimental, during Run I. These included the repeated deterioration of the closed orbit requiring orbit smoothing every two weeks or so, the inability to correct the closed orbit to desired positions due to various correctors running at maximum limits, regions of systematically strong vertical dipole corrections, and the identification of very strong coupling between the two transverse degrees-of-freedom. It became apparent that many of the problems being experienced operationally were connected to a deterioration of the main dipole magnet alignment, and remedial actions were undertaken. However, the alignment alone was not enough to explain the corrector strengths required to handle transverse coupling. With one exception, strong coupling had generally not been an issue in the Tevatron during Run I. Based on experience with the Main Ring, the Tevatron was designed with a very strong skew quadrupole circuit to compensate any quadrupole alignment and skew quadrupole field errors that might present themselves. The circuit was composed of 48 correctors placed evenly throughout the arcs, 8 per sector, evenly placed in every other cell. Other smaller circuits were installed but not initially needed or commissioned. These smaller circuits were composed of individual skew quadrupole correctors on either side of the long straight sections. These circuits were tuned by first bringing the horizontal and vertical tunes near each other. The skew quadrupoles were then adjusted to minimize tune split, usually to less than 0.003. Initially, the main skew quad circuit (designated T:SQ) could accomplish this global decoupling with only 4% of its possible current, and the smaller circuits were not required at all. The start-up of Run Ib was complicated by what was later discovered to be a rolled triplet quadrupole magnet in one of the Interaction Regions

  2. Nonlinear dynamics of a magnetically driven Duffing-type spring-magnet oscillator in the static magnetic field of a coil

    NASA Astrophysics Data System (ADS)

    Donoso, Guillermo; Ladera, Celso L.

    2012-11-01

    We study the nonlinear oscillations of a forced and weakly dissipative spring-magnet system moving in the magnetic fields of two fixed coaxial, hollow induction coils. As the first coil is excited with a dc current, both a linear and a cubic magnet-position dependent force appear on the magnet-spring system. The second coil, located below the first, excited with an ac current, provides the oscillating magnetic driving force on the system. From the magnet-coil interactions, we obtain, analytically, the nonlinear motion equation of the system, found to be a forced and damped cubic Duffing oscillator moving in a quartic potential. The relative strengths of the coefficients of the motion equation can be easily set by varying the coils’ dc and ac currents. We demonstrate, theoretically and experimentally, the nonlinear behaviour of this oscillator, including its oscillation modes and nonlinear resonances, the fold-over effect, the hysteresis and amplitude jumps, and its chaotic behaviour. It is an oscillating system suitable for teaching an advanced experiment in nonlinear dynamics both at senior undergraduate and graduate levels.

  3. Dependence of B1+ and B1− Field Patterns of Surface Coils on the Electrical Properties of the Sample and the MR Operating Frequency

    PubMed Central

    Vaidya, Manushka V.; Collins, Christopher M.; Sodickson, Daniel K.; Brown, Ryan; Wiggins, Graham C.; Lattanzi, Riccardo

    2016-01-01

    In high field MRI, the spatial distribution of the radiofrequency magnetic (B1) field is usually affected by the presence of the sample. For hardware design and to aid interpretation of experimental results, it is important both to anticipate and to accurately simulate the behavior of these fields. Fields generated by a radiofrequency surface coil were simulated using dyadic Green’s functions, or experimentally measured over a range of frequencies inside an object whose electrical properties were varied to illustrate a variety of transmit (B1+) and receive (B1−) field patterns. In this work, we examine how changes in polarization of the field and interference of propagating waves in an object can affect the B1 spatial distribution. Results are explained conceptually using Maxwell’s equations and intuitive illustrations. We demonstrate that the electrical conductivity alters the spatial distribution of distinct polarized components of the field, causing “twisted” transmit and receive field patterns, and asymmetries between |B1+| and |B1−|. Additionally, interference patterns due to wavelength effects are observed at high field in samples with high relative permittivity and near-zero conductivity, but are not present in lossy samples due to the attenuation of propagating EM fields. This work provides a conceptual framework for understanding B1 spatial distributions for surface coils and can provide guidance for RF engineers.

  4. Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children

    NASA Astrophysics Data System (ADS)

    Terada, Y.; Kono, S.; Ishizawa, K.; Inamura, S.; Uchiumi, T.; Tamada, D.; Kose, K.

    2013-05-01

    We adopted a combination of pieces of permanent magnets and a single-channel (SC) shim coil to shim the magnetic field in a magnetic resonance imaging system dedicated for skeletal age assessment of children. The target magnet was a 0.3-T open and compact permanent magnet tailored to the hand imaging of young children. The homogeneity of the magnetic field was first improved by shimming using pieces of permanent magnets. The residual local inhomogeneity was then compensated for by shimming using the SC shim coil. The effectiveness of the shimming was measured by imaging the left hands of human subjects and evaluating the image quality. The magnetic resonance images for the child subject clearly visualized anatomical structures of all bones necessary for skeletal age assessment, demonstrating the usefulness of combined shimming.

  5. Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children.

    PubMed

    Terada, Y; Kono, S; Ishizawa, K; Inamura, S; Uchiumi, T; Tamada, D; Kose, K

    2013-05-01

    We adopted a combination of pieces of permanent magnets and a single-channel (SC) shim coil to shim the magnetic field in a magnetic resonance imaging system dedicated for skeletal age assessment of children. The target magnet was a 0.3-T open and compact permanent magnet tailored to the hand imaging of young children. The homogeneity of the magnetic field was first improved by shimming using pieces of permanent magnets. The residual local inhomogeneity was then compensated for by shimming using the SC shim coil. The effectiveness of the shimming was measured by imaging the left hands of human subjects and evaluating the image quality. The magnetic resonance images for the child subject clearly visualized anatomical structures of all bones necessary for skeletal age assessment, demonstrating the usefulness of combined shimming.

  6. Pulse Coil Tester

    NASA Technical Reports Server (NTRS)

    Simon, Richard A.

    1988-01-01

    Set of relays tested easily and repeatedly. Pulse coil tester causes coil under test to generate transient voltage; waveform indicates condition of coil. Tester accommodates assembly of up to four coils at a time.

  7. Magnetic field dependent stability and quench behavior and degradation limits in conduction-cooled MgB2 wires and coils

    PubMed Central

    Ye, Liyang; Cruciani, Davide; Xu, Minfeng; Mine, Susumu; Amm, Kathleen; Schwartz, Justin

    2015-01-01

    Long lengths of metal/MgB2 composite conductors with high critical current density (Jc), fabricated by the power-in-tube (PIT) process, have recently become commercially available. Owing to its electromagnetic performance in the 20 K – 30 K range and relatively low cost, MgB2 may be attractive for a variety of applications. One of the key issues for magnet design is stability and quench protection, so the behavior of MgB2 wires and magnets must be understood before large systems can emerge. In this work, the stability and quench behavior of several conduction-cooled MgB2 wires are studied. Measurements of the minimum quench energy and normal zone propagation velocity are performed on short samples in a background magnetic field up to 3 T and on coils in self-field and the results are explained in terms of variations in the conductor architecture, electrical transport behavior, operating conditions (transport current and background magnetic field) and experimental setup (short sample vs small coil). Furthermore, one coil is quenched repeatedly with increasing hot-spot temperature until Jc is decreased. It is found that degradation during quenching correlates directly with temperature and not with peak voltage; a safe operating temperature limit of 260 K at the surface is identified. PMID:25883414

  8. Effect of neutral gas heating on the wave magnetic fields of a low pressure 13.56 MHz planar coil inductively coupled argon discharge

    SciTech Connect

    Jayapalan, Kanesh K. Chin, Oi-Hoong

    2014-04-15

    The axial and radial magnetic field profiles in a 13.56 MHz (radio frequency) laboratory 6 turn planar coil inductively coupled plasma reactor are simulated with the consideration of the effect of neutral gas heating. Spatially resolved electron densities, electron temperatures, and neutral gas temperatures were obtained for simulation using empirically fitted electron density and electron temperature and heuristically determined neutral gas temperature. Comparison between simulated results and measured fields indicates that neutral gas heating plays an important role in determining the skin depth of the magnetic fields.

  9. Triple Halo Coil: Development and Comparison with Other TMS Coils

    NASA Astrophysics Data System (ADS)

    Rastogi, Priyam; Hadimani, Ravi; Jiles, David

    Transcranial Magnetic Stimulation (TMS) is a non-invasive stimulation technique that can be used for the treatment of various neurological disorders such as Parkinson's Disease, PTSD, TBI and anxiety by regulating synaptic activity. TMS is FDA approved for the treatment of major depressive disorder. There is a critical need to develop deep TMS coils that can stimulate deeper regions of the brain without excessively stimulating the cortex in order to provide an alternative to surgical methods. We have developed a novel multi-coil configuration called ``Triple Halo Coil'' (THC) that can stimulate deep brain regions. Investigation of induced electric and magnetic field in these regions have been achieved by computer modelling. Comparison of the results due to THC configuration have been conducted with other TMS coils such as ``Halo Coil'', circular coil and ``Figure of Eight'' coil. There was an improvement of more than 15 times in the strength of magnetic field, induced by THC configuration at 10 cm below the vertex of the head when compared with the ``Figure of Eight'' coil alone. Carver Charitable Trust.

  10. An electromagnetic theory of turbulence driven poloidal rotation

    SciTech Connect

    McDevitt, C. J.; Guercan, Oe. D.

    2012-10-15

    An electromagnetic theory of turbulence driven poloidal rotation is developed with particular emphasis on understanding poloidal rotation in finite-{beta} plasmas. A relation linking the flux of polarization charge to the divergence of the total turbulent stress is derived for electromagnetic gyrokinetic modes. This relation is subsequently utilized to derive a constraint on the net electromagnetic turbulent stress exerted on the poloidal flow. Various limiting cases of this constraint are considered, where it is found that electromagnetic contributions to the turbulent stress may either enhance or reduce the net turbulent stress depending upon the branch of turbulence excited.

  11. Poloidal rotation, density asymmetries and momentum confinement in tokamak experiments

    SciTech Connect

    Stacey, W.M.; Jackson, D.R.

    1992-08-01

    Poloidal rotation speeds and density asymmetries are calculated for the deuterium and dominant carbon (oxygen) impurity ions in discharges in ASDEX, DIII, ISX-B, JET, and TFTR for which {upsilon}{sub {phi}} {approximately} {upsilon}{sub th} for the ions. These poloidal rotation speeds and density asymmetries are used to evaluate the neoclassical gyroviscous model for the momentum confinement time. The rather good agreement with experimental momentum confinement times obtained over this wide range of plasma parameters provides a measure of confidence in the calculated density asymmetries and poloidal rotation, as well as arguing for a neoclassical explanation for momentum confinement in tokamaks.

  12. High poloidal beta equilibria in TFTR limited by a natural inboard poloidal field null

    SciTech Connect

    Sabbagh, S.A.; Gross, R.A.; Mauel, M.E.; Navratil, G.A. . Dept. of Applied Physics); Bell, M.G.; Bell, R.; Bitter, M.; Bretz, N.L.; Budny, R.V.; Bush, C.E.; Chance, M.S.; Efthimion, P.C.; Fredrickson, E.D.; Hatcher, R.; Hawryluk, R.J.; Hirshman, S.P.; Janos, A.C.; Jardin, S.C.; Jassby, D.L.; Manickam, J.; McCune, D.C.; McGuire, K.M.; Medley, S.S.; Mueller, D.; Nagayama, Y.; Ow

    1991-07-01

    Recent operation of the Tokamak Fusion Test Reactor TFTR, has produced plasma equilibria with values of {Lambda} {triple bond} {beta}{sub p eq} + l{sub i}/2 as large as 7, {epsilon}{beta}{sub p dia} {triple bond} 2{mu}{sub 0}{epsilon}/{much lt}B{sub p}{much gt}{sup 2} as large as 1.6, and Troyon normalized diamagnetic beta, {beta}{sub N dia} {triple bond} 10{sup 8}<{beta}{sub t}{perpendicular}>aB{sub 0}/I{sub p} as large as 4.7. When {epsilon}{beta}{sub p dia} {approx gt} 1.25, a separatrix entered the vacuum chamber, producing a naturally diverted discharge which was sustained for many energy confinement times, {tau}{sub E}. The largest values of {epsilon}{beta}{sub p} and plasma stored energy were obtained when the plasma current was ramped down prior to neutral beam injection. The measured peak ion and electron temperatures were as large as 24 keV and 8.5 keV, respectively. Plasma stored energy in excess of 2.5 MJ and {tau}{sub E} greater than 130 msec were obtained. Confinement times of greater than 3 times that expected from L-mode predictions have been achieved. The fusion power gain. Q{sub DD}, reached a values of 1.3 {times} 10{sup {minus}3} in a discharge with I{sub p} = 1 MA and {epsilon}{beta}{sub p dia} = 0.85. A large, sustained negative loop voltage during the steady state portion of the discharge indicates that a substantial non-inductive component of I{sub p} exists in these plasmas. Transport code analysis indicates that the bootstrap current constitutes up to 65% of I{sup p}. Magnetohydrodynamic (MHD) ballooning stability analysis shows that while these plasmas are near, or at the {beta}{sub p} limit, the pressure gradient in the plasma core is in the first region of stability to high-n modes. 24 refs., 10 figs.

  13. High field Nb/sub 3/Sn Axicell insert coils for the Mirror Fusion Test Facility-B (MFTF-B) axicell configuration. Final report

    SciTech Connect

    Baldi, R.W.; Tatro, R.E.; Scanlan, R.M.; Agarwal, K.L.; Bailey, R.E.; Burgeson, J.E.; Kim, I.K.; Magnuson, G.D.; Mallett, B.D.; Pickering, J.L.

    1984-03-01

    Two 12-tesla superconducting insert coils are being designed by General Dynamics Convair Division for the axicell regions of MFTF-B for Lawrence Livermore National Laboratory. A major challenge of this project is to ensure that combined fabrication and operational strains induced in the conductor are within stringent limitations of the relatively brittle Nb/sub 3/Sn superconductor filaments. These coils are located in the axicell region of MFTF-B. They have a clear-bore diameter of 36.195cm (14.25 inches) and consist of 27 double pancakes (i.e., 54 pancakes per coil) would on an electrically insulated 304LN stainless steel/bobbin helium vessel. Each pancake has 57 turns separated by G-10CR insulation. The complete winding bundle has 4.6 million ampere-turns and uniform current density of 2007 A/cm/sup 2/. In conjunction with the other magnets in the system, they produce a 12-tesla central field and a 12.52-tesla peak field. A multifilamentary Nb/sub 3/Sn conductor was selected to meet these requirements. The conductor consists of a monolithic insert soldered into a copper stabilizer. Sufficient cross-sectional area and work-hardening of the copper stabilizer has been provided for the conductor to self-react the electromagnetic Lorentz force induced hoop stresses with normal operational tensile strains less than 0.07 percent.

  14. Design and modelling of a SMES coil

    NASA Astrophysics Data System (ADS)

    Yuan, Weijia; Campbell, A. M.; Coombs, T. A.

    2010-06-01

    The design of a Superconducting Magnetic Energy Storage (SMES) coil wound by coated conductors has been presented. Based on an existing model for coated conductor pancake coils, this paper analysed the magnetic field and current density distribution of the coil at two different operation temperatures, 77K and 22K. A comparison table of the critical currents and AC losses at these two temperatures has been presented. Several steps to improve the transport current of the coil have been suggested as well.

  15. A strip-shield improves the efficiency of a solenoid coil in probes for high field solid-state NMR of lossy biological samples

    PubMed Central

    Wu, Chin H.; Grant, Christopher V.; Cook, Gabriel A.; Park, Sang Ho; Opella, Stanley J.

    2009-01-01

    A strip-shield inserted between a high inductance double-tuned solenoid coil and the glass tube containing the sample improves the efficiency of probes used for high-field solid-state NMR experiments on lossy aqueous samples of proteins and other biopolymers. A strip-shield is a coil liner consisting of thin copper strips layered on a PTFE (polytetrafluoroethylene) insulator. With lossy samples, the shift in tuning frequency is smaller, the reduction in Q, and RF-induced heating are all significantly reduced when the strip-shield is present. The performance of 800 MHz 1H/15N and 1H/13C double-resonance probes is demonstrated on aqueous samples of membrane proteins in phospholipid bilayers. PMID:19559634

  16. Trapped field of 1.1 T without flux jumps in an MgB2 bulk during pulsed field magnetization using a split coil with a soft iron yoke

    NASA Astrophysics Data System (ADS)

    Fujishiro, H.; Mochizuki, H.; Ainslie, M. D.; Naito, T.

    2016-08-01

    MgB2 superconducting bulks have promising potential as trapped field magnets. We have achieved a trapped field of B z = 1.1 T on a high-J c MgB2 bulk at 13 K without flux jumps by pulsed field magnetization (PFM) using a split-type coil with a soft iron yoke, which is a record-high trapped field by PFM for bulk MgB2 to date. The flux jumps, which frequently took place using a solenoid-type coil during PFM, were avoided by using the split-type coil, and the B z value was enhanced by the insertion of soft iron yoke. The flux dynamics and heat generation/propagation were analyzed during PFM using a numerical simulation, in which the magnetic flux intruded and attenuated slowly in the bulk and tended to align along the axial direction due to the presence of soft iron yoke. The advantages of the split-type coil and the simultaneous use of a soft iron yoke are discussed.

  17. Engineering Design Status of the Quasi-Poloidal Stellarator (QPS)

    SciTech Connect

    Nelson, Brad E; Benson, Robert D; Berry, Lee A; Brooks, A.; Cole, Michael J; Fogarty, Paul J; Freudenberg, Kevin D; Goranson, Paul L; Hargrove, T.; Heitzenroeder, P.; Hirshman, Steven Paul; Jones, G.; Lovett, G.; Lumsdaine, A.; Lyon, James F; Madhukar, M.; Neilson, G.; Parang, M.; Shannon, T.; Spong, Donald A; Strickler, Dennis J; Williamson, David E

    2006-01-01

    The engineering design status of the Quasi-Poloidal Stellarator Experiment (QPS) is presented. The overall configuration and the design, manufacturing R&D and assembly techniques of the core components are described Keywords-stellarator: experimental fusion device

  18. Poloidal rotation, density asymmetries and momentum confinement in tokamak experiments

    SciTech Connect

    Stacey, W.M.; Jackson, D.R.

    1992-08-01

    Poloidal rotation speeds and density asymmetries are calculated for the deuterium and dominant carbon (oxygen) impurity ions in discharges in ASDEX, DIII, ISX-B, JET, and TFTR for which [upsilon][sub [phi

  19. Direct measurement of kilo-tesla level magnetic field generated with laser-driven capacitor-coil target by proton deflectometry

    NASA Astrophysics Data System (ADS)

    Law, K. F. F.; Bailly-Grandvaux, M.; Morace, A.; Sakata, S.; Matsuo, K.; Kojima, S.; Lee, S.; Vaisseau, X.; Arikawa, Y.; Yogo, A.; Kondo, K.; Zhang, Z.; Bellei, C.; Santos, J. J.; Fujioka, S.; Azechi, H.

    2016-02-01

    A kilo-tesla level, quasi-static magnetic field (B-field), which is generated with an intense laser-driven capacitor-coil target, was measured by proton deflectometry with a proper plasma shielding. Proton deflectometry is a direct and reliable method to diagnose strong, mm3-scale laser-produced B-field; however, this was not successful in the previous experiment. A target-normal-sheath-accelerated proton beam is deflected by Lorentz force in the laser-produced magnetic field with the resulting deflection pattern recorded on a radiochromic film stack. A 610 ± 30 T of B-field amplitude was inferred by comparing the experimental proton pattern with Monte-Carlo calculations. The amplitude and temporal evolutions of the laser-generated B-field were also measured by a differential magnetic probe, independently confirming the proton deflectometry measurement results.

  20. Poloidal ULF wave observed in the plasmasphere boundary layer

    NASA Astrophysics Data System (ADS)

    Liu, W.; Cao, J.; Zong, Q.; Li, X.; Sarris, T. E.; Angelopoulos, V.

    2012-12-01

    We investigate an event on the formation of a plasmasphere boundary layer and its effect on ULF wave generation observed by THEMIS satellites during three consecutive outbound passes. On September 13 2011, TH-D observed a sharp plasmapause at L=3.4. The plasmasphere starts to expand and to be refilled on September 14th. On September 15th, a plasmasphere boundary layer is formed with two density drops at L=4.5 and 6.5, respectively. Strong radial magnetic field and azimuthal electric field oscillations are observed within the two density gradients, suggesting poloidal ULF wave. Even mode signature and bump-on-tail plasma distribution at ~10keV observed in this event favour the mechanism of drift-bounce resonance. We suggest that the plasma density structures in plasmasphere boundary layers can provide conditions for resonances that could generate ULF waves. All the above features suggest that plasmasphere boundary layer may have impact on the generation of ULF wave and potential impact on radiation belt acceleration.

  1. Phase Relationships of Solar Hemispheric Toroidal and Poloidal Cycles

    NASA Astrophysics Data System (ADS)

    Muraközy, J.

    2016-08-01

    The solar northern and southern hemispheres exhibit differences in their intensities and time profiles of the activity cycles. The time variation of these properties was studied in a previous article covering the data from Cycles 12-23. The hemispheric phase lags exhibited a characteristic variation: the leading role was exchanged between hemispheres every four cycles. The present work extends the investigation of this variation using the data of Staudacher and Schwabe in Cycles 1-4 and 7-10 as well as Spörer’s data in Cycle 11. The previously observed variation cannot be clearly recognized using the data of Staudacher, Schwabe, and Spörer. However, it is more interesting that the phase lags of the reversals of the magnetic fields at the poles follow the same variations as those of the hemispheric cycles in Cycles 12-23, i.e., one of the hemispheres leads in four cyles and the leading role jumps to the opposite hemisphere in the next four cycles. This means that this variation is a long-term property of the entire solar dynamo mechanism, for both the toroidal and poloidal fields, which hints at an unidentified component of the process responsible for the long-term memory.

  2. Integrated modeling of high poloidal beta scenario for a next-step reactor

    NASA Astrophysics Data System (ADS)

    McClenaghan, J.; Garofalo, A. M.; Meneghini, O.; Smith, S. P.

    2015-11-01

    In order to fill the scientific and technological gaps between ITER and a nuclear fusion power plant DEMO, a next-step integrated nuclear test facility is critical. A high poloidal beta tokamak regime investigated in recent DIII-D experiments is a promising candidate for steady state operation in such a next-step device because the large bootstrap current fraction (~ 80 %) reduces the demands on the external current drive. Despite the large values of q95 ~10, the normalized fusion performance observed in the experiments meet the target for an economically attractive fusion power plant such as ARIES-ACT2. In this work, we will project the performance for a conducting and superconducting coil next-step steady state reactor using theory-based 0-D modeling and full 1.5D transport modeling. Work supported by U.S. DOE under DE-FC02-04ER54698.

  3. Magnet Coil Shorted Turn Detector

    SciTech Connect

    Dinkel, J.A.; Biggs, J.E.

    1994-03-01

    The Magnet Coil Shorted Turn Detector has been developed to facilitate the location of shorted turns in magnet coils. Finding these shorted turns is necessary to determine failure modes that are a necessary step in developing future production techniques. Up to this point, coils with shorted turns had the insulation burned off without the fault having been located. This disassembly process destroyed any chance of being able to find the fault. In order to maintain a flux balance in a coupled system such as a magnet coil, the current in a shorted turn must be opposed to the incident current. If the direction of the current in each conductor can be measured relative to the incident current, then the exact location of the short can be determined. In this device, an AC voltage is applied to the magnet under test. A small hand held B-dot pickup coil monitors the magnetic field produced by current in the individual magnet conductors. The relative phase of this pickup coil voltage is compared to a reference signal derived from the input current to detect a current reversal as the B-dot pickup coil is swept over the conductors of the coil under test. This technique however, is limited to only those conductors that are accessible to the hand held probe.

  4. The structure and poloidal dynamics of blob filaments in TJ-K

    NASA Astrophysics Data System (ADS)

    Garland, S.; Fuchert, G.; Ramisch, M.; Hirth, T.

    2016-04-01

    Relatively dense, field-aligned, filament-like structures (blobs) have been observed to propagate radially and poloidally through the scrape-off layer (SOL) in magnetically confined fusion plasmas, and contribute significantly to SOL transport. A detailed understanding of blob structure and dynamics, and their dependence on magnetic field geometry, is important in magnetic confinement physics for the prediction of heat loads on reactor wall facing components, as well as for understanding plasma confinement and neutral particle recycling. Experimentally deduced centre of mass poloidal blob velocity components, obtained using the conditional averaging technique, have been compared to an analytical blob model which has been simplified to express blob velocity in terms of the magnetic field curvature vector. Background flows are not incorporated into the analytical model, and must be added in to obtain good agreement with the experimental data. In addition, the 3D structure of blobs in TJ-K has been investigated using the conditional average of density fluctuations in two toroidally separated poloidal planes. Blobs are observed to be aligned to a flux tube near to the last closed flux surface, in the blob birth region. However at positions further along the blob trajectory, the structures do not deform according to the magnetic shear, rather they remain rigid, and retain their original form.

  5. High-field quench behavior and dependence of hot spot temperature on quench detection voltage threshold in a Bi2Sr2CaCu2Ox coil

    NASA Astrophysics Data System (ADS)

    Shen, Tengming; Ye, Liyang; Turrioni, Daniele; Li, Pei

    2015-07-01

    Small insert solenoids have been built using a multifilamentary Ag/Bi2Sr2CaCu2Ox round wire insulated with a mullite sleeve (˜100 μm in thickness) and characterized in background fields to explore the quench behaviors and limits of Bi2Sr2CaCu2Ox superconducting magnets, with an emphasis on assessing the impact of slow normal zone propagation on quench detection. Using heaters of various lengths to initiate a small normal zone, a coil was quenched safely more than 70 times without degradation, with the maximum coil temperature reaching 280 K. Coils withstood a resistive voltage of tens of mV for seconds without quenching, showing the high stability of these coils and suggesting that the quench detection voltage should be greater than 50 mV in order not to falsely trigger protection. The hot spot temperature for the resistive voltage of the normal zone to reach 100 mV increased from ˜40-˜80 K while increasing the operating wire current density Jo from 89 A mm-2 to 354 A mm-2, whereas for the voltage to reach 1 V, it increased from ˜60-˜140 K. This shows the increasing negative impact of slow normal zone propagation on quench detection with increasing Jo and the need to limit the quench detection voltage to <1 V. These measurements, coupled with an analytical quench model, were used to assess the impact of the maximum allowable detection voltage and temperature upon quench detection on the quench protection, assuming a limit of the hot spot temperature to <300 K.

  6. Toroidal coil chromatography: The effect of scale-up and “g” field on stage efficiency

    PubMed Central

    Sutherland, Ian; Hewitson, Peter; de Folter, Joost

    2011-01-01

    Selected test results have been taken from various publications and resolution and stage efficiency measured using an established model. All experiments used the same sample and, where possible, the same sample loading. The results show that stage mixing efficiencies have increased from 1.1% in 1998 to greater than 25% in the latest scaled-up version of a Toroidal coil chromatography (TCC) instrument working at 240 g. PMID:21227439

  7. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, Allan; Boozer, Allen H.

    1987-01-01

    A helical axis stellarator using only noninterlocking planar, non-circular coils, generates magnetic fields having a magnetic well and large rotational transform with resultant large equilibrium beta.

  8. Experimental identification of the kink instability as a poloidal flux amplification mechanism for coaxial gun spheromak formation.

    PubMed

    Hsu, S C; Bellan, P M

    2003-05-30

    The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma. Onset of column kinking agrees quantitatively with the Kruskal-Shafranov limit, and the kink acts as a dynamo which converts toroidal to poloidal flux. Regime II clearly leads to both poloidal flux amplification and the development of a spheromak configuration.

  9. The impact of poloidal asymmetries on tungsten transport in the core of JET H-mode plasmas

    SciTech Connect

    Angioni, C.; Pütterich, T.; Bilato, R.; Casson, F. J.; Giroud, C.; Mantica, P.; Helander, P.

