Magnetic field measurement within superconducting windings by CLTS temperature sensors

Magnetoresistance of the CLTS temperature sensor was determined in dependence on field and temperature. Based on its significant negative magnetoresistance and due to its small dimensions this sensor can be used to measure magnetic field within superconducting magnet windings. This method has been applied in the 3 coil arrangement of our superconducting TESPE torus magnet system and good agreement has been found with calculated field data.     

Magnetic field distribution in a ferromagnetic conductor

The magnetic field distribution in a cylindrical ferromagnetic conductor is determined for the case of a direct current flowing along the axis of the cylinder and a constant external magnetic field applied in a direction transverse to the current flow. The Gauss-Seidel iteration method is employed to obtain the vector potentials for different values of current and external field with the aid of a digital computer. The magnetic fields are then calculated from the resultant vector potentials. Calculations are carried out for currentI = 1.5A, radius of the cylindera = 2mm, and external magnetic fieldB_{0} = 0to 0.6 Wb/m².     

Assessment of inhomogeneous ELF magnetic field exposures

In daily life as well as at workplaces, exposures to inhomogeneous magnetic fields become very frequent. This makes easily applicable compliance assessment methods increasingly important. Reference levels have been defined linking basic restrictions to levels of homogeneous fields at worst-case exposure conditions. If reference levels are met, compliance with basic restrictions can be assumed. If not, further investigations could still prove compliance. Because of the lower induction efficiency, inhomogeneous magnetic fields such as from electric appliances could be allowed exceeding reference levels. To easily assess inhomogeneous magnetic fields, a quick and flexible multi-step assessment procedure is proposed. On the basis of simulations with numerical, anatomical human models reference factors were calculated elevating reference levels to link hot-spot values measured at source surfaces to basic limits and allowing accounting for different source distance, size, orientation and position. Compliance rules are proposed minimising assessment efforts.     

Magnetic junction switching by joint action of current pulse and magnetic field: numerical simulation

The process of magnetic junction switching by a spin-polarized current pulse in the presence of an external magnetic field has been numerically simulated at the current densities and magnetic fields below the corresponding threshold values for separate effects. It is established that the switching can be performed with controlled delay relative to the current pulse.     

Combination of finite and boundary elements for magnetic field analysis

A procedure is proposed which utilizes combined Finite Elements Method and Boundary Elements Method for magnetic field analysis. Given a region constituted by sub-regions, some of which require a dense discretization, the field analysis is carried out by using the Finite Elements Method, and the Boundary Elements Method is used for the other sub-regions which require a large discretization. The procedure is applied for studying the magnetic field due to a coil and the obtained results are compared with the values given by formulas known in the scientific literature[5].     

Computation of the magnetic field in massive conductor systems

Some analytical expressions are reported for the calculation of the magnetic induction and the vector potential in iron-free media due to slab-shaped elements in which a current flows uniformly or linearly distributed in one direction. It is seen that no matter what current distribution functions and conductor geometries are considered, they can be approximated by a series of slabs in which the current distributions are represented by a sum of linear and constant distributions. The algorithms can also be used to calculate the magnetic field in more complicated geometries and to evaluate the self- and mutual-inductance coefficients in systems with massive conductors     

On the motion of macroparticles in inhomogeneous magnetic field

The behavior of macroparticles that form a near-wall dust in tokamaks is described with allowance for the force of gravity, force of entrainment by plasma ion flux, and Lorentz force acting on the motion of charged macroparticles in an inhomogeneous magnetic field. It is shown that, in some cases, the effect of induced currents that arise in the particles during this motion must in some cases be taken into account.     

Formation of a thermal structure in an inhomogeneous metal conductor under a high-density electric current

The heating of a metal conductor with a localized inhomogeneous inclusion by a high-density electric current is discussed.Novosibirsk Electrotechnical Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 4, pp. 617–623, April, 1992.     

Influence of a transverse magnetic field on the current distribution in parallel superconducting wires

In a system of parallel superconducting wires, which are connected at their ends, any two conductors form a closed superconducting loop, in which, according to the law of induction, no variation of the enclosed magnetic flux can occur. If a transverse magnetic field is applied to the system, the closed superconducting loops oppose the penetration of this field. As a consequence currents are induced in the conductors, whose magnetic field generates a certain current distribution, resulting from the geometrical arrangement of the conductors.The theoretical treatment depends upon whether the conductors are in the mixed or in the Meissner state. The current distribution was investigated in planar wire arrangements as well as in systems with wires positioned on a circle.     

