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Inverse analysis of temperature-time data with grossly different time scales using Beck`s second method and the Frankel-Keyhani whole-domain technique

Description: In general, inverse heat conduction analysis utilizes the measured temperature history at one or more internal locations to estimate unknown boundary conditions, energy generation rates, or thermophysical properties. Analysis of these data using conventional numerical heat transfer techniques yields numerically unstable solutions; that is, small perturbations in the input data can produce large variations and instabilities in the output. Previous attempts to overcome this inherent instability have involved the utilization of future information and Tikhonov regularization techniques (Beck et al, 1985). In the 1970`s and 80`s, Beck and coworkers developed a family of techniques that overcome this obstacle by relating the surface property at any time in the transient to temperatures measured after that time in the transient (Beck, 1970, Beck et al, 1982). That is, future information is used to determine present conditions. For many purposes, these techniques are the standard analysis tools. An alternative approach has been developed recently by Frankel and Keyhani (1997). This approach utilizes a whole domain form in which the entire space-time domain of interest is simultaneously resolved; the traditional instability occurs only near the final time endpoint and can be excluded from the resulting solution. Rapid convergence and accurate results have been demonstrated using this approach. Two sets of time-temperature data have been analyzed using both of these techniques.
Date: November 1, 1998
Creator: Park, J.E.; Frankel, J.I.; Keyhani, M. & Osborne, G.E.
Partner: UNT Libraries Government Documents Department

The importance of EBIT data for Z-pinch plasma diagnostics

Description: The results from the last six years of x-ray spectroscopy and spectropolarimetry of high energy density Z-pinch plasmas complemented by experiments with the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory (LLNL) are presented. The two topics discussed are the development of M-shell x-ray W spectroscopic diagnostics and K-shell Ti spectropolarimetry of Z-pinch plasmas. The main focus is on radiation from a specific load configuration called an 'X-pinch'. X-pinches are excellent sources for testing new spectral diagnostics and for atomic modelling because of the high density and temperature of the pinch plasmas, which scale from a few {micro}m to several mm in size. They offer a variety of load configurations, which differ in wire connections, number of wires, and wire materials. In this work the study of X-pinches with tungsten wires combined with wires from other, lower-Z materials is reported. Utilizing data produced with the LLNL EBIT at different energies of the electron beam the theoretical prediction of line positions and intensity of M-shell W spectra were tested and calibrated. Polarization-sensitive X-pinch experiments at the University of Nevada, Reno (UNR) provide experimental evidence for the existence of strong electron beams in Ti and Mo X-pinch plasmas and motivate the development of x-ray spectropolarimetry of Z-pinch plasmas. This diagnostic is based on the measurement of spectra recorded simultaneously by two spectrometers with different sensitivity to the linear polarization of the observed lines and compared with theoretical models of polarization-dependent spectra. Polarization-dependent K-shell spectra from Ti X-pinches are presented and compared with model calculations and with spectra generated by a quasi-Maxwellian electron beam at the LLNL EBIT-II electron beam ion trap.
Date: April 4, 2007
Creator: Safronova, A S; Kantsyrev, V L; Neill, P; Safronova, U I; Fedin, D A; Ouart, N D et al.
Partner: UNT Libraries Government Documents Department