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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

Electromagnetic direct implicit PIC simulation

Description: Interesting modelling of intense electron flow has been done with implicit particle-in-cell simulation codes. In this report, the direct implicit PIC simulation approach is applied to simulations that include full electromagnetic fields. The resulting algorithm offers advantages relative to moment implicit electromagnetic algorithms and may help in our quest for robust and simpler implicit codes.
Date: March 29, 1983
Creator: Langdon, A. Bruce
Partner: UNT Libraries Government Documents Department

Motion of ionized electrons under the intense electromagnetic field of the beam

Description: The motion of an electron ionized from residual gas by the beam becomes relativistic in the case of a high-density beam as in SLC, while the ions produced by the beam remain nonrelativistic. The ionized relativistic electron will be dragged by the beam, and will go away from the beam (electron beam) before the beam passes, even for the very short bunch of SLC. In this note, we discuss the motions of electrons ionized by the electron beam or by the positron beam. We assume that the density of the beam is uniform and the shape cylindrical (transversely round and longitudinally rectangular).
Date: September 1, 1983
Creator: Kamiya, Y.
Partner: UNT Libraries Government Documents Department

FELIX: construction and testing of a facility to study electromagnetic effects for first wall, blanket, and shield systems

Description: An experimental test facility for the study of electromagnetic effects in the FWBS systems of fusion reactors has been constructed over the past 1-1/2 years at Argonne National Laboratory (ANL). In a test volume of 0.76 m/sup 3/ a vertical pulsed 0.5 T dipole field (B < 50 T/s) is perpendicular to a 1 T solenoid field. Power supplies of 2.75 MW and 5.5 MW and a solid state switch rated 13 kV, 13.1 kA (170 MW) control the pulsed magnetic fields. The total stored energy in the coils is 2.13 MJ. The coils are designed for a future upgrade to 4 T or the solenoid and 1 T for the dipole field (a total of 23.7 MJ). This paper describes the design and construction features of the facility. These include the power supplies, the solid state switches, winding and impregnation of large dipole saddle coils, control of the magnetic forces, computer control of FELIX and of experimental data acquisition and analysis, and an initial experimental test setup to analyze the eddy current distribution in a flat disk.
Date: January 1, 1983
Creator: Praeg, W.F.; Turner, L.R.; Biggs, J.A.; Knott, M.J.; Lari, R.J.; McGhee, D.G. et al.
Partner: UNT Libraries Government Documents Department

Study of the tevatron nonlinear acceptance by computer simulation

Description: In this report, the results of computer calculations of nonlinear acceptance reduction caused by nonlinear fields in the TEVATRON are presented. A set of test particles has been traced during many revolutions in the accelerator in order to determine the maximum stable amplitude in the presence of nonlinear fields. Sources of nonlinear fields are designed imperfections of dipole and quadrupole magnets, fluctuations due to manufacturing tolerances, and sextupole fields needed to compensate for chromaticity.
Date: November 1, 1983
Creator: Willeke, F.
Partner: UNT Libraries Government Documents Department

Current sensing in magnetic fusion experiments by Faraday rotation in single-mode optical fibers

Description: We find that sensors exploiting the Faraday effect in single-mode optical fibers are practical means of measuring large currents in the MFE environment. Work still needs to be done to overcome the effects of linear birefringence. We have seen distortion caused by dynamic stress-induced birefringence and shown the importance of physically eliminating it because of the difficulty of treating it analytically.
Date: January 1, 1983
Creator: Chandler, G.I. & Jahoda, F.C.
Partner: UNT Libraries Government Documents Department

Electromagnetic effects on the FED/INTOR limiter

Description: Electromagnetic effects were among the critical issues of the impurity control system examined in the 1982 FED/INTOR design study. During a plasma disruption, the decaying plasma current induces voltages and currents in the first wall and limiter systems which can produce arcing between limiter segments and large forces and torques on the limiter. The effects of first wall time constant, limiter electrical resistance, and limiter segmentation on the voltages, forces, and torques were studied.
Date: January 1, 1983
Creator: Turner, L.R. & Foss, M.H.
Partner: UNT Libraries Government Documents Department

FELIX construction status and experimental program

Description: FELIX (Fusion Electromagnetic Induction Experiment) is an experimental test facility being constructed at Argonne National Laboratory (ANL) for the study of electromagnetic effects in the first wall/blanket/shield (FWBS) systems of fusion reactors. The facility design, construction status, experimental program, instrumentation, and associated computer-code comparisons are described.
Date: January 1, 1983
Creator: Turner, L.R.; Praeg, W.F.; Knott, M.J.; Lari, R.J.; McGhee, D.G. & Wehrle, R.B.
Partner: UNT Libraries Government Documents Department

