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Aluminum Rod

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R.e. Siemon – 1st expert on this subject based on the ideXlab platform

  • Numerical study of plasma formation from conductors exposed to megagauss magnetic fields
    2010 Abstracts IEEE International Conference on Plasma Science, 2010
    Co-Authors: M.a. Angelova, I.r. Lindemuth, B. S. Bauer, R.e. Siemon

    Abstract:

    Summary form only given. Recent Aluminum Rod experiments driven by 1-MA Zebra generator at University of Nevada, Reno (UNR) have provided a benchmark for magnetohydRodynamic (MHD) modeling. The innovative ‘hourglass’ and ‘barbell’ load geometries used in the experiments made it possible to distinguish between plasma formation due to Ohmic heating, which can be studied numerically utilizing MHD codes, and plasma formation due to high electric fields, by intRoducing a large-diameter contact with the electRodes. This prevents the explosive electron emission (EEE) at the contacts which triggers initial plasma formation in the conventional Rod explosion experiments.The UNR megagauss Rod experiments were modeled by employing the state-of-the-art radiation-magnetohydRodynamic code MHRDR. Numerical simulations were performed for a wide range of Rods, varying from 100 to 580 microns in radius. A “cold start” initiation was employed in order to create initial parameters close to the experimental conditions. Material properties of Aluminum, crucial for such simulations, were modeled employing a set of well tested SESAME format equations-of-state (EOS), ionization, and thermal and electrical conductivity tables. The cold start initiation also allowed observation of the numerical phase transitions of the Aluminum Rod, from solid to liquid to vapor and finally to low density plasma as it is ohmically heated by the megaampere driving current. Numerical results indicate that plasma forms at the surface of the expanding low density Aluminum vapor, when and where the magnetic field is about 2.7 MG. This result is in agreement with a previous simulation by Garanin3 et al., as well as with data from the UNR Rod experiments.

  • Numerical study of plasma formation from conductors exposed to megagauss magnetic fields
    2010 Abstracts IEEE International Conference on Plasma Science, 2010
    Co-Authors: M.a. Angelova, B.s. Bauer, I.r. Lindemuth, R.e. Siemon

    Abstract:

    Recent Aluminum Rod experiments1,2 driven by 1-MA Zebra generator at University of Nevada, Reno (UNR) have provided a benchmark for magnetohydRodynamic (MHD) modeling. The innovative ‘hourglass’ and ‘barbell’ load geometries used in the experiments made it possible to distinguish between plasma formation due to Ohmic heating, which can be studied numerically utilizing MHD codes, and plasma formation due to high electric fields, by intRoducing a large-diameter contact with the electRodes. This prevents the explosive electron emission (EEE) at the contacts which triggers initial plasma formation in the conventional Rod explosion experiments.

  • Experimental study of plasma formation on an Aluminum surface pulsed with megagauss magnetic field
    2009 IEEE International Conference on Plasma Science – Abstracts, 2009
    Co-Authors: B.s. Bauer, I.r. Lindemuth, R.e. Siemon, S. Fuelling, V. Makhin

    Abstract:

    Plasma formation on the surface of thick aluminium metal, in response to a pulsed multi-megagauss magnetic field, is experimentally investigated. The dynamics of the pulsed Aluminum Rod and resultant surface plasma are examined with time-resolved imaging, pyrometry, spectroscopy, and laser shadowgraphy; and time gated EUV spectroscopy is used characterised the emission lines from multiply ionised aluminium atoms. The measurement of the time-evolution of the surface temperature, Aluminum expansion rate, and ionization state, as a function of applied field, significantly constrains the choice of models used in radiation-magnetohydRodynamic simulations.

S N Mathaudhu – 2nd expert on this subject based on the ideXlab platform

  • synergetic strengthening far beyond rule of mixtures in gradient structured Aluminum Rod
    Scripta Materialia, 2016
    Co-Authors: Jordan Moering, Jacob Malkin, Muxin Yang, S N Mathaudhu

    Abstract:

    Abstract Gradient structured metals have been reported to exhibit high strength and high ductility. Here we report that the strength of gradient structured Aluminum Rod is much higher than the value calculated using the rule of mixtures. The mechanical incompatibility in the gradient structured round sample pRoduced 3D stress states, extraordinary strengthening and good ductility. An out of plane {111} wire texture was developed during the testing, which contributes to the evolution of the stress state and mechanical behavior.

