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The geometric characteristics of low-frequency magnetic dipole fields and their relative insensitivity to the host media have made low-frequency coils useful for underground geolocation. A robust and succinct method is presented for converting dipole field measurements into estimates of receiver position. A noisy half-space model of the Earth is used to model the receiving environment. A perfectly conducting sphere immersed in a homogeneous conducting background is used to study the localized effects of buried metals. Index Terms--Half-space, loop antennas, magnetic dipoles.

Open-sleeve dipoles are versatile antennas primarily because they have several design parameters that can be varied to achieve a wide range of VSWR performance and operating bandwidth. By properly adjusting their parameters, it is possible to create versions of these antennas that have either a broadband or a dual-band response. In this paper, a new variation of the conventional open-sleeve dipole antenna is introduced, which we call an end-loaded planar open-sleeve dipole (ELPOSD). This configuration provides a degree of miniaturization while retaining a comparable bandwidth in terms of the VSWR response to that of conventional open-sleeve dipoles. Several designs are presented for the conventional and end-loaded configurations that demonstrate the VSWR and miniaturization capabilities of this class of antennas. Measured results have been compared with simulations and found to be in good agreement for an end-loaded planar open-sleeve monopole. Index Terms--Broadband antennas, genetic algorithms (GAs), open-sleeve dipole, printed antennas, small antennas.

We examine that an inductively loaded dipole becomes electrical invisible showing that the influence on a nearby antenna's input impedance and on its radiation pattern (scattering) are minimized. We also verify that the direction of the current reverses on the electrically invisible dipole so that the integral of the dipole current becomes zero. By making an inductive load with a distributed constant line, we fabricate an electrically invisible dipole without using chip devices and evaluate its performance. Furthermore, we propose electrically invisible conductor lines formed by connecting these electrically invisible dipoles in series using open stubs as connectors, and analytically examine their invisible state. Index Terms--Current, dipole, inductive, load, scatter.

In a beamforming system, mutual coupling among the elements can significantly degrade the system performance. However, the mutual coupling effects can be compensated if an accurate model of mutual coupling is available. This paper utilizes a mutual coupling matrix model to compensate mutual coupling in the beamforming of a uniform circular array. In addition, a circular array of dipoles was built and measurements were performed. The predictions are compared with measurements, and verified with results from full-wave simulations. Index Terms--Beamforming, compensation, mutual coupling matrix, uniform circular array.

We study the performance of various beamformers for estimating a current dipole source at a known location using electroencephalography (EEG) and magnetoencephalography (MEG). We present our beamformers in the form of the generalized sidelobe canceler (GSC). Under this structure, the beamformer can be solved by finding a filter that achieves the minimum mean-squared error (MMSE) between the mainbeam response and filtered observed signal. We express the MMSE as a function of the filter's rank and use it as a criterion to evaluate the performance of the beamformers. We do not make any assumptions on the rank of the interference-plus-noise covariance matrix. Instead, we treat it as low-rank and derive a general expression for the MMSE. We present numerical examples to compare the MSE performance of beamformers commonly studied in the literature: principal components (PCs), cross-spectral metrics (CSMs), and eigencanceler (EIG) beamformers. Our results show that good estimates of the dipole source signals can be achieved using reduced-rank beamformers even for low signal-to-noise ratio (SNR) values. Index Terms--Beamforming, dipole source signal, electroencephalography, low-rank covariance matrix, magnetoencephalography, sensor array processing.

The antenna theory model is widely employed to numerically simulate the propagation of current wave along lightning return stroke channels and compute the radiated electromagnetic fields. In this model, the channel is approximated as a vertically straight or a horizontally bent thin-wire antenna above perfectly conducting ground for which the numerical solution of the governing electric field integral equation in frequency domain by the conventional method of moment is prohibitively slow. This paper proposes an efficient algorithm to substantially reduce the computation time of the numerical process for the entire frequency components of the excitation current. In this algorithm, a class of predefined wavelet packet transform is first used to effectively sparsify the resulting moment matrix equations. A proper iterative solver is then utilized to take the full advantages of manipulatory sparse matrices. To accelerate the construction of the original moment matrix, the reciprocal closed-form mutual impedance of sinusoidal electric dipoles and the symmetry of the model are fully exploited. A good agreement is observed with computed data found in technical literature while the overall computational time is reduced remarkably. Index Terms--Antenna theory (AT) model, lightning return stroke, method of moment (MoM), sinusoidal dipoles, thin-wire electric field integral equation (EFIE), wavelet packet transform.