    2015-05-15

    Recent progress in the understanding and prediction of the tungsten behaviour in the core of JET H-mode plasmas with ITER-like wall is presented. Particular emphasis is given to the impact of poloidal asymmetries of the impurity density. In particular, it is shown that the predicted reduction of temperature screening induced by the presence of low field side localization of the tungsten density produced by the centrifugal force is consistent with the observed tungsten behaviour in a JET discharge in H-mode baseline scenario. This provides first evidence of the role of poloidal asymmetries in reducing the strength of temperature screening. The main differences between plasma parameters in JET baseline and hybrid scenario discharges which affect the impact of poloidally asymmetric density on the tungsten radial transport are identified. This allows the conditions by which tungsten accumulation can be avoided to be more precisely defined.

  10. Poloidal monochromatic pulsations in Pc4-5 range observed in the Earth magnetosphere

    NASA Astrophysics Data System (ADS)

    Belakhovsky, Vladimir

    Poloidal monochromatic pulsations in Pc4-5 range observed in the Earth magnetosphere Belakhovsky V.B.1, Pilipenko V.A.2 1 - Polar Geophysical Institute, Apatity, Russia 2 - Institute of Physics of the Earth, Moscow, Russia Monochromatic geomagnetic pulsations in the Pc4-5 frequency range in the morning sector for some events in 2007-2008 years were studied using GOES, THEMIS, and ETS spacecrafts. The satellite observations showed that these pulsations are a poloidal-type fundamental mode of Alfven field line oscillations with the dominant radial and field-aligned magnetic components. The observed pulsations are small-scale in azimuthal direction; it excited during the low geomagnetic activity and are quite similar to Pg type pulsations. Contrary to typical Pg, these pulsations practically cannot be seen on the CARISMA magnetometers. The observed magnetic pulsations were accompanied by the simultaneous pulsations in the fluxes of energetic electrons and protons, as seen by LANL satellites with a great modulation depth. A strong increase of the electron density in the magnetosphere was found before the onset of the geomagnetic pulsations. As seen by THEMIS satellites these pulsations propagate in sunward direction, i.e. in the direction of electron drift in the morning sector. We suppose that the injection of energetic electrons may be responsible for the excitation of the poloidal Pc4-5 pulsations at the morning flank of the magnetosphere, though specific excitation mechanism is still unknown.

  11. Improved plasma equilibrium reconstruction for the HSX stellarator using an optimized array of magnetic coils

    NASA Astrophysics Data System (ADS)

    Chlechowitz, Enrico

    Controlling magnetically confined plasmas in a steady state regime requires knowledge about the plasma equilibrium, which is characterized by the plasma current profile and plasma pressure profile. The aim of this work has been to accurately reconstruct the plasma equilibrium for the HSX stellarator using the V3FIT code and a newly installed and optimized set of radial and poloidal magnetic diagnostics. The results of eddy current modeling are also included in the equilibrium reconstruction. As a result of the diagnostic optimization, which is based on three different concepts, specific magnetic coils have an increased sensitivity to either the bootstrap current or the Pfirsch-Schluter current. This drastically reduces the uncertainty in the reconstruction compared to results from an array of external diagnostics and a set of virtual diagnostics inside the vessel whose position was not optimized. Eddy currents in the vacuum vessel are caused by changes in the plasma current and the main field coil current; the magnitude and impact of these currents on the magnetic diagnostic response is calculated using the SPARK code. Including this eddy current impact in the reconstruction for the existing external and the new internal magnetic diagnostics leads to a better agreement between the reconstruction results in both cases. This is especially true during the plasma decay, when the largest eddy currents are driven from the plasma current ramp-down. The existence of net-toroidal eddy currents also explains the difference between the internal and external Rogowski coil measurement. The suppression of plasma currents in the edge of HSX through the radial insertion of a limiter is successfully reconstructed. Finally, low-order rational surfaces are generated inside the plasma through the use of auxiliary field coils and the evolution of the plasma current. The spontaneous appearance of these surfaces is reconstructed, which validates the results from plasma equilibrium

  12. Performance improvement of a high-temperature superconducting coil by separating and grading the coil edge

    NASA Astrophysics Data System (ADS)

    Ishiguri, Shinichi; Funamoto, Taisuke

    2011-06-01

    In this paper, we establish a model to analyze the transport current performance of a high-temperature superconducting (HTS) coil, considering the dependencies of critical current and n-value of an HTS tape on magnetic field and magnetic field angles. This analysis shows that relatively large electric fields appear at the coil’s edges, preventing improvement in the transport current performance of the coil. To solve this problem, in this paper, we propose a graded coil in which several coil edges of different heights are separated and graded. Analysis of its performance shows that the coil’s critical current increases, thus confirming that there exists an optimum coil cross section at which the stored energy and central magnetic field improve 2.1 times and 45%, respectively, compared with a typical rectangular coil that employs the same total length of the HTS tape. It is recommended that these results of the coil should be applied to SMES.

  13. Poloidal rotation and its relation to the potential vorticity flux

    SciTech Connect

    McDevitt, C. J.; Diamond, P. H.; Guercan, Oe. D.; Hahm, T. S.

    2010-11-15

    A kinetic generalization of a Taylor identity appropriate to a strongly magnetized plasma is derived. This relation provides an explicit link between the radial mixing of a four-dimensional (4D) gyrocenter fluid and the poloidal Reynolds stress. This kinetic analog of a Taylor identity is subsequently utilized to link the turbulent transport of poloidal momentum to the mixing of potential vorticity. A quasilinear calculation of the flux of potential vorticity is carried out, yielding diffusive, turbulent equipartition, and thermoelectric convective components. Self-consistency is enforced via the quasineutrality relation, revealing that for the case of a stationary small amplitude wave population, deviations from neoclassical predictions of poloidal rotation can be closely linked to the growth/damping profiles of the underlying drift wave microturbulence.

  14. Further progresses in the development of large MgB2 Superconducting Coils for the Ignitor Experiment

    NASA Astrophysics Data System (ADS)

    Tumino, A.; Grasso, G.; Coppi, B.

    2013-10-01

    Intermediate temperature superconducting cables have been adopted for the fabrication of the largest poloidal field coils of the Ignitor experiment. This is an important step toward achieving better duty cycles in Ignitor-like machines with innovative magnet technologies compared to traditional superconductors. The commercially available MgB2 strands manufactured by Columbus Superconductors can achieve the target specifications for the considered coils, about 5 meters of outer diameter and maximum field on the conductor below 5 T. These cables are also compatible with the Ignitor cryogenic system, which is designed to cool the machine at about 30 K, although MgB2 may use colder gas at 10 K. The preliminary cable design includes about 300 MgB2 multifilamentary strands of 1 mm in diameter and a copper tube for the He-gas flow in the center. Recently we have succeeded in the development of MgB2 strands with a further improvement in design and electrical properties for cable application. Reaching of a higher critical current density and better current sharing properties between the different strands is allowed by the newest design. The implementation of this progress in wire performance and its impact on the coil design will be discussed. US DOE partly sponsored.

  15. Dynamics of poloidal flows in enhanced reverse shear bifurcation

    SciTech Connect

    Srinivasan, R.; Avinash, K.

    2005-07-15

    A simple reduced enhanced reverse shear (RERS) model is constructed to study the dynamics of poloidal flows during the ERS transition. This model predicts that a reversal of poloidal flow shear occurs just prior to the transition, as seen in experiment [R. E. Bell et al., Phys. Rev. Lett. 81, 1429 (1998)]. This transition front propagates until the radial location where the safety factor (q) is minimum and becomes locked there due to insufficient input power to overcome the threshold requirement for the bifurcation. This study also reveals that there can be many routes to ERS transition depending upon various tunable parameters.

  16. Cool, high-density regime for poloidal divertors

    SciTech Connect

    Petravic, M.; Post, D.; Heifetz, D.; Schmidt, J.

    1981-08-01

    Calculations have been performed which demonstrate the possibility of operating poloidal divertors at high densities and low temperatures. This operating regime is caused primarily by ionization of recycling neutral gas near the divertor neutralizer plate which amplifies the input particle flux thereby raising the plasma density and lowering the plasma temperature. Low temperature, high density operation of poloidal divertors would ease the design requirements for future large tokamaks such as INTOR or FED by reducing the erosion rate in the divertor and reducing the neutral density and the associated charge exchange erosion near the main plasma. This regime may have already been observed on several divertor and limiter experiments.

  17. Ideal MHD beta-limits of poloidally asymmetric equilibria

    SciTech Connect

    Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

    1981-05-01

    The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in ..beta../sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is ..beta../sub critical/ approx. = 6.5%.

  18. Undulator Long Coil Measurement System Tests

    SciTech Connect

    Wolf, Zachary; Levashov, Yurii; /SLAC

    2010-11-24

    The first and second field integrals in the LCLS undulators must be below a specified limit. To accurately measure the field integrals, a long coil system is used. This note describes a set of tests which were used to check the performance of the long coil system. A long coil system was constructed to measure the first and second field integrals of the LCLS undulators. The long coil measurements of the background fields were compared to field integrals obtained by sampling the background fields and numerically calculating the integrals. This test showed that the long coil has the sensitivity required to measure at the levels specified for the field integrals. Tests were also performed by making long coil measurements of short magnets of known strength placed at various positions The long coil measurements agreed with the known field integrals obtained by independent measurements and calculation. Our tests showed that the long coil measurements are a valid way to determine whether the LCLS undulator field integrals are below the specified limits.

  19. A signal input coil made of superconducting thin film for improved signal-to-noise ratio in a high-Tc SQUID-based ultra-low field nuclear magnetic resonance system

    NASA Astrophysics Data System (ADS)

    Chen, Kuen-Lin; Hsu, Chin-Wei; Ku, Yue-Bai; Chen, Hsin-Hsien; Liao, Shu-Hsien; Wang, Li-Min; Horng, Herng-Er; Yang, Hong-Chang

    2013-11-01

    Resonant coupling schemes are commonly used in SQUID-based ultra-low field (ULF) nuclear magnetic resonance (NMR) systems to couple the spin relaxation signals from samples to the SQUID. Generally, in NMR systems, a resonant coupling scheme is composed of two solenoid coils which are made of enamel insulated wires and a capacitor connected in series. In this work, we tried to replace the metal solenoid input coil with a planar high-Tc superconducting spiral coil to improve the signal-to-noise ratio (SNR) of the ULF NMR signal. A measurement of the free induction decay signal of water protons was performed to demonstrate the improved performance of the system. This improvement is due to the fact that the planar superconducting spiral coil possesses a higher mutual inductance with the SQUID. Therefore, it is a promising way to enhance the SNR of high-Tc SQUID-based ULF NMR/MRI systems.

  20. Internal split field generator

    DOEpatents

    Thundat; ,Thomas George; Van Neste, Charles W.; Vass, Arpad Alexander

    2012-01-03

    A generator includes a coil of conductive material. A stationary magnetic field source applies a stationary magnetic field to the coil. An internal magnetic field source is disposed within a cavity of the coil to apply a moving magnetic field to the coil. The stationary magnetic field interacts with the moving magnetic field to generate an electrical energy in the coil.

  1. Self-shielded gradient coils for nuclear magnetic resonance imaging

    SciTech Connect

    Roemer, P.B.; Hickey, J.S.

    1988-04-12

    A gradient coil set for an MR apparatus is described comprising radially disposed coils adapted to be placed within a main field magnet. Each of the coils is adapted to provide a respective surface current distribution. The total magnetic field resulting from the coaction of the surface current distribution has a predetermined gradient in a predetermined single dimension within a predetermined area inside the coil set and a substantially zero value outside the coil set. Magnetic forces between the coil set and the field magnet are substantially eliminated.

  2. Electromagnetic Gun With Commutated Coils

    NASA Technical Reports Server (NTRS)

    Elliott, David G.

    1991-01-01

    Proposed electromagnetic gun includes electromagnet coil, turns of which commutated in sequence along barrel. Electrical current fed to two armatures by brushes sliding on bus bars in barrel. Interaction between armature currents and magnetic field from coil produces force accelerating armature, which in turn, pushes on projectile. Commutation scheme chosen so magnetic field approximately coincides and moves with cylindrical region defined by armatures. Scheme has disadvantage of complexity, but in return, enables designer to increase driving magnetic field without increasing armature current. Attainable muzzle velocity increased substantially.

  3. Design description of the Large Coil Test Facility pulse-coil support and transport system

    SciTech Connect

    Queen, C.C.

    1981-01-01

    In order to simulate the transient fields which would be imposed on superconducting toroidal field coils in an operating tokamak reactor, the Large Coil Test Facility (LCTF) test stand includes a set of pulse coils. This set of pulse coils is designed to be moved from one test location to another within the LCTF vacuum vessel while the vessel is operating under vacuum and the test stand and test coils are at an operating temperature of 4.2K. This operating environment and the extremely high magnetic loads have necessitated some unique design features for the pulse coil support and transport system. The support structure for the pulse coil must react high overturning moments and axial loads induced on the pulse coil by the interaction of the pulse field with the field generated by the large test coils. These loads are reacted into the test stand support structure or spider frame by an arrangement of six pedestals and a support beam. In order to move the pulse coil set from one test location to another, the support beam containing the pulse coils must be driven across rollers mounted on the pedestals, then clamped securely to react the loads. Because these operations must be performed in a vacuum environment at cryogenic tmperature, special consideration was given to component design.

  4. Coil Welding Aid

    NASA Technical Reports Server (NTRS)

    Wiesenbach, W. T.; Clark, M. C.

    1983-01-01

    Positioner holds coil inside cylinder during tack welding. Welding aid spaces turns of coil inside cylinder and applies contact pressure while coil is tack-welded to cylinder. Device facilitates fabrication of heat exchangers and other structures by eliminating hand-positioning and clamping of individual coil turns.

  5. Error Field Correction in ITER

    SciTech Connect

    Park, Jong-kyu; Boozer, Allen H.; Menard, Jonathan E.; Schaffer, Michael J.

    2008-05-22

    A new method for correcting magnetic field errors in the ITER tokamak is developed using the Ideal Perturbed Equilibrium Code (IPEC). The dominant external magnetic field for driving islands is shown to be localized to the outboard midplane for three ITER equilibria that represent the projected range of operational scenarios. The coupling matrices between the poloidal harmonics of the external magnetic perturbations and the resonant fields on the rational surfaces that drive islands are combined for different equilibria and used to determine an ordered list of the dominant errors in the external magnetic field. It is found that efficient and robust error field correction is possible with a fixed setting of the correction currents relative to the currents in the main coils across the range of ITER operating scenarios that was considered.

  6. Generation of 24.0 T at 4.2 K and 23.4 T at 27 K with a high-temperature superconductor coil in a 22.54 T background field

    NASA Astrophysics Data System (ADS)

    Ohkura, K.; Sato, K.; Ueyama, M.; Fujikami, Jun; Iwasa, Y.

    1995-09-01

    The 4.2 K and 27 K current-carrying performance of a high-temperature superconducting (HTS) coil was measured in background fields up to 22.54 T generated by a hybrid magnet (Hybrid III) at the MIT Francis Bitter National Magnet Laboratory. The coil, 40 mm winding i.d., 108 mm winding o.d., and 113 mm high, consists of 17 double pancakes, each wound with silver-sheathed BSCCO-2223 tapes. Each pancake is the product of a react-and-wind method. In total, the test coil contains ˜1200 m of BSCCO-2223 conductor weighing ˜7 kg. Prior to the measurements in Hybrid III, the coil was tested in zero background field in the temperature range from 4.2 to 77 K. It was coupled to a Gifford-McMahon type cryocooler and at 15 K generated a peak field of 2.1 T; at 18 K, it generated 1.9 T, operating continuously for ˜50 h. In a 22.54 T background field of Hybrid III, the coil reached critical currents of 116.5 A ([Jc]sc, critical current density based on the BSCCO cross-sectional area only, of 261 A/mm) at 4.2 K and 67 A ([Jc]sc=150 A/mm) at 27 K, establishing record net fields at respective temperatures of 24.0 and 23.4 T for HTS magnets. These currents correspond to overall winding current densities of 47 and 27 A/mm. High-field critical current data for short samples of the tape of the same formulation at 4.2 and 27 K are also presented. Although a [J]sc of 261 A/mm at 24 T and 4.2 K for the test coil is significantly less than ˜600 A/mm for the short samples at the same operating point, if factors such as length, bending, and even differences in defining critical current are considered, the coil and short samples have nearly the same critical current performance. Electromagnetic stresses do not seem to have any negative effects on coil performance. Record fields of 24.0 and 23.4 T were achieved after the test coil had experienced, over a period of 15 months, 20 thermal cycles between room temperature and cryogenic temperatures.

  7. A Compact Non-Planar Coil Design for the SFLM Hybrid

    NASA Astrophysics Data System (ADS)

    Hagnestål, A.; Ågren, O.; Moiseenko, V. E.

    2012-08-01

    A non-planar single layer semiconductor coil set for a version of the Straight Field Line Mirror Hybrid concept with reduced magnetic field has been computed. The coil set consists of 30 coils that are somewhat similar to baseball coils with skewed sides. The coil set has been modeled with filamentary current distributions and basic scaling assumptions have been made regarding the coil widths. This coil set is expected to be considerably cheaper than a previous computed coil set. The coils can probably be produced with technologies known today.

  8. Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system

    NASA Astrophysics Data System (ADS)

    Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

    2016-04-01

    An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process.

  9. Intra-coil interactions in split gradient coils in a hybrid MRI-LINAC system.

    PubMed

    Tang, Fangfang; Freschi, Fabio; Sanchez Lopez, Hector; Repetto, Maurizio; Liu, Feng; Crozier, Stuart

    2016-04-01

    An MRI-LINAC system combines a magnetic resonance imaging (MRI) system with a medical linear accelerator (LINAC) to provide image-guided radiotherapy for targeting tumors in real-time. In an MRI-LINAC system, a set of split gradient coils is employed to produce orthogonal gradient fields for spatial signal encoding. Owing to this unconventional gradient configuration, eddy currents induced by switching gradient coils on and off may be of particular concern. It is expected that strong intra-coil interactions in the set will be present due to the constrained return paths, leading to potential degradation of the gradient field linearity and image distortion. In this study, a series of gradient coils with different track widths have been designed and analyzed to investigate the electromagnetic interactions between coils in a split gradient set. A driving current, with frequencies from 100 Hz to 10 kHz, was applied to study the inductive coupling effects with respect to conductor geometry and operating frequency. It was found that the eddy currents induced in the un-energized coils (hereby-referred to as passive coils) positively correlated with track width and frequency. The magnetic field induced by the eddy currents in the passive coils with wide tracks was several times larger than that induced by eddy currents in the cold shield of cryostat. The power loss in the passive coils increased with the track width. Therefore, intra-coil interactions should be included in the coil design and analysis process. PMID:26852418

  10. High resolution NMR measurements using a 400MHz NMR with an (RE)Ba2Cu3O7-x high-temperature superconducting inner coil: Towards a compact super-high-field NMR.

    PubMed

    Piao, R; Iguchi, S; Hamada, M; Matsumoto, S; Suematsu, H; Saito, A T; Li, J; Nakagome, H; Takao, T; Takahashi, M; Maeda, H; Yanagisawa, Y

    2016-02-01

    Use of high-temperature superconducting (HTS) inner coils in combination with conventional low-temperature superconducting (LTS) outer coils for an NMR magnet, i.e. a LTS/HTS NMR magnet, is a suitable option to realize a high-resolution NMR spectrometer with operating frequency >1GHz. From the standpoint of creating a compact magnet, (RE: Rare earth) Ba2Cu3O7-x (REBCO) HTS inner coils which can tolerate a strong hoop stress caused by a Lorentz force are preferred. However, in our previous work on a first-generation 400MHz LTS/REBCO NMR magnet, the NMR resolution and sensitivity were about ten times worse than that of a conventional LTS NMR magnet. The result was caused by a large field inhomogeneity in the REBCO coil itself and the shielding effect of a screening current induced in that coil. In the present paper, we describe the operation of a modified 400MHz LTS/REBCO NMR magnet with an advanced field compensation technology using a combination of novel ferromagnetic shimming and an appropriate procedure for NMR spectrum line shape optimization. We succeeded in obtaining a good NMR line shape and 2D NOESY spectrum for a lysozyme aqueous sample. We believe that this technology is indispensable for the realization of a compact super-high-field high-resolution NMR. PMID:26778351

  11. A comparative study of flat coil and coil sensor for landslide detection

    NASA Astrophysics Data System (ADS)

    Sanjaya, Edi; Muslimin, Ahmad Novi; Djamal, Mitra; Suprijadi, Handayani, Gunawan; Ramli

    2016-03-01

    The landslide is one of the most costly catastrophic events in terms of human lives and infrastructure damage, thus an early warning monitoring for landslides becomes more and more important. Currently existing monitoring systems for early warning are available in terms of monolithic systems. This is a very cost-intensive way, considering installation as well as operational and personal expenses. We have been developing a landslide detection system based on flat coil and coil sensor. The flat coil element being developed is an inductive proximity sensor for detection mass of soil movement. The simple method of flat coil manufactures and low cost, is an attraction that is still inspired to develop flat coil sensors. Meanwhile, although it has a drawback in terms of their size, the coil sensor is still required in many fields due to their sensitivity and robustness. The simple method of coil manufacture and the materials are commonly available and low cost, is an attraction that is still inspired to develop induction coil sensors. A comparative study of alternative configuration of sensor based on flat coil elements and a coil in application to landslide detection has been discussed in this paper. The purpose of this comparison is to show the ideal conditions and the challenges for each sensor. Furthermore, a comparison between flat coil and coil sensor is presented.

  12. Optimized Geometry for Superconducting Sensing Coils

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Pananen, Konstantin; Hahn, Inseob

    2008-01-01

    An optimized geometry has been proposed for superconducting sensing coils that are used in conjunction with superconducting quantum interference devices (SQUIDs) in magnetic resonance imaging (MRI), magnetoencephalography (MEG), and related applications in which magnetic fields of small dipoles are detected. In designing a coil of this type, as in designing other sensing coils, one seeks to maximize the sensitivity of the detector of which the coil is a part, subject to geometric constraints arising from the proximity of other required equipment. In MRI or MEG, the main benefit of maximizing the sensitivity would be to enable minimization of measurement time. In general, to maximize the sensitivity of a detector based on a sensing coil coupled with a SQUID sensor, it is necessary to maximize the magnetic flux enclosed by the sensing coil while minimizing the self-inductance of this coil. Simply making the coil larger may increase its self-inductance and does not necessarily increase sensitivity because it also effectively increases the distance from the sample that contains the source of the signal that one seeks to detect. Additional constraints on the size and shape of the coil and on the distance from the sample arise from the fact that the sample is at room temperature but the coil and the SQUID sensor must be enclosed within a cryogenic shield to maintain superconductivity.

  13. Poloidal divertor experiment with applied E vector x B vector/B/sup 2/ drift

    SciTech Connect

    Strait, E J

    1980-05-01

    It has been proposed that the E vector x B vector/B/sup 2/ drift arising from an externally applied electric field could be used in a tokamak or other toroidal device to remove plasma and impurities from the region near the wall and to reduce the amount of plasma striking the wall, either assisting or replacing a conventional magnetic field divertor. A poloidal magnetic divertor (without pumping chamber) was added to the Wisconsin Levitated Toroidal Octupole, and the octupole was operated with a tokamak-like magnetic field configuration (q = 0.7). A radial electric field was applied in the scrape-off zone, causing an E vector x B vector/B/sup 2/ drift with a large poloidal component. This reduced plasma flux reaching the wall of the toroid by up to a factor of 5 beyond the effect of the magnetic divertor, for divertor configurations with both high and low magnetic mirror ratios, in good agreement with a simple theoretical model. Plasma density and density scale length were also reduced in the scrape-off zone, in qualitative agreement with the model. This was not accompanied by any new instabilities in the scrape-off zone, nor by any appreciable degradation of confinement of the central plasma.

  14. Protective link for superconducting coil

    DOEpatents

    Umans, Stephen D.

    2009-12-08

    A superconducting coil system includes a superconducting coil and a protective link of superconducting material coupled to the superconducting coil. A rotating machine includes first and second coils and a protective link of superconducting material. The second coil is operable to rotate with respect to the first coil. One of the first and second coils is a superconducting coil. The protective link is coupled to the superconducting coil.

  15. Characteristics of bowl-shaped coils for transcranial magnetic stimulation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Keita; Suyama, Momoko; Takiyama, Yoshihiro; Kim, Dongmin; Saitoh, Youichi; Sekino, Masaki

    2015-05-01

    Transcranial magnetic stimulation (TMS) has recently been used as a method for the treatment of neurological and psychiatric diseases. Daily TMS sessions can provide continuous therapeutic effectiveness, and the installation of TMS systems at patients' homes has been proposed. A figure-eight coil, which is normally used for TMS therapy, induces a highly localized electric field; however, it is challenging to achieve accurate coil positioning above the targeted brain area using this coil. In this paper, a bowl-shaped coil for stimulating a localized but wider area of the brain is proposed. The coil's electromagnetic characteristics were analyzed using finite element methods, and the analysis showed that the bowl-shaped coil induced electric fields in a wider area of the brain model than a figure-eight coil. The expanded distribution of the electric field led to greater robustness of the coil to the coil-positioning error. To improve the efficiency of the coil, the relationship between individual coil design parameters and the resulting coil characteristics was numerically analyzed. It was concluded that lengthening the outer spherical radius and narrowing the width of the coil were effective methods for obtaining a more effective and more uniform distribution of the electric field.

  16. Helical axis stellarator with noninterlocking planar coils

    DOEpatents

    Reiman, A.; Boozer, A.H.

    1984-03-06

    The present invention generates stellarator fields having favorable properties (magnetic well and large rotational transform) by a simple coil system consisting only of unlinked planar non-circular coils. At large rotational transform toroidal effects on magnetic well and rotational transform are small and can be ignored. We do so herein, specializing in straight helical systems.

  17. Poloidal velocity of impurity ions in neoclassical theory

    SciTech Connect

    Wong, S. K.; Chan, V. S.; Solomon, W. M.

    2008-08-15

    A formula for the poloidal velocity of impurity ions in a two-species plasma is derived from neoclassical theory in the banana regime, with corrections from the boundary layer separating the trapped and transiting ions. The formula is applicable to plasmas with toroidal rotations that can approach the thermal speeds of the ions. Using the formula to determine the poloidal velocity of C{sup +6} ions in a recently reported experiment [W. M. Solomon et al., Phys. Plasmas 13, 056116 (2006)] leads to agreement in the direction of the central region when it is otherwise from theories without strong toroidal rotations. Comparisons among these theories are made, demonstrating the degree of uncertainty of theoretical predictions.

  18. Predictions of the poloidal asymmetries and transport frequencies in KSTAR

    SciTech Connect

    Bae, C. Lee, S. G.; Terzolo, L.; Stacey, W. M.

    2014-01-15

    The extended neoclassical rotation theory formulated in Miller flux surface geometry enables unprecedented neoclassical calculations of the poloidal asymmetries in density, rotation velocities, electrostatic potential along the flux surfaces, and of the inertial (Reynolds stress) and gyroviscous transport frequencies, which are strong functions of these asymmetries. This paper presents such calculations of the poloidal asymmetries and non-negligible inertial and gyroviscous transport frequencies in two KSTAR (Korea Superconducting Tokamak Advanced Research) [Kwon et al., Nucl. Fusion 51, 094006 (2011)] Neutral Beam Injection H-mode discharges. The in-out asymmetries in the velocities are an order of magnitude larger than their up-down asymmetries. The magnitudes of the predicted inertial and gyroviscous transport frequencies depend on the magnitudes of the density and velocity asymmetries. The neoclassically predicted density asymmetries are shown to correspond with the reported measurements in tokamaks and the predicted carbon toroidal velocities agree very well with the measurements in KSTAR.

  19. Modular Coils and Plasma Configurations for Quasi-axisymmetric Stellarators

    SciTech Connect

    L.P. Ku and A.H. Boozer

    2010-09-10

    Characteristics of modular coils for quasi-axisymmetric stellarators that are related to the plasma aspect ratio, number of field periods and rotational transform have been examined systematically. It is observed that, for a given plasma aspect ratio, the coil complexity tends to increase with the increased number of field periods. For a given number of field periods, the toroidal excursion of coil winding is reduced as the plasma aspect ratio is increased. It is also clear that the larger the coil-plasma separation is, the more complex the coils become. It is further demonstrated that it is possible to use other types of coils to complement modular coils to improve both the physics and the modular coil characteristics.