V. Makhin – 3rd expert on this subject based on the ideXlab platform

  • Numerical study of plasma formation from Aluminum Rods driven by megaampere currents
    2009 IEEE International Conference on Plasma Science – Abstracts, 2009
    Co-Authors: M.a. Angelova, B.s. Bauer, I.r. Lindemuth, V. Makhin, R.e. Siemon

    Abstract:

    Summary form only given. Recent Aluminum Rod experiments driven by 1-MA Zebra generator at University of Nevada, Reno (UNR) have provided a benchmark for magnetohydRodynamic (MHD) modeling. The innovative ‘hourglass’ and ‘barbell’ load geometries used in the experiments made it possible to distinguish between plasma formation due to Ohmic heating, which can be studied numerically utilizing MHD codes, and plasma formation due to high electric fields, by intRoducing a large-diameter contact with the electRodes. This prevents the explosive electron emission (EEE) at the contacts which triggers initial plasma formation in the conventional Rod explosion experiments. The UNR megagauss Rod experiments were modeled by employing the state-of-the-art radiation-magneto- hydRodynamic code MHRDR. Numerical simulations were performed for a wide range of Rods, varying from 25 to 575 microns in radius. A “cold start” initiation was employed in order to create initial parameters close to the experimental conditions. Material properties of Aluminum, crucial for such simulations, were modeled employing a set of well tested SESAME format equations-of-state (EOS), ionization, and thermal and electrical conductivity tables. The cold start initiation also allowed observation of the numerical phase transitions of the Aluminum Rod, from solid to liquid to vapor and finally to low density plasma as it is Ohmically heated by the megaampere driving current. Numerical results indicate that plasma forms at the surface of the expanding low density Aluminum vapor, when and where the magnetic field is about 2.7 MG. This result is in agreement with a previous simulation by Garanin et al., as well as with data from the UNR Rod experiments.

  • Experimental study of plasma formation on an Aluminum surface pulsed with megagauss magnetic field
    2009 IEEE International Conference on Plasma Science – Abstracts, 2009
    Co-Authors: B.s. Bauer, I.r. Lindemuth, R.e. Siemon, S. Fuelling, V. Makhin

    Abstract:

    Plasma formation on the surface of thick aluminium metal, in response to a pulsed multi-megagauss magnetic field, is experimentally investigated. The dynamics of the pulsed Aluminum Rod and resultant surface plasma are examined with time-resolved imaging, pyrometry, spectroscopy, and laser shadowgraphy; and time gated EUV spectroscopy is used characterised the emission lines from multiply ionised aluminium atoms. The measurement of the time-evolution of the surface temperature, Aluminum expansion rate, and ionization state, as a function of applied field, significantly constrains the choice of models used in radiation-magnetohydRodynamic simulations.

  • Plasma formation in MHD simulations of the UNR Megagauss Experiment using MACH2
    2009 IEEE International Conference on Plasma Science – Abstracts, 2009
    Co-Authors: Michael H. Frese, Sherry D. Frese, V. Makhin

    Abstract:

    Summary form only given. In the University of Nevada Reno Megagauss Experiment small Rods with diameters near 1 mm were driven by the Zebra pulser resulting in a current pulse that rises to a peak just over 930 kA in 160 ns. A green filtered photodiode in an experiment with a 1 mm diameter Aluminum Rod shows a strong signal rising at about 100 ns on this same time scale when the current is near 450 kA1. Lagrangian magnetohydRodynamic (MHD) simulations of the experiment with MACH2 using three different equations of state – two with van der Waals loops and one with Maxwell constructions – and two different resistivity models all show plasma formation in the 96 to 102 ns range. Plasma forms in these simulations when a thin layer of the outer edge expands to 5% or less of solid density, cooling as it expands. The resistivity of this warm vapor layer is a few thousand times that of solid Aluminum and is increasing rapidly as the density and temperature fall. The effect in our simulations that reverses the cooling of this vapor and creates plasma is, paradoxically, Ohmic heating since that should decrease with increasing resistivity in a constant electric field. However, the numerical error in the field increases substantially with increasing resistivity intRoducing erroneous Ohmic heating. In fact, we were able to suppress the plasma formation by decreasing the simulation time step and tightening up on the field diffusion error tolerance. The vapor then continued to expand and cool, a more reasonable behavior for the MHD model. Nevertheless, we believe that our MHD simulations’ correct prediction of the time of plasma formation in the experiment is more than a coincidence. Rather, we believe that plasma formation in the experiment is associated with non-MHD electrical breakdown of the vapor expanding from the surface, and that it is the timing of this expansion that is correctly predicted by MHD. In this presentation, we will show these simulation results and will offer a simple physical explanation for the agreement between the timing of the vapor expansion across all three simulations and the experiment.