Far field radiation from an arbitrarily oriented Hertzian dipole for two-layered uniaxially anisotropic medium with a tilted optic axis is treated analytically by using the dyadic Green's function of the problem when the dipole is placed over or embedded in a two-layered uniaxially anisotropic medium. The radiation fields are evaluated using the steepest descent method. Parameter studies including anistoropy, layer thickness and dipole location are performed to investigate the effects of changing different variables on the radiation fields. Results of this work can be applied in microstrip circuits and antennas. Index Terms--Anisotropic medium, dyadic Green's function, far field radiation, Hertzian dipole.

The dipole-dipole interaction is significantly responsible for the dielectric behaviour of matter. In the past, several analytic models have been developed to describe these dielectric properties. With increasing performance of personal computers, bigger and bigger systems can be simulated numerically on a microscopic scale by calculating the local electric fields at each dipole site. In doing so and applying the method of image dipoles in order to consider the electrodes we can easily calculate the local fields, polarization and effective susceptibility for a system of nanometric size with dimensions smaller than 100 A which consists of more than one sort of atoms, e. g. binary mixtures, or different lattice constants. With this method all depolarization fields within the sample are regarded inherently. The different phases can be arranged differently so that we can investigate the influence of the granularity of the mixture. Defects and inclusions can also be easily included. We have studied for example the impact of an air-filled sphere in a dielectric on the effective susceptibility and simulated local fields for a pyramidal inclusion. For a given plane in the three-dimensional sample we can determine the local fields at (grain) boundaries. Index Terms--Local field, computational materials science, Lorentz field, dielectric polarization, induced dipoles, dipole-dipole interaction, nanodielectric composites, binary mixture, method of image dipoles, electrode effects.

For transient, time dependent polarization processes stretched exponential functions and power laws referred to as Kohlrausch relaxations are often observed in disordered dielectrics. These relaxations can be distributed in time or frequency over more than 12 decades. Among the various existing models for an interpretation two of them based on similar mathematics but different physical grounds are repeated. In these models charges, either electrons or protons, hop between adjacent sites. The distances between the sites are distributed resulting in a distribution of relaxation times. Then two new models which emerged in the last years are discussed. (I) It is shown that the dipolar interaction between dipoles of the same kind, i.e. without a distribution of any property, can result in Kohlrausch relaxations. (II) In solid electrolytic capacitors charges can be attracted by their images in the electrode. After application of an external voltage this charge attraction leads to an external current with a power law time dependence. Index Terms--Insulators, dielectric polarization, relaxation processes, Monte Carlo methods, distribution function, dipolar interaction, electrodes, Kohlrausch relaxations.

ALICE dipole magnet has a singe arm forward muon detector, which requires a dipole magnet with a very large aperture that would be installed next to the solenoid used in the L3 experiment of LEP. The magnet is currently assembled in the experiment underground carven in a location with convenient access conditions where it would be powered and tested during the last quarter of 2003.

The status of the test activities, showing results obtained on the first pre-series dipoles, including crosschecks of various measurements systems and correlation between measurements at room and cryogenic temperatures is reported.

The problems encountered to shape correctly the cold masses, their effect on interconnection of the dipole cold masses and on the mechanical aperture are described. On one side measures to improve the production process in terms of accuracy and reproducibility are taken, whereas on the other side the assembly tolerances could be relaxed following a through review of the machine requirements.

The results of a comprehensive analysis from the geometric point of view of the pre-series LHC dipoles are described. Data concerning the error on sagitta, extremity positions and sextupolar corrector positions are provided for the pre-series magnets.

The mechanical activity of full-scale prototype and first preseries LHC dipole magnets is assessed and correlations with magnet manufacturing procedures and quench performance are demonstrated. The statistical properties of different features of spike such as the maximal amplitude, the energy, the duration and the time correlation between events are presented.

Innovative concepts in transverse field magnet design are described and discussed.

Development of a single-layer common-coil magnet is being finalized at Fermilab. The magnet, which incorporates innovative design and technology features, is meant to be used in a future Very Large Hadron Collider.

A series of magnets, based on the 'Common Coil' configuration,' have been designed, fabricatedand tested. Tests of magnets RD-2 and RT-1 have been successfully completed, and RD-3 has tested to a record dipole field of 14.7 Tesla.

