The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
R.e. Siemon - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of plasma formation from conductors exposed to megagauss magnetic fields
2010 Abstracts IEEE International Conference on Plasma Science, 2010Co-Authors: M.a. Angelova, I.r. Lindemuth, B. S. Bauer, R.e. SiemonAbstract: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.
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Numerical study of plasma formation from conductors exposed to megagauss magnetic fields
2010 Abstracts IEEE International Conference on Plasma Science, 2010Co-Authors: M.a. Angelova, B.s. Bauer, I.r. Lindemuth, R.e. SiemonAbstract: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.
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Experimental study of plasma formation on an Aluminum surface pulsed with megagauss magnetic field
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: B.s. Bauer, R.e. Siemon, S. Fuelling, I.r. Lindemuth, V. MakhinAbstract: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.
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Numerical study of plasma formation from Aluminum Rods driven by megaampere currents
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: M.a. Angelova, B.s. Bauer, V. Makhin, I.r. Lindemuth, R.e. SiemonAbstract: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.
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Numerical study of plasma formation from Aluminum Rods driven by megaampere currents
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: M.a. Angelova, B.s. Bauer, I.r. Lindemuth, Volodymyr Makhin, R.e. SiemonAbstract: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.
S N Mathaudhu - One of the best experts on this subject based on the ideXlab platform.
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synergetic strengthening far beyond rule of mixtures in gradient structured Aluminum Rod
Scripta Materialia, 2016Co-Authors: Jordan Moering, Jacob Malkin, Muxin Yang, S N MathaudhuAbstract: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 - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of plasma formation from Aluminum Rods driven by megaampere currents
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: M.a. Angelova, B.s. Bauer, V. Makhin, I.r. Lindemuth, R.e. SiemonAbstract: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.
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Experimental study of plasma formation on an Aluminum surface pulsed with megagauss magnetic field
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: B.s. Bauer, R.e. Siemon, S. Fuelling, I.r. Lindemuth, V. MakhinAbstract: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.
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Plasma formation in MHD simulations of the UNR Megagauss Experiment using MACH2
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: Michael H. Frese, Sherry D. Frese, V. MakhinAbstract: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.
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Plasma Formation and Evolution from an Aluminum Surface Driven by a MG Field
2007 IEEE 34th International Conference on Plasma Science (ICOPS), 2007Co-Authors: B.s. Bauer, Le B. Galloudec, R.e. Siemon, S. Fuelling, V. Makhin, M.a. Angelova, Andrey Esaulov, T. Goodrich, I.r. LindemuthAbstract:Summary form only given. Applying a magnetic field of several megagauss to a surface drives an interesting interplay of magnetic diffusion, hydRodynamics, and radiative energy transfer. This physics is important in wire-array Z-pinches, high current fuses, magnetically insulated transmission lines, ultrahigh magnetic field generators, magnetized target fusion, and astrophysics. To investigate such plasmas experimentally, 1 MA was driven through a 1 -mm-diameter cylindrical Aluminum Rod, using the UNR Zebra generator. The 70-ns current rise was sufficiently short that the current skin depth was a small fraction of the conductor radius. Diagnostics included optical imaging to a time-gated intensified CCD camera and a streak camera, magnetic field probes, photodiodes, photomultipliers, and laser shadowgraphy, schlieren, interferometry, and Faraday rotation. These yielded information on the threshold for plasma formation, the expansion of the Aluminum, the temperature at the transition between optically thick and optically thin matter, and the growth of the unstable m=0 mode driven by the curvature of the magnetic field. Plasma formation due to ohmic heating was distinguished from plasma formation due to high electric fields or electrical contacts by comparing shots with wire loads vs. loads machined from a solid Aluminum cylinder to have a 1-mm-diameter central length but large-diameter contacts. Time-gated images show markedly more uniform light from the machined load than from the wire load. The relatively simple experimental setup was chosen in the hope of providing a benchmark with which to test and improve radiation-magnetohydRodynamics modeling. Measurements have been compared with the results of RAVEN and MHRDR computer simulations, using various assumptions for equation of state, electrical conductivity, and radiation. The simulations yield observed quantities such as luminosity, laser shadowgraphs, and m=0 mode growth. They also yield many additional interesting details, such as the propagation of a compression wave from the surface to the axis and back, with a resultant rapid radial expansion of the surface after peak current.
I.r. Lindemuth - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of plasma formation from conductors exposed to megagauss magnetic fields
2010 Abstracts IEEE International Conference on Plasma Science, 2010Co-Authors: M.a. Angelova, I.r. Lindemuth, B. S. Bauer, R.e. SiemonAbstract: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.
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Numerical study of plasma formation from conductors exposed to megagauss magnetic fields
2010 Abstracts IEEE International Conference on Plasma Science, 2010Co-Authors: M.a. Angelova, B.s. Bauer, I.r. Lindemuth, R.e. SiemonAbstract: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.
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Experimental study of plasma formation on an Aluminum surface pulsed with megagauss magnetic field
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: B.s. Bauer, R.e. Siemon, S. Fuelling, I.r. Lindemuth, V. MakhinAbstract: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.
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Numerical study of plasma formation from Aluminum Rods driven by megaampere currents
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: M.a. Angelova, B.s. Bauer, V. Makhin, I.r. Lindemuth, R.e. SiemonAbstract: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.
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Numerical study of plasma formation from Aluminum Rods driven by megaampere currents
2009 IEEE International Conference on Plasma Science - Abstracts, 2009Co-Authors: M.a. Angelova, B.s. Bauer, I.r. Lindemuth, Volodymyr Makhin, R.e. SiemonAbstract: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.
Kouichi Uetoko - One of the best experts on this subject based on the ideXlab platform.
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measurement of pressure distribution on die surface and deformation of extrusion die in hot extrusion of 1050 Aluminum Rod
Journal of Materials Processing Technology, 2002Co-Authors: Tsutomu Mori, Norio Takatsuji, Kenji Matsuki, Tetsuo Aida, Kazuo Murotani, Kouichi UetokoAbstract:Abstract In this report, the pressure on the extrusion die surface in a Rod (diameter=32 mm, extrusion ratio=10 and billet diameter=100 mm) of 1050 Aluminum extrusion is measured at a position 27–45 mm from the die center using the semiconductor-strain-gauge-type pressure sensor available on the market. In addition, the deformation of extrusion die in a Rod of 1050 Aluminum extrusion is measured by using the laser-displacement-meter, and the relationship of the pressure distribution and the deformation of extrusion die is investigated. The pressure on the die surface decreases or becomes constant at a central region in a position about 30 mm from the die center where the pressure is highest, also the pressure decreases as a measurement position approaches the container wall. The total deflection of the extrusion die gradually increased with increasing the ram stroke.