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An Electric and Magnetic Field Sensor for Simultaneous Electromagnetic Near-Field Measurements -- Theory

Description: Abstract: This paper describes the theory of a single sensor to perform simultaneous electric and magnetic near-field measurements. The theory indicates that it is possible to obtain the magnetic-loop and electric-dipole currents using a loop terminated with identical loads at diametrically opposite points. The theory also indicates that it is possible to obtain an ideal load impedance for achieving equal electric and magnetic field responses of the loop. Preliminary experiments have been performed using plane waves to verify these results. Key words: electric field, electromagnetic interference, electromagnetic radiation, loop, magnetic field, near fields.
Date: April 1983
Creator: Kanda, Motohisa
Partner: UNT Libraries Government Documents Department

An Enhanced Magnetic Mirror Machine

Description: Abstract: "A dc magnetic mirror machine has been built and tested by the ARC Research Group. Radiofrequency enhancement has been included in the design through the use of rf plates in the vacuum chamber of the machine. For the proton beams of the order of 1[mu]a, the mirror action has been observed as a function of both the rf voltage and the magnitude of the mirror field relative to the main magnetic field. Current measurements were performed with the aid of a Faraday cup with suitable bias grids."
Date: July 15, 1954
Creator: Ford, Franklin C.
Partner: UNT Libraries Government Documents Department

Final report [The 15th Workshop on Electromagnetic Induction in the Earth, held 8/20-26/2000, and The 5th Magnetotelluric Data Interpretation Workshop, 8/17-19/2000]

Description: This document reports on how the DOE helped to support travel of students and scientists to the conferences in Brazil. Attendee names, funding, and session titles are listed.
Date: June 25, 2002
Creator: Alumbaugh, David L.
Partner: UNT Libraries Government Documents Department


Description: SEPARATORS. C. W. Sheridan, H. R. Gwinn, and L. O. Descriptions are given of procedures, techniques, and equipment used to prepare charge materials for electromagnetic isotope separators at ORNL. Data on ion outputs during processing, charge consumption rates, and process efficiencies are given for 54 elements. (auth)
Date: August 1, 1962
Creator: Sheridan, C W; Gwinn, H R & Love, L O
Partner: UNT Libraries Government Documents Department

Small Aperture Analysis of the Dual TEM Cell and an Investigation of Test Object Scattering in a Single TEM Cell

Description: Introduction: Small aperture theory is used to investigate the dual TEM cell. Analyzing coupling through an empty versus a loaded aperture leads to a model of dual TEM cell shielding effectiveness measurements. Small obstacle scattering yields results for both the field perturbation and the change in a cell's transmission line characteristics due to the presence of a test object in a TEM cell. In each case, theoretical values are compared to experimental data.
Date: 1984
Creator: Wilson, Perry F. & Ma, Mark T.
Partner: UNT Libraries Government Documents Department

A Study of Techniques for Measuring the Electromagnetic Shielding Effectiveness of Materials

Description: Abstract: Shielding effectiveness relates to a material's ability to reduce the transmission of propagating fields in order to electromagnetically isolate one region from another. Because a complex material's shielding capability is difficult to predict, it often must be measured. A number of measurement approaches are studied including the use of a shielded room, coaxial transmission line holders, time domain signals, the dual TEM cell, and an apertured TEM cell in a reverberation chamber. In each case, we consider the system's frequency range, test sample requirements, test field type, dynamic range, time required, analytical background, and present data taken on a common set of materials.
Date: May 1986
Creator: Wilson, Perry F. & Ma, Mark T.
Partner: UNT Libraries Government Documents Department

A Theory of Mutual Impedances and Multiple Reflections in an N-Element Array Environment

Description: Abstract: A general theoretical approach is formulated to describe the complex electromagnetic environment of an N-element array. The theory reveals the element-to-element interactions and multiple reflections within the array. From the formulation, it is found that the interaction between an excited element and an open-circuited element can be viewed as the sum of terms describing all possible signal paths within the array environment which start from the radiating element and terminate on the element under observation. Within all paths except the most direct one, multiple reflections between subgroups of elements take place. The resulting solution is highly structured and recursive and is discussed in detail in the text. Illustrative examples are provided to facilitate understanding of these ideas.
Date: February 1985
Creator: Muth, Lorant A.
Partner: UNT Libraries Government Documents Department