Simultaneous measurement of two DC magnetic field components by asingle magnetoresistor

The method relies on a special excitation mode which causes uniform rotation of magnetization in the plane of a barber-pole magnetoresistive sensor. It is interesting that the uniform rotation of the magnetization is attained when the excitation field is not uniformly rotating. The rotation of this field should rather be elliptically polarized. The two orthogonal components of an external in-plane measured dc field disturb the uniform rotation of the magnetization in different instances of time. This behavior of the magnetization enables simultaneous but still separate measurements of both external field components by detection of the time shifts between the corresponding zero-crossing points of the sensor ac output and the zero-crossing points of the corresponding orthogonal components of the excitation field. The experimental results confirm the applicability of the method. Possible applications are reviewed     

Magnetic field perturbation and magnetic stress analysis due to aferromagnetic first wall

Based on a magnetization integral equation, a magnetic field analysis method was developed for 3-D complicated components formed by thin shells. The agreement between numerical results and experimental ones was good, confirming the validity of this method. The method was applied to the analysis of magnetic induction and stress in a ferromagnetic first wall for a tokamak power reactor. It was found that the wall could be used in a fusion reactor without much problem     

Computation of magnetic field produced by two plane-parallel keepered current straps

An integral/matrix-equation formulation is utilized to calculate the two-dimensional magnetic field produced by two plane and parallel keepered current straps. The mathematical formulation of the problem and its numerical solution are discussed in detail. Results are presented for the magnetic field inside and outside the permeable keepers, assuming different values for the thickness, width, and relative permeability of the keepers.     

Magnetic chains of Co spheres synthesized by hydrothermal process under magnetic field

Hydrothermal process under magnetic fields is successfully used to synthesize Co chains using reduction approach by carefully controlling the reaction conditions. The formation of the chain structure might be that magnetic fields drive the nanoscale crystals of Co to form chains. The Co sphere size and chain length are analyzed by X-ray diffraction (XRD) and scan electron microscopy (SEM). The result of the vibrating sample magnetometer (VSM) shows that the magnetic chains possess the saturation magnetization of 102 emu/g. The factors on the magnetic properties of the magnetic nanochains are discussed.     

Mixed magnetooptical contrast induced by an inhomogeneous magnetic field in metal films with planar anisotropy

Magnetooptical (MO) images induced by a strongly inhomogeneous external magnetic field in magnetic metal films with planar anisotropy have been studied. In the polar Kerr effect geometry, MO images created by the normal magnetization component is observed. In the meridional Kerr effect geometry, a superposition of the MO images (mixed MO contrast) is observed, which is determined by the distribution of the normal and horizontal magnetization components. Calculation of distribution of magnetization in a film is carried out, a field of magnetic system corresponding to coordinate dependence and are simulated corresponding MO images and the corresponding MO images have been simulated, which demonstrate satisfactory agreement between the theory and experiment.     

The identification of the switching field distribution components

A direct method for measuring the ratio of the interaction field distribution and the critical field distribution in a wide variety of longitudinal recording media is presented. The method requires only the measurement of m_p, the normalized remanence of the sample at the conclusion of the magnetizing process H_sal, -h_ci , +h_ci, where H_sat is a field large enough to saturate it and h_ci is the operative remanence coercivity. In conjunction with major loop measurements, the method obtains both the standard deviation in the interaction field distribution and the standard deviation in the critical field distribution. Experimental verification of the proposed technique is presented     

Degradation of critical current in an HTS coated conductor considering curvature of ellipse for rotating flux pump

A rotating HTS flux pump is used to study the charging characteristics of superconducting synchronous motor. In order to design the rotating flux pump, the elliptical winding is essential. Numerous studies have been conducted on the degradation of the critical current with respect to the bending condition of the second generation (2G) high-temperature superconducting (HTS) tape. These studies focused on the same radius of curvature depending on the bending position. Therefore, in this paper, the critical current in a HTS coated conductor (CC) considering the curvature of elliptical shape is measured with regard to nine mandrels. These are a tall prolate ellipsoid, oblate ellipsoid and semicircle. In the tall prolate ellipsoid, the degradation of the critical current was the least. The diameters of each shape are 20, 30 and 40 mm, respectively. Finally, the experimental observations have been compared with the theoretical predictions.     

Formation of coulomb clusters from charged diamagnetic microparticles in inhomogeneous magnetic field

The possibility of levitating Coulomb clusters formed by charged diamagnetic microparticles in an inhomogeneous magnetic field has been theoretically substantiated and experimentally confirmed. An experimental setup is described, in which the Coulomb clusters can be formed from charged graphite particles 100–300 μm in size and maintained stable between the poles of an electromagnet generating a magnetic field with induction B ∼ 10⁴ G and gradient |∂B| ∼ 10⁵ G/cm.     

Output microwave radiation power of low-voltage vircator with external inhomogeneous magnetic field

Dependence of the power of a broadband microwave radiation generated by a low-voltage oscillator with virtual cathode (vircator) on the parameters of an external inhomogeneous magnetic field has been studied by numerical simulations using a two-dimensional model. It is established that there are optimum parameters of the generator (configuration of the external magnetic field, electron beam current) for which the output radiation power is maximum. A relationship between the optimum conditions of virtual cathode formation in the electron beam and the microwave generation regime is established.     

智能球铰链空间磁场分布仿真及其影响分析

智能球铰链中球头周边磁场分布对其测量范围和分辨率有直接的影响。该文设计一种新的结构形式,采用多个永磁体和多个磁效应传感器沿球面阵列布置的方案改善测量分辨率,给出其理论模型和新的数值积分算法。Maxwell软件的仿真结果证实理论模型的正确性,并运用理论建模完成相应的理论分析,得出永磁体和传感器的最佳空间位置匹配,对于进一步提高智能球铰链的分辨率和精度有重要意义。