AC loss and dynamic magnetic field distortion in the main LHC dipoles is significant for assessment of the accelerator performance and for understanding the properties of assembled magnets. The loss due to current cycling in some 1-meter-long model dipoles, 15-meter-long dipole prototypes and pre-series magnets are measured, resitance between strands of opposite layers of the cable, R[subscript c], is evaluated for the inner winding of the dipole, and the method to estimate the R[subscript c] value in the outer winding is discussed.

Dynamic processes in a synchrotron bending magnet are investigated at the Heavy Ion Research Center (GSI), in Darmstadt, Germany. A hybrid method, based on an integro-differential approach to eddy currents in laminated structures and a volume integral formulation for the magnetization vector, is applied, and data obtained from the numerical simulation are compared with experimental results.

In this paper, we extend a previous prototype study [1] of frequency-domain (FD) and time-domain (TD) Green's functions for an infinite periodic phased line array of dipoles to account for the effects of truncation, as modeled by a semi-infinite array. These canonical problems are to be used eventually for the systematic analysis and synthesis of actual rectangular TD plane phased arrays. In the presentation, we rely on the analytic results and phenomenologies pertaining to the infinite array, which are reviewed. Major emphasis is then placed on the modifications introduced by the truncation. Finite Poisson summation is used to convert the individual dipole radiations into collective truncated wavefields, the FD and TD Floquet waves (FW). In the TD, exact closed-form solutions are obtained, and are examined asymptotically to extract FD and TD periodicity-matched conical truncated FW fields (both propagating and nonpropagating), corresponding tip-diffracted periodicity-matched spherical waves, and uniform transition functions connecting both across the FD and TD-FW truncation boundaries. These new effects can again be incorporated in a FW-modulated geometrical theory of diffraction. A numerical example of radiation from a [text unreadable in original source] phased TD dipole array with band-limited excitation demonstrates the accuracy and efficiency of the FW-(diffracted field) asymptotic algorithm when compared with an element-by-element summation reference solution. Index Terms--Antenna arrays, antenna transient analysis, arrays, Floquet waves (FW), periodic structures, time-domain analysis, time-domain Green's functions, transient analysis.

Two in one shell-type Nb3Sn dipole models for Very Large Haddron Colliders were designed and analyzed.

The high field dipole at Fermilab is discussed in terms of coil end parts design and fabrication issues.

BSCCO common coil dipoles were studied to determine persistent current effects.

Conductor development goals of the Advanced Technology Development Program are discussed, in terms of long term program strategy and results to date.

The Levitated Dipole Experiment is discussed in the context of the high temperature superconducting levitation coil.

Research describing a superconducting dipole, under construction at the National High Magnetic Field Laboratory, Florida, is presented. The purpose of the magnet is to bend beams of charged particles in nuclear physics experiments.

The development of high field superconducting dipole NB3Sn magnets for very large hadron collider by Fermilab is discussed.

Quenches in Large Hadron Collider superconducting dipole magnets protected by quench heaters were investigated with regard to temperature profiles.

Particle trajectories in dipoles of the ANKE magnetic spectrometer were determined using the floating wire method, and the measurements were found to compare well with field map trajectory calculations based on the GEANT code.

Warm magnetic measurements in a LHC main dipole prototype were analyzed and measured field harmonics compared to a numerical model.

A new system for sextupole measurements based on three Hall plates mounted on a ring is presented.

A new harmonic coil method for field measurements of the superconducting two LHC dipoles and linked corrector magnets is proposed.

Integrated and point measurements were undertaken of the Fermilab Main Injector dipoles, and the hysteretic field strength was also determined.

Stability against disturbances of the CMS coil have been evaluated and the minimum quench energy is shown to be between 0.43 and 0.85J.

The react and wind technique for a Nb3Sn common coil dipole is described and the results of measurements on strands and cable layout are reported.

The estimation of random errors problem in the Large Hadron Collider dipole is discussed, with regard to superconducting windings.

Friction effects in two LHC main dipole structures were studied using FEM computations.

The program of six LHC superconducting main dipole final prototypes is examined with regard to design, manufacturing status and first results.

Semi-statistical and full-statistical methods were used to study the effects of tolerance of the components on the structure of the Large Hadron Collider main dipole.

The effects of mechanical tolerances on the field quality of in the Large Hadron Collider dipoles are examined.

Fringe fields in the Large Hadron Collider main dipoles were calculated using the boundary element and the finite element technique.

