Discussion of the Influence of Multiple Factors on the Shielding of Magnetic Field in the Railgun’s Bore

Shielding of magnetic fields (magnetic shielding) by rare earth-based REBCO coated conductors with a highly oriented superconducting layer was measured. The shielding of magnetic fields was measured using a Hall effect sensor installed between bundles consisting of commercial REBCO conductors 12 mm in width. Measurements of the shielding of magnetic fields by other commercial high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconductors were performed for comparison. The shielding of magnetic fields was found to depend on the number of conductors in the bundle and the route of the applied magnetic fields and was observed even for fields over 10 T. In steady magnetic fields, a temporal change in the shielding of magnetic fields, that is, a decay of shielding currents induced in conductors against applied magnetic fields, was measured. The temporal change of the shielding of magnetic fields exhibited the behavior typical of high-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconductors, as explained by the flux creep model. Remanent magnetic fields measured in the experiments of the shielding of magnetic fields suggest that the bundle can be used as a magnet. A quasi-bulk magnet consisting of 100 Zr-doped Zr:REBCO conductors could hold over 3 T at 4.2 K.

The method of adjustment of a two-circuit system of the active shielding of the magnetic field generated by single-circuit overhead transmission lines with a triangular arrangement of wires based on experimental measurements space-time characteristics was developed. The problem of synthesis of two degree of freedom robust two circuit system of active shielding of initial magnetic field comes down to a decision of the multi-criteria two-player zero-sum antagonistic game. During the design of system spatial location coordinates of two shielding windings, the currents in the both shielding windings and the vector of parameters of regulators were determined. The vector of payoff game calculated based on Biot-Savart's law. The game decision calculated based on the stochastic particles multiswarm optimization algorithms. Computer simulation and field experimental research of two circuit system of active shielding of magnetic field, generated by overhead power lines with phase conductor's triangle arrangements are given. The possibility of initial magnetic field reducing to the sanitary standards level is shown.

Modeling of the magnetic field generated by overhead power lines with different type of arrangements of wires and with different space-time characteristic carried out. Two degree of freedom robust system of active shielding of magnetic field for such magnetic field synthesized. The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis of the Maxwell equations quasi-stationary approximation solution. The game decision is based on the stochastic particles multiswarm optimization algorithms. It is shown, that for effective shielding of the magnetic field generated by power lines with horizontal arrangement of wires, single shielding winding is sufficient. However, with a triangular arrangement of wires, two shielding windings are required. It is show that synthesized system of active shielding is reduced magnetic flux density up to the sanitary standards of Ukraine on reference levels of power frequency magnetic fields in shielding space located near the overhead power lines.

An experimental investigation of the shielding of electric and magnetic fields is reported, for both constant and changing fields. The effect of using iron shells, or sheets, for shielding against the fields of permanent magnets, as well as those set up by electric currents, is considered; the best form for the iron sheets is deduced and an expression for a measure of the shielding action is suggested. The reason for the leakage of magnetic and electric fields is shown to be due to differences of magnetic or electric potentials in the circuit in which the fluxes are being set up; several cases are cited in which no external fields are set up, as the circuits exhibit no differences in potential. An expression for the shielding effect of a short-circuited coil is deduced and experimental verification is offered for frequencies between 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cycles per second. Finally the shielding effect of metal sheets against changing magnetic fields is analyzed and experimental results are given to show how the action depends upon the characteristics of the material of which the shielding plate is made, its thickness, and upon the frequency being used. The effect of slits in the metal sheet, and the value of wire mesh, is indicated.

Power frequency magnetic field shielding is used for protection of sensitive electronic devices and data storage media and for prevention of interference in video display unit operation. The interest in magnetic field shielding is growing due to increasing concern of possible health effects on persons exposed to power frequency magnetic field. In the surrounding of substations, magnetic fields of power frequency can arise with flux densities in the range between 1 /spl mu/T and 10 /spl mu/T. These fields are mainly produced by busbars, cables and transformers. A primary source of the magnetic field in the substation is generally the cable section from the transformer secondary terminal. Eddy currents and magnetisation induced in metal enclosures, special shields and other conductive and ferromagnetic structures are secondary sources. When the rearrangement of substation equipment is not possible, magnetic field shielding around the sources can be implemented to reduce power frequency magnetic fields in the vicinity of a substation. It is common to associate ferromagnetic materials with magnetic field shielding. Various types of steel have frequently been used for shielding. However, conductive materials with no ferromagnetic properties, such as aluminium and copper, can also perform well as magnetic field shielding materials.