  20. An interim report on the materials and selection criteria analysis for the Compact Ignition Tokamak Toroidal Field Coil Turn-to-Turn Insulation System

    SciTech Connect

    Campbell, V.W.; Dooley, J.B.; Hubrig, J.G.; Janke, C.J.; McManamy, T.J.; Welch, D.E.

    1990-01-01

    Design criteria for the Compact Ignition Tokamak, Toroidal-Field (TF) Coil, Turn-to-Turn Insulation System require an insulation sheet and bonding system that will survive cryogenic cycling in a radiation environment and maintain structural integrity during exposure to the significant compressive and shear loads associated with each operating cycle. For thermosetting resin systems, a complex interactive dependency exists between optimum peak value, in-service property performance capabilities of candidate generic materials; key handling and processing parameters required to achieve their optimum in-service property performance as an insulation system; and suitability of their handling and processing parameters as a function of design configuration and assembly methodology. This dependency is assessed in a weighted study matrix in which two principal programmatic approaches for the development of the TF Coil Subassembly Insulation System have been identified. From this matrix study, two viable approaches to the fabrication of the insulation sheet were identified: use of a press-formed sheet bonded in place with epoxy for mechanical bonding and tolerance take-up and formation of the insulation sheet by placement of dry cloth and subsequent vacuum pressure impregnation. Laboratory testing was conducted to screen a number of combinations of resins and hardeners on a generic basis. These combinations were chosen for their performance in similar applications. Specimens were tested to screen viscosity, thermal-shock tolerance, and cryogenic tolerance. Cryogenic shock and cryogenic temperature proved to be extremely lethal to many combinations of resin, hardener, and cure. Two combinations survived: a heavily flexibilized bisphenol A resin with a flexibilized amine hardener and a bisphenol A resin with cycloaliphatic amine hardener. 7 refs., 12 figs., 6 tabs.

  1. Analytic expression for poloidal flow velocity in the banana regime

    SciTech Connect

    Taguchi, M.

    2013-01-15

    The poloidal flow velocity in the banana regime is calculated by improving the l = 1 approximation for the Fokker-Planck collision operator [M. Taguchi, Plasma Phys. Controlled Fusion 30, 1897 (1988)]. The obtained analytic expression for this flow, which can be used for general axisymmetric toroidal plasmas, agrees quite well with the recently calculated numerical results by Parker and Catto [Plasma Phys. Controlled Fusion 54, 085011 (2012)] in the full range of aspect ratio.

  2. Pulsed-coil magnet systems for applying 10-30 Tesla Fields to cm-scale targets on Sandia's Z facility

    DOE PAGES

    Rovang, Dean C.; Lamppa, Derek C.; Cuneo, Michael Edward; Owen, Albert; Mckenney, John; Johnson, Drew; Radovich, Shawn; Kaye, Ronald J.; McBride, Ryan D; Alexander, C. Scott; et al

    2014-12-04

    We have successfully integrated the capability to apply uniform, high magnetic fields (10–30 T) to high energy density experiments on the Z facility. This system uses an 8-mF, 15-kV capacitor bank to drive large-bore (5 cm diameter), high-inductance (1–3 mH) multi-turn, multi-layer electromagnets that slowly magnetize the conductive targets used on Z over several milliseconds (time to peak field of 2–7 ms). This system was commissioned in February 2013 and has been used successfully to magnetize more than 30 experiments up to 10 T that have produced exciting and surprising physics results. These experiments used split-magnet topologies to maintain diagnosticmore » lines of sight to the target. We then describe the design, integration, and operation of the pulsed coil system into the challenging and harsh environment of the Z Machine. We also describe our plans and designs for achieving fields up to 20 T with a reduced-gap split-magnet configuration, and up to 30 T with a solid magnet configuration in pursuit of the Magnetized Liner Inertial Fusion concept.« less

  3. Pulsed-coil magnet systems for applying uniform 10–30 T fields to centimeter-scale targets on Sandia's Z facility

    SciTech Connect

    Rovang, D. C. Lamppa, D. C.; Cuneo, M. E.; Owen, A. C.; McKenney, J.; Johnson, D. W.; Radovich, S.; Kaye, R. J.; McBride, R. D.; Alexander, C. S.; Awe, T. J.; Slutz, S. A.; Sefkow, A. B.; Haill, T. A.; Jones, P. A.; Argo, J. W.; Dalton, D. G.; Robertson, G. K.; Waisman, E. M.; Sinars, D. B.; and others

    2014-12-15

    Sandia has successfully integrated the capability to apply uniform, high magnetic fields (10–30 T) to high energy density experiments on the Z facility. This system uses an 8-mF, 15-kV capacitor bank to drive large-bore (5 cm diameter), high-inductance (1–3 mH) multi-turn, multi-layer electromagnets that slowly magnetize the conductive targets used on Z over several milliseconds (time to peak field of 2–7 ms). This system was commissioned in February 2013 and has been used successfully to magnetize more than 30 experiments up to 10 T that have produced exciting and surprising physics results. These experiments used split-magnet topologies to maintain diagnostic lines of sight to the target. We describe the design, integration, and operation of the pulsed coil system into the challenging and harsh environment of the Z Machine. We also describe our plans and designs for achieving fields up to 20 T with a reduced-gap split-magnet configuration, and up to 30 T with a solid magnet configuration in pursuit of the Magnetized Liner Inertial Fusion concept.

  4. Pulsed-coil magnet systems for applying 10-30 Tesla Fields to cm-scale targets on Sandia's Z facility

    SciTech Connect

    Rovang, Dean C.; Lamppa, Derek C.; Cuneo, Michael Edward; Owen, Albert; Mckenney, John; Johnson, Drew; Radovich, Shawn; Kaye, Ronald J.; McBride, Ryan D; Alexander, C. Scott; Awe, Thomas James; Slutz, Stephen A.; Sefkow, Adam B; Haill, Thomas A.; Jones, Peter Andrew; Argo, Jeffrey W; Dalton, Devon; Robertson, Grafton Kincannon; Waisman, Eduardo Mario; Sinars, Daniel Brian; Meissner, Joel; Milhous, Mark; Nguyen, Doan; Mielke, Chuck

    2014-12-04

    We have successfully integrated the capability to apply uniform, high magnetic fields (10–30 T) to high energy density experiments on the Z facility. This system uses an 8-mF, 15-kV capacitor bank to drive large-bore (5 cm diameter), high-inductance (1–3 mH) multi-turn, multi-layer electromagnets that slowly magnetize the conductive targets used on Z over several milliseconds (time to peak field of 2–7 ms). This system was commissioned in February 2013 and has been used successfully to magnetize more than 30 experiments up to 10 T that have produced exciting and surprising physics results. These experiments used split-magnet topologies to maintain diagnostic lines of sight to the target. We then describe the design, integration, and operation of the pulsed coil system into the challenging and harsh environment of the Z Machine. We also describe our plans and designs for achieving fields up to 20 T with a reduced-gap split-magnet configuration, and up to 30 T with a solid magnet configuration in pursuit of the Magnetized Liner Inertial Fusion concept.

  5. Pulsed-coil magnet systems for applying uniform 10-30 T fields to centimeter-scale targets on Sandia's Z facility

    NASA Astrophysics Data System (ADS)

    Rovang, D. C.; Lamppa, D. C.; Cuneo, M. E.; Owen, A. C.; McKenney, J.; Johnson, D. W.; Radovich, S.; Kaye, R. J.; McBride, R. D.; Alexander, C. S.; Awe, T. J.; Slutz, S. A.; Sefkow, A. B.; Haill, T. A.; Jones, P. A.; Argo, J. W.; Dalton, D. G.; Robertson, G. K.; Waisman, E. M.; Sinars, D. B.; Meissner, J.; Milhous, M.; Nguyen, D. N.; Mielke, C. H.

    2014-12-01

    Sandia has successfully integrated the capability to apply uniform, high magnetic fields (10-30 T) to high energy density experiments on the Z facility. This system uses an 8-mF, 15-kV capacitor bank to drive large-bore (5 cm diameter), high-inductance (1-3 mH) multi-turn, multi-layer electromagnets that slowly magnetize the conductive targets used on Z over several milliseconds (time to peak field of 2-7 ms). This system was commissioned in February 2013 and has been used successfully to magnetize more than 30 experiments up to 10 T that have produced exciting and surprising physics results. These experiments used split-magnet topologies to maintain diagnostic lines of sight to the target. We describe the design, integration, and operation of the pulsed coil system into the challenging and harsh environment of the Z Machine. We also describe our plans and designs for achieving fields up to 20 T with a reduced-gap split-magnet configuration, and up to 30 T with a solid magnet configuration in pursuit of the Magnetized Liner Inertial Fusion concept.

  6. Pulsed-coil magnet systems for applying uniform 10-30 T fields to centimeter-scale targets on Sandia's Z facility.

    PubMed

    Rovang, D C; Lamppa, D C; Cuneo, M E; Owen, A C; McKenney, J; Johnson, D W; Radovich, S; Kaye, R J; McBride, R D; Alexander, C S; Awe, T J; Slutz, S A; Sefkow, A B; Haill, T A; Jones, P A; Argo, J W; Dalton, D G; Robertson, G K; Waisman, E M; Sinars, D B; Meissner, J; Milhous, M; Nguyen, D N; Mielke, C H

    2014-12-01

    Sandia has successfully integrated the capability to apply uniform, high magnetic fields (10-30 T) to high energy density experiments on the Z facility. This system uses an 8-mF, 15-kV capacitor bank to drive large-bore (5 cm diameter), high-inductance (1-3 mH) multi-turn, multi-layer electromagnets that slowly magnetize the conductive targets used on Z over several milliseconds (time to peak field of 2-7 ms). This system was commissioned in February 2013 and has been used successfully to magnetize more than 30 experiments up to 10 T that have produced exciting and surprising physics results. These experiments used split-magnet topologies to maintain diagnostic lines of sight to the target. We describe the design, integration, and operation of the pulsed coil system into the challenging and harsh environment of the Z Machine. We also describe our plans and designs for achieving fields up to 20 T with a reduced-gap split-magnet configuration, and up to 30 T with a solid magnet configuration in pursuit of the Magnetized Liner Inertial Fusion concept. PMID:25554308

  7. Terrace retro-reflector array for poloidal polarimeter on ITER.

    PubMed

    Imazawa, R; Kawano, Y; Ono, T; Kusama, Y

    2011-02-01

    A new concept of a terrace retro-reflector array (TERRA) as part of the poloidal polarimeter for ITER is proposed in this paper. TERRA reflects a laser light even from a high incident angle in the direction of the incident-light path, while a conventional retro-reflector array cannot. Besides, TERRA can be installed in a smaller space than a corner-cube retro-reflector. In an optical sense, TERRA is equivalent to a Littrow grating, the blaze angle of which varies, depending on the incident angle. The reflected light generates a bright and dark fringe, and the bright fringe is required to travel along the incident-light path to achieve the objects of laser-aided diagnostics. In order to investigate the propagation properties of laser light reflected by TERRA, we have developed a new diffraction formula. Conditions for the propagation of the bright fringe in the direction of the incident light have been obtained using the Littrow grating model and have been confirmed in a simulation applying the new diffraction formula. Finally, we have designed laser transmission optics using TERRA for the ITER poloidal polarimeter and have calculated the light propagation of the system. The optical design obtains a high transmission efficiency, with 88.6% of the incident power returned. These results demonstrate the feasibility of applying TERRA to the ITER poloidal polarimeter.

  8. Simultaneous poloidal measurements using new magnetically driven reciprocating probes in COMPASS

    NASA Astrophysics Data System (ADS)

    Dejarnac, R.; Gunn, J. P.; Dimitrova, M.; Hron, M.; Panek, R.; Pascal, J.-Y.; Saragosti-Chausy, C.; Tamain, P.; the COMPASS team

    2016-03-01

    Particles and heat transport in the scrape-off layer (SOL) of tokamaks is not yet fully understood. COMPASS is a small-size tokamakp where the edge plasma is well diagnosed in view of studying the competition between the parallel and the cross-field transport in the SOL. In order to better characterize SOL dynamics, in particular the poloidal asymmetry of the main parameters' radial profiles, two new in-situ magnetically driven reciprocating manipulators have been recently installed in COMPASS. These manipulators, the so-called pecker probes, are two additional poloidal measurement points to the existing two (vertical and horizontal) reciprocating manipulators. The pecker probes are located at the low field side of COMPASS at ±47.5o with respect to the outer mid-plane and are equipped with identical tunnel probe heads, providing simultaneous measurements of the ion saturation current density Jsat, the electron temperature Te and the parallel Mach number M// with high temporal resolution. In this paper, a detailed description of the pecker probe system in COMPASS is described and first measurements are presented.

  9. NCSX Trim Coil Design

    SciTech Connect

    M. Kalish, A. Brooks, J. Rushinski, R. Upcavage

    2009-05-29

    The National Compact Stellarator Experiment (NCSX) was being constructed at the Princeton Plasma Physics Laboratory in partnership with Oak Ridge National Laboratory before work was stopped in 2008. The objective of this experiment was to develop the stellarator concept and evaluate it's potential as a model for future fusion power plants. Stellarator design requires very precisely positioned Modular Coils of complex shape to form 3D plasmas. In the design of NCSX, Trim Coils were required to compensate for both the positioning of the coils during assembly and the fabrication tolerances of the Modular Coils. Use of the Trim Coils allowed for larger tolerances increasing ease of assembly and decreasing overall cost. A set of Trim coils was developed to suppress the toroidal flux in island regions due to misalignment, magnetic materials, and eddy currents. The requirement imposed upon the design forced the toroidal flux in island regions below 10% of the total toroidal flux in the plasma. An analysis was first performed to evaluate candidate Trim Coil configurations iterating both the size, number, and position of the coils. The design was optimized considering both performance and cost while staying within the tight restraints presented by the space limited geometry. The final design of the Trim Coils incorporated a 48 Coil top bottom symmetric set. Fabrication costs were minimized by having only two coil types and using a planar conventional design with off the shelf commercial conductor. The Trim Coil design incorporated supports made from simple structural shapes assembled together in a way which allowed for adjustment as well as accommodation for the tolerance build up on the mating surfaces. This paper will summarize the analysis that led to the optimization of the Trim Coils set, the trim coil mechanical design, thermal and stress analysis, and the design of the supporting Trim Coil structure.

  10. Study on the performance improvement of the high temperature superconducting coil with several separated coils at the edges

    NASA Astrophysics Data System (ADS)

    Ishiguri, S.; Oka, T.; Fukui, S.; Ogawa, J.; Sato, T.

    2008-09-01

    In designing high temperature superconducting (HTS) coils, it is important to secure large magnetic fields and stored energy using shorter tape length. Thus, it is necessary to improve the transport current performance of the coils. The critical current and n-value of an HTS tape depend on magnetic fields and flux angles under constant temperature. Considering these dependencies, we established a model to analyze coil critical current. This model clarifies that relatively large electric fields are generated at the coil edges. This adversely affects the transport current performance. In this study, the coil edge is separated into several coils, keeping the total tape length constant. This increases the coil critical current, stored energy, central magnetic field, and also the coil volume, which contains vacancies created by the separation. To estimate coil performance, we calculated the stored energy density, whose denominator is the increased coil volume. This stored energy density reaches its maximum value when the number of the separated coils is eight. At this optimum separation, the central magnetic field increases by 13%, and the stored energy improves by 43%, compared to a rectangular coil wound with the same tape length.

  11. Energization of Radiation Belt Electrons by High and Low Azimuthal Mode Number Poloidal Mode ULF Waves

    NASA Astrophysics Data System (ADS)

    Hudson, M. K.; Brito, T.; Elkington, S. R.; Kress, B. T.; Liang, Y.

    2011-12-01

    CME-shock and CIR-driven geomagnetic storms are characterized by enhanced ULF wave activity in the magnetosphere. This enhanced ULF wave power produces both coherent and diffusive transport and energization, as well as pitch angle modification of radiation belt electrons in drift resonance with azimuthally propagating ULF waves. Recent observations of two CME-driven storms1,2 have suggested that poloidal mode waves with both low and high azimuthal mode number may be efficient at accelerating radiation belt electrons. We extend up to m = 50 the analysis of Ozeke and Mann3 who examined drift resonance for poloidal modes up to m = 40. We calculate radial diffusion coefficients for source population electrons in the 50 -500 keV range, and continued resonance with lower m-numbers at higher energies for ULF waves in the Pc 5, 0.4 - 10 mHz range. We use an analytic model for ULF waves superimposed on a compressed dipole, developed for equatorial plane studies by Elkington et al.4 and extended to 3D by Perry et al.4 Assuming a power spectrum which varies as ω-2, consistent with earlier observations, we find greater efficiency for radial transport and acceleration at lower m number where there is greater power for drift resonance at a given frequency. This assumption is consistent with 3D global MHD simulations using the Lyon-Fedder-Mobarry code which we have carried out for realistic solar wind driving conditions during storms. Coherent interaction with ULF waves can also occur at a rate which exceeds nominal radial diffusion estimates but is slower than prompt injection on a drift time scale. Depending on initial electron drift phase, some electrons are accelerated due to the westward azimuthal electric field Eφ, while others are decelerated by eastward Eφ, decreasing their pitch angle. A subset of trapped electrons are seen to precipitate to the atmosphere in 3D LFM simulations, showing modulation at the coherent poloidal mode ULF wave frequency in both simulations

  12. Electromagnetic pump stator coil

    DOEpatents

    Fanning, Alan W.; Dahl, Leslie R.

    1996-01-01

    An electrical stator coil for an electromagnetic pump includes a continuous conductor strip having first and second terminals at opposite ends thereof and an intermediate section disposed therebetween. The strip is configured in first and second coil halves, with the first coil half including a plurality of windings extending from the first terminal to the intermediate section, and the second coil half including a plurality of windings extending from the second terminal to the intermediate section. The first and second coil halves are disposed coaxially, and the first and second terminals are disposed radially inwardly therefrom with the intermediate section being disposed radially outwardly therefrom.

  13. Electromagnetic pump stator coil

    DOEpatents

    Fanning, A.W.; Dahl, L.R.

    1996-06-25

    An electrical stator coil for an electromagnetic pump includes a continuous conductor strip having first and second terminals at opposite ends thereof and an intermediate section disposed therebetween. The strip is configured in first and second coil halves, with the first coil half including a plurality of windings extending from the first terminal to the intermediate section, and the second coil half including a plurality of windings extending from the second terminal to the intermediate section. The first and second coil halves are disposed coaxially, and the first and second terminals are disposed radially inwardly therefrom with the intermediate section being disposed radially outwardly therefrom. 9 figs.

  14. First Trial of Real-time Poloidal Beta Control in KSTAR

    NASA Astrophysics Data System (ADS)

    Han, Hyunsun; Hahn, S. H.; Bak, J. G.; Walker, M. L.; Woo, M. H.; Kim, J. S.; Kim, Y. J.; Bae, Y. S.; KSTAR Team

    2014-10-01

    Sustaining the plasma in a stable and a high performance condition is one of the important control issues for future steady state tokamaks. In the 2014 KSTAR campaign, we have developed a real-time poloidal beta (βp) control technique and carried out preliminary experiments to identify its feasibility. In the control system, the βp is calculated in real time using the measured diamagnetic loop signal (DLM03) with coil pickup corrections, and compared with the target value leading to the change of the neutral beam (NB) heating power using a feedback PID control algorithm. To match the required power of NB which is operated with constant voltage, the duty cycles of the modulation were adjusted as the ratio of the required power to the maximum achievable one. This paper will present the overall procedures of the βp control, the βp estimation process implemented in the plasma control system, and the analysis on the preliminary experimental results. This work is supported by the KSTAR research project funded by the Ministry of Science, ICT & Future Planning of Korea.

  15. Open coil structure for bubble-memory-device packaging

    NASA Technical Reports Server (NTRS)

    Chen, T. T.; Ypma, J. E.

    1975-01-01

    Concept has several important advantages over close-wound system: memory and coil chips are separate and interchangeable; interconnections in coil level are eliminated by packing memory chip and electronics in single structure; and coil size can be adjusted to optimum value in terms of power dissipation and field uniformity.

  16. Predicting coiled coils by use of pairwise residue correlations.

    PubMed Central

    Berger, B; Wilson, D B; Wolf, E; Tonchev, T; Milla, M; Kim, P S

    1995-01-01

    A method is presented that predicts coiled-coil domains in protein sequences by using pairwise residue correlations obtained from a (two-stranded) coiled-coil database of 58,217 amino acid residues. A program called PAIRCOIL implements this method and is significantly better than existing methods at distinguishing coiled coils from alpha-helices that are not coiled coils. The database of pairwise residue correlations suggests structural features that stabilize or destabilize coiled coils. Images Fig. 1 Fig. 2 PMID:7667278

  17. Novel transcranial magnetic stimulation coil for mice

    NASA Astrophysics Data System (ADS)

    March, Stephen; Stark, Spencer; Crowther, Lawrence; Hadimani, Ravi; Jiles, David

    2014-03-01

    Transcranial magnetic stimulation (TMS) shows potential for non-invasive treatment of various neurological disorders. Significant work has been performed on the design of coils used for TMS on human subjects but few reports have been made on the design of coils for use on the brains of animals such as mice. This work is needed as TMS studies utilizing mice can allow rapid preclinical development of TMS for human disorders but the coil designs developed for use on humans are inadequate for optimal stimulation of the much smaller mouse brain. A novel TMS coil has been developed with the goal of inducing strong and focused electric fields for the stimulation of small animals such as mice. Calculations of induced electric fields were performed utilizing an MRI derived inhomogeneous model of an adult male mouse. Mechanical and thermal analysis of this new TMS helmet-coil design have also been performed at anticipated TMS operating conditions to ensure mechanical stability of the new coil and establish expected linear attraction and rotational force values. Calculated temperature increases for typical stimulation periods indicate the helmet-coil system is capable of operating within established medical standards. A prototype of the coil has been fabricated and characterization results are presented.

  18. Fivefold confinement time increase in the Madison Symmetric Torus using inductive poloidal current drive

    SciTech Connect

    Stoneking, M.R.; Lanier, N.E.; Prager, S.C.; Sarff, J.S.; Sinitsyn, D.

    1996-12-01

    Current profile control is employed in the Madison Symmetric Torus reversed field pinch to reduce the magnetic fluctuations responsible for anomalous transport. An inductive poloidal electric field pulse is applied in the sense to flatten the parallel current profile, reducing the dynamo fluctuation amplitude required to sustain the equilibrium. This technique demonstrates a substantial reduction in fluctuation amplitude (as much as 50%), and improvement in energy confinement (from 1 ms to 5 ms); a record low fluctuation (0.8%) and record high temperature (615 eV) for this device were observed simultaneously during current drive experiments. Plasma beta increases by 50% and the Ohmic input power is three times lower. Particle confinement improves and plasma impurity contamination is reduced. The results of the transient current drive experiments provide motivation for continuing development of steady-state current profile control strategies for the reversed field pinch.

  19. FIRST 100 T NON-DESTRUCTIVE MAGNET OUTER COIL SET

    SciTech Connect

    J. BACON; A. BACA; ET AL

    1999-09-01

    The controlled power outer coil set of the first 100 T non-destructive (100 T ND) magnet is 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 controlled power outer coil set consists of seven nested, mechanically independent externally reinforced coils. These coils, in combination, will produce a 47 T platform field in a 225-mm diameter bore. Using inertial energy storage a synchronous motor/generator provides ac power to a set of seven ac-dc converters rated at 64 MW/80 MVA each. These converters energize three independent coil circuits to create 170 MJ of field energy in the outer coil set at the platform field of 47 T. Each coil consists of a multi-layer winding of high strength conductor supported by an external high strength stainless steel shell. Coils with the highest magnetic loads will utilize a reinforcing shell fabricated from highly cold worked 301 stainless steel strip. The autofrettage conditioning method will be used to pre-stress the coils and thereby limit conductor and reinforcement strains to the elastic range. The purpose of pre-stressing the coils is to attain a design life of 10,000 full field pulses. The operation and conditioning of the coil set will be described along with special features of its design, magnetic and structural analyses and construction.

  20. ENGINEERING OF THE AGS SNAKE COIL ASSEMBLY.

    SciTech Connect

    ANERELLA,M.GUPTA,R.KOVACH,P.MARONE,A.PLATE,S.POWER,K.SCHMALZLE,J.WILLEN,E.

    2003-05-12

    A 30% Snake superconducting magnet is proposed to maintain polarization in the AGS proton beam, the magnetic design of which is described elsewhere. The required helical coils for this magnet push the limits of the technology developed for the RHIC Snake coils. First, fields must be provided with differing pitch along the length of the magnet. To accomplish this, a new 3-D CAD system (''Pro/Engineer'' from PTC), which uses parametric techniques to enable fast iterations, has been employed. Revised magnetic field calculations are then based on the output of the mechanical model. Changes are made in turn to the model on the basis of those field calculations. To ensure that accuracy is maintained, the final solid model is imported directly into the CNC machine programming software, rather than by the use of graphics translating software. Next, due to the large coil size and magnetic field, there was concern whether the structure could contain the coil forces. A finite element analysis was performed, using the 3-D model, to ensure that the stresses and deflections were acceptable. Finally, a method was developed using ultrasonic energy to improve conductor placement during coil winding, in an effort to minimize electrical shorts due to conductor misplacement, a problem that occurred in the RHIC helical coil program. Each of these activities represents a significant improvement in technology over that which was used previously for the RHIC snake coils.

  1. Modular test facility for HTS insert coils

    SciTech Connect

    Lombardo, V; Bartalesi, A.; Barzi, E.; Lamm, M.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2009-10-01

    The final beam cooling stages of a Muon Collider may require DC solenoid magnets with magnetic fields in the range of 40-50 T. In this paper we will present a modular test facility developed for the purpose of investigating very high field levels with available 2G HTS superconducting materials. Performance of available conductors is presented, together with magnetic calculations and evaluation of Lorentz forces distribution on the HTS coils. Finally a test of a double pancake coil is presented.

  2. Poloidal flow damping with potato orbits in tokamaks

    SciTech Connect

    Shaing, K.C.

    2005-10-01

    The poloidal flow damping rate in the vicinity of the magnetic axis in tokamaks is calculated using the time-dependent plasma viscosity. It is found that the damping rate is of the order of {nu}{sub ii}/f{sub t}{sup 2}, where {nu}{sub ii} is the ion-ion collision frequency, and f{sub t} is the fraction of the trapped potatoes. The corresponding neoclassical polarization or inertia enhancement factor is [1+({sigma}{sub p}q{sup 2}/f{sub t})], where {sigma}{sub p} is a numerical number of the order of unity, and q is the safety factor.

  3. Method and apparatus for balancing the magnetic field detecting loops of a cryogenic gradiometer using trimming coils and superconducting disks

    SciTech Connect

    Lutes, C.L.

    1982-03-16

    An apparatus for and a method of measuring the difference in intensity between two coplanar magnetic field vector components at two different points in space. The device is comprised of two interconnected, relatively large, loop patterns of opposite, flux cancelling, winding sense. One or both loops include a trimming element that is itself formed of two interconnected, relatively small, loop patterns of opposite, flux cancelling, winding sense. The device is analyzed for imbalance between the two large loops and is then balanced by placing a balancing superconducting disk of the proper characteristic in or near one of the two small loops of the trimming element. The so-trimmed apparatus forms a gradiometer of substantially improved mensuration.

  4. In situ calibration of rotating sensor coils for magnet testing

    SciTech Connect

    Arpaia, P.; Golluccio, G.; Buzio, M.; Walckiers, L.

