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Advanced design and modeling concepts for recombination x-ray lasers

Description: Geometric, kinetic, and trapping issues, in short and ultrashort recombination x-ray lasers, are discussed. The design of a composite target consisting of a lasant strip on a plastic backing is described. Examples of modeling showing the effect of photon trapping and uncertainties in other physical processes on calculated gain coefficients are given. A simple and accurate expression for photon trapping in cylindrical geometry is presented. Recombination lasers that have the ground state as the … more
Date: November 29, 1990
Creator: Eder, D.C.; Rosen, M.D.; Shephard, R.; Staffin, R.; Nash, J.K. & Keane, C.J.
Partner: UNT Libraries Government Documents Department
open access

Particle distributions in collisionless magnetic reconnection: An implicit Particle-In-Cell (PIC) description

Description: Evidence from magnetospheric and solar flare research supports the belief that collisionless magnetic reconnection can proceed on the Alfven-wave crossing timescale. Reconnection behavior that occurs this rapidly in collisionless plasmas is not well understood because underlying mechanisms depend on the details of the ion and electron distributions in the vicinity of the emerging X-points. We use the direct implicit Particle-In-Cell (PIC) code AVANTI to study the details of these distributions … more
Date: June 29, 1990
Creator: Hewett, D. W.; Francis, G. E. & Max, C. E.
Partner: UNT Libraries Government Documents Department
open access

Modified-Yee field solutions in the AMOS wakefield code

Description: A new numerical procedure by which field calculations in AMOS are upgraded to model rotationally symmetric cavity structures in a more accurate fashion is described. The development work is aimed at implementing a modified finite difference update scheme on an irregular grid system. Elements of an irregular grid may be chosen to better fit object boundaries, resulting in increased solution accuracy. Our approach involves the placement of field components on a non-orthogonal body fitting grid an… more
Date: August 29, 1990
Creator: Shang, C. C. & DeFord, J. F.
Partner: UNT Libraries Government Documents Department
open access

Preprocessing of ion microtomography data for improved reconstruction quality

Description: In Ion Microtomography (IMT), material densities are determined from the energy lost by ions as they pass through a specimen. For fine-scale measurements with micron-size beams, mechanical stability and precision of motion can impact the quality of the reconstruction. We describe several preprocessing procedures used to minimize imperfect specimen manipulation, including adjustment of the center of mass motion in sinograms and correction for vertical translations. In addition, the amount of noi… more
Date: November 29, 1990
Creator: Weirup, D. L.; Pontau, A. E.; Antolak, Arlyn J.; Morse, Dan H.; Bench, G.; Cholewa, M. et al.
Partner: UNT Libraries Government Documents Department
open access

Bit-string scattering theory

Description: We construct discrete space-time coordinates separated by the Lorentz-invariant intervals h/mc in space and h/mc{sup 2} in time using discrimination (XOR) between pairs of independently generated bit-strings; we prove that if this space is homogeneous and isotropic, it can have only 1, 2 or 3 spacial dimensions once we have related time to a global ordering operator. On this space we construct exact combinatorial expressions for free particle wave functions taking proper account of the interfer… more
Date: January 29, 1990
Creator: Noyes, H. P.
Partner: UNT Libraries Government Documents Department
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