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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 62 (1958), S. 1574-1578 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7520-7527 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intense heliumlike sodium 11-A(ring) line radiation is required to resonantly photopump a neon plasma in the Na-Ne soft x-ray laser scheme. The implosion of a NaF capillary-discharge plasma with a 3-MA peak current is used to produce a power exceeding 100 GW in this Heα line. The power is optimized by varying both the initial radius of the 3-cm-long NaF plasma column and the time delay between the capillary current and the generator current. Maximum power of 115 GW is obtained for implosions which occur just after peak current. Burn-through of the heliumlike sodium stage is evident in spectroscopic measurements where sodium Lyα line emission is 2–4 times stronger than Heα emission. Mass loadings of 200–400 μg/cm are inferred from measured implosion times and initial plasma diameters. The nearly pure density dependence of the Heα power and the nearly pure temperature dependence of the Lyα/Heα ratio allow the state of the plasma to be determined by measuring both quantities on a single shot. For these implosions, electron temperatures are 350–560 eV and total ion densities approach 1020 cm−3. The mass load inferred from implosion dynamics is consistent with the ion density deduced from spectral measurements.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Implosions of 2.5-cm-diam neon gas shells on a 1.2 μs quarter-period, 3 MA driver, FALCON, have produced no more than 7.6 kJ of kilovolt neon K-shell radiation. The incorporation of a plasma opening switch produces faster current pulses: up to 1.8 MA in 190 ns. With the higher rate of rise of current, neon gas puffs have produced up to 13.5 kJ of kilovolt K-shell radiation. Numerical calculations indicate that this increase in radiation is due to the achievement of a higher kinetic energy per ion at higher current levels. Spectroscopic measurements confirm that a significant fraction of the plasma is heated into the K-shell ionization states and that the faster current pulses increase this fraction up to 40%.
    Type of Medium: Electronic Resource
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  • 4
    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.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2188-2203 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Annular Al-wire Z-pinch implosions on the Saturn accelerator [D. D. Bloomquist et al., Proceedings, 6th Pulsed Power Conference (Institute of Electrical and Electronics Engineers, New York, 1987), p. 310] that have high azimuthal symmetry exhibit both a strong first and weaker second x-ray burst that correlate with strong and weaker radial compressions, respectively. Measurements suggest that the observed magnetic Rayleigh–Taylor (RT) instability prior to the first compression seeds an m=0 instability observed later. Analyses of axially averaged spectral data imply that, during the first compression, the plasma is composed of a hot core surrounded by a cooler plasma halo. Two-dimensional (2-D) radiation magnetohydrodynamic computer simulations show that a RT instability grows to the classic bubble and spike structure during the course of the implosion. The main radiation pulse begins when the bubble reaches the axis and ends when the spike finishes stagnating on axis and the first compression ends. These simulations agree qualitatively with the measured characteristics of the first x-ray pulse and the overall energetics, and they provide a 2-D view into the plasma hydrodynamics of the implosion.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1673-1691 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quasianalytic model of the dynamic hohlraum is presented. Results of the model are compared to both experiments and full numerical simulations with good agreement. The computational simplicity of the model allows one to find the behavior of the hohlraum radiation temperature as a function of the various parameters of the system and thus find optimum parameters as a function of the driving current. The model is used to investigate the benefits of ablative standoff and quasispherical Z pinches. © 2001 American Institute of Physics.
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  • 7
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Z-pinch radiation source has been developed that generates 60±20 kJ of x rays with a peak power of 13±4 TW through a 4-mm-diam axial aperture on the Z facility. The source has heated National Ignition Facility-scale (6-mm-diam by 7-mm-high) hohlraums to 122±6 eV and reduced-scale (4-mm-diam by 4-mm-high) hohlraums to 155±8 eV—providing environments suitable for indirect-drive inertial confinement fusion studies. Eulerian-RMHC (radiation-magnetohydrodynamics code) simulations that take into account the development of the Rayleigh–Taylor instability in the r–z plane provide integrated calculations of the implosion, x-ray generation, and hohlraum heating, as well as estimates of wall motion and plasma fill within the hohlraums. Lagrangian-RMHC simulations suggest that the addition of a 6 mg/cm3 CH2 fill in the reduced-scale hohlraum decreases hohlraum inner-wall velocity by ∼40% with only a 3%–5% decrease in peak temperature, in agreement with measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Aluminum wire array, Z-pinch experiments have been performed on an 8 MA generator using arrays consisting of 24, 30, and 42 wires. These experiments were designed to scan through a region of (array mass, implosion velocity) space in which greater than 30% conversion of the implosion kinetic energy into K-shell x rays was predicted to occur [Thornhill et al., Phys. Plasmas 1, 321 (1994)]. Array masses between 120 and 2050 μg/cm were used in these experiments. An analysis of the x-ray data taken using 24 wire arrays, shows a one-to-one correspondence between the observed kilo-electron-volt yields (5–64 kJ) and the fraction of initial array mass (0.3%–60%) that is radiating from the K shell. The 30 and 42 wire experiments demonstrated that tighter pinches with increased radiated powers were achieved with these larger wire number, improved symmetry arrays. In addition, increases in the implosion mass and array diameter in the 30 and 42 wire number cases resulted in increases in the radiated yield over the corresponding 24 wire shots, up to 88 kJ, which can be interpreted as due to improved coupling and thermalization of the kinetic energy. Moreover, spectroscopic analyses of the 30 and 42 wire experiments have shown that the increased wire numbers also resulted in K-shell radiating mass fractions of greater than 50%. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2807-2809 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: X-ray pinhole images are formed on microchannel plate striplines to time-resolve Z-pinch emissions. Applications include a study of Z-pinch linearity necessary for x-ray lasers, the evolution of hot spots, and a study of Z-pinch heating mechanisms. In particular, multiple pinholes per strip with different filters allow the spatial and temporal variation of different temperature regions to be studied.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2804-2806 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A stripline gated microchannel plate framing camera is used as a detector in a crystal spectrometer. Typical 10 ns time gates are fast enough to record the evolution of both heating and expansion of Z pinches. By introducing spatially imaging cross slits, an x-ray spectrum from a Z pinch has been simultaneously space and time resolved.
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