    2012-01-15

    An in situ procedure for calibrating equivalent magnetic area and rotation radius of rotating coils is proposed for testing accelerator magnets shorter than the measuring coil. The procedure exploits measurements of magnetic field and mechanical displacement inside a reference quadrupole magnet. In a quadrupole field, an offset between the magnet and coil rotation axes gives rise to a dipole component in the field series expansion. The measurements of the focusing strength, the displacement, and the resulting dipole term allow the equivalent area and radius of the coil to be determined analytically. The procedure improves the accuracy of coils with large geometrical irregularities in the winding. This is essential for short magnets where the coil dimensions constrain the measurement accuracy. Experimental results on different coils measuring small-aperture permanent magnets are shown.

  5. Artificial Neural Networks: a viable tool to design heat load smoothing strategies for the ITER Toroidal Field coils

    NASA Astrophysics Data System (ADS)

    Froio, A.; Bonifetto, R.; Carli, S.; Quartararo, A.; Savoldi, L.; Zanino, R.

    2015-12-01

    In superconducting tokamaks, cryoplants provide the helium needed to cool the superconducting magnet systems. The evaluation of the heat load from the magnets to the cryoplant is fundamental for the design of the latter and the assessment of suitable strategies to smooth the heat load pulses induced by the pulsed plasma scenarios is crucial for the operation. Here, a simplified thermal-hydraulic model of an ITER Toroidal Field (TF) magnet, based on Artificial Neural Networks (ANNs), is developed and inserted into a detailed model of the ITER TF winding and casing cooling circuits based on the state-of-the-art 4C code, which also includes active controls. The low computational effort requested by such a model allows performing a fast parametric study, to identify the best smoothing strategy during standard plasma operation. The ANNs are trained using 4C simulations, and the predictive capabilities of the simplified model are assessed against 4C simulations, both with and without active smoothing, in terms of accuracy and computational time.

  6. Two-Fluid Equilibrium for Transonic Poloidal Flows

    NASA Astrophysics Data System (ADS)

    Guazzotto, Luca; Betti, Riccardo

    2012-03-01

    Much analytical and numerical work has been done in the past on ideal MHD equilibrium in the presence of macroscopic flow. In recent years, several authors have worked on equilibrium formulations for a two-fluid system, in which inertial ions and massless electrons are treated as distinct fluids. In this work, we present our approach to the formulation of the two-fluid equilibrium problem. Particular attention is given to the relation between the two-fluid equations and the equilibrium equations for the single-fluid ideal MHD system. Our purpose is to reconsider the results of one-fluid calculation with the more accurate two-fluid model, referring in particular to the so-called transonic discontinuities, which occur when the poloidal velocity spans a range crossing the poloidal sound speed (i.e., the sound speed reduced by a factor Bp/B). It is expected that the one-fluid discontinuity will be resolved into a sharp gradient region by the two-fluid model. Also, contrary to the ideal MHD case, in the two-fluid model the equations governing the equilibrium are elliptic in the whole range of interest for transonic equilibria. The numerical solution of the two-fluid system of equations is going to be based on a code built on the structure of the existing ideal-MHD code FLOW.

  7. COMMON COIL MAGNET PROGRAM AT BNL.

    SciTech Connect

    GUPTA, R.; ANERELLA, M.; COZZOLINO, J.; ESCALLIER, J.; GANETIS, G.; GHOSH, A.; HARRISON, M.; MORGAN, G.; MURATORE, J.; PARKER, B.; SAMPSON, W.; WANDERER, P.

    2000-09-17

    The goal of the common coil magnet R&D program at Brookhaven National Laboratory (BNL) is to develop a 12.5 T, 40 mm aperture dipole magnet using ''React and Wind Technology'' with High Temperature Superconductors (HTS) playing a major role. Due to its ''conductor friendly'' nature, the common coil design is attractive for building high field 2-in-1 dipoles with brittle materials such as HTS and Nb{sub 3}Sn. At the current rate of development, it is expected that a sufficient amount of HTS with the required performance would be available in a few years for building a short magnet. In the interim, the first generation dipoles will be built with Nb{sub 3}Sn superconductor. They will use a ''React and Wind'' technology similar to that used in HTS and will produce a 12.5 T central field in a 40 mm aperture. The Nb{sub 3}Sn coils and support structure of this magnet will become a part of the next generation hybrid magnet with inner coils made of HTS. To develop various aspects of the technology in a scientific and experimental manner, a 10-turn coil program has been started in parallel. The program allows a number of concepts to be evaluated with a rapid throughput in a cost-effective way. Three 10-turn Nb{sub 3}Sn coils have been built and one HTS coil is under construction. The initial test results of this ''React & Wind'' 10-turn coil program are presented. It is also shown that a common coil magnet design can produce a field quality that is as good as a conventional cosine theta design.

  8. AC loss measurements in HTS coil assemblies with hybrid coil structures

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Long, Nicholas J.; Staines, Mike; Badcock, Rodney A.; Bumby, Chris W.; Buckley, Robert G.; Amemiya, Naoyuki

    2016-09-01

    Both AC loss and wire cost in coil windings are critical factors for high temperature superconductor (HTS) AC machinery applications. We present AC loss measurement results in three HTS coil assemblies at 77 K and 65 K which have a hybrid coil structure comprising one central winding (CW) and two end windings (EWs) wound with ReBCO and BSCCO wires with different self-field I c values at 77 K. All AC loss results in the coil assemblies are hysteretic and the normalized AC losses in the coil assemblies at different temperatures can be scaled with the I c value of the coil assemblies. The normalised results show that AC loss in a coil assembly with BSCCO CW can be reduced by using EWs wound with high I c ReBCO wires, whilst further AC loss reduction can be achieved by replacing the BSCCO CW with ReBCO CW. The results imply that a flexible hybrid coil structure is possible which considers both AC loss and wire cost in coil assemblies.

  9. Coiled bodies without coilin.

    PubMed Central

    Bauer, D W; Gall, J G

    1997-01-01

    Nuclei assembled in vitro in Xenopus egg extract contain coiled bodies that have components from three different RNA processing pathways: pre-mRNA splicing, pre-rRNA processing, and histone pre-mRNA 3'-end formation. In addition, they contain SPH-1, the Xenopus homologue of p80-coilin, a protein characteristic of coiled bodies. To determine whether coilin is an essential structural component of the coiled body, we removed it from the egg extract by immunoprecipitation. We showed that nuclei with bodies morphologically identical to coiled bodies (at the light microscope level) formed in such coilin-depleted extract. As expected, these bodies did not stain with antibodies against coilin. Moreover, they failed to stain with an antibody against the Sm proteins, although Sm proteins associated with snRNAs were still present in the extract. Staining of the coilin- and Sm-depleted coiled bodies was normal with antibodies against two nucleolar proteins, fibrillarin and nucleolin. Similar results were observed when Sm proteins were depleted from egg extract: staining of the coiled bodies with antibodies against the Sm proteins and coilin was markedly reduced but bright nucleolin and fibrillarin staining remained. These immunodepletion experiments demonstrate an interdependence between coilin and Sm snRNPs and suggest that neither is essential for assembly of nucleolar components in coiled bodies. We propose that coiled bodies are structurally heterogeneous organelles in which the components of the three RNA processing pathways may occur in separate compartments. Images PMID:9017596

  10. Transition of poloidal viscosity by electrode biasing in the Large Helical Device

    NASA Astrophysics Data System (ADS)

    Kitajima, S.; Takahashi, H.; Ishii, K.; Sato, Y.; Kanno, M.; Tachibana, J.; Okamoto, A.; Sasao, M.; Inagaki, S.; Takayama, M.; Masuzaki, S.; Shoji, M.; Ashikawa, N.; Tokitani, M.; Yokoyama, M.; Suzuki, Y.; Satake, S.; Ido, T.; Shimizu, A.; Suzuki, C.; Nagayama, Y.; Tokuzawa, T.; Nishimura, K.; Morisaki, T.; the LHD Experiment Group

    2013-07-01

    Electrode biasing experiments were carried out in various magnetic configurations on the Large Helical Device (LHD). The transitions of poloidal viscosity, which were accompanied with bifurcation phenomena characterized by a negative resistance in an electrode characteristic, were clearly observed on LHD by the electrode biasing. The critical external driving force required for transition was compared with the local maximum in ion viscosity, and the radial resistivity before the transition also compared with the expected value from a neoclassical theory. The critical driving force increased and the radial resistivity decreased with the major radius of the magnetic axis Rax going outwards. The configuration dependence of the transition condition and the radial resistivity qualitatively agreed with neoclassical theories. The radial electric field and the viscosity were also evaluated by the neoclassical transport code for a non-axisymmetric system, and estimated electrode voltage required for the transition, which was consistent with the experimental results.

  11. Observation of dust torus with poloidal rotation in direct current glow discharge plasma

    NASA Astrophysics Data System (ADS)

    Kaur, Manjit; Bose, Sayak; Chattopadhyay, P. K.; Sharma, Devendra; Ghosh, J.; Saxena, Y. C.

    2015-03-01

    Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (˜130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.

  12. Observation of dust torus with poloidal rotation in direct current glow discharge plasma

    SciTech Connect

    Kaur, Manjit Bose, Sayak; Chattopadhyay, P. K. Sharma, Devendra; Ghosh, J.; Saxena, Y. C.

    2015-03-15

    Observation of dust cloud rotation in parallel-plate DC glow discharge plasma is reported here. The experiments are carried out at high pressures (∼130 Pa) with a metallic ring placed on the lower electrode (cathode). The dust cloud rotates poloidally in the vertical plane near the cathode surface. This structure is continuous toroidally. Absence of magnetic field rules out the possibility of E × B induced ion flow as the cause of dust rotation. The dust rotational structures exist even with water cooled cathode. Therefore, temperature gradient driven mechanisms, such as thermophoretic force, thermal creep flow, and free convection cannot be causing the observed dust rotation. Langmuir probe measurement reveals the existence of a sharp density gradient near the location of the rotating dust cloud. The gradient in the density, giving rise to a gradient in the ion drag force, has been identified as the principal cause behind the rotation of dust particles.

  13. New radiant coil technology

    SciTech Connect

    Yonezawa, M.; Amano, T.; Maruta, T.; Wall, F.

    1983-12-01

    This article demonstrates how the retrofitting of an ethylene furnace by replacing pyrolysis coils with a new design sharply improved its performance. The revamped furnace was designed and built for a 300,000 MTA (metric ton/yr) ethylene plant in the early 70s. Basic design considerations for the furnace were the use of high-severity cracking to provide high C/sub 2/H/sub 4/ and total olefin yields; by a careful selection of pyrolysis coil dimensions and materials, the coil was equipped with feedstock flexibility; and the furnace can handle four different gas fuels and two different liquid fuels. The furnace is a vertical twin-cell type with induced draft fans, and its four-pass pyrolysis coils (vertical/and single diameter) are arranged in a double staggered row. The cracked gas streams from the four-pass coils are combined at the furnace outlet by a special fitting and exit the furnace.

  14. Extraction of Poloidal Velocity from Charge Exchange Recombination Spectroscopy Measurements

    SciTech Connect

    W.M. Solomon; K.H. Burrell; P. Gohil; R.J. Groebner; L.R. Baylor

    2004-07-16

    A novel approach has been implemented on DIII-D to allow the correct determination of the plasma poloidal velocity from charge exchange spectroscopy measurements. Unlike usual techniques, the need for detailed atomic physics calculations to properly interpret the results is alleviated. Instead, the needed atomic physics corrections are self-consistently determined directly from the measurements, by making use of specially chosen viewing chords. Modeling results are presented that were used to determine a set of views capable of measuring the correction terms. We present the analysis of a quiescent H-mode discharge, illustrating that significant modifications to the velocity profiles are required in these high ion temperature conditions. We also present preliminary measurements providing the first direct comparison of the standard cross-section correction to the atomic physics calculations.

  15. Preliminary activation calculations for the Poloidal Divertor Experiment

    SciTech Connect

    Judd, J.L.; Scott, A.J.; Nigg, D.W.; Bohn, T.S.

    1981-01-01

    The Poloidal Divertor Experiment (PDX) tokamak is being operated by the Princeton Plasma Physics Laboratory (PPPL) to study plasma cross section shaping, high power neutral beam heating, and divertor control of plasma impurities in tokamaks. Experiments to date have been performed at relatively low power, but with 6 MW of neutral beam power eventually available, high D-D plasma reaction rates are expected that will yield up to 10/sup 15/ 2.45-MeV neutrons per pulse. This neutron emission level is high enough to cause significant neutron-induced machine activation that will limit the occupancy time of personnel entering the room to repair or change parts. The dose rate depends on the location in the room and, of course, the pulsing history prior to entry. This paper describes one-dimensional activation calculations that have been done for PDX to provide preliminary dose rate information for various times after shutdown following one week of high power operation.

  16. Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

    SciTech Connect

    Nigg, D.W.; Wheeler, F.J.

    1981-01-01

    A calculational model is presented to estimate the radiation dose, due to the skyshine effect, in the control room and at the site boundary of the Poloidal Diverter Experiment (PDX) facility at Princeton University which requires substantial radiation shielding. The required composition and thickness of a water-filled roof shield that would reduce this effect to an acceptable level is computed, using an efficient one-dimensional model with an Sn calculation in slab geometry. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab Sn calculation, and the capture gamma dose is computed using a simple point-kernel single-scatter method. It is maintained that the slab model provides the exact probability of leakage out the top surface of the roof and that it is nearly as accurate as and much less costly than multi-dimensional techniques.

  17. Deep brain transcranial magnetic stimulation using variable "Halo coil" system

    NASA Astrophysics Data System (ADS)

    Meng, Y.; Hadimani, R. L.; Crowther, L. J.; Xu, Z.; Qu, J.; Jiles, D. C.

    2015-05-01

    Transcranial Magnetic Stimulation has the potential to treat various neurological disorders non-invasively and safely. The "Halo coil" configuration can stimulate deeper regions of the brain with lower surface to deep-brain field ratio compared to other coil configurations. The existing "Halo coil" configuration is fixed and is limited in varying the site of stimulation in the brain. We have developed a new system based on the current "Halo coil" design along with a graphical user interface system that enables the larger coil to rotate along the transverse plane. The new system can also enable vertical movement of larger coil. Thus, this adjustable "Halo coil" configuration can stimulate different regions of the brain by adjusting the position and orientation of the larger coil on the head. We have calculated magnetic and electric fields inside a MRI-derived heterogeneous head model for various positions and orientations of the coil. We have also investigated the mechanical and thermal stability of the adjustable "Halo coil" configuration for various positions and orientations of the coil to ensure safe operation of the system.

  18. Hexagonal zero mode TEM coil: a single-channel coil design for imaging multiple small animals.

    PubMed

    Lazovic, Jelena; Stojkovic, Dragan S; Collins, Christopher M; Yang, Qing X; Vaughan, J Thomas; Smith, Michael B

    2005-05-01

    A novel hexagonal coil design for simultaneous imaging of multiple small animals is presented. The design is based on a coaxial cavity and utilizes the magnetic field formed between two coaxial conductors with hexagonal cross-sections. An analytical solution describing the B(1) field between conductors of the hexagonal coil was found from the Biot-Savart law. Both experimental results and analytical calculations showed a variation in the B(1) field within the imaging region of less than 10%. Numerical calculations predicted approximately 35% improvement in B(1) field homogeneity with the hexagonal coil design compared to a cylindrical coaxial cavity design. The experimentally-measured signal-to-noise ratio (SNR) of the hexagonal coil loaded with six 50-mM phantoms was only 4-5% lower than that of a single parallel plate resonator loaded with one phantom. In vivo spin-echo (SE) images of six 7-day-old rat pups acquired simultaneously demonstrated sufficient SNR for microimaging. The construction scheme of the coil, simple methods for tuning and matching, and an anesthesia device and animal holder designed for the coil are described. The hexagonal coil design utilizes a single receiver and allows for simultaneous imaging of six small animals with no significant compromise in SNR. PMID:15844165

  19. Resonance parallel viscosity in the banana regime in poloidally rotating tokamak plasmas

    SciTech Connect

    Shaing, K.C.; Hsu, C.T.; Dominguez, N. )

    1994-05-01

    Parallel viscosity in the banana regime in a poloidally ([bold E][times][bold B]) rotating tokamak plasma is calculated to include the effects of orbit squeezing and to allow the poloidal [bold E][times][bold B] Mach number [ital M][sub [ital p

  20. Two-dimensional magnetohydrodynamic simulations of poloidal flows in tokamaks and MHD pedestal

    SciTech Connect

    Guazzotto, L.; Betti, R.

    2011-09-15

    Poloidal rotation is routinely observed in present-day tokamak experiments, in particular near the plasma edge and in the high-confinement mode of operation. According to the magnetohydrodynamic (MHD) equilibrium theory [R. Betti and J. P. Freidberg, Phys. Plasmas 7, 2439 (2000)], radial discontinuities form when the poloidal velocity exceeds the poloidal sound speed (or rather, more correctly, the poloidal magneto-slow speed). Two-dimensional compressible magnetohydrodynamic simulations show that the transonic discontinuities develop on a time scale of a plasma poloidal revolution to form an edge density pedestal and a localized velocity shear layer at the pedestal location. While such an MHD pedestal surrounds the entire core, the outboard side of the pedestal is driven by the transonic discontinuity while the inboard side is caused by a poloidal redistribution of the mass. The MHD simulations use a smooth momentum source to drive the poloidal flow. Soon after the flow exceeds the poloidal sound speed, the density pedestal and the velocity shear layer form and persist into a quasi steady state. These results may be relevant to the L-H transition, the early stages of the pedestal and edge transport barrier formation.

  1. Poloidal rotation driven by nonlinear momentum transport in strong electrostatic turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Wen, Tiliang; Diamond, P. H.

    2016-10-01

    Virtually, all existing theoretical works on turbulent poloidal momentum transport are based on quasilinear theory. Nonlinear poloidal momentum flux—< {{\\tilde{v}}r}\\tilde{n}{{\\tilde{v}}θ}> is universally neglected. However, in the strong turbulence regime where relative fluctuation amplitude is no longer small, quasilinear theory is invalid. This is true at the all-important plasma edge. In this work, nonlinear poloidal momentum flux < {{\\tilde{v}}r}\\tilde{n}{{\\tilde{v}}θ}> in strong electrostatic turbulence is calculated using the Hasegawa-Mima equation, and is compared with quasilinear poloidal Reynolds stress. A novel property is that symmetry breaking in fluctuation spectrum is not necessary for a nonlinear poloidal momentum flux. This is fundamentally different from the quasilinear Reynold stress. Furthermore, the comparison implies that the poloidal rotation drive from the radial gradient of nonlinear momentum flux is comparable to that from the quasilinear Reynolds force. Nonlinear poloidal momentum transport in strong electrostatic turbulence is thus not negligible for poloidal rotation drive, and so may be significant to transport barrier formation.

  2. Eight channel transmit array volume coil using on-coil radiofrequency current sources

    PubMed Central

    Kurpad, Krishna N.; Boskamp, Eddy B.

    2014-01-01

    Background At imaging frequencies associated with high-field MRI, the combined effects of increased load-coil interaction and shortened wavelength results in degradation of circular polarization and B1 field homogeneity in the imaging volume. Radio frequency (RF) shimming is known to mitigate the problem of B1 field inhomogeneity. Transmit arrays with well decoupled transmitting elements enable accurate B1 field pattern control using simple, non-iterative algorithms. Methods An eight channel transmit array was constructed. Each channel consisted of a transmitting element driven by a dedicated on-coil RF current source. The coil current distributions of characteristic transverse electromagnetic (TEM) coil resonant modes were non-iteratively set up on each transmitting element and 3T MRI images of a mineral oil phantom were obtained. Results B1 field patterns of several linear and quadrature TEM coil resonant modes that typically occur at different resonant frequencies were replicated at 128 MHz without having to retune the transmit array. The generated B1 field patterns agreed well with simulation in most cases. Conclusions Independent control of current amplitude and phase on each transmitting element was demonstrated. The transmit array with on-coil RF current sources enables B1 field shimming in a simple and predictable manner. PMID:24834418

  3. Commercial applications for COIL

    NASA Astrophysics Data System (ADS)

    Solomon, Wayne C.; Carroll, David L.; King, D. M.; Fockler, L. A.; Stromberg, D. S.; Sexauer, M.; Milmoe, A.; Sentman, Lee H.

    2000-01-01

    The chemical oxygen-iodine laser (COIL) is a high power, fiber deliverable tool, which can be used for a number of different industrial applications. COIL is of particular interest because of its short fiber deliverable wavelength, high scaleable continuous wave power, and excellent material interaction properties. In past research the University of Illinois at Urbana-Champaign identified and decommissioning and decontamination (DD) of nuclear facilities as a primary focus for COIL technology. DD will be a major challenge in the coming decades. The use of a robotically driven fiber delivered cutting/ablation tool in contaminated areas promises to lower risks to workers for the DD mission. Further, the high cutting speed of COIL will significantly reduce the time required to cut contaminated equipment, reducing costs. The high power of COIL will permit the dismantling of thick stacks of piping and equipment as well as reactor vessels. COIL is very promising for the removal of material from contaminated surfaces, perhaps to depths thicker than an inch. Laser cutting and ablation minimizes dust and fumes, which reduces the required number of high efficiency particulate accumulator filters, thus reducing costly waste disposal. Other potential industrial applications for COIL are shipbuilding, automotive manufacturing, heavy machinery manufacturing, tasks requiring underwater cutting or welding, and there appear to be very promising applications for high powers lasers in the oil industry.

  4. Coil in coil - components for the high voltage superconducting resistive current limiter CULT 110

    NASA Astrophysics Data System (ADS)

    Elschner, S.; Stemmle, M.; Breuer, F.; Walter, H.; Frohne, C.; Noe, M.; Bock, J.

    2008-02-01

    The German government (BMBF/VDI) funded project CULT 110 is presently the largest European current limiter project and aims at the development of a one-phase resistive limiter for the voltage level of 110 kV. The contribution presents the actual state of development of the superconducting components. As in the successful predecessor project CURL 10 these are made of melt cast processed BSCCO 2212 bulk material, however monofilar instead of bifilar coils are used. The electrical protection concept is based on a normal conducting coil arranged around a superconducting coil and connected in parallel. Simultaneously this coil serves as an electrical bypass and, under fault conditions, generates a magnetic field for quench homogenisation. Since no continuously connected shunt is needed, a much higher voltage during faults can be applied. The rules for an optimum superconductor and coil design are given and the viability of the whole concept is demonstrated by both, experiment and numerical simulation.

  5. Correction coil cable

    DOEpatents

    Wang, S.T.

    1994-11-01

    A wire cable assembly adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies for the Superconducting Super Collider. The correction coil cables have wires collected in wire array with a center rib sandwiched therebetween to form a core assembly. The core assembly is surrounded by an assembly housing having an inner spiral wrap and a counter wound outer spiral wrap. An alternate embodiment of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable on a particle tube in a particle tube assembly. 7 figs.

  6. ELECTRICAL COIL STRUCTURE

    DOEpatents

    Baker, W.R.; Hartwig, A.

    1962-09-25

    A compactly wound electrical coil is designed for carrying intense pulsed currents such as are characteristic of controlled thermonuclear reaction devices. A flat strip of conductor is tightly wound in a spiral with a matching flat strip of insulator. To provide for a high fluid coolant flow through the coil with minimum pumping pressure, a surface of the conductor is scored with parallel transverse grooves which form short longitudinal coolant pasaages when the conductor is wound in the spiral configuration. Owing to this construction, the coil is extremely resistant to thermal and magnetic shock from sudden high currents. (AEC)

  7. Coil spring venting arrangement

    DOEpatents

    McCugh, R.M.

    1975-10-21

    A simple venting device for trapped gas pockets in hydraulic systems is inserted through a small access passages, operated remotely, and removed completely. The device comprises a small diameter, closely wound coil spring which is pushed through a guide temporarily inserted in the access passage. The guide has a central passageway which directs the coil spring radially upward into the pocket, so that, with the guide properly positioned for depth and properly oriented, the coil spring can be pushed up into the top of the pocket to vent it. By positioning a seal around the free end of the guide, the spring and guide are removed and the passage is sealed.

  8. [Development of RF coil of permanent magnet mini-magnetic resonance imager and mouse imaging experiments].

    PubMed

    Hou, Shulian; Xie, Huantong; Chen, Wei; Wang, Guangxin; Zhao, Qiang; Li, Shiyu

    2014-10-01

    In the development of radio frequency (RF) coils for better quality of the mini-type permanent magnetic resonance imager for using in the small animal imaging, the solenoid RF coil has a special advantage for permanent magnetic system based on analyses of various types.of RF coils. However, it is not satisfied for imaging if the RF coils are directly used. By theoretical analyses of the magnetic field properties produced from the solenoid coil, the research direction was determined by careful studies to raise further the uniformity of the magnetic field coil, receiving coil sensitivity for signals and signal-to-noise ratio (SNR). The method had certain advantages and avoided some shortcomings of the other different coil types, such as, birdcage coil, saddle shaped coil and phased array coil by using the alloy materials (from our own patent). The RF coils were designed, developed and made for keeled applicable to permanent magnet-type magnetic resonance imager, multi-coil combination-type, single-channel overall RF receiving coil, and applied for a patent. Mounted on three instruments (25 mm aperture, with main magnetic field strength of 0.5 T or 1.5 T, and 50 mm aperture, with main magnetic field strength of 0.48 T), we performed experiments with mice, rats, and nude mice bearing tumors. The experimental results indicated that the RF receiving coil was fully applicable to the permanent magnet-type imaging system. PMID:25764715

  9. [Development of RF coil of permanent magnet mini-magnetic resonance imager and mouse imaging experiments].

    PubMed

    Hou, Shulian; Xie, Huantong; Chen, Wei; Wang, Guangxin; Zhao, Qiang; Li, Shiyu

    2014-10-01

    In the development of radio frequency (RF) coils for better quality of the mini-type permanent magnetic resonance imager for using in the small animal imaging, the solenoid RF coil has a special advantage for permanent magnetic system based on analyses of various types.of RF coils. However, it is not satisfied for imaging if the RF coils are directly used. By theoretical analyses of the magnetic field properties produced from the solenoid coil, the research direction was determined by careful studies to raise further the uniformity of the magnetic field coil, receiving coil sensitivity for signals and signal-to-noise ratio (SNR). The method had certain advantages and avoided some shortcomings of the other different coil types, such as, birdcage coil, saddle shaped coil and phased array coil by using the alloy materials (from our own patent). The RF coils were designed, developed and made for keeled applicable to permanent magnet-type magnetic resonance imager, multi-coil combination-type, single-channel overall RF receiving coil, and applied for a patent. Mounted on three instruments (25 mm aperture, with main magnetic field strength of 0.5 T or 1.5 T, and 50 mm aperture, with main magnetic field strength of 0.48 T), we performed experiments with mice, rats, and nude mice bearing tumors. The experimental results indicated that the RF receiving coil was fully applicable to the permanent magnet-type imaging system.

  10. Bootstrap current control and the effects of the radial electric field in stellarators

    SciTech Connect

    Shaing, K.C.; Carreras, B.A.; Crume, E.C.; Dominguez, N.; Hirshman, S.P.; Lynch, V.E.; Tolliver, J.S.; van Rij, W.I.

    1989-01-01

    The effects of the radial electric field E/sub r/ on the bootstrap current in ATF-type configurations are studied with the Drift Kinetic Equation Solver (DKES). It is found that there is a range of E/sub r/ values over which the bootstrap current does not depend on E/sub r/. The effects of E/sub r/ on the bootstrap current are due to the resonance between the parallel velocity and the poloidal E /times/ B drift. The poloidal coil system of a stellarator can be used to modify the /vert bar/B/vert bar/ spectrum and, as a consequence, change the magnitude of the bootstrap current. The addition of a small l = 1 field component to a stellarator field can cancel or reverse the direction of the bootstrap current. It is shown that currentless operation in the collisionless regime is not impaired by the bootstrap current, because the effects of the bootstrap current can be eliminated by an appropriate external coil system. These results can be tested in ATF. 15 refs., 11 figs.

  11. Phylogenetic occurrence of coiled coil proteins: implications for tissue structure in metazoa via a coiled coil tissue matrix.