The purpose of the work is to design an electromagnetic shield to reduce the level of the magnetic field generated by double-circuit overhead power lines to increase the shielding efficiency of the initial magnetic field in residential buildings to the level of sanitary standards and reduce the sys-tem's sensitivity to changes in system parameters. To achieve this goal, the structure of the electro-magnetic shield is determined, which consists of a single-circuit active and multi-circuit passive parts and is characterized by an increased efficiency of reducing the magnetic field of industrial frequency. The design of an electromagnetic shield is reduced to solving a minimax vector optimization problem, in which the vector objective function is calculated based on solutions of Maxwell's equations in a quasi-stationary approximation using the COMSOL Multiphysics software package. The solution of the minimax vector optimization problem is calculated on the basis of optimization algorithms by a multiswarm of particles from Pareto-optimal solutions. The most important results are theoretical and experimental studies of the effectiveness of the designed electromagnetic shield of the magnetic field generated by double-circuit overhead power lines. The significance of the results obtained lies in the fact that practical recommendations are given on the reasonable choice of the spatial arrangement of the contours of the multi-circuit passive screen and the shielding winding of the robust system of elec-tromagnetic shielding of the magnetic field generated by double-circuit overhead power lines. The possibility of reducing the induction of the initial magnetic field to the level of sanitary standards has been shown as well.

Aim. Development of the method of designing a combined electromagnetic shield, consisting of active and passive parts, to improve the effectiveness of reduction of industrial frequency magnetic field created by two-circuit overhead power lines in residential buildings. Methodology. The problem of design of combined electromagnetic shield including robust system of active shielding and electromagnetic passive shield of initial magnetic field solved based on of the multi-criteria two-player antagonistic game. The game payoff vector calculated based on the finite element calculations system COMSOL Muliphysics. The game solution calculated based on the particles multiswarm optimization algorithms. During the design of combined electromagnetic shields spatial location coordinates of shielding winding, the currents and phases in the shielding winding of active shielding, geometric dimensions and thickness of the electromagnetic passive shield are calculated. Results. The results of theoretical and experimental studies of combined electromagnetic passive and active shielding of magnetic field in residential building from power transmission line with a «Barrel» type arrangement of wires presented. Originality. For the first time the method of designing a combined electromagnetic shield, consisting of active and passive parts, for more effective reduction of the magnetic field of industrial frequency created by two-circuit overhead power lines in residential buildings is developed. Practical value. Based on results of calculated and experimental study the shielding efficiency of the initial magnetic field determined that shielding factors whith only electromagnetic passive shield is more 2 units, whith only active shield is more 4 units and with combined electromagnetic passive and active shield is more 10 units. It is shown the possibility to reduce the level of magnetic field induction in residential building from power transmission line with a «Barrel» type arrangement of wires by means of a combined electromagnetic passive and active shielding with single compensating winding to 0.5 μT level safe for the population. References 53, figures 15.

The aim of the work is to design a robust hybrid active-passive magnetic field shielding system created by overhead power lines with a triangular arrangement of phase wires, designed to increase the shielding efficiency of the initial magnetic field in residential premises to the level of sanitary standards and reduce the system's sensitivity to changes in system parameters. To achieve this goal, the following tasks were solved: the structure of a hybrid system of active-passive shielding was developed, and the synthesis of a system consisting of a double-circuit active and multi-circuit passive parts was performed. The synthesis of the system is reduced to solving a vector game, in which the vector payoff is calculated based on the solutions of the Maxwell equations in the quasi-stationary approximation using the COMSOL Multiphysics software. The solution of a multicriteria game is found on the basis of algorithms for optimizing a multi-swarm of particles from Pareto optimal solutions, taking into account binary preference relations. The most important results are theoretical and experimental studies of the effectiveness of the synthesized hybrid active-passive shielding system for the magnetic field created by overhead power lines with a triangular arrangement of phase wires in the shielding zone. The significance of the results obtained lies in the fact that in the course of designing a hybrid active and multiloop passive screens, the parameters of passive and active screens were calculated; as well as practical recommendations are given on the reasonable choice of the spatial arrangement of a multi-loop passive shield and two shielding windings of a robust system of hybrid shielding of the magnetic field created by overhead power lines with a triangular arrangement of phase wires.

