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  • 1
    Electronic Resource
    Electronic Resource
    Radiation diagnostics for x-ray laser experiments on Proto-II (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2195-2195 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: X-ray laser experiments on the Sandia Proto-II accelerator (10 TW, 40-ns FWHM, 0.125 Ω) use a wide array of radiation diagnostics. Precise x-ray measurements are difficult in the environment of a large pulsed power accelerator. Machine shock, EMP, and large x-ray fluences are significant problems. X-ray diodes and resistive bolometers provide excellent time-resolved information. Crystal and grazing-incidence grating spectrographs and x-ray pinhole cameras give time-integrated data. A recent major effort at Sandia has been the development of time-resolved x-ray pinhole cameras, crystal spectrographs, and grazing-incidence spectrographs. These diagnostics use microchannel plates or a scintillator and streak camera system to obtain time resolution. Precise alignment, nanosecond time resolution, and high spectral precision are all needed for successful x-ray laser experiments. We will present descriptions of the diagnostics and data taken on recent x-ray laser experiments. This work was supported by the U.S. DOE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138730
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  • 2
    Electronic Resource
    Electronic Resource
    Photoconducting x-ray detectors for Z-pinch experiments (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 1804-1806 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have used GaAs and GaAs:Cr photoconducting detectors (PCDs) to measure the absolute x-ray output from 1 to 10 keV from Z-pinch plasma radiation sources. We calibrated the detectors over the spectral range of 900–3000 eV and found the spectral response to be constant to within the accuracy of the measurements. The flat spectral response, increased sensitivity (compared with bolometers), and good time response of the PCDs, coupled with their reliability and long lifetimes, have allowed us to acquire absolute x-ray data of significantly higher quality than possible with resistive bolometers or x-ray diodes (XRDs). An added attraction of PCDs is their smooth saturation at high incident x-ray fluxes. Unlike other types of electrical x-ray detectors, this feature allows a PCD to operate over a wide range of incident x-ray powers (10–104 W/cm2 ). We present results from gas puff Z-pinch experiments on Proto-II and Supermite comparing PCD, XRD, and resistive bolometer performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140118
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  • 3
    Electronic Resource
    Electronic Resource
    Long implosion time tungsten wire array Z pinches on the Saturn generator (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 2945-2958 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent success on the Saturn [C. Deeney et al., Phys. Rev. E 56, 5945 (1997)] and Z [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] accelerators at Sandia National Laboratories have demonstrated the ability to scale Z-pinch parameters to increasingly larger current pulsed power facilities. Next generation machines will require even larger currents (〉20 MA), placing further demands on pulsed power technology. To this end, experiments have been carried out on Saturn operating in a long pulse mode, investigating the potential of lower voltages and longer implosion times while still maintaining pinch fidelity. High wire number, 25 mm diam tungsten arrays were imploded with implosion times ranging from 130 to 240 ns. The results were comparable to those observed in the Saturn short pulse mode, with rise times on the order of 4.5–6.5 ns. Experimental data will be presented, along with two-dimensional radiation magnetohydrodynamic simulations used to explain and reproduce the experiment. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874146
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  • 4
    Electronic Resource
    Electronic Resource
    Implosion dynamics of long-pulse wire array Z pinches : The 41st annual meeting of the division of plasma physics of the american physical society (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 1935-1944 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent improvements in Z-pinch wire array load design at Sandia National Laboratories have led to a substantial increase in pinch performance as measured by radiated powers of up to 280 TW in 4 ns and 1.8 MJ of total radiated energy. Next generation, higher-current machines will allow for larger mass arrays and comparable or higher velocity implosions to be reached, possibly extending these results. As the current is pushed above 20 MA, a conventional machine design based on a 100 ns implosion time results in higher voltages, hence higher cost and power flow risk. Another approach, which shifts the risk to the load configuration, is to increase the implosion time to minimize the voltage. This approach is being investigated in a series of experimental campaigns on the Saturn [C. Deeney et al., Phys. Plasmas 6, 3576 (1999)] and Z [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] machines. In this paper, both experimental and two-dimensional computational modeling of the first long implosion time Z experiments will be presented. The experimental data shows broader pulses, lower powers, and larger pinch diameters compared to the corresponding short pulse data. By employing a nested array configuration, the pinch diameter was reduced by 50% with a corresponding increase in power of 〉30%. Numerical simulations suggest that load velocity is the dominating mechanism behind these results. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.874018
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  • 5
    Electronic Resource
    Electronic Resource