    PubMed

    Odgren, P R; Harvie, L W; Fey, E G

    1996-04-01

    We examined GenBank sequence files with a heptad repeat analysis program to assess the phylogenetic occurrence of coiled coil proteins, how heptad repeat domains are organized within them, and what structural/functional categories they comprise. Of 102,007 proteins analyzed, 5.95% (6,074) contained coiled coil domains; 1.26% (1,289) contained "extended" (> 75 amino acid) domains. While the frequency of proteins containing coiled coils was surprisingly constant among all biota, extended coiled coil proteins were fourfold more frequent in the animal kingdom and may reflect early events in the divergence of plants and animals. Structure/function categories of extended coils also revealed phylogenetic differences. In pathogens and parasites, many extended coiled coil proteins are external and bind host proteins. In animals, the majority of extended coiled coil proteins were identified as constituents of two protein categories: 1) myosins and motors; or 2) components of the nuclear matrix-intermediate filament scaffold. This scaffold, produced by sequential extraction of epithelial monolayers in situ, contains only 1-2% of the cell mass while accurately retaining morphological features of living epithelium and is greatly enriched in proteins with extensive, interrupted coiled coil forming domains. The increased occurrence of this type of protein in metazoa compared with plants or protists leads us to hypothesize a tissue-wide matrix of coiled coil interactions underlying metazoan differentiated cell and tissue structure.

  12. Nonaxisymmetric field effects on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Wolfe, S. M.; Hutchinson, I. H.; Granetz, R. S.; Rice, J.; Hubbard, A.; Lynn, A.; Phillips, P.; Hender, T. C.; Howell, D. F.; La Haye, R. J.; Scoville, J. T.

    2005-05-01

    A set of external coils (A-coils) capable of producing nonaxisymmetric, predominantly n =1, fields with different toroidal phase and a range of poloidal mode m spectra has been used to determine the threshold amplitude for mode locking over a range of plasma parameters in Alcator C-Mod [I. H. Hutchinson, R. Boivin, F. Bombarda, P. Bonoli, S. Fairfax, C. Fiore, J. Goetz, S. Golovato, R. Granetz, M. Greenwald et al., Phys. Plasmas 1, 1511 (1994)]. The threshold perturbations and parametric scalings, expressed in terms of (B21/BT), are similar to those observed on larger, lower field devices. The threshold is roughly linear in density, with typical magnitudes of order 10-4. This result implies that locked modes should not be significantly more problematic for the International Thermonuclear Experimental Reactor [I. P. B. Editors, Nucl. Fusion 39, 2286 (1999)] than for existing devices. Coordinated nondimensional identity experiments on the Joint European Torus [Fusion Technol. 11, 13 (1987)], DIII-D [Fusion Technol. 8, 441 (1985)], and C-Mod, with matching applied mode spectra, have been carried out to determine more definitively the field and size scalings. Locked modes on C-Mod are observed to result in braking of core toroidal rotation, modification of sawtooth activity, and significant reduction in energy and particle confinement, frequently leading to disruptions. Intrinsic error fields inferred from the threshold studies are found to be consistent in amplitude and phase with a comprehensive model of the sources of field errors based on "as-built" coil and bus-work details and coil imperfections inferred from measurements using in situ magnetic diagnostics on dedicated test pulses. Use of the A-coils to largely cancel the 2/1 component of the intrinsic nonaxisymmetric field has led to expansion of the accessible operating space in C-Mod, including operation up to 2 MA plasma current at 8 T.

  13. Modelling the influence of temperature anisotropies on poloidal asymmetries of density in the core of rotating plasmas

    NASA Astrophysics Data System (ADS)

    Bilato, R.; Maj, O.; Angioni, C.

    2014-07-01

    A consistent set of equations is derived to model poloidal density asymmetries induced by temperature anisotropies in tokamak rotating plasmas. The model can be applied to compute poloidal density asymmetry of highly charged impurities due to additional plasma heating.

  14. A periodic table of coiled-coil protein structures.

    PubMed

    Moutevelis, Efrosini; Woolfson, Derek N

    2009-01-23

    Coiled coils are protein structure domains with two or more alpha-helices packed together via interlacing of side chains known as knob-into-hole packing. We analysed and classified a large set of coiled-coil structures using a combination of automated and manual methods. This led to a systematic classification that we termed a "periodic table of coiled coils," which we have made available at http://coiledcoils.chm.bris.ac.uk/ccplus/search/periodic_table. In this table, coiled-coil assemblies are arranged in columns with increasing numbers of alpha-helices and in rows of increased complexity. The table provides a framework for understanding possibilities in and limits on coiled-coil structures and a basis for future prediction, engineering and design studies.

  15. Enhancing Induction Coil Reliability

    NASA Astrophysics Data System (ADS)

    Kreter, K.; Goldstein, R.; Yakey, C.; Nemkov, V.

    2014-12-01

    In induction hardening, thermal fatigue is one of the main copper failure modes of induction heat treating coils. There have been papers published that describe this failure mode and others that describe some good design practices. The variables previously identified as the sources of thermal fatigue include radiation from the part surface, frequency, current, concentrator losses, water pressure and coil wall thickness. However, there is very little quantitative data on the factors that influence thermal fatigue in induction coils is available in the public domain. By using finite element analysis software this study analyzes the effect of common design variables of inductor cooling, and quantifies the relative importance of these variables. A comprehensive case study for a single shot induction coil with Fluxtrol A concentrator applied is used for the analysis.

  16. Comparison of Edge Turbulence Imaging at Two Different Poloidal Locations in the Scrape-off Layer of Alcator C-Mod

    SciTech Connect

    S.J. Zweben, et. al.

    2013-03-29

    This paper describes 2-D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging (GPI) diagnostics, which were not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and Xregions, even within the same flux surface in the same shot, and in most cases the fluctuations in poloidal velocity in these two regions were not correlated. These structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various poloidal flow models.

  17. High-m Poloidal Waves Observed in Low Earth Orbit and Their Implications for Energetic Particles in the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Chi, P. J.; Johnson, J.; Porazik, P.

    2015-12-01

    Recent studies of the magnetic field data collected by the NASA ST-5 satellites in the low Earth orbit have revealed many wave events with frequencies of 30-200 mHz (in the Pc 2-3 band). It was soon realized that these waves were in fact Doppler-shifted waves in the magnetosphere, with wave frequencies of merely a few mHz (in the Pc 5 band) and azimuthal wavenumbers (m) of the order of 100. Oscillating in the poloidal direction, high-mwaves are known to engage in drift or drift bounce resonance with energetic ring current particles, and therefore they are expected to play a role in modulating the energetic particles in the inner magnetosphere. Using a new method that examines the differences in wave phase detected by the three ST-5 satellites in a "pearls-on-a-string" configuration, we confirm that the frequencies of the observed poloidal waves are mainly between 3 and 5 mHz in the Earth frame. In some events, the NOAA satellites were located at the equator and close to the field lines connected to the ST-5 satellites, confirming the wave frequencies estimated using only ST-5 observations. In each of the poloidal wave events observed by ST-5, the azimuthal wavenumber may change with L, but the wave frequency in the Earth frame remains the same. We have also found cases where poloidal waves were observed in both dayside and nightside of the magnetosphere when ST-5 satellite passed through the same Lshells within a single orbit, supporting the theoretical prediction of a global poloidal mode, which is also known as the transverse Alfvén resonator. Satellite observations in low Earth orbits have shown that high-m poloidal waves can last many hours even during geomagnetically quiet conditions, suggesting that a very weak ring current may be capable of supplying enough energetic particles to excite poloidal waves. We will address the implications for energetic particles in the inner magnetosphere with theoretical and modeling considerations.

  18. Coiled transmission line pulse generators

    DOEpatents

    McDonald, Kenneth Fox

    2010-11-09

    Methods and apparatus are provided for fabricating and constructing solid dielectric "Coiled Transmission Line" pulse generators in radial or axial coiled geometries. The pour and cure fabrication process enables a wide variety of geometries and form factors. The volume between the conductors is filled with liquid blends of monomers, polymers, oligomers, and/or cross-linkers and dielectric powders; and then cured to form high field strength and high dielectric constant solid dielectric transmission lines that intrinsically produce ideal rectangular high voltage pulses when charged and switched into matched impedance loads. Voltage levels may be increased by Marx and/or Blumlein principles incorporating spark gap or, preferentially, solid state switches (such as optically triggered thyristors) which produce reliable, high repetition rate operation. Moreover, these Marxed pulse generators can be DC charged and do not require additional pulse forming circuitry, pulse forming lines, transformers, or an a high voltage spark gap output switch. The apparatus accommodates a wide range of voltages, impedances, pulse durations, pulse repetition rates, and duty cycles. The resulting mobile or flight platform friendly cylindrical geometric configuration is much more compact, light-weight, and robust than conventional linear geometries, or pulse generators constructed from conventional components. Installing additional circuitry may accommodate optional pulse shape improvements. The Coiled Transmission Lines can also be connected in parallel to decrease the impedance, or in series to increase the pulse length.

  19. Underbalanced coiled tubing sidetrack successful

    SciTech Connect

    Adam, J.; Berry, M.

    1995-12-18

    The technique of drilling through a completion string, underbalanced, with coiled tubing eliminated some of the problems encountered with overbalanced drilling in a group of offset wells. This project confirmed that performing drilling operations in live wells can be carried out safely and effectively. Dalen is a sour gas field in the eastern part of The Netherlands and produces from vertical fractures in the Zechstein carbonate reservoir. The proposal for Dalen 2 was to abandon the lower section of the original hole and subsequently sidetrack conventionally to the top of the reservoir, run and cement a 5-in. liner, complete the well with a 5-in. monobore completion, and install the christmas tree. This part of the operation would be performed with a workover hoist. Thereafter, a 3 3/4-in. hole would be drilled through the completion and into the reservoir, underbalanced with coiled tubing. The drilling proposal had to address a number of key issues: creating underbalanced conditions; handling sour gas production at surface; handling and treating drilling fluids at surface; removing drilled solids from the returned fluid system; and deploying a long coiled tubing drilling bottom hole assembly (BHA) into a live well. The paper discusses planning, legislative issues, well preparation, the drilling program, and lessons learned.

  20. Complex Coil Assisted Single Coil Embolization for Small Intracranial Aneurysm

    PubMed Central

    Yang, Tzu-Hsien; Ou, Chang-Hsien; Chan, Si-Wa; Chen, Tai-I; Yang, Chia-Jung; Chiang, Chia-Ming; Huang, Wen-Chien

    2013-01-01

    The purpose of the technical note is to introduce the complex coil assisted coil embolization method in the treatment of intracranial small aneurysm, in order to enhance the safety of the procedure. The first microcatheter was navigated into the aneurysm sac and the ultrasoft coil was used as the embolization coil. If the embolizations coil could not stay within the aneurysm sac smoothly, such as coil herniation into parent artery during the delivery process. The second microcatheter would be navigated to the aneurysm level in the parent artery. Another complex coil was delivered within the parent artery via the second microcatheter to provide the neck bridge effect in order to enhance the stability of embolization coil. Besides, the protection coil will not disturb the parent artery flow. While the embolization coil was put into the aneurysm sac smoothly under the help of complex protective coil, the protective coil was then withdrawn gently. We use the most magnified view, dual-plane approach simultaneously to observe the stability of embolization coil. The embolization coil would be detached without any evidence of coil motion or vibration. The new method could provide the physiological protective method, without leaving any protective device such as stent within the parent artery. PMID:24024075

  1. Numerical optimization of perturbative coils for tokamaks

    NASA Astrophysics Data System (ADS)

    Lazerson, Samuel; Park, Jong-Kyu; Logan, Nikolas; Boozer, Allen; NSTX-U Research Team

    2014-10-01

    Numerical optimization of coils which apply three dimensional (3D) perturbative fields to tokamaks is presented. The application of perturbative 3D magnetic fields in tokamaks is now commonplace for control of error fields, resistive wall modes, resonant field drive, and neoclassical toroidal viscosity (NTV) torques. The design of such systems has focused on control of toroidal mode number, with coil shapes based on simple window-pane designs. In this work, a numerical optimization suite based on the STELLOPT 3D equilibrium optimization code is presented. The new code, IPECOPT, replaces the VMEC equilibrium code with the IPEC perturbed equilibrium code, and targets NTV torque by coupling to the PENT code. Fixed boundary optimizations of the 3D fields for the NSTX-U experiment are underway. Initial results suggest NTV torques can be driven by normal field spectrums which are not pitch-resonant with the magnetic field lines. Work has focused on driving core torque with n = 1 and edge torques with n = 3 fields. Optimizations of the coil currents for the planned NSTX-U NCC coils highlight the code's free boundary capability. This manuscript has been authored by Princeton University under Contract Number DE-AC02-09CH11466 with the U.S. Department of Energy.

  2. Nonlinear evolution of resistive wall mode in a cylindrical tokamak with poloidal rotation

    SciTech Connect

    Sato, M.; Nakajima, N.

    2006-10-15

    Nonlinear simulations of resistive wall modes (RWMs) with a Doppler shift dominant equilibrium poloidal rotation have been carried out by using reduced magnetohydrodynamic equations in a low beta cylindrical tokamak, where the core plasma is surrounded by a cold plasma with a high resistivity. When the equilibrium poloidal rotation frequency is small and the Doppler shift is predominant, the wall mode becomes unstable, which is one of the RWMs nearly locked to the resistive wall. Since the slowing down torque increases with equilibrium poloidal rotation frequency and the poloidal rotation decreases to almost zero near the plasma surface before the saturation, the nonlinear saturation level does not depend on either the equilibrium poloidal rotation frequency or the density of the cold plasma. When the equilibrium poloidal rotation frequency becomes larger than a critical value, the plasma mode rotating to the resistive wall becomes unstable. When the cold plasma has the same density as that in the core plasma, neither the centrifugal force nor the Coriolis force has any effect. In such a case, as the equilibrium poloidal rotation frequency increases, the magnetic flux is so hard to diffuse into the resistive wall that the slowing down torque decreases and the rotation tends to survive in the nonlinear phase, which makes the saturation level decrease.

  3. Output beam analysis of high power COIL

    NASA Astrophysics Data System (ADS)

    Yu, Deli; Sang, Fengting; Jin, Yuqi; Sun, Yizhu

    2003-03-01

    As the output power of a chemical oxygen iodine laser (COIL) increases, the output laser beam instability appears as the far-field beam spot drift and deformation for the large Fresnel number unstable resonator. In order to interpret this phenomenon, an output beam mode simulation code was developed with the fast Fourier transform method. The calculation results show that the presence of the nonuniform gain in COIL produces a skewed output intensity distribution, which causes the mirror tilt and bulge due to the thermal expansion. With the output power of COIL increases, the mirror surfaces, especially the back surface of the scraper mirror, absorb more and more heat, which causes the drift and deformation of far field beam spot seriously. The initial misalignment direction is an important factor for the far field beam spot drifting and deformation.

  4. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Chiba, Masashi

    The magnetic-field characteristics in spiral galaxies are investigated, with emphasis on the Milky Way. The dynamo theory is considered, and axisymmetric spiral (ASS) and bisymmetric spiral (BSS) magnetic fields are analyzed. Toroidal and poloidal magnetic fields are discussed.

  5. MHD Instabilities and Toroidal Field Effects on Plasma Column Behavior in Tokamak

    SciTech Connect

    Khorshid, Pejman; Wang, L.; Ghoranneviss, M.; Arvin, R.; Dorranian, D.; Talebitaher, A.; Salem, M. K.; Abhari, A.

    2006-12-04

    In the edge plasma of the CT-6B and IRAN-T1 tokamaks the shape of plasma column based on MHD behavior has been studied. The bulk of plasma behavior during plasma column rotation as non-rigid body plasma has been investigated. We found that mode number and rotation frequency of plasma column are different in angle position, so that the mode number detected from Mirnov coils array located in poloidal angle on the inner side of chamber is more than outer side which it can be because of toroidal magnetic field effects. The results of IR-T1 and CT-6B tokamaks compared with each other, so that in the CT-6B because of its coils number must be less, but because of its Iron core the effect of toroidal magnetic field became more effective with respect to IR-T1. In addition, it is shown that the plasma column behaves as non-Rigid body plasma so that the poloidal rotation velocity variation in CT-6B is more than IR-T1. A relative correction for island rotation frequency has been suggested in connection with IRAN-T1 and CT-6B tokamak results, which can be considered for optical measurement purposes and also for future advanced tokamak control design.

  6. Hierarchical Cascades of Instability Govern the Mechanics of Coiled Coils: Helix Unfolding Precedes Coil Unzipping

    PubMed Central

    Hamed, Elham; Keten, Sinan

    2014-01-01

    Coiled coils are a fundamental emergent motif in proteins found in structural biomaterials, consisting of α-helical secondary structures wrapped in a supercoil. A fundamental question regarding the thermal and mechanical stability of coiled coils in extreme environments is the sequence of events leading to the disassembly of individual oligomers from the universal coiled-coil motifs. To shed light on this phenomenon, here we report atomistic simulations of a trimeric coiled coil in an explicit water solvent and investigate the mechanisms underlying helix unfolding and coil unzipping in the assembly. We employ advanced sampling techniques involving steered molecular dynamics and metadynamics simulations to obtain the free-energy landscapes of single-strand unfolding and unzipping in a three-stranded assembly. Our comparative analysis of the free-energy landscapes of instability pathways shows that coil unzipping is a sequential process involving multiple intermediates. At each intermediate state, one heptad repeat of the coiled coil first unfolds and then unzips due to the loss of contacts with the hydrophobic core. This observation suggests that helix unfolding facilitates the initiation of coiled-coil disassembly, which is confirmed by our 2D metadynamics simulations showing that unzipping of one strand requires less energy in the unfolded state compared with the folded state. Our results explain recent experimental findings and lay the groundwork for studying the hierarchical molecular mechanisms that underpin the thermomechanical stability/instability of coiled coils and similar protein assemblies. PMID:25028889

  7. Laminar flow effects in the coil planet centrifuge

    NASA Technical Reports Server (NTRS)

    Herrmann, F. T.

    1984-01-01

    The coil planet centrifuge designed by Ito employs flow of a single liquid phase, through a rotating coiled tube in a centrifugal force field, to provide a separation of particles based on sedimentation rates. Mathematical solutions are derived for the linear differential equations governing particle behavior in the coil planet centrifuge device. These solutions are then applied as the basis of a model for optimizing particle separations.

  8. Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

    SciTech Connect

    Nigg, D.W.; Wheeler, F.J.

    1981-01-01

    The Poloidal Diverter Experiment (PDX) facility at Princeton University is the first operating tokamak to require substantial radiation shielding. A calculational model has been developed to estimate the radiation dose in the PDX control room and at the site boundary due to the skyshine effect. An efficient one-dimensional method is used to compute the neutron and capture gamma leakage currents at the top surface of the PDX roof shield. This method employs an S /SUB n/ calculation in slab geometry and, for the PDX, is superior to spherical models found in the literature. If certain conditions are met, the slab model provides the exact probability of leakage out the top surface of the roof for fusion source neutrons and for capture gamma rays produced in the PDX floor and roof shield. The model also provides the correct neutron and capture gamma leakage current spectra and angular distributions, averaged over the top roof shield surface. For the PDX, this method is nearly as accurate as multidimensional techniques for computing the roof leakage and is much less costly. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab S /SUB n/ calculation. The capture gamma dose is computed using a simple point-kernel single-scatter method.

  9. Heterogeneous Superconducting Low-Noise Sensing Coils

    NASA Technical Reports Server (NTRS)

    Hahn, Inseob; Penanen, Konstantin I.; Ho Eom, Byeong

    2008-01-01

    A heterogeneous material construction has been devised for sensing coils of superconducting quantum interference device (SQUID) magnetometers that are subject to a combination of requirements peculiar to some advanced applications, notably including low-field magnetic resonance imaging for medical diagnosis. The requirements in question are the following: The sensing coils must be large enough (in some cases having dimensions of as much as tens of centimeters) to afford adequate sensitivity; The sensing coils must be made electrically superconductive to eliminate Johnson noise (thermally induced noise proportional to electrical resistance); and Although the sensing coils must be cooled to below their superconducting- transition temperatures with sufficient cooling power to overcome moderate ambient radiative heat leakage, they must not be immersed in cryogenic liquid baths. For a given superconducting sensing coil, this combination of requirements can be satisfied by providing a sufficiently thermally conductive link between the coil and a cold source. However, the superconducting coil material is not suitable as such a link because electrically superconductive materials are typically poor thermal conductors. The heterogeneous material construction makes it possible to solve both the electrical- and thermal-conductivity problems. The basic idea is to construct the coil as a skeleton made of a highly thermally conductive material (typically, annealed copper), then coat the skeleton with an electrically superconductive alloy (typically, a lead-tin solder) [see figure]. In operation, the copper skeleton provides the required thermally conductive connection to the cold source, while the electrically superconductive coating material shields against Johnson noise that originates in the copper skeleton.

  10. Poloidal beta and internal inductance measurement on HT-7 superconducting tokamak.

    PubMed

    Shen, B; Sun, Y W; Wan, B N; Qian, J P

    2007-09-01

    Poloidal beta beta(theta) and internal inductance l(i) measurements are very important for tokamak operation. Much more plasma parameters can be inferred from the two parameters, such as the plasma energy confinement time, the plasma toroidal current profile, and magnetohydrodynamics instability. Using diamagnetic and compensation loop, combining with poloidal magnetic probe array signals, poloidal beta beta(theta) and internal inductance l(i) are measured. In this article, the measurement system and arithmetic are introduced. Different experimental results are given in different plasma discharges on HT-7 superconducting tokamak.

  11. The role of parallel and poloidal heat flux in setting the detachment threshold in DIII-D

    NASA Astrophysics Data System (ADS)

    Hill, D. N.; Allen, S. L.; Lasnier, C. J.; McLean, A. G.; Petrie, T. W.; Leonard, A. W.; Groth, M.

    2014-10-01

    Experimental results show that the threshold density for divertor detachment is reduced even as the parallel scrape-off-layer (SOL) heat flux (q| |) is more than doubled, contrary to expectation. The work is part of a systematic study to identify the physics basis for obtaining detached divertors in future high power burning plasma experiments, consistent with requirements for high confinement steady-state operation. Parallel heat flux [PSOL * (Btor /Bpol) / 2 πRλq ; λq is the SOL width] is independent of poloidal flux expansion and is commonly used to quantify the divertor heat flux challenge. In these experiments, the parallel heat flux was varied either by changing the heating power (thereby PSOL), plasma current (the SOL width), or toroidal field (the projection of PSOL onto Btor). The data point to poloidal-field physics effects (e.g., neutral penetration field, line length, and impurity radiation volume) playing a dominant role in setting the detachment threshold. Comparison with 2D simulation will be shown. Work supported by the US DOE under DE-AC52-07NA27344 and DE-FC02-04ER54698.

  12. Planar gradient coil design by scaling the spatial frequencies of minimum-inductance current density.

    PubMed

    Lee, S Y; Park, B S; Yi, J H; Yi, W

    1997-11-01

    Gradient coil inductance has been remarkably reduced by the minimum-inductance design technique, which minimizes the magnetic energy stored by the gradient coil. The planar gradient coil designed by this technique, however, often has poor magnetic field linearity. Scaling the spatial frequencies of the current density function derived by this method, the magnetic field linearity of the planar gradient coil can be greatly improved with a small sacrifice of gradient coil inductance. A figure of merit of the planar gradient coil has been found to be improved by scaling the spatial frequencies.

  13. Characteristics of SC Coil Configuration for EDS Maglev to Reduce Leakage Flux with Strengthened Magnetomotive Force

    NASA Astrophysics Data System (ADS)

    Murai, Toshiaki; Sasakawa, Takashi

    Vehicles of superconducting maglev system are suspended and driven by superconducting (SC) coils, which have strong magnetic field, and their passenger cabin must be shielded from leakage flux by the SC coils. In order to reduce the leakage flux, we have studied an improved configuration of SC coils, which has small size coils on its end. This configuration can reduce the environmental magnetic field, so that it can strengthen the magnetomotive force of SC coils. This paper describes the characteristics of levitation, guidance and propulsion performance at strengthening the magnetomotive force on the improved configuration of SC coils.

  14. Coil Array Design Inspired on the Kepler's Lenten Pretzel

    SciTech Connect

    Vazquez, F.; Solis, S. E.; Rodriguez, A. O.

    2008-08-11

    The RF coil arrays are an important part in Magnetic Resonance Imaging, since they are the main device for transmission and reception of the magnetic resonance signal. An RF coil array with a new configuration based on the Kepler's Lenten pretzel for the geocentric path of Mars is proposed in this work. The evenly distributed trajectories may serve as the basic configuration to form a coil array to adequately cover a region of interest for magnetic resonance experiments. The main goal is to investigate the electromagnetic properties of this coil array geometry to obtain an optimal design for its further construction. Hence, the electromagnetic properties of the coil array were numerical simulated using the finite element method and the quasi-static approach. Resulting simulations showed that there is an important concentration of magnetic field lines at the centre of the coil array. This is an advantage over other coil arrays where the magnetic field usually decreased at their geometrical centre. Both the electric and magnetic fields had also a very good uniformity. These characteristics made this coil design a good candidate for applications where the use of multi-coil technology is mandatory.

  15. Superconductor coil geometry and ac losses

    NASA Technical Reports Server (NTRS)

    Pierce, T. V., Jr.; Zapata, R. N.

    1976-01-01

    An empirical relation is presented which allows simple computation of volume-averaged winding fields from central fields for coils of small rectangular cross sections. This relation suggests that, in certain applications, ac-loss minimization can be accomplished by use of low winding densities, provided that hysteresis losses are independent of winding density. The ac-loss measurements on coils wound of twisted multifilamentary composite superconductors show no significant dependence on ac losses on winding density, thus permitting the use of winding density as an independent design parameter in loss minimization.

  16. Model coil for the international thermonuclear experimental reactor (ITER) magnet systems

    NASA Astrophysics Data System (ADS)

    Okuno, K.

    1994-07-01

    The model coil program for the ITER EDA includes the manufacture and testing of one Central Solenoid (CS) model coil and one Toroidal Field (TF) model coil, and test facility preparations. The CS model coil has an inner diameter of 1.6 m and produces a full field of 13 T. The TF model coil is race-track shaped with an outer dimension of 3 m x 4 m. It will be tested in conjunction with an LCT coil to simulate mechanical load conditions. Different kinds of conductors can be tested as inserts to be placed in the bore of the CS model coil. Two facilities at JAERI and KfK can provide ITER-relevant conditions for testing the model coils and inserts. The model coil program will validate the ITER magnet design and the manufacturing feasibility.

  17. Compact stellarators with modular coils

    PubMed Central

    Garabedian, P. R.

    2000-01-01

    Compact stellarator designs with modular coils and only two or three field periods are now available; these designs have both good stability and quasiaxial symmetry providing adequate transport for a magnetic fusion reactor. If the bootstrap current assumes theoretically predicted values a three field period configuration is optimal, but if that net current turns out to be lower, a device with two periods and just 12 modular coils might be better. There are also attractive designs with quasihelical symmetry and four or five periods whose properties depend less on the bootstrap current. Good performance requires that there be a satisfactory magnetic well in the vacuum field, which is a property lacking in a stellarator-tokamak hybrid that has been proposed for a proof of principle experiment. In this paper, we present an analysis of stability for these configurations that is based on a mountain pass theorem asserting that, if two solutions of the problem of magnetohydrodynamic equilibrium can be found, then there has to be an unstable solution. We compare results of our theory of equilibrium, stability, and transport with recently announced measurements from the large LHD experiment in Japan. PMID:10899993

  18. Correction coil cable

    DOEpatents

    Wang, Sou-Tien

    1994-11-01

    A wire cable assembly (10, 310) adapted for the winding of electrical coils is taught. A primary intended use is for use in particle tube assemblies (532) for the superconducting super collider. The correction coil cables (10, 310) have wires (14, 314) collected in wire arrays (12, 312) with a center rib (16, 316) sandwiched therebetween to form a core assembly (18, 318 ). The core assembly (18, 318) is surrounded by an assembly housing (20, 320) having an inner spiral wrap (22, 322) and a counter wound outer spiral wrap (24, 324). An alternate embodiment (410) of the invention is rolled into a keystoned shape to improve radial alignment of the correction coil cable (410) on a particle tube (733) in a particle tube assembly (732).

