Effect Of Inductive Coupling Research Articles

Modeling of Quench in the Coupled HTS Insert/LTS Outsert Magnet System of the NHMFL

The National High Magnetic Field Laboratory (NHMFL), Tallahassee, FL, USA, has developed a 32-T all-superconducting user magnet system combining two series-connected high-field high-temperature superconductor (HTS) nested inner coils (insert) wound with SuperPower REBCO tapes and a low-temperature superconducting (LTS) outer magnet (outsert) composed of five coils (broken in 17 electrical sections). As a part of the magnet development work, a number of quench tests were done on the HTS insert dual-coil prototype in the actual LTS outsert, mimicking the actual magnet configuration and operation. The tests on the coupled insert/outsert system were performed at 4.2 K, using a set of tailor-made quench protection heaters to be employed in the actual insert. In these tests, in the transition to the normal state, a noticeable part of the outsert stored energy could be transferred to the insert through the inductive coupling. The experimental results are analyzed here by means of a quasi-3-D COMSOL FEM model. The model, developed at the University of Bologna in collaboration with the NHMFL, enables one to calculate the coil temperature distributions, the internal voltages, and current evolution through the increase of normal zone resistances over the insert coils. A lumped parameter equivalent model of the magnet electric circuit permits including appropriately the effect of mutual inductive coupling between the insert and the outsert coils on the currents in them. Also, the model accounts for a time-varying 2-D distribution of the magnet field generated by both the insert and outsert within their coils in the event of a quench. The REBCO insert coils are described in terms of an anisotropic homogenized medium, albeit with due regard for the essentially nonlinear characteristics of the superconducting tapes and for the interturn stainless steel reinforcement and sol-gel alumina insulation. A detailed comparison between the numerical and experimental results provides detailed insights into the modes of propagation of the normal zones.

Effect of inter-tissue inductive coupling on multi-frequency imaging of intracranial hemorrhage by magnetic induction tomography

Magnetic induction tomography (MIT) is a promising technique for continuous monitoring of intracranial hemorrhage due to its contactless nature, low cost and capacity to penetrate the high-resistivity skull. The inter-tissue inductive coupling increases with frequency, which may lead to errors in multi-frequency imaging at high frequency. The effect of inter-tissue inductive coupling was investigated to improve the multi-frequency imaging of hemorrhage. An analytical model of inter-tissue inductive coupling based on the equivalent circuit was established. A set of new multi-frequency decomposition equations separating the phase shift of hemorrhage from other brain tissues was derived by employing the coupling information to improve the multi-frequency imaging of intracranial hemorrhage. The decomposition error and imaging error are both decreased after considering the inter-tissue inductive coupling information. The study reveals that the introduction of inter-tissue inductive coupling can reduce the errors of multi-frequency imaging, promoting the development of intracranial hemorrhage monitoring by multi-frequency MIT.

Effect of inductive and capacitive coupling on the current–voltage characteristic and electromagnetic radiation from a system of Josephson junctions

We have studied the current–voltage characteristic of a system of long Josephson junctions taking into account the inductive and capacitive coupling. The dependence of the average time derivative of the phase difference on the bias current and spatiotemporal dependences of the phase difference and magnetic field in each junction are considered. The possibility of branching of the current–voltage characteristic in the region of zero field step, which is associated with different numbers of fluxons in individual Josephson junctions, is demonstrated. The current–voltage characteristic of the system of Josephson junctions is compared with the case of a single junction, and it is shown that the observed branching is due to coupling between the junctions. The intensity of electromagnetic radiation associated with motion of fluxons is calculated, and the effect of coupling between junctions on the radiation power is analyzed.