    Lithium niobate stress gauge current diagnostic for noninductive measurement of fast-rise-time multimegampere currents (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4917-4928 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Accurate modeling of load behavior in Z-pinch plasma radiation sources driven by high-current generators requires the measurement of fast-rise-time multimegampere currents close to the load. Conventional current diagnostics mounted in inductive cavities (such as B-dot loops and Rogowski coils) fail at small radius because of electrical breakdown produced by high dI/dt. In this paper, we describe the use of large-signal, nanosecond-time-resolution lithium niobate piezoelectric stress gauges to directly measure the magnetic pressure B2/2μ0=μ0I2/8π2r2 generated at radius r by a current I flowing in a radial transmission line. Current measurements have been performed at radius r=2.54×10−2 m on Sandia National Laboratories' Proto-II (10 TW) and SATURN (30 TW) gas puff Z-pinch experiments with maximum currents of 10.1 MA and dI/dt to 2.1×1014 A/s. Comparisons with Faraday rotation and B-dot current diagnostic measurements at large radius are presented. Bremsstrahlung noise problems unique to the SATURN gas puff source are discussed. For a Y-cut lithium niobate stress gauge on a pure tungsten electrode, current densities up to I/2πr=78 MA/m can be measured before the electrode yield strength and the piezoelectric operating stress limit are exceeded. Above the Hugoniot elastic limit of the electrode material, the dynamic range and accuracy of the diagnostic are greatly reduced, but it appears that the technique can be extended to higher current densities using an X-cut quartz piezoelectric element and a tungsten-sapphire electrode impedance stack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347077
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  • 6
    Electronic Resource
    Electronic Resource
    Radiative properties of high wire number tungsten arrays with implosion times up to 250 ns (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3576-3586 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High wire number, 25-mm-diameter tungsten wire arrays have been imploded on the 8-MA Saturn generator [R. B. Spielman et al., AIP Conference Proceeding 195, 3 (American Institute of Physics, Woodbury, NY 1989)], operating in a long-pulse mode. By varying the mass of the arrays from 710 to 6140 μg/cm, implosion times of 130–250 ns have been obtained with implosion velocities of 50–25 cm/μs, respectively. These Z-pinch implosions produced plasmas with millimeter diameters that radiated 600–800 kJ of x-rays, with powers of 20–49 TW; the corresponding pulsewidths were 19–7.5 ns, with risetimes ranging from 6.5 to 4.0 ns. These powers and pulsewidths are similar to those achieved with 50-ns implosion times on Saturn. Two-dimensional, radiation-magnetohydrodynamic calculations indicate that the imploding shells in these long implosion time experiments are comparable in width to those in the short-pulse cases. This can be due to lower initial perturbations. A heuristic wire array model suggests that the reduced perturbations, in the long-pulse cases, may be due to the individual wire merger occurring well before the acceleration of the shell. The experiments and modeling suggest that 150–200 ns implosion time Z-pinches could be employed for high-power, x-ray source applications. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873617
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  • 7
    Electronic Resource
    Electronic Resource
    Optimization of power density by decreasing the length of tungsten wire array Z pinches (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2605-2608 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reducing the length of 30 mm diam tungsten wire arrays on the 20 MA Z pulsed power accelerator [R. B. Spielman, S. F. Breeze, C. Deeney et al., Proceedings of the 11th International Conference on Particle Beams, Prague, Czech Republic, edited by K. Junwirth and J. Ullschmied (Czech Academy of Sciences, Prague, 1996), p. 150] from 2 to 0.75 cm has shown that the radiated powers are energies that remain constant at 170±30 TW and 1600±150 kJ. The length-independent nature of the power and energy results in the radiated power per unit length increasing from 85±10 to 240±30 TW/cm. These high-power densities should result in approximately a 20% increase in radiation temperatures produced by a Z-pinch-driven vacuum or internal hohlarums. Two-dimensional radiation magnetohydrodynamic calculations indicate that the constant radiated energies with varying pinch lengths is consistent with the energy input being due to the work done by the Lorentz forces during the radial collapse, resulting in kinetic energy and during the on-axis pinch phase, resulting in pdV or compressional heating. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872947
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  • 8
    Electronic Resource
    Electronic Resource
    Improved large diameter wire array implosions from increased wire array symmetry and on-axis mass participation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2431-2441 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.872919
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  • 9
    Electronic Resource
    Electronic Resource
    Tungsten wire-array Z-pinch experiments at 200 TW and 2 MJ : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2105-2111 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Here Z, a 60 TW/5 MJ electrical accelerator located at Sandia National Laboratories, has been used to implode tungsten wire-array Z pinches. These arrays consisted of large numbers of tungsten wires (120–300) with wire diameters of 7.5 to 15 μm placed in a symmetric cylindrical array. The experiments used array diameters ranging from 1.75 to 4 cm and lengths from 1 to 2 cm. A 2 cm long, 4 cm diam tungsten array consisting of 240, 7.5 μm diam wires (4.1 mg mass) achieved an x-ray power of ∼200 TW and an x-ray energy of nearly 2 MJ. Spectral data suggest an optically thick, Planckian-like radiator below 1000 eV. One surprising experimental result was the observation that the total radiated x-ray energies and x-ray powers were nearly independent of pinch length. These data are compared with two-dimensional radiation magnetohydrodynamic code calculations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872881
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  • 10
    Electronic Resource
    Electronic Resource
    Titanium K-shell x-ray production from high velocity wire array implosions on the 20-MA Z accelerator : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2081-2088 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The advent of the 20-MA Z accelerator [R. B. Spielman, C. Deeney, G. A. Chandler et al., Phys. Plasmas 5, 2105 (1997)] has enabled implosions of large diameter, high-wire-number arrays of titanium to begin testing Z pinch K-shell scaling theories. The 2 cm long titanium arrays, which were mounted on a 40 mm diameter, produced between 75±15 to 125±20 kJ of K-shell x rays. A mass scan indicates that, as predicted, higher velocity implosions in the series produced higher x-ray yields. Spectroscopic analyses indicate that these high velocity implosions achieved peak electron temperatures from 2.7±0.1 to 3.2±0.2 keV and obtained a K-shell emission mass participation of up to 12%. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873461
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