  19. Measuring the orthogonality error of coil systems

    USGS Publications Warehouse

    Heilig, B.; Csontos, A.; Pajunpää, K.; White, Tim; St. Louis, B.; Calp, D.

    2012-01-01

    Recently, a simple method was proposed for the determination of pitch angle between two coil axes by means of a total field magnetometer. The method is applicable when the homogeneous volume in the centre of the coil system is large enough to accommodate the total field sensor. Orthogonality of calibration coil systems used for calibrating vector magnetometers can be attained by this procedure. In addition, the method can be easily automated and applied to the calibration of delta inclination–delta declination (dIdD) magnetometers. The method was tested by several independent research groups, having a variety of test equipment, and located at differing geomagnetic observatories, including: Nurmijärvi, Finland; Hermanus, South Africa; Ottawa, Canada; Tihany, Hungary. This paper summarizes the test results, and discusses the advantages and limitations of the method.

  20. Design and optimization of efficient magnetic coils for biomedical applications

    NASA Astrophysics Data System (ADS)

    Ram Rakhyani, Anil Kumar

    Magnetic fields are permeable to the biological tissues and can induce electric field in the conductive structures. Some medical devices take advantage of this ability to transfer energy from the source to the receiving site without direct contact. Prosthetic devices such as retinal implants use time-varying magnetic field to achieve wireless power transfer to the implanted magnetic coil. However, devices such as magnetic stimulators use the induction principle to create an electric field at the stimulation site. Efficiency of these devices is primarily dependent on the design of the magnetic coils. Therefore, in this work, we designed and validated efficient magnetic coils for wireless power transfer to implanted devices and magnetic stimulation of the peripheral nerves. Typical wireless power transfer (WPT) systems uses two-coil based design to achieve contactless power transfer to the implanted electronics. These systems achieve low power transfer efficiency (< 30%) and frequency bandwidth. Moreover, efficient wireless system requires high coupling and load variation tolerance during device operation. To design an electromagnetic safe WPT system, the power absorbed by the tissue and radiated field due to the proximal magnetic coils needs to be minimized. In this work, we proposed a multi-coil power transfer system which solves some of the current challenges. The proposed multi-coil WPT system achieves more than twice the power transfer efficiency, controllable voltage gain, wider frequency bandwidth, higher tolerance to coupling and load variations, lower absorbed power in the tissue and lower radiated field from the magnetic coil than a comparable two-coil system. In this work, we have developed analytic models of the multi-coil WPT system and validated the accuracy of the solutions using experiments. Magnetic coils play an important role in controlling the distribution of induced electric field inside the nerve during magnetic stimulation. In the past

  1. Service life of counter-current chromatography coils.

    PubMed

    Conway, Walter D

    2007-06-01

    A multilayer coil of PTFE tubing, which failed after being used each workday for about 3 years in a type J centrifuge, was examined. Two types of defects were found. One, called crazes, occurs throughout the coil and does not leak initially, but may eventually lead to a short, axially oriented slit. Another, called indentations, is seen primarily in the innermost and other nearby layers. They are elongated, about 5 mm, indentations, usually on the central side of the tubing. These eventually crack and leak. PTFE tubing is permeable to air and hexane and expands by more than 1% when immersed in hexane, heptane or chloroform for a few days. It is suggested that the crazes result from exposure of the somewhat flexible tubing to the undulating centripetal force field in the coil-planet centrifuge, especially when further softened by solvent absorption. The indentations may result from carriage of the excess tubing length, created by solvent absorption, from the coil periphery to the coil center by the centripetal force field, which continuously travels from the peripheral tail to the central head of the coil. A 1% increase in coil length creates 74 cm of excess tubing in the 160-ml coils examined in this study. It is suggested that fluorinated ethylene propylene (FEP) tubing, especially when etched on the outside, may provide more stable CCC coils, since its expansion when exposed to organic solvents is 0.1 or less than that of PTFE. PMID:17428490

  2. Fast damping of poloidal Alfven waves by bounce-resonant ions: observations and modeling

    NASA Astrophysics Data System (ADS)

    Wang, C.; Rankin, R.; Sydorenko, D.; Zong, Q.

    2015-12-01

    Interplanetary shocks and solar wind dynamic pressure variations can excite intense ultra-low-frequency (ULF) waves in the inner magnetosphere. An analysis of two interplanetary shocks observed by Cluster on 7 November 2004 and 30 August 2001 shows that the poloidal waves excited in these events are damped away rapidly in tens of minutes. This damping is the result of wave-particle interactions involving H+ and O+ ions with energies in the range of several to a few tens of keV [Wang et al., J. Geophys. Res., 2015]. Damping is found to be more effective in the plasmasphere boundary layer due to the relatively higher proportion of Landau resonant ions that exists in that region. In the November 2004 shock event it has been suggested that energy-dispersed ions observed travelling parallel and anti-parallel direction to the geomagnetic field immediately after the shockare locally accelerated rather than originating from Earth's ionosphere. We use test-particle simulations to show that adiabatic advection of the particle differential flux caused bydrift-bounce-resonance with ULF waves is responsible for the energy-dispersed ions observed in these events. In the simulations,Liouville's theorem is used to reconstruct the iondistribution function and differential flux in a model dipole magnetosphere.It is shown that flux modulations of H and O ions can be reproduced when test-particle ions are advanced in the electric fields of the 3D ULF wave model we have developed.

  3. Method and apparatus for magnetic resonance imaging and spectroscopy using microstrip transmission line coils

    DOEpatents

    Zhang, Xiaoliang; Ugurbil, Kamil; Chen, Wei

    2006-04-04

    Apparatus and method for MRI imaging using a coil constructed of microstrip transmission line (MTL coil) are disclosed. In one method, a target is positioned to be imaged within the field of a main magnetic field of a magnet resonance imaging (MRI) system, a MTL coil is positioned proximate the target, and a MRI image is obtained using the main magnet and the MTL coil. In another embodiment, the MRI coil is used for spectroscopy. MRI imaging and spectroscopy coils are formed using microstrip transmission line. These MTL coils have the advantageous property of good performance while occupying a relatively small space, thus allowing MTL coils to be used inside restricted areas more easily than some other prior art coils. In addition, the MTL coils are relatively simple to construct of inexpensive components and thus relatively inexpensive compared to other designs. Further, the MTL coils of the present invention can be readily formed in a wide variety of coil configurations, and used in a wide variety of ways. Further, while the MTL coils of the present invention work well at high field strengths and frequencies, they also work at low frequencies and in low field strengths as well.

  4. Coil planet centrifugation as a means for small particle separation

    NASA Technical Reports Server (NTRS)

    Herrmann, F. T.

    1983-01-01

    The coil planet centrifuge uses a centrifugal force field to provide separation of particles based on differences in sedimentation rates by flow through a rotating coiled tube. Three main separations are considered: (1) single phase fresh sheep and human erythrocytes, (2) single phase fixed heep and human erythrocytes, and (3) electrophoretically enhanced single phase fresh sheep and human erythrocytes.

  5. Optimization of the detection coil of high-Tc superconducting quantum interference device-based nuclear magnetic resonance for discriminating a minimum amount of liver tumor of rats in microtesla fields

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Hsien; Huang, Kai-Wen; Yang, Hong-Chang; Horng, Herng-Er; Liao, Shu-Hsien

    2013-08-01

    This study presents an optimization of the detection coil of high-Tc superconducting quantum interference device (SQUID)-based nuclear magnetic resonance (NMR) in microtesla fields for discriminating a minimum amount of liver tumor in rats by characterizing the longitudinal relaxation rate, T1-1, of tested samples. The detection coil, which was coupled to the SQUID through a flux transformer, was optimized by varying the copper wires' winding turns and diameters. When comparing the measured NMR signals, we found that the simulated NMR signal agrees with simulated signals. When discriminating liver tumors in rats, the averaged longitudinal relaxation rate was observed to be T1-1 = 3.3 s-1 for cancerous liver tissue and T1-1 = 6.6 s-1 for normal liver tissue. The results suggest that it can be used to successfully discriminate cancerous liver tissue from normal liver tissues in rats. The minimum amount of samples that can be detected is 0.2 g for liver tumor and 0.4 g for normal liver tissue in 100 μT fields. The specimen was not damaged; it can be used for other pathological analyses. The proposed method provides more possibilities for examining undersized specimens.

  6. Imprinted Clay Coil Vessels

    ERIC Educational Resources Information Center

    Lohr, Tresa Rae

    2006-01-01

    The author teaches clay vessel construction in the fifth grade, and it is amazing what can be accomplished in one forty-five minute period when the expectations are clarified in the initial lesson. The author introduces clay coil vessels with a discussion of the sources of clay and how clay relates to fifth-grade science curriculum concepts such…

  7. Coiled coil interactions for the targeting of liposomes for nucleic acid delivery

    NASA Astrophysics Data System (ADS)

    Oude Blenke, Erik E.; van den Dikkenberg, Joep; van Kolck, Bartjan; Kros, Alexander; Mastrobattista, Enrico

    2016-04-01

    encapsulating a splice correcting oligonucleotide or siRNA. These peptide-functionalized vesicles are highly stable in solution but start to cluster when vesicles modified with complementary peptides are mixed together, demonstrating that the peptides quickly coil and crosslink the vesicles. When one of the peptides was anchored to the cell membrane using a hydrophobic cholesterol anchor, vesicles functionalized with the complementary peptide could be docked to these cells, whereas non-functionalized cells did not show any vesicle tethering. Although the anchored peptides do not have a downstream signaling pathway, microscopy pictures revealed that after four hours, the majority of the docked vesicles were internalized by endocytosis. Finally, for the first time, it was shown that the coiled coil assembly at the interface between the vesicles and the cell membrane induces active uptake and leads to cytosolic delivery of the nucleic acid cargo. Both the siRNA and the splice correcting oligonucleotide were functionally delivered, resulting respectively in the silencing or recovery of luciferase expression in the appropriate cell lines. These results demonstrate that the docking to the cell by coiled coil interaction can induce active uptake and achieve the successful intracellular delivery of otherwise membrane impermeable nucleic acids in a highly specific manner. Electronic supplementary information (ESI) available: Two videos of the experiment are shown in Fig. 5, demonstrating the distinctive characteristics of the peptide pair in a mixed population of cells are available in online. Video S1 shows the experiment in the bright field channel including the green channel (calcein-AM stained unfunctionalized cells) and orange channel (rhodamine labeled liposomes). Video S2 shows the exact same frames but combining the fluorescent channels only, including the blue channel for Hoechst nuclear staining. Both videos consist of 31 frames at a frame rate of 5 fps. The labeled liposomes

  8. Coiled coil interactions for the targeting of liposomes for nucleic acid delivery

    NASA Astrophysics Data System (ADS)

    Oude Blenke, Erik E.; van den Dikkenberg, Joep; van Kolck, Bartjan; Kros, Alexander; Mastrobattista, Enrico

    2016-04-01

    encapsulating a splice correcting oligonucleotide or siRNA. These peptide-functionalized vesicles are highly stable in solution but start to cluster when vesicles modified with complementary peptides are mixed together, demonstrating that the peptides quickly coil and crosslink the vesicles. When one of the peptides was anchored to the cell membrane using a hydrophobic cholesterol anchor, vesicles functionalized with the complementary peptide could be docked to these cells, whereas non-functionalized cells did not show any vesicle tethering. Although the anchored peptides do not have a downstream signaling pathway, microscopy pictures revealed that after four hours, the majority of the docked vesicles were internalized by endocytosis. Finally, for the first time, it was shown that the coiled coil assembly at the interface between the vesicles and the cell membrane induces active uptake and leads to cytosolic delivery of the nucleic acid cargo. Both the siRNA and the splice correcting oligonucleotide were functionally delivered, resulting respectively in the silencing or recovery of luciferase expression in the appropriate cell lines. These results demonstrate that the docking to the cell by coiled coil interaction can induce active uptake and achieve the successful intracellular delivery of otherwise membrane impermeable nucleic acids in a highly specific manner. Electronic supplementary information (ESI) available: Two videos of the experiment are shown in Fig. 5, demonstrating the distinctive characteristics of the peptide pair in a mixed population of cells are available in online. Video S1 shows the experiment in the bright field channel including the green channel (calcein-AM stained unfunctionalized cells) and orange channel (rhodamine labeled liposomes). Video S2 shows the exact same frames but combining the fluorescent channels only, including the blue channel for Hoechst nuclear staining. Both videos consist of 31 frames at a frame rate of 5 fps. The labeled liposomes

  9. Performance correlation between YBa2Cu3O7-δ coils and short samples for coil technology development

    NASA Astrophysics Data System (ADS)

    Wang, X.; Dietderich, D. R.; Godeke, A.; Gourlay, S. A.; Marchevsky, M.; Prestemon, S. O.; Sabbi, G. L.

    2016-06-01

    A robust fabrication technology is critical to achieve the high performance in YBa2Cu3O{}7-δ (YBCO) coils as the critical current of the brittle YBCO layer is subject to the strain-induced degradation during coil fabrication. The expected current-carrying capability of the magnet and its temperature dependence are two key inputs to the coil technology development. However, the expected magnet performance is not straightforward to determine because the short-sample critical current depends on both the amplitude and orientation of the applied magnetic field with respect to the broad surface of the tape-form conductor. In this paper, we present an approach to calculate the self-field performance limit for YBCO racetrack coils at 77 and 4.2 K. Critical current of short YBCO samples was measured as a function of the applied field perpendicular to the conductor surface from 0 to 15 T. This field direction limited the conductor critical current. Two double-layer racetrack coils, one with three turns and the other with 10 turns, were wound and tested at 77 and 4.2 K. The test coils reached at least 80% of the expected critical current. The ratio between the coil critical currents at 77 and 4.2 K agreed well with the calculation. We conclude that the presented approach can determine the performance limit in YBCO racetrack coils based on the short-sample critical current and provide a useful guideline for assessing the coil performance and fabrication technology. The correlation of the coil critical current between 77 K and 4.2 K was also observed, allowing the 77 K test to be a cost-effective tool for the development of coil technology.

  10. Pulse Test of Coil Insulation

    NASA Technical Reports Server (NTRS)

    Kroy, Ralph E.

    1987-01-01

    Waveform of back-electromotive force reveals defects. Simple pulse test reveals defects in inductor coils. Devised for use on servovalve solenoid coils on Space Shuttle, test also applicable to transformer windings, chokes, relays, and the like.

  11. TFTR Mirnov coil analysis at plasma start-up

    SciTech Connect

    Harley, T.R.; Buchenauer, D.A.; Coonrod, J.; McGuire, K.M.

    1986-01-01

    The methods for finding poloidal and toroidal numbers of MHD oscillations from Mirnov coils are reviewed and modified. Examples of various MHD phenomena occurring during start-up on TFTR are illustrated. It is found that the MHD mode structure best fits a model with the toroidal correction included. A new algorithm which finds m,n numbers can accommodate toroidal effects which are manifested in the phase data. The algorithm can find m,n numbers with a given toroidal correction parameter lambda', (lambda' = 0 cylindrical). This algorithm is also used to find the optimal value of lambda' automatically, eliminating the need for ''guesswork.'' The algorithm finds the best parameters to the fit much faster than more conventional computational techniques. 9 refs., 21 figs., 2 tabs.

  12. Wet Winding Improves Coil Encapsulation

    NASA Technical Reports Server (NTRS)

    Hill, A. J.

    1987-01-01

    Wet-winding process encapsulates electrical coils more uniformily than conventional processes. Process requires no vacuum pump and adapts easily to existing winding machines. Encapsulant applied to each layer of wire as soon as added to coil. Wet-winding process eliminates voids, giving more uniformly encapsulated coil.

  13. Design of printed circuit coils

    NASA Technical Reports Server (NTRS)

    Higgins, W. T.

    1969-01-01

    Spiral-like coil is printed with several extra turns which increase the realizable coil inductance. Included are shorting connections which not only short the extra turns, but also short out several turns of the main body. Coil tuning is accomplished by removing the shorts until the desired inductance is obtained.

  14. Parametric design of tri-axial nested Helmholtz coils

    SciTech Connect

    Abbott, Jake J.

    2015-05-15

    This paper provides an optimal parametric design for tri-axial nested Helmholtz coils, which are used to generate a uniform magnetic field with controllable magnitude and direction. Circular and square coils, both with square cross section, are considered. Practical considerations such as wire selection, wire-wrapping efficiency, wire bending radius, choice of power supply, and inductance and time response are included. Using the equations provided, a designer can quickly create an optimal set of custom coils to generate a specified field magnitude in the uniform-field region while maintaining specified accessibility to the central workspace. An example case study is included.

  15. ECH Plasma Experiments on an Internal Coil Device with a High Temperature Superconductor Coil

    SciTech Connect

    Ogawa, Yuichi; Morikawa, Junji; Ohkuni, Kotaro; Yamakoshi, Shigeo; Goto, Takuya; Mito, Toshiyuki; Yanagi, Nagato; Iwakuma, Masataka

    2005-01-15

    Self-organization related with relaxation phenomenon is playing an important role in various aspects of magnetic confined plasmas. Recently a relaxation theory including the plasma flow has been developed by Mahajan-Yoshida, and a new relaxation state has been identified. The two-fluid relaxation condition is given by {beta} + (V/V{sub A}){sup 2} = const. To study a self-organized structure with strong plasma flow, we have introduced an internal coil device. By inducing a radial electric field with appropriate methods, we could drive a toroidal plasma flow, and confine a high beta plasma in a core region. The internal coil device Mini-RT with a high temperature superconductor(HTS) coil(Rc=0.15m, Ic=50kA) has been constructed. The vacuum chamber is 1 m in diameter and {approx}0.7 m in height. The magnetic field strength near the internal coil is around 0.1 T, and a radio-frequency wave of 2.45 GHz is applied for the plasma production. We have started ECH plasma experiments with the coil supported mechanically. The electron density, which has a peak near the internal coil, is of order 10{sup 16} m{sup -3}, reaching the cut-off density of the microwave. While, the electron temperature is of order 10 eV with a broad profile. Estimated energy confinement time is of order 10{sup -(5-6)} sec. The levitation experiment of the HTS coil has been carried out. The position of the HTS coil is measured with laser sensors, and is feedback-controlled with the levitation coil current. We have succeeded to levitating the HTS coil during one hour with an accuracy of less than 20 {omega}m. A preliminary experiment for the plasma production at the floating condition of the HTS coil has been initiated. It is affirmed that the levitation system works well and plasma with separatrix configuration is produced.

  16. Development of real-time rotating waveplate Stokes polarimeter using multi-order retardation for ITER poloidal polarimeter.

    PubMed

    Imazawa, R; Kawano, Y; Ono, T; Itami, K

    2016-01-01

    The rotating waveplate Stokes polarimeter was developed for ITER (International Thermonuclear Experimental Reactor) poloidal polarimeter. The generalized model of the rotating waveplate Stokes polarimeter and the algorithm suitable for real-time field-programmable gate array (FPGA) processing were proposed. Since the generalized model takes into account each component associated with the rotation of the waveplate, the Stokes parameters can be accurately measured even in unideal condition such as non-uniformity of the waveplate retardation. Experiments using a He-Ne laser showed that the maximum error and the precision of the Stokes parameter were 3.5% and 1.2%, respectively. The rotation speed of waveplate was 20 000 rpm and time resolution of measuring the Stokes parameter was 3.3 ms. Software emulation showed that the real-time measurement of the Stokes parameter with time resolution of less than 10 ms is possible by using several FPGA boards. Evaluation of measurement capability using a far-infrared laser which ITER poloidal polarimeter will use concluded that measurement error will be reduced by a factor of nine. PMID:26827317

  17. Development of real-time rotating waveplate Stokes polarimeter using multi-order retardation for ITER poloidal polarimeter.

    PubMed

    Imazawa, R; Kawano, Y; Ono, T; Itami, K

    2016-01-01

    The rotating waveplate Stokes polarimeter was developed for ITER (International Thermonuclear Experimental Reactor) poloidal polarimeter. The generalized model of the rotating waveplate Stokes polarimeter and the algorithm suitable for real-time field-programmable gate array (FPGA) processing were proposed. Since the generalized model takes into account each component associated with the rotation of the waveplate, the Stokes parameters can be accurately measured even in unideal condition such as non-uniformity of the waveplate retardation. Experiments using a He-Ne laser showed that the maximum error and the precision of the Stokes parameter were 3.5% and 1.2%, respectively. The rotation speed of waveplate was 20 000 rpm and time resolution of measuring the Stokes parameter was 3.3 ms. Software emulation showed that the real-time measurement of the Stokes parameter with time resolution of less than 10 ms is possible by using several FPGA boards. Evaluation of measurement capability using a far-infrared laser which ITER poloidal polarimeter will use concluded that measurement error will be reduced by a factor of nine.

  18. Gas Filled Coaxial Accelerator with Compression Coil

    NASA Technical Reports Server (NTRS)

    Espy, Patrick N. (Inventor)

    1976-01-01

    A self-energized plasma compressor which compresses plasma discharged from a coaxial plasma generator. The device includes a helical shaped coil which is coaxially aligned with the center axis of the coaxial plasma generator. The plasma generator creates a current through the helical coil which, in turn, generates a time varying magnetic field that generates a force which acts radially upon the plasma. A seal is carried on the end of the coaxial plasma generator for containing gas therein. As the plasma is accelerated out the outer end of the generator, it forces the gas outwardly also compressing such. Beads are carried adjacent the small end of the helical shaped coil for being accelerated to hypervelocities by the plasma and gas. As a result of utilizing gas in the coaxial plasma generator, such minimizes ablation of the beads as well as accelerates such to higher velocities.

  19. Coupled wave model for large magnet coils

    NASA Technical Reports Server (NTRS)

    Gabriel, G. J.

    1980-01-01

    A wave coupled model based on field theory is evolved for analysis of fast electromagnetic transients on superconducting coils. It is expected to play a useful role in the design of protection methods against damage due to high voltages or any adverse effects that might arise from unintentional transients. The significant parameters of the coil are identified to be the turn to turn wave coupling coefficients and the travel time of an electromagnetic disturbance around a single turn. Unlike circuit theoretic inductor, the coil response evolves in discrete steps having durations equal to this travel time. It is during such intervals that high voltages are likely to occur. The model also bridges the gap between the low and high ends of the frequency spectrum.

  20. Effective arrangement of separated transmit-only/receive-only RF coil for improvement of B1 homogeneity at 7 Tesla

    NASA Astrophysics Data System (ADS)

    Im, Geun Ho; Seo, Jeong-Hoon; Kim, Kyoung-Nam; Heo, Phil; Chung, Julius Juhyun; Jang, Moon-Sun; Lee, Jung Hee; Kim, Jae-Hun; Kim, Sun I.

    2014-09-01

    This article presents an effective arrangement with shifted transmit (Tx)-only and receive (Rx)-only (TORO) radiofrequency (RF) coils in a single-channel surface coil for improving the magnetic flux ( B 1) homogeneity in an ultra-high field (UHF) magnetic resonance imaging (MRI) scanner. The proposed new methodology for the coil arrangement using the shifted TORO RF coils was demonstrated for coils with 50-mm, 100-mm, and 150-mm-square surfaces and the results were compared to those for general Tx/Rx surface coils with the same dimensions. The computational analysis indicated that a homogeneous B1 field was achieved when the Rx-only coil was shifted in the two-dimensional xy-plane away from the Tx-only coils. Because the proposed coil configuration provides a unique opportunity for increasing the B 1 homogeneity, this feature is likely to increase the feasibility via new coil arrangements of UHF surface design and fabrication.

  1. Linear and non-linear numerical simulations of poloidal Alfven waves

    NASA Astrophysics Data System (ADS)

    Ribeiro, A.

    2013-05-01

    Among the many of numerical simulations of MHD turbulence, few studies had been made of Alfven waves interacting with realistic boundaries. Thus, we have developed a novel hybrid spectral/finite element code, which is capable of simulate properly realistic boundaries properties. Our model is based on a Fourier decompositions of all variables in the azimuthal direction and on a finite element projection in the meridian plan. In order to simulate realistic boundary conditions for the magnetic field we solve the induction equation enforcing continuity of the magnetic field H at the interface with the external insulating medium through a Interior Penalty Galerkin method (IPG) [1]. I will present the results of our investigation of Alfven waves propagating in a cylinder filled of liquid metal submitted to an axial magnetic field. Poloidal Alfven waves are excited magnetically by imposing an azimuthal current pulse at the bottom of the cylinder. In the linear axisymmetric model we find a good agreement with previous experiments in liquid metals by Lundquist and by Lenhert and more recently by Alboussiere et al [2]. This axisymmetric study is extended to the non linear regime, where the amplitudes of the perturbations are comparable to the external applied magnetic field,in this conditions a complex response is found due to waves waves interactions. [1] J. L. Guermond, J.L Leorat, F. Luddens, C. Nore, A. Ribeiro. Effects of discontinuous magnetic permeability on magnetodynamic problems, Journal of Computational Physics Volume 230, Issue 16, 10 July 2011, Pages 6299 -- 6319. [2] T. Alboussiere, P. Cardin, F. Debray, H. C. Nataf, F. Plunian, A. Ribeiro, D. Schmitt, Experimental evidence of Alfven wave propagation in a Gallium alloy, Physics of fluids, 2011, vol. 23, nb 9.

  2. Coil Tolerance Impact on Plasma Surface Quality for NCSX

    SciTech Connect

    Art Brooks; Wayne Reiersen

    2003-10-20

    The successful operation of the National Compact Stellarator Experiment (NCSX) machine will require producing plasma configurations with good flux surfaces, with a minimum volume of the plasma lost to magnetic islands or stochastic regions. The project goal is to achieve good flux surfaces over 90% of the plasma volume. NCSX is a three period device designed to be operated with iota ranging from {approx}0.4 on axis to {approx}0.7 at the edge. The field errors of most concern are those that are resonant with 3/5 and 3/6 modes (for symmetry preserving field errors) and the 1/2 and 2/3 modes (for symmetry breaking field errors). In addition to losses inherent in the physics configuration itself, there will be losses from field errors arising from coil construction and assembly errors. Some of these losses can be recovered through the use of trim coils or correction coils. The impact of coil tolerances on plasma surface quality is evaluated herein for the NCSX design. The methods used in this evaluation are discussed. The ability of the NCSX trim coils to correct for field errors is also examined. The results are used to set coils tolerances for the various coil systems.

  3. Superconducting sextupole correction coil operating in persistent mode

    SciTech Connect

    Gilbert, W.; Borden, A.; Hassenzahl, W.; Mortiz, G.; Taylor, C.

    1984-09-01

    Error fields in a dipole due to superconductor magnetization and conductor misplacements add unwanted multipole, mainly sextupole and decapole, terms to the desired dipole field. Two persistent mode sextupole correction coils inside the bore of model SSC dipoles have been built and tested. A shorted superconducting sextupole coil has a current induced in it by the error sextupole field such that no sextupole field can penetrate into the proton beam region. The correction sextupole coils are one layer thick and are wound from a single length of insulated composite Nb-Ti and copper wire 0.60 mm in diameter. Each of the six poles has ten turns and is mounted on a 1.75 cm radius stainless steel bore tube. Details of testing and trimming of the correction coils are described. Test results of the measured magnetic field within the model SSC dipoles with the correction coils in and out of persistent mode operation are presented. An electrical heater is used to drive the coil out of the persistent mode. Measurements of joint resistance and coil decay time constants are also given.

  4. Apparatus and method for reducing inductive coupling between levitation and drive coils within a magnetic propulsion system

    DOEpatents

    Post, Richard F.

    2001-01-01

    An apparatus and method is disclosed for reducing inductive coupling between levitation and drive coils within a magnetic levitation system. A pole array has a magnetic field. A levitation coil is positioned so that in response to motion of the magnetic field of the pole array a current is induced in the levitation coil. A first drive coil having a magnetic field coupled to drive the pole array also has a magnetic flux which induces a parasitic current in the levitation coil. A second drive coil having a magnetic field is positioned to attenuate the parasitic current in the levitation coil by canceling the magnetic flux of the first drive coil which induces the parasitic current. Steps in the method include generating a magnetic field with a pole array for levitating an object; inducing current in a levitation coil in response to motion of the magnetic field of the pole array; generating a magnetic field with a first drive coil for propelling the object; and generating a magnetic field with a second drive coil for attenuating effects of the magnetic field of the first drive coil on the current in the levitation coil.