Complex image method for RF antenna-plasma inductive coupling calculation in planar geometry. Part II: measurements on a resonant network

Measurements and analysis of a radio-frequency planar antenna are presented for applications in inductively-coupled plasma processing. The network of inductive and capacitive elements exhibits high currents under resonance which are efficient for plasma generation. Mode frequencies and impedances are accurately calculated by accounting for the mutual partial inductances using the impedance matrix. The effect of plasma inductive coupling on mode frequency shift and mode impedance is estimated using the complex image method, giving good agreement with experiment. It is proposed that the complex image method combined with the partial inductance concept (see the accompanying paper, Part I (Howling et al 2015 Plasma Sources Sci. Technol. 24 065014)) offers a general way to calculate the impedance characteristics of inductively-coupled plasma sources in planar geometry.

Effect of Second-Neighbor Inductive Coupling on the Modulational Instability in a Coupled Line of Transmission

In this work, the dynamics of modulated waves in a couple nonlinear LC transmission line is investigated. By employing the standard linear stability analysis, the growth rate of the instability is derived as a function of the wave numbers and system parameters. The regions of modulational instability can then be obtained and the influence of second-neighbor occuring via inductors in a nonlinear transmission line can be studied. As result, we found that the second-neighbor couplings add new maxima of gain; increase the group velocity, and the magnitude of the wave. Therefore, the network becomes more stable to small external perturbations.

Measurement and Analysis of Inductive Coupling Noise in 90 nm Global Interconnects

Inductive coupling is becoming a design concern for global interconnects in nanometer technologies. We present measurement results of the effect of inductive coupling on timing, and demonstrate that inductive coupling noise is a practical design issue in 90 nm technology. The measured delay change curve is consistent with circuit simulation results for an RLC interconnect model, and clearly different from those for a conventional RC model. The long-range coupling effect of inductive coupling, and noise reduction caused by ground insertion or decreased driver size were clearly observed on silicon. Examination of noise cancellation and superposition effects shown in measurement results confirm that the summation of delay variations due to each individual aggressor is a reasonable approximation of the total delay variation.

Subsurface resistivity measurements using square waveforms

This work analyzes the effect of inductive and capacitive coupling between the injecting circuit and the detecting circuit in resistive field surveys. Theoretical and experimental results demonstrate that if a square waveform is injected into the soil, and synchronous sampling is used to sample at the flat zone of the detected voltage, then the effect of the interference is greatly reduced. Furthermore, square waveforms are easier to generate than sinusoidal waveforms, so they offer a new approach to subsurface resistivity measurements.

Frequency response of metal-clad inductive magnetic field probes

The frequency response of an inductive magnetic field probe enclosed in a metal shell is calculated, including the important effect of inductive coupling between the probe coil and the shell. With an appropriate passive external circuit, the bandwidth of the system can be extended significantly beyond the cutoff frequency of the shell alone. A simple, noninvasive test shows that the model accurately predicts the behavior of magnetic probes in the DIII-D tokamak.

Terminal Response of Braided-Shield Cables to External Monochromatic Electromagnetic Fields

This paper has two purposes: (1) to assess the relative importance of magnetic and electric coupling parameters of braided shields in the determination of terminal response of braided-shield cables to external electromagnetic fields and (2) to compare a postulated coupling model with those on which various experimental determinations of shielding effectiveness have been based. In the first case, formulas for certain special conditions of wave incidence and sheath-conductor terminations are obtained, but their implications are not explored in detail. In the second case, certain discrepancies among various published methods of measurement and between the measurements and the postulated model are noted. The paper also shows formally how the external-field coupling parameters to each conductor of a multiconductor cable may be determined. A review of earlier work indicated that measurements made in the past have been largely incomplete. In some cases, only the effect of the inductance parameter was measured; in others, the composite effect of both inductive and capacitive coupling was measured, but attributed to inductance only. In either category, this analysis shows that the use of such a limited physical model will generally lead to inaccurate predictions of cable terminal response.

Design and Construction of High Magnetic Field Traveling Wave Lines

A pulsed, capacitively loaded helical line capable of generating 5000-G pulses is described. The line velocity is 15 cm/μsec. Titanate ceramics are used as the dielectric elements. The analysis and design take into account the often overlooked effect of inductive coupling between line elements. A formalism suitable for numerical computation of complicated systems is illustrated. The design can be extended to give a variable velocity 9-kG line.