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Evaluation of the discrete complex-image method for a NEC-like moment-method solution

Description: The discrete image approximation for the field of a half-space is tested in the NEC antenna modeling program as an alternative to the interpolation method presently used. The accuracy and speed of the discrete image approximation are examined for varying number of images and approximation contour, and the solution for current is obtained on a horizontal wire approaching the interface.
Date: January 5, 1996
Creator: Burke, G.J.
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

Quantitative measurements of magnetic vortices using position resolved diffraction in Lorentz STEM

Description: A number of electron column techniques have been developed over the last forty years to permit visualization of magnetic fields in specimens. These include: Fresnel imaging, Differential Phase Contrast, Electron Holography and Lorentz STEM. In this work we have extended the LSTEM methodology using Position Resolved Diffraction (PRD) to quantitatively measure the in-plane electromagnetic fields of thin film materials. The experimental work reported herein has been carried out using the ANL AAEM HB603Z 300 kV FEG instrument 5. In this instrument, the electron optical column was operated in a zero field mode, at the specimen, where the objective lens is turned off and the probe forming lens functions were reallocated to the C1, C2, and C3 lenses. Post specimen lenses (P1, P2, P3, P4) were used to magnify the transmitted electrons to a YAG screen, which was then optically transferred to a Hamamatsu ORCA ER CCD array. This CCD was interfaced to an EmiSpec Data Acquisition System and the data was subsequently transferred to an external computer system for detailed quantitative analysis. In Position Resolved Diffraction mode, we digitally step a focused electron probe across the region of interest of the specimen while at the same time recording the complete diffraction pattern at each point in the scan.
Date: March 5, 2002
Creator: Zaluzec, N. J.
Partner: UNT Libraries Government Documents Department

CSR IMPEDANCE DUE TO A BEND MAGNET OF FINITE LENGTH WITH A VACUUM CHAMBER OF RECTANGULAR CROSS SECTION

Description: We study the impedance due to coherent synchrotron radiation (CSR) generated by a short bunch of charged particles passing through a dipole magnet of finite length in a vacuum chamber of a given cross section. Our method represents a further development of the previous studies: we decompose the electromagnetic field of the beam over the eigenmodes of the toroidal chamber and derive a system of equations for the expansion coefficients in the series. We illustrate our general method by calculating the CSR impedance of a beam moving in a toroidal vacuum chamber of rectangular cross section.
Date: June 5, 2009
Creator: Stupakov, G.; /SLAC; Kotelnikov, I.A. & U., /Novosibirsk State
Partner: UNT Libraries Government Documents Department