Evoked dipole responses in unknown spatially correlated noise with EEG/MEG arrays have been estimated. Maximum likelihood (ML) ways of estimating evoked dipole responses using magnetoencephalography (MEG) and electroencephalography (EEG) arrays and an ML-based method for scanning brain response data are proposed. They make possible space-correlated noise between sensors with covariance not known. The electric source is modeled as a collection of current dipoles at fixed locations and the head as a spherical conductor. It can be used to state the multidimensional search needed to get the true dipole location estimates. Simulations show performance.

The systems for AC loss and magnetic field calculations developed for the Large Hadron Collider superconducting magnets are described. Loss measurements were conducted via an electric approach while field measurements were carried out through rotating coils or fixed pick-ups. Emphasis was on tests performed on a series of 1-m long dipole models. A summary of measurement results in terms of inter-strand contact resistance and measured field distortion is provided.

The need for a relatively inexpensive trouble free material for use in intermediate field accelerator magnets was the main purpose behind a study to produce ductile material with superior properties. Three alloys were tested. These were Tal7Ti44Nb39, Ta28Ti41Nb31 and Ta12Ti46Nb42. Processing as monofilamentary material was done for the three alloys and were then tested after a series of heat treatments. The samples were then tested at 1.9K with the shift in the field for a constant J(sub c') determined.

A new large bore 10 T @4.5 K Nb3Sn model is under the development stage in the Netherlands following the successful operation of the 11 T Nb3Sn experimental dipole magnet MSUT. An innovative 'powder in tube' type of Nb3Sn conductor with an increased number of filaments was developed by ShapeMetal Innovation for application in the system. The diameter of the filaments was reduced to about 20 microns after reacting for only 33 hours at 675 degrees C. The strand diameter used was 0.9 mm.

In contemporary imaging methods the magnitude of the electromagnetic signals is assumed to be independent of the distance between the radiating region and the receiver. The veracity of this assumption is evaluated for a typical Magnetic Resonance Imaging (MRI) scenario. Further, a more exact model of the MR signal based on magnetic dipoles is proposed and used for image reconstruction. The received signals are modeled using the complete electromagnetic field representation and the reconstructed images are compared with that using the models reported in literature. The difference that the complete form of the electromagnetic fields makes to the final reconstructed image is seen to be significant. Index terms - Magnetic Resonance Imaging, Magnetic dipole, Near Fields, Magnitude/Phase Modifying Factor

The effects of artifact repression by signal-space projection on dipole localization accuracy for magnetoencephalography measurements were investigated. Approximate analytical formulas, equivalent to the Cramer-Rao bound, were used and checked by Monte Carlo simulations which correlate the increase of localization error for individual coordinates to the similarity of the artifact field and respective quadrupole fields acquired by differentiating the dipole field with respect to its origin.

A study was conducted to analyze alternative expressions of doublets and rooftop basis functions that promote continuity equation at the junction. The basic characteristics of such doublets were examined and evaluated against other kinds of doublets. Results indicated that the exact formulation supports the continuity of equation and a constant current component normal to the interconnection.

The electromagnetic field generated by a current dipole situated at an arbitrary position inside a conducting sphere is derived using the expansions of the spherical vector wave functions. The first few terms in a series expansion of this field with respect to the frequency are given for the normal magnetic field (used in magnetoencephalogram) and the tangential electric field (used in electroencephalogram) outside the conducting sphere at low frequency. It is shown that the first correction term to the static solution is linear in the frequency [Omega] (the second correction term is proportional to [[Omega].sup.3/2]) and, thus, the static solution can be used as a good approximation for the solution at a very low frequency. Index Terms - Conducting sphere, current dipole, electroencephalogram, expansion, frequency series, low-frequency, magnetoencephalogram, spherical vector wave functions.

The generalized inverse method and singular value decomposition were used to reconstruct the magnetic image of small spherical inclusions in ferromagnetic structures. These techniques were used on the magnetic flux leakage generated when the structure is magnetized. The leakage field from the inclusions was simulated by using a simple constant-permeability model. The recovery model used a grid of magnetic dipoles at the region of the inclusions. The ability of the technique to distinguish between different distributions of inclusions with similar leakage fields is analyzed. The results demonstrates the feasibility of imaging multiple inclusions within the structure. Index terms - Nondestructive testing; inverse problems, magnetic measurements, magnetostatics.