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Effects of mass ablation on the scaling of X-ray power with current in wire-array Z pinches

Physical Review Letters

Lemke, R.W.; Sinars, Daniel S.; Waisman, E.M.; Cuneo, M.E.; Yu, E.P.; Haill, Thomas A.; Hanshaw, Heath L.; Brunner, Thomas A.; Jennings, C.A.; Stygar, William A.; Desjarlais, Michael P.; Mehlhorn, Thomas A.; Porter, J.L.

X-ray production by imploding wire-array Z pinches is studied using radiation magnetohydrodynamics simulation. It is found that the density distribution created by ablating wire material influences both x-ray power production, and how the peak power scales with applied current. For a given array there is an optimum ablation rate that maximizes the peak x-ray power, and produces the strongest scaling of peak power with peak current. This work is consistent with trends in wire-array Z pinch x-ray power scaling experiments on the Z accelerator. © 2009 The American Physical Society.

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TYPE Journal Article YEAR 2009
ScopusOSTI

Shaping the output pulse of a linear-transformer-driver module

Proposed for publication in Physical Review Special Topics: Accelerators and Beams.

Stygar, William A.; Stoltzfus, Brian S.; Woodworth, Joseph R.; Fowler, William E.; LeChien, Keith R.; Long, Finis W.; Mazarakis, Michael G.; McKee, George R.; Mckenney, John M.; Savage, Mark E.

We demonstrate that a wide variety of current-pulse shapes can be generated using a linear-transformer-driver (LTD) module that drives an internal water-insulated transmission line. The shapes are produced by varying the timing and initial charge voltage of each of the module's cavities. The LTD-driven accelerator architecture outlined in [Phys. Rev. ST Accel. Beams 10, 030401 (2007)] provides additional pulse-shaping flexibility by allowing the modules that drive the accelerator to be triggered at different times. The module output pulses would be combined and symmetrized by water-insulated radial-transmission-line impedance transformers [Phys. Rev. ST Accel. Beams 11, 030401 (2008)].

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TYPE Journal Article YEAR 2008
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The refurbished Z facility : capabilities and recent experiments

Matzen, M.K.; Long, Finis W.; McKee, George R.; Mehlhorn, Thomas A.; Schneider, Larry X.; Struve, Kenneth W.; Stygar, William A.; Weinbrecht, Edward A.; Atherton, B.W.; Cuneo, M.E.; Donovan, Guy L.; Hall, Clint A.; Herrmann, Mark H.; Kiefer, Mark L.; Leeper, Ramon J.; Leifeste, Gordon T.

The Z Refurbishment Project was completed in September 2007. Prior to the shutdown of the Z facility in July 2006 to install the new hardware, it provided currents of {le} 20 MA to produce energetic, intense X-ray sources ({approx} 1.6 MJ, > 200 TW) for performing high energy density science experiments and to produce high magnetic fields and pressures for performing dynamic material property experiments. The refurbishment project doubled the stored energy within the existing tank structure and replaced older components with modern, conventional technology and systems that were designed to drive both short-pulse Z-pinch implosions and long-pulse dynamic material property experiments. The project goals were to increase the delivered current for additional performance capability, improve overall precision and pulse shape flexibility for better reproducibility and data quality, and provide the capacity to perform more shots. Experiments over the past year have been devoted to bringing the facility up to full operating capabilities and implementing a refurbished suite of diagnostics. In addition, we have enhanced our X-ray backlighting diagnostics through the addition of a two-frame capability to the Z-Beamlet system and the addition of a high power laser (Z-Petawatt). In this paper, we will summarize the changes made to the Z facility, highlight the new capabilities, and discuss the results of some of the early experiments.

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TYPE Conference YEAR 2008
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Electromagnetic wave propagation through the ZR Z-pinch accelerator

Stygar, William A.; Struve, Kenneth W.

A fully three-dimensional electromagnetic model of the major pulsed power components of the 26-MA ZR accelerator is presented. This large-scale simulation model tracks the evolution of electromagnetic waves through the intermediate storage capacitors, laser-triggered gas switches, pulse-forming lines, water switches, tri-plate transmission lines, and water convolute to the vacuum insulator stack. The plates at the insulator stack are coupled to a transmission line circuit model of the four-level magnetically-insulated transmission line section and post-hole convolutes. The vacuum section circuit model is terminated by either a short-circuit load or dynamic models of imploding z-pinch loads. The simulations results are compared with electrical measurements made throughout the ZR accelerator and good agreement is found, especially for times before and up to peak load power. This modeling effort represents new opportunities for modeling existing and future large-scale pulsed power systems used in a variety of high energy density physics and radiographic applications.

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TYPE Conference YEAR 2008
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Lower bounds for the kinetic energy and resistance of wire array Z pinches on the Z pulsed-power accelerator

Physics of Plasmas

Waisman, Eduardo M.; Cuneo, M.E.; Lemke, Raymond W.; Sinars, Daniel S.; Stygar, William A.

Approximate lower bounds for the kinetic energy and magnetic flux dissipation for tungsten wire arrays on the Z pulsed-power accelerator at Sandia National Laboratories [R. B. Spielman, Phys. Plasmas 5, 2105 (1998)] are obtained. A procedure, extending previous work determining pinch inductance as a function of time [E. M. Waisman, Phys. Plasmas 11, 2009 (2004)], is introduced and applied to electrical and x-ray energy measurements. It employs the pinch energy balance to determine lower bounds for the plasma kinetic energy just before the main pinch reaches the axis and for the magnetic flux dissipation during stagnation. From the lower bound for the dissipated flux, a lower bound for pinch resistance after x-ray peak power is estimated. The results of applying the introduced energy balance procedure to selected tungsten wire array implosions on Z are given. It is believed that this is the first time that a measure of wire array Z-pinch resistance at stagnation is obtained purely from data analysis without recourse to specific assumptions on the plasma motion. © 2008 American Institute of Physics.

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TYPE Journal Article YEAR 2008
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Results 126–150 of 200
Results 126–150 of 200