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  • 1
    Electronic Resource
    Electronic Resource
    Time-dependent collisional-radiative model for quantitative study of nonequilibrium plasma (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5016-5027 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper fully time-dependent collisional-radiative (CR) calculations are used to study the highly dynamic nonequilibrium anode plasma in a magnetically insulated-diode experiment. The CR model for the C i–C iv atomic system is described in detail, including the radiative and collisional rates and the level structure of the system. The electron temperature is determined by comparing time-dependent line intensities for C ii and C iii ions to calculations of level-population ratios in which continuous particle injection from the anode surface into the plasma is taken into account. The electron temperature is approximately 7 eV. The time-dependent injected fluxes and the fluxes accelerated away from the plasma for C i, C ii, and C iii are determined by inverting the coupled CR rate equations. The calculated extracted flux near the end of the pulse is consistent with the measured carbon-ion current drawn from the plasma. Injection of excited particles is also investigated and is found to be important during the rise of the current pulse (≤50 ns). The importance of including multiple branching for ionization into excited final states is also shown. The time-dependent cooling rate due to inelastic electron-ion collisions and radiative processes is derived for general level-population distributions and is used to investigate the anode plasma. This work should also be relevant in the study of other pulsed-power nonequilibrium plasmas, such as recombining plasmas that have applications for UV and x-ray lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347089
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  • 2
    Electronic Resource
    Electronic Resource
    Treatment of ionization in plasma collisional-radiative calculations (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5028-5032 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper a method for treating electron collisional ionization in collisional-radiative calculations is presented that includes the effects of direct ionization into multiple excited states. Ionization from a given state proceeds to terms of the next ionization state using appropriate cross sections and branching ratios. Level populations are calculated for the case of a low-temperature (7 eV), moderate-density (ne=5×1015 cm−3) ionizing carbon plasma using a time-dependent collisional-radiative model. These results show appreciable differences when compared with calculations in which ionization is assumed to couple only into the ground state of the next ionization stage. Applications of these results to astrophysical and laboratory plasmas are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347196
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Radiation science using Z-pinch x rays : 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. 2186-2194 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Present-day Z-pinch experiments generate 200 TW peak power, 5–10 ns duration x-ray bursts that provide new possibilities to advance radiation science. The experiments support both the underlying atomic and plasma physics, as well as inertial confinement fusion and astrophysics applications. A typical configuration consists of a sample located 1–10 cm away from the pinch, where it is heated to 10–100 eV temperatures by the pinch radiation. The spectrally-resolved sample-plasma absorption is measured by aiming x-ray spectrographs through the sample at the pinch. The pinch plasma thus both heats the sample and serves as a backlighter. Opacity measurements with this source are promising because of the large sample size, the relatively long radiation duration, and the possibility to measure opacities at temperatures above 100 eV. Initial opacity experiments are under way with CH-tamped NaBr foil samples. The Na serves as a thermometer and absorption spectra are recorded to determine the opacity of Br with a partially-filled M-shell. The large sample size and brightness of the Z pinch as a backlighter are also exploited in a novel method measuring re-emission from radiation-heated gold plasmas. The method uses a CH-tamped layered foil with Al+MgF2 facing the radiation source. A gold backing layer that covers a portion of the foil absorbs radiation from the source and provides re-emission that further heats the Al+MgF2. The Al and Mg heating is measured using space-resolved Kα absorption spectroscopy and the difference between the two regions enables a determination of the gold re-emission. Measurements are also performed at lower densities where photoionization is expected to dominate over collisions. Absorption spectra have been obtained for both Ne-like Fe and He-like Ne, confirming production of the relevant charge states needed to benchmark atomic kinetics models. Refinement of the methods described here is in progress to address multiple issues for radiation science. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1459454
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  • 4
    Electronic Resource
    Electronic Resource
    Interferometric investigation of femtosecond laser-heated expanded states (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3869-3872 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simultaneous temporally and spatially resolved measurements of the phase change and reflectivity of S- and P-polarized femtosecond laser probes are obtained from hot expanded states produced by femtosecond laser heating of a solid aluminum target. The combined set of data provides an integral test of equation-of-state models in a regime up to 10 Mbar and densities of 0.01–1 times solid. The results suggest that target stoichiometry at the few Å level should be considered in the analysis of phase and reflectivity measurements in such experiments. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1394759
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  • 5
    Electronic Resource
    Electronic Resource
    Visible-light spectroscopy of pulsed-power plasmas (invited) : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 5127-5131 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the investigations of the plasma behavior in three pulsed-power systems: a magnetically insulated ion diode, and plasma opening switch, and a gas-puffed Z pinch. Recently developed spectroscopic diagnostic techniques allow for measurements with relatively high spectral, temporal, and spatial resolutions. The particle velocity and density distributions within a few tens of microns from the dielectric-anode surface are observed using laser spectroscopy. Fluctuating electric fields in the plasma are inferred from anisotropic Stark broadening. For the plasma opening switch experiment, a novel gaseous plasma source was developed which is mounted inside the high-voltage inner conductor. The properties of this source, together with spectroscopic observations of the electron density and particle velocities of the injected plasma, are described. Emission line intensities during the switch operation are discussed. In the Z-pinch experiment, spectral emission-line profiles of various charge-state ions are studied during the implosion phase. Radial velocity distributions are observed from the line Doppler shifts and widths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143461
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