  5. Anomalous toroidal field penetration in Tormac V

    SciTech Connect

    Feinberg, B.; Vaucher, B.G.; Shaw, R.S.; Vella, M.C.

    1981-07-01

    Magnetic field penetration into a cool, collisional, magnetized plasma has been investigated in Tormac V. Magnetic probe and laser interferometer studies reveal anomalous penetration of the applied toroidal field into a plasma with an initial parallel bias toroidal field. The applied poloidal field, however, formed a well-defined magnetic front which was effective at sweeping up particles. Strong shear in the vacuum magnetic field does not inhibit the apparent decoupling of the applied toroidal field from the applied poloidal field.

  6. Anomalous toroidal field penetration in Tormac V

    SciTech Connect

    Feinberg, B.; Vaucher, B. G.; Shaw, R. S.; Vella, M. C.

    1981-07-01

    We investigate magnetic field penetration into a cool, collisional, magnetized plasma in Tormac V. Magnetic probe and laser interferometer studies reveal anomalous penetration of the applied toroidal field into a plasma with an initial parallel bias toroidal field. The applied poloidal field, however, formed a well-defined magnetic front which was effective at sweeping up particles. Lastly, strong shear in the vacuum magnetic field does not inhibit the apparent decoupling of the applied toroidal field from the applied poloidal field.

  7. Development of Ground Coils with Low Eddy Current Loss by Applying the Compression Molding Method after the Coil Winding

    NASA Astrophysics Data System (ADS)

    Suzuki, Masao; Aiba, Masayuki; Takahashi, Noriyuki; Ota, Satoru; Okada, Shigenori

    In a magnetically levitated transportation (MAGLEV) system, a huge number of ground coils will be required because they must be laid for the whole line. Therefore, stable performance and reduced cost are essential requirements for the ground coil development. On the other hand, because the magnetic field changes when the superconducting magnet passes by, an eddy current will be generated in the conductor of the ground coil and will result in energy loss. The loss not only increases the magnetic resistance for the train running but also brings an increase in the ground coil temperature. Therefore, the reduction of the eddy current loss is extremely important. This study examined ground coils in which both the eddy current loss and temperature increase were small. Furthermore, quantitative comparison for the eddy current loss of various magnet wire samples was performed by bench test. On the basis of the comparison, a round twisted wire having low eddy current loss was selected as an effective ground coil material. In addition, the ground coils were manufactured on trial. A favorable outlook to improve the size accuracy of the winding coil and uneven thickness of molded resin was obtained without reducing the insulation strength between the coil layers by applying a compression molding after winding.

  8. Preliminary design of a superconducting coil array for NASA prototype magnetic balance. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Alishahi, M. M.

    1980-01-01

    Using a computer program a partly optimized configuration for a supeconducting version of side and lift coil system of NASA-MIT prototype is presented. Cable size for the mentioned coils and also for superconducting drag and magnetizing coils regarding the overall computed field was determined.

  9. A multi-slot surface coil for MRI of dual-rat imaging at 4T

    SciTech Connect

    Solis, S.E.; Tomasi, D.; Solis, S.E.; Wang, R.; Tomasi, D.; Rodriguez, A.O.

    2011-07-01

    A slotted surface coil inspired by the hole-and-slot cavity magnetron was developed for magnetic resonance imaging of obese rats at 4 T. Full-wave analysis of the magnetic field was carried out at 170 MHz for both the slotted and circular-shaped coils. The noise figure values of two coils were investigated via the numerical calculation of the quality factors. Fat simulated phantoms to mimic overweight rats were included in the analysis with weights ranging from 300 to 900 g. The noise figures were 1.2 dB for the slotted coil and 2.4 dB for the circular coil when loaded with 600 g of simulated phantom. A slotted surface coil with eight circular slots and a circular coil with similar dimensions were built and operated in the transceiver mode, and their performances were experimentally compared. The imaging tests in phantoms demonstrated that the slotted surface coil has a deeper RF-sensitivity and better field uniformity than the single-loop RF-coil. High quality images of two overweight Zucker rats were acquired simultaneously with the slotted surface coil using standard spin-echo pulse sequences. Experimental results showed that the slotted surface coil outperformed the circular coil for imaging considerably overweight rats. Thus, the slotted surface coil can be a good tool for MRI experiments in rats on a human whole-body 4 T scanner.

  10. A multi-slot surface coil for MRI of dual-rat imaging at 4 T

    NASA Astrophysics Data System (ADS)

    Solis, S. E.; Wang, R.; Tomasi, D.; Rodriguez, A. O.

    2011-06-01

    A slotted surface coil inspired by the hole-and-slot cavity magnetron was developed for magnetic resonance imaging of obese rats at 4 T. Full-wave analysis of the magnetic field was carried out at 170 MHz for both the slotted and circular-shaped coils. The noise figure values of two coils were investigated via the numerical calculation of the quality factors. Fat simulated phantoms to mimic overweight rats were included in the analysis with weights ranging from 300 to 900 g. The noise figures were 1.2 dB for the slotted coil and 2.4 dB for the circular coil when loaded with 600 g of simulated phantom. A slotted surface coil with eight circular slots and a circular coil with similar dimensions were built and operated in the transceiver mode, and their performances were experimentally compared. The imaging tests in phantoms demonstrated that the slotted surface coil has a deeper RF-sensitivity and better field uniformity than the single-loop RF-coil. High quality images of two overweight Zucker rats were acquired simultaneously with the slotted surface coil using standard spin-echo pulse sequences. Experimental results showed that the slotted surface coil outperformed the circular coil for imaging considerably overweight rats. Thus, the slotted surface coil can be a good tool for MRI experiments in rats on a human whole-body 4 T scanner.

  11. Mid-Range Coil Array for Magnetic Resonance Imaging of Small Animals

    SciTech Connect

    Solis, S. E.; Tomasi, D.; Rodriguez, A. O.

    2008-08-11

    The vast majority of articles on MRI RF coils over the past two decades have focused on large coils, where sample losses dominate, or on micro-coils, where sample and capacitor losses are negligible. Few have addressed the mid-range coils, seen in the majority of small-animal applications, where all the sources of loss are important, for example, mouse brain and body coils from 125 to 750 MHz. We developed a four-saddle coil array for magnetic resonance imaging of small animals. The saddle coil elements in the array were evenly distributed to cover the rat's head. The coil array was tuned to the resonant frequency of 170 MHz. Due to the close proximity of the coil elements, it was necessary to decouple the coil array using nonmagnetic trimmers and, it was operated in the transceiver mode and quadrature-driven. To test the coil array performance at high field, phantom images were acquired with our saddle coil array and standard pulse sequences on a research-dedicated 4 Tesla scanner. Ex vivo brain images of a rat were also acquired, and proved the feasibility of the scaled version of a saddle coil array and, its compatibility with standard pulse sequences when used in a high field magnetic resonance imager.

  12. Upgraded coil configuration for ISABELLE magnets

    SciTech Connect

    Hahn, H.; Dahl, P.F.; Kaugerts, J.E.; Prodell, A.G.

    1981-01-01

    Achievement of the design field of 5 T in the ISABELLE dipole magnets is turning out to be more arduous than expected and several avenues of improvement are being pursued. One possibility for improving training and peak field performance is discussed in this paper. It has been recognized that the inert spacers with their adjacent active turns in the cosine magnet windings can be replaced by a double thickness braid operating at approximately half-current density in 46 of the 190 turns. Since the high-field region occurs in the low current density turns near the poles, a performance improvement can be expected. It has been verified that the proposed coil configuration satisfies the field requirements and details thereof are given. Results from an experimental magnet in which superconducting spacer turns are used to simulate half-current density windings are presented. Construction of thick braid coils is being planned and the status of these magnets is reviewed.

  13. Nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

    DOEpatents

    Fukushima, Eiichi; Roeder, Stephen B. W.; Assink, Roger A.; Gibson, Atholl A. V.

    1986-01-01

    An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio-frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

  14. Considerations in the design and optimization of coiled coil structures.

    PubMed

    Mason, Jody M; Müller, Kristian M; Arndt, Katja M

    2007-01-01

    Coiled coil motifs are, despite their apparent simplicity, highly specific, and play a significant role in the understanding of tertiary structure and its formation. The most commonly observed of the coiled coils, the parallel dimeric, is yet to be fully characterized for this structural class in general. Nonetheless, strict rules have emerged for the necessity of specific types of amino acids at specific positions. In this chapter, we discuss this system in light of existing coiled coil structures and in applying rules to coiled coils that are to be designed or optimized. Understanding and expanding on these rules is crucial in using these motifs, which play key roles in virtually every cellular process, to act as drug-delivery agents by sequestering other proteins that are not behaving natively or that have been upregulated (for example, by binding to coiled coil domains implicated in oncogenesis). The roles of the a and d "hydrophobic" core positions and the e and g "electrostatic" edge positions in directing oligomerization and pairing specificity are discussed. Also discussed is the role of these positions in concert with the b, c, and f positions in maintaining alpha-helical propensity, helix solubility, and dimer stability. PMID:17041258

  15. Considerations in the design and optimization of coiled coil structures.

    PubMed

    Mason, Jody M; Müller, Kristian M; Arndt, Katja M

    2007-01-01

    Coiled coil motifs are, despite their apparent simplicity, highly specific, and play a significant role in the understanding of tertiary structure and its formation. The most commonly observed of the coiled coils, the parallel dimeric, is yet to be fully characterized for this structural class in general. Nonetheless, strict rules have emerged for the necessity of specific types of amino acids at specific positions. In this chapter, we discuss this system in light of existing coiled coil structures and in applying rules to coiled coils that are to be designed or optimized. Understanding and expanding on these rules is crucial in using these motifs, which play key roles in virtually every cellular process, to act as drug-delivery agents by sequestering other proteins that are not behaving natively or that have been upregulated (for example, by binding to coiled coil domains implicated in oncogenesis). The roles of the a and d "hydrophobic" core positions and the e and g "electrostatic" edge positions in directing oligomerization and pairing specificity are discussed. Also discussed is the role of these positions in concert with the b, c, and f positions in maintaining alpha-helical propensity, helix solubility, and dimer stability.

  16. Choice of coils for a fusion reactor

    PubMed Central

    Alexander, Romeo; Garabedian, Paul R.

    2007-01-01

    In a fusion reactor a hot plasma of deuterium and tritium is confined by a strong magnetic field to produce helium ions and release energetic neutrons. The 3D geometry of a stellarator provides configurations for such a device that reduce net toroidal current that might lead to disruptions. We construct smooth coils generating an external magnetic field designed to prevent the plasma from deteriorating. PMID:17640879

  17. Meta-analysis of stent-assisted coiling versus coiling-only for the treatment of intracranial aneurysms.

    PubMed

    Phan, Kevin; Huo, Ya R; Jia, Fangzhi; Phan, Steven; Rao, Prashanth J; Mobbs, Ralph J; Mortimer, Alex M

    2016-09-01

    Endovascular coil embolization is a widely accepted and useful treatment modality for intracranial aneurysms. However, the principal limitation of this technique is the high aneurysm recurrence. The adjunct use of stents for coil embolization procedures has revolutionized the field of endovascular aneurysm management, however its safety and efficacy remains unclear. Two independent reviewers searched six databases from inception to July 2015 for trials that reported outcomes according to those who received stent-assisted coiling versus coiling-only (no stent-assistance). There were 14 observational studies involving 2698 stent-assisted coiling and 29,388 coiling-only patients. The pooled immediate occlusion rate for stent-assisted coiling was 57.7% (range: 20.2%-89.2%) and 48.7% (range: 31.7%-89.2%) for coiling-only, with no significant difference between the two (odds ratio [OR}=1.01; 95% confidence intervals [CI}: 0.68-1.49). However, progressive thrombosis was significantly more likely in stent-assisted coiling (29.9%) compared to coiling-only (17.5%) (OR=2.71; 95% CI: 1.95-3.75). Aneurysm recurrence was significantly lower in stent-assisted coiling (12.7%) compared to coiling-only (27.9%) (OR=0.43; 95% CI: 0.28-0.66). In terms of complications, there was no significant difference between the two techniques for all-complications, permanent complications or thrombotic complications. Mortality was significantly higher in the stent-assisted group 1.4% (range: 0%-27.5%) compared to the coiling-only group 0.2% (range: 0%-19.7%) (OR=2.16; 95% CI: 1.33-3.52). Based on limited evidence, stent-assisted coiling shows similar immediate occlusion rates, improved progressive thrombosis and decreased aneurysm recurrence compared to coiling-only, but is associated with a higher mortality rate. Future randomized controlled trials are warranted to clarify the safety of stent-associated coiling. PMID:27344091

  18. Critical Current Measurements in Commercial Tapes, Coils, and Magnets.

    NASA Astrophysics Data System (ADS)

    Gubser, D. U.; Soulen, R. J., Jr.; Fuller-Mora, W. W.; Francavilla, T. L.

    1996-03-01

    We have measured a number of tapes, coils, and magnets produced by commercial vendors and determined their properties as functions of magnetic field and temperature. The tapes were measured at the National High Magnetic Field Laboratory in magnetic fields to 20 tesla and at temperatures of 4.2 K, 27 K, 65 K, and 77 K. For the tapes we report critical currents and current-voltage characteristics. Six inch diameter coils were measured at NRL in zero magnetic field. Critical currents, current-voltage characteristics, and reliability studies are reported for the coils. Larger 10 inch diameter coils, which are to be used in a 200 hp superconducting motor, were also measured and results will be presented. The talk will also review the status of the most recent tests of the superconducting motor.

  19. Bi-2223 HTS winding in toroidal configuration for SMES coil

    NASA Astrophysics Data System (ADS)

    Kondratowicz-Kucewicz, B.; Janowski, T.; Kozak, S.; Kozak, J.; Wojtasiewicz, G.; Majka, M.

    2010-06-01

    Energy can be stored in the magnetic field of a coil. Superconducting Magnetic Energy Storage (SMES) is very promising as a power storage system for load levelling or power stabilizer. However, the strong electromagnetic force caused by high magnetic field and large coil current is a problem in SMES systems. A toroidal configuration would have a much less extensive external magnetic field and electromagnetic forces in winding. The paper describes the design of HTS winding for SMES coil in modular toroid configuration consist of seven Bi-2223 double-pancakes as well as numerical analysis of SMES magnet model using FLUX 3D package. As the results of analysis the paper presents the optimal coil configuration and the parameters such as radius of toroidal magnet, energy stored in magnet and magnetic field distribution.

  20. Numerical dosimetry of transcranial magnetic stimulation coils

    NASA Astrophysics Data System (ADS)

    Crowther, Lawrence; Hadimani, Ravi; Jiles, David

    2014-03-01

    Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique capable of stimulating neurons by means of electromagnetic induction. TMS can be used to map brain function and shows promise for the diagnosis and treatment of neurological and psychiatric disorders. Calculation of fields induced in the brain are necessary to accurately identify stimulated neural tissue during TMS. This allows the development of novel TMS coil designs capable of stimulating deeper brain regions and increasing the localization of stimulation that can be achieved. We have performed numerical calculations of magnetic and electric field with high-resolution anatomically realistic human head models to find these stimulated brain regions for a variety of proposed TMS coil designs. The realistic head models contain heterogeneous tissue structures and electrical conductivities, yielding superior results to those obtained from the simplified homogeneous head models that are commonly employed. The attenuation of electric field as a function of depth in the brain and the localization of stimulating field have been methodically investigated. In addition to providing a quantitative comparison of different TMS coil designs the variation of induced field between subjects has been investigated. We also show the differences in induced fields between adult, adolescent and child head models to preemptively identify potential safety issues in the application of pediatric TMS.

  1. Constrained length minimum inductance gradient coil design.

    PubMed

    Chronik, B A; Rutt, B K

    1998-02-01

    A gradient coil design algorithm capable of controlling the position of the homogeneous region of interest (ROI) with respect to the current-carrying wires is required for many advanced imaging and spectroscopy applications. A modified minimum inductance target field method that allows the placement of a set of constraints on the final current density is presented. This constrained current minimum inductance method is derived in the context of previous target field methods. Complete details are shown and all equations required for implementation of the algorithm are given. The method has been implemented on computer and applied to the design of both a 1:1 aspect ratio (length:diameter) central ROI and a 2:1 aspect ratio edge ROI gradient coil. The 1:1 design demonstrates that a general analytic method can be used to easily obtain very short gradient coil designs for use with specialized magnet systems. The edge gradient design demonstrates that designs that allow imaging of the neck region with a head sized gradient coil can be obtained, as well as other applications requiring edge-of-cylinder regions of uniformity.

  2. Stellarator Coil Design and Plasma Sensitivity

    SciTech Connect

    Long-Poe Ku and Allen H. Boozer

    2010-11-03

    The rich information contained in the plasma response to external magnetic perturbations can be used to help design stellarator coils more effectively. We demonstrate the feasibility by first devel- oping a simple, direct method to study perturbations in stellarators that do not break stellarator symmetry and periodicity. The method applies a small perturbation to the plasma boundary and evaluates the resulting perturbed free-boundary equilibrium to build up a sensitivity matrix for the important physics attributes of the underlying configuration. Using this sensitivity information, design methods for better stellarator coils are then developed. The procedure and a proof-of-principle application are given that (1) determine the spatial distributions of external normal magnetic field at the location of the unperturbed plasma boundary to which the plasma properties are most sen- sitive, (2) determine the distributions of external normal magnetic field that can be produced most efficiently by distant coils, (3) choose the ratios of the magnitudes of the the efficiently produced magnetic distributions so the sensitive plasma properties can be controlled. Using these methods, sets of modular coils are found for the National Compact Stellarator Experiment (NCSX) that are either smoother or can be located much farther from the plasma boundary than those of the present design.

  3. Collisional bulk ion transport and poloidal rotation driven by neutral beam injection

    SciTech Connect

    Newton, Sarah L.; Helander, Per; Catto, Peter J.

    2007-06-15

    Neutral beam injection (NBI) is known to significantly affect radial transport in a tokamak plasma. Furthermore, recent observations have shown poloidal velocities, in the presence of NBI, significantly in excess of the standard neoclassical value. Motivated by this, the additional collisional radial bulk ion fluxes of particles, heat and toroidal angular momentum, and the poloidal velocity, driven by fast ions from NBI have been evaluated for a low-collisionality, pure plasma, with strong toroidal rotation and arbitrary aspect ratio. Higher order velocity space structure of the fast ion distribution function can be significant, whilst the effects of toroidal acceleration caused by strong NBI dominate at large aspect ratio. The driven poloidal velocity depends strongly on system parameters, becoming larger at higher beam density and lower beam energy.

  4. TEST PLAN FOR MONITORING COOLING COILS IN A LABORATORY SETTING

    SciTech Connect

    Don B. Shirey, III

    2002-04-01

    The objective of this research project is to understand and quantify the moisture removal performance of cooling coils at part-load conditions. The project will include a comprehensive literature review, detailed measurement of cooling coil performance in a laboratory facility, monitoring cooling systems at several field test sites, and development/validation of engineering models that can be used in energy calculations and building simulations. This document contains the detailed test plan for monitoring cooling coil performance in a laboratory setting. Detailed measurements will be taken on up to 10 direct expansion (DX) and chilled water cooling coils in various configurations to understand the impact of coil geometry and operating conditions on transient moisture condensation and evaporation.

  5. Modular tokamak magnetic system

    DOEpatents

    Yang, Tien-Fang

    1988-01-01

    A modular tokamak system comprised of a plurality of interlocking moldules. Each module is comprised of a vacuum vessel section, a toroidal field coil, moldular saddle coils which generate a poloidal magnetic field and ohmic heating coils.

  6. Common Coil Magnet System for VLHC

    SciTech Connect

    Gupta, R.

    1999-02-12

    This paper introduces the common coil magnet system for the proposed very large hadron collider (VLHC). In this system, the high energy booster (HEB), the injector to VLHC, is integrated as the iron dominated low field aperture within the coldmass of the common coil magnet design introduced earlier. This 4-in-1 magnet concept for a 2-in-1 machine should provide a major cost reduction in building and operating VLHC. Moreover, the proposed design reduces the field quality problems associated with the large persistent currents in Nb{sub 3}Sn magnets. The paper also shows that the geometric field harmonics can be made small. In this preliminary magnetic design. the current dependence in harmonics is significant but not umnanageable.

  7. Magnetically Damped Furnace Bitter Magnet Coil 1

    NASA Technical Reports Server (NTRS)

    Bird, M. D.

    1997-01-01

    A magnet has been built by the National High Magnetic Field Laboratory for NASA on a cost reimbursement contract. The magnet is intended to demonstrate the technology and feasibility of building a magnet for space based crystal growth. A Bitter magnet (named after Francis Bitter, its inventor) was built consisting of four split coils electrically in series and hydraulically in parallel. The coils are housed in a steel vessel to reduce the fringe field and provide some on-axis field enhancement. The steel was nickel plated and Teflon coated to minimize interaction with the water cooling system. The magnet provides 0.14 T in a 184 mm bore with 3 kW of power.

  8. Magnetic field transfer device and method

    DOEpatents

    Wipf, Stefan L.

    1990-01-01

    A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180.degree. from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180.degree. from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils.

  9. Magnetic field transfer device and method

    DOEpatents

    Wipf, S.L.

    1990-02-13

    A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

  10. Reduced-magnetohydrodynamic simulations of toroidally and poloidally localized edge localized modes

    SciTech Connect

    Hoelzl, M.; Guenter, S.; Mueller, W.-C.; Lackner, K.; Krebs, I.; Wenninger, R. P.; Huysmans, G. T. A.; Collaboration: ASDEX Upgrade Team

    2012-08-15

    We use the non-linear reduced-magnetohydrodynamic code JOREK to study edge localized modes (ELMs) in the geometry of the ASDEX Upgrade tokamak. Toroidal mode numbers, poloidal filament sizes, and radial propagation speeds of filaments into the scrape-off layer are in good agreement with observations for type-I ELMs in ASDEX Upgrade. The observed instabilities exhibit a toroidal and poloidal localization of perturbations which is compatible with the 'solitary magnetic perturbations' recently discovered in ASDEX Upgrade [R. Wenninger et al., 'Solitary magnetic perturbations at the ELM onset,' Nucl. Fusion (accepted)]. This localization can only be described in numerical simulations with high toroidal resolution.

  11. Quench current improvement through shape modification of racetrack coil

    NASA Astrophysics Data System (ADS)

    Baik, Seung-Kyu; Sohn, Myung-Hwan; Ko, Rock-Kil; Kwon, Young-Kil; Ryu, Kang-Sik; Jo, Young-Sik

    2002-01-01

    Superconducting racetrack coils have different shapes from those of ordinary solenoid coils which have the same curvature along the windings. So they have different or worse performance from the viewpoint of quench characteristics due to the different structures. Racetrack coils also have round curvatures along their end portions; however, the main difference of their structures from solenoid coils exists in the straight portions. It is considered that the worse performance is due to the straight portions. In the round portions, there exists strong continuous constraint along the windings against the movement toward the perpendicular direction during coil excitation. On the contrary, in the straight portions, there is almost no constraining. As a result, especially in the case of dry magnet, they show even worse characteristics than solenoid counterparts. For the compensation of this worse performance, we proposed one idea to improve quench characteristics of racetrack coils. We manufactured one racetrack coil with an ordinary shape and the other with the proposed idea. By experiments we made sure that the proposed one had a higher quench current. Moreover, after we had made an application of the proposed idea to the four field coils of an actual 30 kVA superconducting generator, we could get very good output voltage and current waveforms.

  12. Stacked phased array coils for increasing the signal-to-noise ratio in magnetic resonance imaging.

    PubMed

    Dandan Liang; Hon Tat Hui; Tat Soon Yeo; Bing Keong Li

    2013-02-01

    A new concept of using a stacked phased coil array to increase the signal-to-circuit noise ratio (SCNR) in magnetic resonance imaging (MRI) is introduced. Unlike conventional phased coil arrays, the proposed stacked phased coil array is constructed by stacking the coil elements closely together in the vertical direction. Through a proper combination of the coil terminal voltages, the SCNR is shown to increase with the square root of the number of coil elements. A prototype two-element array is constructed and an experimental method is designed to determine the combiner coefficients in a simulated MRI electromagnetic field environment. The experimental results show that the mutual coupling effect among the array coils can be totally removed and the combiner output voltage increases with the number of coil elements. This demonstrates the feasibility of the proposed method.

  13. Designing with null flux coils

    SciTech Connect

    Davey, K.R.

    1997-09-01

    Null flux were suggested by Danby and Powell in the late 1960`s as a useful means for realizing induced lift with little drag. As an array of alternating magnets is translated past a set of null flux coils, the currents induced in these coils act to vertically center the magnets on those coils. At present, one Japanese MAGLEV system company and two American-based companies are employing either null flux or flux eliminating coils in their design for high speed magnetically levitated transportation. The principle question addressed in paper is: what is the proper choice of coil length to magnet length in a null flux system? A generic analysis in the time and frequency domain is laid out with the intent of showing the optimal design specification in terms of coil parameters.

  14. Charge-exchange measurements of beam ion thermalization in MHD-quiescent plasmas in the Poloidal Divertor Experiment

    SciTech Connect

    Kaita, R.; Goldston, R.J.; Beiersdorfer, P.; Herndon, D.L.; Kaye, S.M.; Kugel, H.W.; McCann, R.T.; McCune, D.C.; Meyerhofer, D.D.; Towner, H.H.

    1984-10-01

    The horizontally scanning, multiangle charge-exchange analyzer on the Poloidal Divertor Experiment (PDX) was used to study the beam ion slowing-down process with high-power perpendicular injection. Measurements were made over a wide range in toroidal field (8 kG < B(T) < 22 kG), plasma current (200 kA < I(p) < 500 kA), and beam power (1 MW < P/sub B/ < 7 MW). In MHD-quiescent plasmas, good agreement is found between the measured slowing-down spectra and theoretical predictions as a function of both angle and energy. Classes of prompt orbit losses are observed with both co- and counter-injection which have been understood and applied to plasma diagnostics. The effects of MHD activity on fast ion thermalization will be the subject of a companion paper.

  15. External split field generator

    DOEpatents

    Thundat, Thomas George; Van Neste, Charles W.; Vass, Arpad Alexander

    2012-02-21

    A generator includes a coil disposed about a core. A first stationary magnetic field source may be disposed on a first end portion of the core and a second stationary magnetic field source may be disposed on a second end portion of core. The first and second stationary magnetic field sources apply a stationary magnetic field to the coil. An external magnetic field source may be disposed outside the coil to apply a moving magnetic field to the coil. Electrical energy is generated in response to an interaction between the coil, the moving magnetic field, and the stationary magnetic field.

  16. Operation of a 400MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7-x high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1GHz.

    PubMed

    Yanagisawa, Y; Piao, R; Iguchi, S; Nakagome, H; Takao, T; Kominato, K; Hamada, M; Matsumoto, S; Suematsu, H; Jin, X; Takahashi, M; Yamazaki, T; Maeda, H

    2014-10-18

    High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1GHz (23.5T). (RE)Ba2Cu3O7-x (REBCO, RE: rare earth) conductors have an advantage over Bi2Sr2Ca2Cu3O10-x (Bi-2223) and Bi2Sr2CaCu2O8-x (Bi-2212) conductors in that they have very high tensile strengths and tolerate strong electromagnetic hoop stress, thereby having the potential to act as an ultra-compact super-high field NMR magnet. As a first step, we developed the world's first NMR magnet comprising an inner REBCO coil and outer low-temperature superconducting (LTS) coils. The magnet was successfully charged without degradation and mainly operated at 400MHz (9.39T). Technical problems for the NMR magnet due to screening current in the REBCO coil were clarified and solved as follows: (i) A remarkable temporal drift of the central magnetic field was suppressed by a current sweep reversal method utilizing ∼10% of the peak current. (ii) A Z2 field error harmonic of the main coil cannot be compensated by an outer correction coil and therefore an additional ferromagnetic shim was used. (iii) Large tesseral harmonics emerged that could not be corrected by cryoshim coils. Due to those harmonics, the resolution and sensitivity of NMR spectra are ten-fold lower than those for a conventional LTS NMR magnet. As a result, a HSQC spectrum could be achieved for a protein sample, while a NOESY spectrum could not be obtained. An ultra-compact 1.2GHz NMR magnet could be realized if we effectively take advantage of REBCO conductors, although this will require further research to suppress the effect of the screening current. PMID:25462945

  17. Operation of a 400 MHz NMR magnet using a (RE:Rare Earth)Ba2Cu3O7-x high-temperature superconducting coil: Towards an ultra-compact super-high field NMR spectrometer operated beyond 1 GHz

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Y.; Piao, R.; Iguchi, S.; Nakagome, H.; Takao, T.; Kominato, K.; Hamada, M.; Matsumoto, S.; Suematsu, H.; Jin, X.; Takahashi, M.; Yamazaki, T.; Maeda, H.

