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  • 1
    Digitale Medien
    Digitale Medien
    Clinical chemistry (1983)
    s.l. : American Chemical Society
    Analytical chemistry 55 (1983), S. 202-214 
    Details
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac00256a008
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  • 2
    Digitale Medien
    Digitale Medien
    An efficient tabulated collisional radiative equilibrium radiation transport model suitable for multidimensional hydrodynamics calculations (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3480-3489 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A computationally efficient method for transporting radiation in multidimensional plasmas has been developed and evaluated. The basis of this method is a uniform plasma approximation that allows one to utilize existing escape probability techniques that are successfully used in one-dimensional (1D) calculations to approximately solve the multidimensional radiation transport problem. This method is superior to diffusion methods because (1) the probability of escape technique insures that the plasma goes to the correct optically thin and thick limits, (2) the effects of line absorption due to photoexcitations are modeled, and (3) this method uses source functions that are based on a self-consistent nonlocal thermodynamic equilibrium calculation, not an ad hoc assumption that the source functions are Planckian. This method is highly efficient because equation of state information from 1D calculations is tabulated as a function of plasma internal energy, ion density, and the line probability of escape from a uniform plasma, and then used in multidimensional calculations. Given the internal energy and ion density, and by calculating the line probability of escape from a zone of the multidimensional plasma, the equation of state, including emissivities and absorption coefficients, of the zone is determined from the table. Total radiative power, K-shell radiative power, total radiative yield, K-shell radiative yield, and plasma density and temperature profiles obtained from 1D Z-pinch calculations employing this method are in good agreement with the same powers, yields, and profiles calculated using a full radiation transport model. This method has been implemented in the 2D plasma radiating imploding source model code [F. L. Cochran et al., Phys. Plasmas 2, 2765 (1995)] to determine the influence of radiation transport in argon Z-pinch experiments performed on the Z machine [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1373415
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  • 3
    Digitale Medien
    Digitale Medien
    Trends in plasma conditions inferred from an analysis of x-ray data from high wire-number, Z-pinch load implosions (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3708-3717 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: An analysis of x-ray data from two series of Z-pinch shots taken on the short current-risetime Saturn accelerator at Sandia National Laboratories [Proceedings of 6th International IEEE Pulsed Power Conference, Arlington, VA, edited by P. J. Turchi and B. H. Bernstein (IEEE, New York, 1987), p. 310] is presented. In one series, the array radius was held constant and the array mass was varied; in the other series, the array mass was held constant and its radius varied. In both sets of experiments, large wire-number loads (N≥93) of aluminum were used in contrast to earlier small wire-number aluminum array experiments on Saturn where N≤42. Average electron temperatures and ion densities were inferred from the data. In addition, from the measured size of the emission region of K-shell x rays and from the inferred ion density, a fraction of the total array mass that participated in the K-shell emission was inferred and found to be directly correlated to the K-shell yields that were measured. This paper also demonstrates that the yields varied as a function of array mass and radius in much closer agreement with predictions [J. Appl. Phys. 67, 1725 (1990)] than had been observed in the earlier small wire-number experiments. Thus, a serious misperception that the reason for the early disagreement was in the calculations and not in the experiments is corrected. These predictions were made using one-dimensional (1D) magnetohydrodynamics calculations. The density and temperature trends inferred from the data analysis are well-behaved and consistent with the 1D calculations. This data analysis confirms the importance of achieving uniform plasma initial conditions and implosion symmetry when comparing computer code calculations with experiment. When the wire number of an array load is increased, a more uniform shell of plasma is calculated initially as the wires explode and, as the plasma stagnates on axis, the x-ray powers and yields are found experimentally to approach the powers and yields predicted by 1D calculations. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1380695
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  • 4
    Digitale Medien
    Digitale Medien
    High energy photon radiation from a Z-pinch plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4509-4517 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A new approach to the generation of kilovolt x ray radiation in Z-pinch plasma radiation sources is proposed. In cases where the pulse power machine has insufficient energy to efficiently produce K-shell emission from the atomic number element that emits in the required kilovolt energy range, it may be advantageous to produce x rays by recombination radiation emitted from a lower atomic number plasma. The optimal load conditions for maximizing the high energy free–bound continuum radiation that can be produced in a given spectral range are analyzed. The largest yield is expected from a highest-atomic-number element that could efficiently produce K-shell yield on a given pulse power machine. Two options available for the choice of a wire array material to generate x rays with photon energies above 7–8 keV are identified and discussed, aluminum and titanium. The analytical estimates and simulation results for "Z" machine implosions show that continuum radiation from an aluminum plasma in this spectral range could exceed the K-shell output from nickel. If a titanium plasma could be ionized to a H-like state on "Z," then its yield above 7 keV should be higher compared to that of aluminum by a factor of 3 to 4. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1398572
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  • 5
    Digitale Medien
    Digitale Medien
    Comparative analysis of time-resolved and time-integrated x-ray data from long pulse Z-pinch implosions on Saturn (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3799-3809 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Two series of Al:Mg wire array Z-pinch implosions were performed on the Saturn pulsed-power generator [R. B. Spielman et al., in Proceedings of the 2nd International Conference on Dense Z-Pinches, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3]. In one series, the wire number was varied, in the other, the load mass was varied. In all cases an initial array diameter of 40 mm was maintained. Sufficient x-ray data were obtained in these experiments to allow the plasma conditions to be inferred by matching x-ray data to that calculated by a collisional-radiative equilibrium (CRE) model. In fitting the data, the plasma has been assumed to be either uniform [zero dimension (0D)] or to vary one-dimensionally (1D) with radius. On one shot, a comparison of these two methods of data analysis performed with both time-resolved and time-integrated data has been carried out. While the same trends in plasma conditions as a function of load mass and wire number are seen, the uniform plasma assumption yields higher electron temperatures, lower core densities, but higher K-shell radiating mass fractions than those obtained from the 1D assumption. When comparing time-resolved and time-integrated spectroscopic data, a pronounced difference is seen in a density-sensitive line ratio whose time-resolved values corroborate experimental evidence that much of the K-shell radiation is emitted from a high density core plasma of spatial extent less than about 300 μm. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1381565