Possible Estimation Methodologies for Electromagnetic Field Distributions in Complex Environments

Description: Abstract: The problem of measuring and characterizing complicated multiple-source, multiple-frequency electromagnetic environments is becoming more important and more difficult as electrical devices proliferate. This paper outlines three general approaches to the problem which are currently under investigation at the National Bureau of Standards. The three approaches are: 1) a statistical treatment of the spatial distribution of electromagnetic field intensities, 2) a numerical computation using a finite-difference (or lattice) form of the electromagnetic action functional, and 3) use of a directional probe to scan a volume. All three methods are still in the development stage, but each appears promising.
Date: March 1985
Creator: Kanda, Motohisa; Randa, J. & Nahman, N. S.
Partner: UNT Libraries Government Documents Department

Design of the National Bureau of Standards Isotropic Magnetic Field Meter (MFM-10) 300 kHz to 100 MHz

Description: From introduction: In this report the following will he discussed: (1) design consideration of the broadband magnetic field sensor, (2) overall design of the magnetic field meter, (3) performance of the meter, (4) calibration and operating procedures, (5) alignment and adjustment procedures, and (6) summary and conclusions.
Date: October 1985
Creator: Cruz, J. E.; Driver, L. D. & Kanda, Motohisa
Partner: UNT Libraries Government Documents Department


Description: Most methods of separating isotopes depend on the use of a large magnetic field. The isotron is an electromagnetic device for separating isotopes, but it effects the separation by the use of radiofrequency voltages instead of magnetic fields. It has the advantage that plane sources of large area can be used instead of the slit sources to which most magnetic methods are limited. Before entering into any discussion of the details, a simplified description of the principles of the method is given.
Date: July 30, 1950
Creator: Wilson, R.R.
Partner: UNT Libraries Government Documents Department

Inverse Cherenkov and inverse FEL accelerator experiments at the Brookhaven Accelerator Test Facility

Description: Status update on the ongoing inverse Cherenkov acceleration experiment and prospects to its 100 MeV short-term upgrade. The first report on 1 MeV electron acceleration with the 0.5 GW CO{sub 2} laser used in the inverse FEL scheme. (author). 22 refs., 8 figs., 1 tab.
Date: December 31, 1995
Creator: Pogorelsky, I.V.; vanSteenbergen, A. & Babzien, M.
Partner: UNT Libraries Government Documents Department

Use of the continuity equation for electromagnetic energy flow to describe radiation transport

Description: The continuity equation for electromagnetic (EM) energy flow is used to describe radiation flow in the transport regime. The scheme of a discrete representation of H<sub>z</sub> and a stochastic representation of H<sub>x</sub>, H<sub>y</sub> gives an effectively continuous representation of directed energy in the x-y plane, such that the ray effect of transport theory is absent. Since the in-plane amplitudes are generated at each time step, it is necessary to store only the perpendicular amplitudes and the results appear to be robust with respect to the coarse of this discretization.
Date: February 5, 1999
Creator: Ritchie, A B
Partner: UNT Libraries Government Documents Department

Excitation of a TEM Cell by a Vertical Electric Hertzian Dipole

Description: From abstract: The excitation of a transverse electromagnetic (TEM) cell by a vertical electric Hertzian dipole is analyzed where the gap between the septum and side wall is assumed to be small. Approximate expressions for the field distribution and characteristic impedance are derived. These expressions are numerically evaluated for some typical geometries, and good agreement with previously published results is shown. The formation also allows a vertical offset for the septum position, thus offering more flexibility of increasing the size of the test area to accommodate larger pieces of test equipment.
Date: March 1981
Creator: Wilson, Perry F.; Chang, David C. & Ma, Mark T.
Partner: UNT Libraries Government Documents Department

Low-Frequency Electromagnetic Backscattering from Tunnels

Description: Low-frequency electromagnetic scattering from one or more tunnels in a lossy dielectric half-space is considered. The tunnel radii are assumed small compared to the wavelength of the electromagnetic field in the surrounding medium; a tunnel can thus be modeled as a thin scatterer, described by an equivalent impedance per unit length. We examine the normalized backscattering width for cases in which the air-ground interface is either smooth or rough.
Date: January 16, 2007
Creator: Casey, K & Pao, H
Partner: UNT Libraries Government Documents Department