In terms of electrical safety, electric shock prevention and arc protection are the two most common topics. In such special fields like live-line maintenance — especially at high voltage levels — some “invisible” sources of danger also occur. Long-term health effects of extra-low frequency electric and magnetic fields are mostly unknown, yet. One of the aims of electrical engineering is to keep even the occupational values of these fields below the limits during any time and type of live-line activities. Effective shielding of electric fields can be achieved by conductive clothing acting as Faraday-cages; this paper focuses on the critical points of high voltage LLM in terms of the protection against magnetic fields.

Active shielding of overhead line magnetic field: Design and applications

8 Data Acquisition in Chemistry

&lt;sec&gt;Polarized neutron scattering, as one of the experimental techniques of neutron scattering, is a powerful tool for exploring the microstructure of matter. In polarized neutron scattering experiments, magnetic field maintains and guides the neutron polarization, and determines the sample magnetic environment. For complex magnetic sample, it is often necessary to apply zero-field environment at the sample position, so that general polarization analysis becomes feasible. To achieve effective zero-field environment for polarized neutron experiment, carefully designed magnetic field is required.&lt;/sec&gt;&lt;sec&gt;In this work, we demonstrate a zero-field sample chamber designed for polarized neutron experiment by utilizing both permalloy material and high-&lt;i&gt;T&lt;/i&gt;&lt;sub&gt;C&lt;/sub&gt; superconducting films. This design adopts a simple and low-maintenance ‘deep-well’ shape to achieve effective shielding. The study uses finite element simulation method to analyze the effect of dimensions on the magnetic field shielding performance of the device of the model, including height, arm length, opening radius, and superconductor distance. At optimal dimensions, the designed zero field chamber achieves an internal magnetic field integral of 0.67 G·cm along the neutron path under the geomagnetic field condition. The maximum neutron depolarization for 0.4 nm neutrons is 0.76%, which sufficient for general polarization analysis application. The finite element method simulation results are examined by neutron Bloch equation dynamics simulations and in-lab measurement . Based on the established effective zero-field shielding design, we further discuss the relationship between magnetic field shielding and the dimensions of the device. The application of the device to spectrometers and the future improvement in the device structure are also discussed.&lt;/sec&gt;

A worst-case wideband model for estimation of effectiveness of electric and magnetic field shielding by a rectangular metallic enclosure, the walls of which can contain rectangular or circular apertures, is developed. The model is based on a combination of analytical solutions of the following two problems: transmission of electromagnetic radiation through the aperture and propagation of the radiation in lossy waveguides. The analytical solutions ensure high computational efficiency of the model in a wide frequency range. The developed model makes it possible to estimate the effectiveness of external field shielding by a metallic board-system hull (the hull of a car, aircraft, ship, etc.) the internal compartments of which can be approximated by a rectangular waveguide. In order to do this, it is necessary to define the amplitude-frequency characteristic (AFC) for the loaded Q-factor of the compartment under consideration. Such AFC takes into account the presence of objects inside the compartment as well as the field absorption in the compartment walls, and it can be calculated (analytically or numerically) or measured. The developed model is validated by comparison of calculation results obtained by the model with known experimental results and with results of numerical simulation (ratios of the wavelength to the maximum dimension of the enclosure from 0.1 to 1000 are examined). Examples of modeling of the shielding enclosures containing the apertures of various sizes and shapes (circular, rectangular with different ratios of the sides) are considered; the number of apertures is varied from 1 (window) to 1000 (mesh).

Influences of the axial magnetic field and Faraday shield on the performance of RF produced plasma using a spiral antenna are investigated. The RF power and filling pressure dependences, antenna-plasma coupling, Ar line intensities and spatial profiles of plasma parameters are studied. With the magnetic field and/or without a Faraday shield, the threshold input power for plasma initiation is lowered and the antenna-plasma coupling is improved. In addition, a collisionless heating mechanism is suggested. With the increase in the applied magnetic field, the ion saturation current increases and shows a peaked radial profile; in the low-pressure range it shows a nearly flat axial profile.

Magnetic field trapping and shielding by several unirradiated single-grain YBa2Cu3O7−δ disks have been investigated between 4.2 and 71 K up to 20 T. Flux avalanches due to thermal instabilities limited the trapping field to ∼5 T below 45 K and often caused microcracks in the disks. However, a shielding field greater than 19 T was detected at 4.2 K in the same sample assembly even after it was damaged by flux avalanches. This violates the expected symmetry between shielding and trapping fields. The shielding field of ≳19 T exceeds the total quench field of 10 T predicted by the Swartz–Bean model. The observations suggest that thermomechanical properties play an important role in field shielding and trapping and mechanical stress may be effectively used to enhance the field trapped by disks of high temperature superconductors.