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  • 6
    Digitale Medien
    Digitale Medien
    Model of enhanced energy deposition in a Z-pinch plasma (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3265-3277 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In numerous experiments, magnetic energy coupled to strongly radiating Z-pinch plasmas exceeds the thermalized kinetic energy, sometimes by a factor of 2–3. An analytical model describing this additional energy deposition based on the concept of macroscopic magnetohydrodynamic (MHD) turbulent pinch heating proposed by Rudakov and Sudan [Phys. Reports 283, 253 (1997)] is presented. The pinch plasma is modeled as a foam-like medium saturated with toroidal "magnetic bubbles" produced by the development of surface m=0 Rayleigh-Taylor and MHD instabilities. As the bubbles converge to the pinch axis, their magnetic energy is converted to thermal energy of the plasma through pdV work. Explicit formulas for the average dissipation rate of this process and the corresponding contribution to the resistance of the load, which compare favorably to the experimental data and simulation results, are presented. The possibility of using this enhanced (relative to Ohmic heating) dissipation mechanism to power novel plasma radiation sources and produce high K-shell yields using long current rise time machines is discussed. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.874192
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  • 7
    Digitale Medien
    Digitale Medien
    The physics of radiation transport in dense plasmas : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 2411-2419 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Radiation transport redistributes energy within a medium through the emission and reabsorption of photons. These processes also have a pronounced effect on the spectrum of radiation that escapes the medium. As the deliverable energies of plasma drivers such as lasers and pulsed-power generators steadily increase, denser and/or more massive plasmas can be created. Such plasmas are more absorptive to their own emitted radiation, with portions of the line spectrum frequently being highly opaque. Thus, radiation transport becomes more important, along with the need to consider its impact on the design of experiments and their diagnosis. This tutorial paper covers the basic theory and equations describing radiation transport, its physical effects, experimental examples of transport phenomena, and current challenges and issues. Among the specific topics discussed are requirements for local thermodynamic equilibrium (LTE), conditions for diffusion and the use of the diffusion approximation, the formation of emission and absorption lines, the approach of an emitted spectrum to the Planck limit, and diagnostic applications of transport effects. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1446038
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  • 8
    Digitale Medien
    Digitale Medien
    Analyzing spatially resolved line spectra emitted by Z pinches (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3399-3404 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The spatial profiles of key physical variables such as electron temperature and density are crucial in determining the overall radiating efficiency of a Z pinch as well as the emitted photon energy distribution. The present work uses spatially resolved x-ray lines emitted from shots taken on the 4 MA Double EAGLE generator [C. Deeney et al., Phys. Rev. A 44, 6762 (1991)] at Maxwell Physics International to infer such profiles. The loads were arrays of 15 wires consisting of 95% Al, 5% Si, producing nearly 50 kJ of K-shell radiation with relatively long pulsewidths of 41–43 ns. It is found that the spatial profile of the He-like intercombination to resonance line ratio is critically affected by self-absorption and re-emission (scattering) of resonance line photons emitted from the hot, dense interior of the pinch. This ratio cannot be correctly interpreted without taking the scattering into account. Also, at densities somewhat lower than those achieved by these pinches, this line ratio becomes more temperature than density dependent. The inferred temperature gradient is much less steep than that which had been diagnosed previously for a pinch emitting a much shorter x-ray pulsewidth of 13 ns. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.874203
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  • 9
    Digitale Medien
    Digitale Medien
    Cervical intraepithelial neoplasia and ‘warty’ atypia: a study of colposcopic, histological and cytological characteristics (1982)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 89 (1982), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary. Colposcopic, histological and cytological characteristics of 168 consecutive patients attending a colposcopy clinic were reviewed. A group of patients demonstrated a cluster of histological features previously related to possible human papilloma virus infection of cervical epithelium, including particularly koilocytosis, double nucleation and dyskeratosis. These patients had a significantly greater occurrence of colposcopic ‘finger-like’ lesion outline and colposcopic impression of warty change, but not of other specific colposcopic features. Over two-thirds of patients with histological warty features did not show these colposcopic changes. Cytological changes previously related to warty lesions did not occur commonly, and appeared to underestimate the histological occurrence of such changes. Histological changes considered to represent CIN were uncommon in patients who said that they had begun sexual activity less than 10 years ago, whereas patients with warty characteristics on histology showed no such bias.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1982.tb03662.x
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  • 10
    Digitale Medien
    Digitale Medien
    Treatment of cervical intraepithelial neoplasia by colposcopically directed cryosurgery and subsequent pregnancy experience (1982)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 89 (1982), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Summary. Of 420 patients attending a colposcopy clinic 204 were treated with outpatient cryosurgery for cervical intraepithelial neoplasia. It was possible to assess a definite outcome of therapy in 159 patients, and the lesion was successfully eradicated in 87% of them. Treatment failure appeared to be more common in patients of high parity, when the lesion extended into the cervical canal, and in those patients with large lesions. Failure appeared to be unrelated to patient age and to the histological grade of the lesion. In subsequent pregnancies utero-cervical function was preserved.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1982.tb05082.x
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