    2014-12-01

    High-temperature superconductors (HTS) are the key technology to achieve super-high magnetic field nuclear magnetic resonance (NMR) spectrometers with an operating frequency far beyond 1 GHz (23.5 T). (RE)Ba2Cu3O7-x (REBCO, RE: rare earth) conductors have an advantage over Bi2Sr2Ca2Cu3O10-x (Bi-2223) and Bi2Sr2CaCu2O8-x (Bi-2212) conductors in that they have very high tensile strengths and tolerate strong electromagnetic hoop stress, thereby having the potential to act as an ultra-compact super-high field NMR magnet. As a first step, we developed the world's first NMR magnet comprising an inner REBCO coil and outer low-temperature superconducting (LTS) coils. The magnet was successfully charged without degradation and mainly operated at 400 MHz (9.39 T). Technical problems for the NMR magnet due to screening current in the REBCO coil were clarified and solved as follows: (i) A remarkable temporal drift of the central magnetic field was suppressed by a current sweep reversal method utilizing ∼10% of the peak current. (ii) A Z2 field error harmonic of the main coil cannot be compensated by an outer correction coil and therefore an additional ferromagnetic shim was used. (iii) Large tesseral harmonics emerged that could not be corrected by cryoshim coils. Due to those harmonics, the resolution and sensitivity of NMR spectra are ten-fold lower than those for a conventional LTS NMR magnet. As a result, a HSQC spectrum could be achieved for a protein sample, while a NOESY spectrum could not be obtained. An ultra-compact 1.2 GHz NMR magnet could be realized if we effectively take advantage of REBCO conductors, although this will require further research to suppress the effect of the screening current.

  18. Designing HTS coils for magnetic circuits

    SciTech Connect

    Jenkins, R.G.; Jones, H.; Goodall, R.M.

    1996-07-01

    The authors discuss some of the main considerations involved in the design of HTS coils to operate in liquid nitrogen and provide ampere-turns for magnetic circuits in general, and then in particular for a small-scale electromagnetic (i.e, attractive) maglev demonstrator. The most important factor affecting design is the sensitive and strongly anisotropic dependence of HTS tape`s critical current on magnetic field. Any successful design must limit the field in the windings, especially components perpendicular to the tape`s surface (radial components in the case of solenoids), to acceptably low levels such that local critical currents nowhere fall below the operating current. This factor is relevant to the construction of HTS coils for all applications. A second important factor is that the presence of an iron magnetic circuit can greatly alter the flux distribution within the coils from that found when they are in free space. FE modelling has been used to calculate accurate field profiles in proposed designs for comparison with short sample I{sub c}(B) data. They present a design for a maglev demonstrator, illustrating how some of the problems, in particular the reduction of radial field components, may be addressed, and describe its predicted performance.

  19. Coiled coils ensure the physiological ectodomain shedding of collagen XVII.

    PubMed

    Nishie, Wataru; Jackow, Joanna; Hofmann, Silke C; Franzke, Claus-Werner; Bruckner-Tuderman, Leena

    2012-08-24

    α-Helical coiled coils, frequent protein oligomerization motifs, are commonly observed in vital proteins. Here, using collagen XVII as an example, we provide evidence for a novel function of coiled coils in the regulation of ectodomain shedding. Transmembrane collagen XVII, an epithelial cell surface receptor, mediates dermal-epidermal adhesion in the skin, and its dysfunction is linked to human skin blistering diseases. The ectodomain of this collagen is constitutively shed from the cell surface by proteinases of a disintegrin and metalloprotease family; however, the mechanisms regulating shedding remain elusive. Here, we used site-specific mutagenesis to target the coiled-coil heptad repeats within the juxtamembranous, extracellular noncollagenous 16th A (NC16A) domain of collagen XVII. This resulted in a substantial increase of ectodomain shedding, which was not mediated by disintegrin and metalloproteases. Instead, conformational changes induced by the mutation(s) unmasked a furin recognition sequence that was used for cleavage. This study shows that apart from their functions in protein oligomerization, coiled coils can also act as regulators of ectodomain shedding depending on the biological context.

  20. Optimization of gradient coil technology for human magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Chronik, Blaine Alexander

    The general problem of identifying the optimal gradient coil design for any given application is addressed in this thesis. The problem is divided into stages. The first step is the development of an optimal mathematical solution for single designs conforming to some set of constraints. The second step is the systematic implementation of the mathematical algorithm to search for the optimal set of design constraints for an intended application, two examples of which are investigated. The final step is the consideration of gradient coil dependent physiological limits specific to the application of strong gradient fields in human subjects. A modified minimum inductance target field method that allows the placement of a set of constraints on the final current density is developed. This constrained current minimum inductance (CCMI) method is derived in the context of previous target field methods. The method has been fully implemented on computer and applied to the design of both central and edge uniformity gradient coils. A three axis gradient coil set that utilizes interleaved, multilayer axes to achieve maximum gradient strengths of over 2000mT/m in rise times of less than 50μs with an inner coil diameter of 5cm was designed. Water cooling was incorporated into the coil to assist in thermal management. The duty cycle for the most extreme cases of single shot EPI is limited by the thermal response and expressions for maximum rates of image collection are given for burst and continuous modes of operation. A three axis gradient coil set with an imaging region extending outside the physical edge of the coil was designed, constructed, and tested. The configuration is compatible with both neck and brain imaging in humans. The coil produces a cylindrical imaging region 16cm in diameter and 16cm in length. The coil axes produce gradient strengths between 80mT/m and 100mT/m at 250A peak current, with minimum rise times of approximately 400μs. Heating tests were performed

  1. Molecular dynamics guided study of salt bridge length dependence in both fluorinated and non-fluorinated parallel dimeric coiled-coils

    PubMed Central

    Pendley, Scott S.; Yu, Yihua B.; Cheatham, Thomas E.

    2009-01-01

    The α-helical coiled-coil is one of the most common oligomerization motifs found in both native and engineered proteins. To better understand the stability and dynamics of coiled-coil motifs, including those modified by fluorination, several fluorinated and non-fluorinated parallel dimeric coiled-coil protein structures were designed and modeled. We also attempt to investigate how changing the length and geometry of the important stabilizing salt bridges influences the coiled-coil protein structure. Molecular dynamics (MD) and free energy simulations with AMBER employed a particle mesh Ewald treatment of the electrostatics in explicit TIP3P solvent with balanced force field treatments. Preliminary studies with legacy force fields (ff94, ff96, ff99) show a profound instability of the coiled-coil structures in short MD simulation. Significantly better behavior is evident with the more balanced ff99SB and ff03 protein force fields. Overall, the results suggest that the coiled-coil structures can readily accommodate the larger acidic arginine or S-2,7-diaminoheptanedoic acid mutants in the salt bridge, whereas substitution of the smaller L-ornithine residue leads to rapid disruption of the coiled-coil structure on the MD simulation time scale. This structural distortion of the secondary structure allows both the formation of large hydration pockets proximal to the charged groups and within the hydrophobic core. Moreover, the increased structural fluctuations and movement lead to a decrease in the water occupancy lifetimes in the hydration pockets. In contrast, analysis of the hydration in the stable dimeric coiled coils shows high occupancy water sites along the backbone residues with no water occupancy in the hydrophobic core, although transitory water interactions with the salt bridge residues are evident. The simulations of the fluorinated coiled-coils suggest that in some cases fluorination electrostatically stabilizes the intermolecular coiled-coil salt bridges

  2. Magnetic field measurements in tokamak plasmas

    SciTech Connect

    Feldman, U.; Seely, J.F.; Sheeley,Jr., N.R.; Suckewer, S.; Title, A.M.

    1984-11-01

    The measurement of the poloidal magnetic field in a tokamak plasma from the Zeeman splitting and polarization of the magnetic dipole radiation from heavy ions is discussed. When viewed from a direction perpendicular to the toroidal field, the effect of the poloidal field on the circularly polarized radiation is detectable using a photoelectric polarimeter. The Zeeman splittings for a number of magnetic dipole transitions with wavelengths in the range 2300--9300 A are presented. An imaging polarimeter is proposed that can measure the poloidal magnetic field with space and time resolution.

  3. Superconducting properties of experimental YBCO coils for FFAG accelerator magnets

    NASA Astrophysics Data System (ADS)

    Takayama, S.; Koyanagi, K.; Tosaka, T.; Tasaki, K.; Kurusu, T.; Ishii, Y.; Amemiya, N.; Ogitsu, T.

    2014-05-01

    A project to develop fundamental technologies for accelerator magnets using high-Tc coated conductors is currently in progress. The primary applications of this project are fixed field alternating gradient (FFAG) accelerators for carbon cancer therapy systems and accelerator-driven subcritical reactors. Several types of superconducting coils for FFAG accelerators have been conceptually designed. These coils have complicated shapes, including a negative-bend part or a three-dimensional bent part. One of the aims of the project is to establish winding technologies for complicated coil shapes using coated conductors. To demonstrate winding technologies for YBa2Cu3O7-x (YBCO) coils, small test coils having a negative-bend part or a three-dimensional bent part were designed and fabricated according to the present design of the FFAG magnet. The outside dimensions of the negative-bend test coil were 460 mm long and 190 mm wide, and the radius of curvature of the negative-bend part was 442 mm. The outside dimensions of the three-dimensional test coil were 380 mm long and 280 mm wide, and the radius of curvature of the mandrel of the three-dimensional coil was 700 mm. The test coils were wound using YBCO coated conductors with a length of about 100 m and were then impregnated with epoxy resin. The coils were placed in liquid nitrogen and excited to measure their V-I characteristics. From the V-I characteristics throughout a voltage range down to 10-9 V/cm, the V-I characteristics before and after impregnation were approximately the same, demonstrating that the superconducting properties were not degraded.

  4. An introduction to coil array design for parallel MRI.

    PubMed

    Ohliger, Michael A; Sodickson, Daniel K

    2006-05-01

    The basic principles of radiofrequency coil array design for parallel MRI are described from both theoretical and practical perspectives. Because parallel MRI techniques rely on coil array sensitivities to provide spatial information about the sample, a careful choice of array design is essential. The concepts of coil array spatial encoding are first discussed from four qualitative perspectives. These qualitative descriptions include using coil arrays to emulate spatial harmonics, choosing coils with selective sensitivities to aliased pixels, using coil sensitivities with broad k-space reception profiles, and relying on detector coils to provide a set of generalized projections of the sample. This qualitative discussion is followed by a quantitative analysis of coil arrays, which is discussed in terms of the baseline SNR of the received images as well as the noise amplifications (g-factor) in the reconstructed data. The complications encountered during the experimental evaluation of coil array SNR are discussed, and solutions are proposed. A series of specific array designs are reviewed, with an emphasis on the general design considerations that motivate each approach. Finally, a set of special topics is discussed, which reflect issues that have become important, especially as arrays are being designed for more high-performance applications of parallel MRI. These topics include concerns about the depth penetration of arrays composed of small elements, the use of adaptive arrays for systems with limited receiver channels, the management of inductive coupling between array elements, and special considerations required at high field strengths. The fundamental limits of spatial encoding using coil arrays are discussed, with a primary emphasis on how the determination of these limits impacts the design of optimized arrays. This review is intended to provide insight into how arrays are currently used for parallel MRI and to place into context the new innovations that are

  5. Two-Slotted Surface Coil Array for Magnetic Resonance Imaging at 4 Tesla

    SciTech Connect

    Solis, S. E.; Hernandez, J. A.; Rodriguez, A. O.; Tomasi, D.

    2008-08-11

    Arrays of antennas have been widely accepted for magnetic resonance imaging applications due to their high signal-to-noise ratio (SNR) over large volumes of interest. A new surface coil based on the magnetron tube and called slotted surface coil, has been recently introduced by our group. This coil design experimentally demonstrated a significant improvement over the circular-shaped coil when used in the receive-only mode. The slotted coils formed a two-sheet structure with a 90 deg. separation and each coil had 6 circular slots. Numerical simulations were performed using the finite element method for this coil design to study the behaviour of the array magnetic field. Then, we developed a two-coil array for brain magnetic resonance imaging to be operated at the resonant frequency of 170 MHz in the transceiver mode. Phantom images were acquired with our coil array and standard pulse sequences on a research-dedicated 4 Tesla scanner. Numerical simulations demonstrated that electromagnetic interaction between the coil elements is negligible, and that the magnetic field showed a good uniformity. In vitro images showed the feasibility of this coil array for standard pulses for high field magnetic resonance imaging.

  6. NSTX Protection And Interlock Systems For Coil And Powers Supply Systems

    SciTech Connect

    X. Zhao, S. Ramakrishnan, J. Lawson, C.Neumeyer, R. Marsala, H. Schneider, Engineering Operations

    2009-09-24

    NSTX at Princeton Plasma Physics Laboratory (PPPL) requires sophisticated plasma positioning control system for stable plasma operation. TF magnetic coils and PF magnetic coils provide electromagnetic fields to position and shape the plasma vertically and horizontally respectively. NSTX utilizes twenty six coil power supplies to establish and initiate electromagnetic fields through the coil system for plasma control. A power protection and interlock system is utilized to detect power system faults and protect the TF coils and PF coils against excessive electromechanical forces, overheating, and over current. Upon detecting any fault condition the power system is restricted, and it is either prevented from initializing or suppressed to de-energize coil power during pulsing. Power fault status is immediately reported to the computer system. This paper describes the design and operation of NSTX's protection and interlocking system and possible future expansion.

  7. Marshall N. Rosenbluth Outstanding Doctoral Thesis Award Talk: Control of Non-Axisymmetric Fields With Static and Dynamic Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Paz-Soldan, C.

    2013-10-01

    Small deformations of the otherwise axisymmetric field, known as ``error fields'' (EFs), lead to large changes in global MHD stability. This talk will compare results from both 1) a line-tied screw-pinch with rotating conducting walls and 2) the DIII-D tokamak to illustrate that in both devices the EF has greatest effect where it overlaps with the spatial structure of its global kink mode. In both configurations the kink structure in the symmetry direction is well described by a single mode number (azimuthal m = 1 , toroidal n = 1 , respectively) and EF ordering is clear. In the asymmetric direction (axial and poloidal, respectively) the harmonics of the kink are coupled (by line-tying and toroidicity, respectively) and thus EF ordering is not straightforward. In the pinch, the kink is axially localized to the anode region and consequently the anode EF dominates the MHD stability. In DIII-D, the poloidal harmonics of the n = 1 EF whose pitch is smaller than the local field-line pitch are empirically shown to be dominant across a wide breadth of EF optimization experiments. In analogy with the pinch, these harmonics are also where overlap with the kink is greatest and thus where the largest plasma kink response is found. The robustness of the kink structure further enables vacuum-field cost-function minimization techniques to accurately predict optimal EF correction coil currents by strongly weighting the kink-like poloidal harmonics in the minimization. To test the limits of this paradigm recent experiments in DIII-D imposed field structures that lack kink-overlapping harmonics, yielding ~10X less sensitivity. The very different plasmas of the pinch and tokamak thus both demonstrate the dominance of the kink mode in determining optimal EF correction. Supported by US DOE under DE-AC05-06OR23100, DE-FG02-00ER54603, DE-FC02-04ER54698, and NSF 0903900.

  8. Edge turbulence flows at two different poloidal angles in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Zweben, Stewart; Terry, James; Agostini, Matteo; Davis, William; Grulke, Olaf; Hughes, Jerry; Labombard, Brian; Landreman, Matt; Ma, Yunxing; Pace, David; Scott, Bruce

    2012-10-01

    High resolution edge turbulence movies have been obtained simultaneously at both the outer midplane and near the lower X-point region of C-Mod, using gas puff imaging (GPI) with two high speed cameras at 400,000 frames/sec. The time-resolved turbulence flow speeds at the outer midplane GPI view was previously estimated using a time-resolved cross-correlation technique [1], but previous results also showed a significantly different turbulence structure in these two regions [2]. Preliminary results indicate that the poloidal turbulence flows are not necessarily the same at these two poloidal angles. For instance, in one shot there is a strong time-averaged poloidal flow near the X-region toward the outer midplane, but mainly poloidally-fluctuating flows at the outer midplane. Examples of these flow measurements will be shown for plasmas with and without ICRH and in L-mode and H-mode plasmas. Evidence for fluctuating zonal flows preceding the L-H transition will be assessed. This work is supported in part by DOE Contracts DE-AC02-09CH11466 and DE-FC02-99ER5412.[4pt] [1] S.J. Zweben, J.L. Terry et al, Plasma Phys. Cont. Fusion 54 (2012) 025008[0pt] [2] J.L. Terry, S.J. Zweben et al, J. Nucl. Mat. 390-291 (2009) 339

  9. Effects of orbit squeezing on poloidal mass flow and bootstrap current in tokamak plasmas

    SciTech Connect

    Shaing, K.C. ); Hsu, C.T. ); Hazeltine, R.D. )

    1994-10-01

    It is shown, by solving the drift kinetic equation, that the asymptotic values of the poloidal mass flow and the bootstrap current in the banana regime of large-aspect-ratio tokamak plasmas are not affected by orbit squeezing. However, because the definition of ion collisionality [upsilon][sub *[ital i

  10. Time dependent parallel viscosity and relaxation rate of poloidal rotation in the banana regime

    SciTech Connect

    Hsu, C.T.; Shaing, K.C.; Gormley, R. )

    1994-01-01

    Time dependent ion parallel viscous force in the banana regime with arbitrary inverse aspect ratio [epsilon] is calculated using the eigenfunction approach. The flux surface averaged viscosity is then used to study the relaxation process of the poloidal rotation which leads to oscillatory relaxation behavior. The relaxation rate [nu][sub [ital p

  11. Relaxation rate of poloidal rotation in the banana regime in tokamaks

    SciTech Connect

    Shaing, K.C.; Hirshman, S.P.

    1989-03-01

    The relaxation rate ..nu../sub p/ of poloidal rotation in the banana regime in tokamaks is calculated using a time-dependent parallel viscosity. It is found that ..nu../sub p/ is on the order of ..nu../sub i//sub i/, the ion--ion collision frequency, with no geometric enhancement factor associated with toroidicity.

  12. Testing neoclassical and turbulent effects on poloidal rotation in the core of DIII-Da)

    NASA Astrophysics Data System (ADS)

    Chrystal, C.; Burrell, K. H.; Grierson, B. A.; Staebler, G. M.; Solomon, W. M.; Wang, W. X.; Rhodes, T. L.; Schmitz, L.; Kinsey, J. E.; Lao, L. L.; deGrassie, J. S.; Mordijck, S.; Meneghini, O.

    2014-07-01

    Experimental tests of ion poloidal rotation theories have been performed on DIII-D using a novel impurity poloidal rotation diagnostic. These tests show significant disagreements with theoretical predictions in various conditions, including L-mode plasmas with internal transport barriers (ITB), H-mode plasmas, and QH-mode plasmas. The theories tested include standard neoclassical theory, turbulence driven Reynolds stress, and fast-ion friction on the thermal ions. Poloidal rotation is observed to spin up at the formation of an ITB and makes a significant contribution to the measurement of the E→×B→ shear that forms the ITB. In ITB cases, neoclassical theory agrees quantitatively with the experimental measurements only in the steep gradient region. Significant quantitative disagreement with neoclassical predictions is seen in the cores of ITB, QH-, and H-mode plasmas, demonstrating that neoclassical theory is an incomplete description of poloidal rotation. The addition of turbulence driven Reynolds stress does not remedy this disagreement; linear stability calculations and Doppler backscattering measurements show that disagreement increases as turbulence levels decline. Furthermore, the effect of fast-ion friction, by itself, does not lead to improved agreement; in QH-mode plasmas, neoclassical predictions are closest to experimental results in plasmas with the largest fast ion friction. Predictions from a new model that combines all three effects show somewhat better agreement in the H-mode case, but discrepancies well outside the experimental error bars remain.

  13. Magnetic turbulence and resistive MHD instabilities in a 0. 6 < q < 3 poloidal divertor tokamak

    SciTech Connect

    Agim, Y.Z.; Callen, J.D.; Chang, Z.; Dexter, R.N.; Goetz, J.A.; Graessle, D.E.; Haines, E.; Kortbawi, D.; LaPointe, M.A.; Moyer, R.A.

    1988-09-01

    Detailed statistical properties of internal magnetic turbulence, and internal disruptions in magnetically- and materially-limited discharges, are studied in the Tokapole II poloidal divertor tokamak over the safety factor range 0.6 < q{sub a} < 3. A nonlinear MHD code treats tearing modes in the divertor geometry. 9 refs., 2 figs.

  14. Testing neoclassical and turbulent effects on poloidal rotation in the core of DIII-D

    SciTech Connect

    Chrystal, C.; Burrell, K. H.; Staebler, G. M.; Kinsey, J. E.; Lao, L. L.; Grassie, J. S. de; Grierson, B. A.; Solomon, W. M.; Wang, W. X.; Rhodes, T. L.; Schmitz, L.; Mordijck, S.; Meneghini, O.

    2014-07-15

    Experimental tests of ion poloidal rotation theories have been performed on DIII-D using a novel impurity poloidal rotation diagnostic. These tests show significant disagreements with theoretical predictions in various conditions, including L-mode plasmas with internal transport barriers (ITB), H-mode plasmas, and QH-mode plasmas. The theories tested include standard neoclassical theory, turbulence driven Reynolds stress, and fast-ion friction on the thermal ions. Poloidal rotation is observed to spin up at the formation of an ITB and makes a significant contribution to the measurement of the E{sup →}×B{sup →} shear that forms the ITB. In ITB cases, neoclassical theory agrees quantitatively with the experimental measurements only in the steep gradient region. Significant quantitative disagreement with neoclassical predictions is seen in the cores of ITB, QH-, and H-mode plasmas, demonstrating that neoclassical theory is an incomplete description of poloidal rotation. The addition of turbulence driven Reynolds stress does not remedy this disagreement; linear stability calculations and Doppler backscattering measurements show that disagreement increases as turbulence levels decline. Furthermore, the effect of fast-ion friction, by itself, does not lead to improved agreement; in QH-mode plasmas, neoclassical predictions are closest to experimental results in plasmas with the largest fast ion friction. Predictions from a new model that combines all three effects show somewhat better agreement in the H-mode case, but discrepancies well outside the experimental error bars remain.

  15. A Parallel Coiled-Coil Tetramer with Offset Helices

    SciTech Connect

    Liu,J.; Deng, Y.; Zheng, Q.; Cheng, C.; Kallenbach, N.; Lu, M.

    2006-01-01

    Specific helix-helix interactions are fundamental in assembling the native state of proteins and in protein-protein interfaces. Coiled coils afford a unique model system for elucidating principles of molecular recognition between {alpha} helices. The coiled-coil fold is specified by a characteristic seven amino acid repeat containing hydrophobic residues at the first (a) and fourth (d) positions. Nonpolar side chains spaced three and four residues apart are referred to as the 3-4 hydrophobic repeat. The presence of apolar amino acids at the e or g positions (corresponding to a 3-3-1 hydrophobic repeat) can provide new possibilities for close-packing of {alpha}-helices that includes examples such as the lac repressor tetramerization domain. Here we demonstrate that an unprecedented coiled-coil interface results from replacement of three charged residues at the e positions in the dimeric GCN4 leucine zipper by nonpolar valine side chains. Equilibrium circular dichroism and analytical ultracentrifugation studies indicate that the valine-containing mutant forms a discrete {alpha}-helical tetramer with a significantly higher stability than the parent leucine-zipper molecule. The 1.35 {angstrom} resolution crystal structure of the tetramer reveals a parallel four-stranded coiled coil with a three-residue interhelical offset. The local packing geometry of the three hydrophobic positions in the tetramer conformation is completely different from that seen in classical tetrameric structures yet bears resemblance to that in three-stranded coiled coils. These studies demonstrate that distinct van der Waals interactions beyond the a and d side chains can generate a diverse set of helix-helix interfaces and three-dimensional supercoil structures.

  16. Measured strain in Nb3Sn coils during excitation and quence

    SciTech Connect

    Caspi, S.; Barlett, S.E.; Dietderich, D. R.; Ferracin, P.; Gourlay, S. A.; Hannaford, C. R.; Hafalia, A.R.; Lietzke, A.F.; Mattafirri, S.; Nyman, M.; Sabbi, G.

    2005-06-01

    The strain in a high field Nb{sub 3}Sn coil was measured during magnet assembly, cool-down, excitation and spot heater quenches. Strain was measured with a full bridge strain gauge mounted directly over the turns and impregnated with the coil. Two such coils were placed in a 'common coil' fashion capable of reaching 11 T at 4.2 K. The measured steady state strain in the coil is compared with results obtained using the FEM code ANSYS. During quenches, the transient strain (due to temperature rise) was also measured and compared with the calculated mechanical time response to a quench.

  17. Measured Strain of Nb3Sn Coils During Excitation and Quench

    SciTech Connect

    Caspi, S.; Bartlett, S.E.; Dietderich, D.R.; Ferracin, P.; Gourlay, S.A.; Hannaford, C.R.; Hafalia, A.R.; Lietzke, S.; Mattafirri,M.; Nyman, M.; Sabbi, G.

    2005-04-16

    The strain in a high field Nb{sub 3}Sn coil was measured during magnet assembly, cool-down, excitation and spot heater quenches. Strain was measured with a full bridge strain gauge mounted directly over the turns and impregnated with the coil. Two such coils were placed in a ''common coil'' fashion capable of reaching 11T at 4.2K. The measured steady state strain in the coil is compared with results obtained using the FEM code ANSYS. During quenches, the transient strain (due to temperature rise) was also measured and compared with the calculated mechanical time response to a quench.

  18. Numerical characterization of a flexible circular coil for magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Bautista, T.; Hernandez, R.; Solis-Najera, S. E.; Rodriguez, A. O.

    2012-10-01

    Numerical simulations of the magnetic field generated by a flexible surface coil were conducted to study its behavior for applications of animal models at 7 Tesla. This coil design is able to fully cover a volume of interest. The Finite Difference Method in Time Domain (FDTD) was used because of its ability to accurately model complex problems in electromagnetism. This particular coil design is best suited for regions of interests with a spherical shape, since B1 uniformity is not significantly attenuated as in the case of a circular-loop coil. It still remains to investigate the feasibility to actually construct a coil prototype.

  19. Method of preloading superconducting coils by using materials with different thermal expansion coefficients

    DOEpatents

    Heim, J.R.

    1993-02-23

    The invention provides a high magnetic field coil. The invention provides a preloaded compressive force to the coil maintain the integrity of the coil. The compressive force is obtained by reinforcing the coil with two materials of different thermal expansion rates and then heating the coil to 700 C to obtain the desired compression. The embodiment of the invention uses Nb[sub 3]Sn as the conducting wire, since Nb[sub 3]Sn must be heated to 700 C to cause a reaction which makes Nb[sub 3]Sn superconducting.

  20. Method of preloading superconducting coils by using materials with different thermal expansion coefficients

    DOEpatents

    Heim, Joseph R.

    1993-01-01

    The invention provides a high magnetic field coil. The invention provides a preloaded compressive force to the coil maintain the integrity of the coil. The compressive force is obtained by reinforcing the coil with two materials of different thermal expansion rates and then heating the coil to 700.degree. C. to obtain the desired compression. The embodiment of the invention uses Nb.sub.3 Sn as the conducting wire, since Nb.sub.3 Sn must be heated to 700.degree. C. to cause a reaction which makes Nb.sub.3 Sn superconducting.