Design of the electromagnetic fluctuations diagnostic for MFTF-B

Description: The Electromagnetic Fluctuations (EMF) diagnostic will be used to monitor ion fluctuations which could be unstable in MFTF-B. Each probe assembly includes a high impedance electrostatic probe to measure potential fluctuations, and a group of nested, single turn loops to measure magnetic fluctuations in three directions. Eventually, more probes and loops will be added to each probe assembly for making more detailed measurements. The sensors must lie physically close to the plasma edge and are radially positionable. Also, probes at separate axial locations can be positioned to connect along the same magnetic field line. These probes are similar in concept to the rf probes used on TMX, but the high thermal load for 30-second shots on MFTF-B requires a water-cooled design along with temperature monitors. Each signal channel has a bandwidth of .001 to 150 MHz and is monitored by up to four different data channels which obtain amplitude and frequency information. This paper describes the EMF diagnostic and presents the detailed mechanical and electrical designs.
Date: November 28, 1983
Creator: House, P.A.; Goerz, D.A. & Martin, R.
Partner: UNT Libraries Government Documents Department

Electromagnetic analysis for fusion reactors: status and needs

Description: Electromagnetic effects have far-reaching implications for the design, operation, and maintenance of future fusion reactors. Two-dimensional (2-D) eddy current computer codes are available, but are of limited value in analyzing reactors. Three-dimensional (3-D) codes are needed, but are only beginning to be developed. Both 2-D and 3-D codes need verification against experimental data, such as that provided by the upcoming FELIX experiments. Coupling between eddy currents and deflections has application in fusion reactor design and is being studied both by analysis and experiment.
Date: January 1, 1983
Creator: Turner, L.R.
Partner: UNT Libraries Government Documents Department

Beam-shape distortion caused by transverse wake fields

Description: As a particle bunch in a storage ring passes through a region with a transverse impedance, it generates a transverse wake electromagnetic field that is proportional to the transverse displacement of the bunch in the region. The field acts back on the bunch, causing various effects (such as instabilities) in the motion of the bunch. We study one such effect in which a transverse impedance causes the beam to be distorted in its shape. Observed at a fixed location in the storage ring, this distortion does not change from turn to turn; rather, the distortion is static in time. To describe the distortion, the bunch is considered to be divided longitudinally into many slices and the centers of change of the slices are connected into a curve. In the absence of transverse impedance, this curve is a straight line parallel to the direction of motion of the bunch. Perturbed by the transverse wake field, the curve becomes distorted. What we find in this paper is the shape of such a curve. The results obtained are applied to the PEP storage ring. The impedance is assumed to come solely from the rf cavities. We find that the beam shape is sufficiently distorted and hence that loss of luminosity due to this effect becomes a possibility.
Date: February 1, 1983
Creator: Chao, A.W. & Kheifets, S.
Partner: UNT Libraries Government Documents Department

MAGFOR: a magnetics code to calculate field and forces in twisted helical coils of constant cross section

Description: The machine-independent computer program MAGFOR calculates electromagnetic fields and forces in coil systems of arbitrary geometry. The coils may be modeled by using 20-node isoparametric hexahedrons; 8-node rectangular cross-sectional straight segments; rectangular cross-sectional circular arcs; and/or filamenting circular loops. A combination of analytical and numerical integration of the Biot-Savart law for a volume distribution of current is used for calculating magnetic fields. Volumetric body forces are calculated for the 20-node isoparametric brick by numerically integrating the vector product J x B over its volume, where the magnetic field at each Gauss point is obtained by interpolating the magnetic field at the node points by using shape functions. The force is distributed to the node points of the element, again using the shape functions in a consistent manner that maintains inter-element torsion. Body forces obtained from MAGFOR are compared with body forces from the computer code EFFI for several coil configurations considered in the design of the Advanced Toroidal Facility (ATF).
Date: January 1, 1983
Creator: Cain, W.D.
Partner: UNT Libraries Government Documents Department

Higher-order modes calculation of rf cavity with cylindrical symmetry

Description: This paper represents a new computer calculating method for cylindrical symmetry cavities. This method can calculate not only the fundamental mode and longitudinal modes but also the transverse higher modes. The Hertz vector is used as fundamental quantity and the separated variable method is applied. An empty cylindrical cavity has been calculated. The calculating result is in accord with analytic solution fairly well.
Date: January 1, 1983
Creator: Zhou, W.; Xuanwen, C. & Mingda, Z.
Partner: UNT Libraries Government Documents Department

Wide-bandwidth test fixture for electromagnetic-beam sensors

Description: The Fusion Materials Irradiation Test (FMIT) accelerator will supply the neutron flux required for studying materials that may be used in a fusion environment. The diagnostic measurement instrumentation, which will characterize the accelerator beam, must be noninterceptive because of the beam's power density. Instrumentation also must be fully functional for start up of the FMIT accelerator. To this end, three types of test facility were proposed: (1) a low-energy electron accelerator, (2) a large electron-gun assembly, and (3) a coaxial structure that produces electromagnetic fields similar to that of the proposed FMIT accelerator. The third type was chosen. This paper describes the design and some experimental results of the coaxial test fixture.
Date: January 1, 1983
Creator: Gilpatrick, J.D.; Sherwood, B.A.; Hahn, J. & Chamberlin, D.D.
Partner: UNT Libraries Government Documents Department

Physics of the synchrotron model of cosmic gamma-ray bursts

Description: We review the theoretical arguments leading to the thermal synchrotron model of cosmic gamma-ray bursts. We propose a magnetic flare-resonant absorption mechanism for the production of the hot electrons that can account for most of the unusual properties of the emission layer.
Date: September 27, 1983
Creator: Liang, E.P.
Partner: UNT Libraries Government Documents Department